UBC Theses and Dissertations

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UBC Theses and Dissertations

Mechanism of pyrolysis of 1-pyrazolines Masters, Ian M.E. 1968

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M E C H A N I S M O F P Y R O L Y S I S , O F 1 - P Y R A Z O L I N E S by I A N M . E . M A S T E R S B . S c . , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1 9 6 5 A T H E S I S S U B M I T T E D I N P A R T I A L F U L F I L M E N T O F T H P _ R E Q U I R E M E N T S F O R T H E D E G R E E O F D O C T O R O F P H I L O S O P H Y i n t h e D e p a r t m e n t o f C H E M I S T R Y W e a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d T H E U N I V E R S I T Y O F B R I T I S H C O L U M B I A D e c e m b e r , 1 9 6 8 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h C olumbia, I a g r e e t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and Study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f VvQ.VVr\.\ y\ The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date ft\ JT^ vJJC \9^\°V i i A B S T R A C T The k i n e t i c s for the liquid-phase t h e r m a l decomposition of a number of 1 - p y r a z o l i n e s have been determined. F a c t o r s d e t e r m i n i n g the r e l a t i v e rates of decomposition were: 1} the nature of the p o l a r sub-stituent at the C - 3 position; ii) the position and s t e r e o c h e m i s t r y of a l k y l substitution on positions C - 4 and C - 5 ; and iii) the p o l a r i t y of the solvent employed. T h e p y r o l y s i s rates were found to i n c r e a s e with the i n c r e a s i n g e lectron-withdrawing a b i l i t y of the C - 3 substituent. A l k y l substitution at C - 4 d e c r e a s e d the rate of p y r o l y s i s r e l a t i v e to hydrogen at C - 4 but this d e c r e a s e also depended on the s t e r e o c h e m i s t r y of the C - 4 substituted p y r a z o l i n e . A l k y l substitution at C - 5 i n c r e a s e d the rate of p y r o l y s i s r e l a t i v e to hydrogen at C - 5 but the s t e r e o c h e m i s t r y of substitution at C - 5 had l i t t l e effect on the r a t e s . A d r a s t i c p o l a r i t y i n c r e a s e upon going f r o m n - b u t y l phthalate to f o r m a m i d e solvent d e c r e a s e d the rate of py-r o l y s i s of 3-cyano and 3-carbomethoxy substituted 1 -pyrazolones by a f a c t o r of about two. However, the rate of p y r o l y s i s of 3 - a c e t y l s u b s t i -tuted 1 - p y r a z o l i n e s was i n c r e a s e d by a f a c t o r of about two upon going f r o m n-butyl phthalate to f o r m a m i d e solvent. T h e s e r e s u l t s are d i s -c u s s e d in r e l a t i o n to the c u r r e n t views on p y r a z o l i n e p y r o l y s i s . D e u t e r i u m substitution at the C - 5 p o s i t i o n was found to d e c r e a s e the p y r o l y s i s rate due to a secondary deuterium k i n e t i c isotope effect. A c o m p a r i s o n of the magnitudes of these effects with those found for s i m i l a r s y s t ems indicated that there i s c o n s i d e r a b l e breakage of the C ( 5)-N bond in the t r a n s i t i o n states for p y r o l y s i s i n both n-butyl phthalate and f o r m a -mide solvents. D e u t e r i u m substitution at C - 5 had v e r y l i t t l e effect on the I l l p r o d u c t d i s t r i b u t i o n . A p y r a z o l i n e w i t h d e u t e r i u m at the C-4 p o s i t i o n was p r e p a r e d , 3-mothyl-: 3-carbomethoxy- 1-pyrazolone-4, 4-d£, The p r o d u c t d i s t r i b v . t -t i o n , c o m p a r e d to the n a t u r a l compound, showed that o l e f i n f o r m a t i o n was d e c r e a s e d due to the d e u t e r i u m s u b s t i t u t i o n . T h e k i n e t i c i s o t o p e ef-f e c t on the r a t e of p y r o l y s i s was found to be 1. 36 i n n - b u t y l phthalate s o l v e n t . It has been p r e v i o u s l y suggested that t h e r e m a y be s e p a r a t e t r a n s i t i o n states f o r o l e f i n and c y c l o p r o p a n e f o r m a t i o n . C a l c u l a t i o n s u s i n g the above i s o t o p e e f f e c t and the p r o d u c t d i s t r i b u t i o n s f o r the deu-t e r a t e d and n a t u r a l p y r a z o l i n e gave a v a l u e of 1. 94 f o r the d e u t e r i u m i s o t o p e e f f e c t on the o l e f i n - f o r m i n g r e a c t i o n . T h i s s u p p o r t s a m e c h a -n i s m f o r o l e f i n f o r m a t i o n w h e r e the m i g r a t i o n of a C-4 h y d r o g e n to the C-5 p o s i t i o n i s c o n c e r t e d w i t h b r e a k a g e of the c a r b o n - n i t r o g e n bond. In f o r m a m i d e solvent, however, the k i n e t i c i s o t o p e e f f e c t was found to be only 1. 06. T h i s was t a k e n as an i n d i c a t i o n that C (4)-H bond b r e a k a g e was not advanced i n the t r a n s i t i o n state f o r p y r a z o l i n e p y r o l y s i i n t h i s p o l a r s o l v e n t . However, the e f f e c t of d e u t e r i u m s u b s t i t u t i o n on the p r o d u c t d i s t r i b u t i o n s u g gests that a. n i t r o g e n - f r e e i n t e r m e d i a t e i s f o r m e d i n the r a t e - d e t e r m i n i n g step. The d e u t e r i u m i s o t o p e e f f e c t on t h o l e f i n f o r m i n g step, l a r g e l y p r i m a r y , was e s t i m a t e d to be 2.2. T h e s y n t h e s i s and d e c o m p o s i t i o n p r o d u c t s of a new p y r a z o l i n e , 3, 5, 5, - t r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e , a r e d e s c r i b e d . The p r e p a r a -t i o n s of the d e u t e r a t e d p y r a z o l o n e s a r e d e s c r i b e d and t h e i r n u c l e a r mag-n e t i c r e s o n a n c e s p e c t r a a r c d i s c u s s e d i n d e t a i l . iv T A B L E O F C O N T E N T S . P a.g e . I. I N T R O D U C T I O N P r e p a r a t i o n o f P y r a z o l i n e s 1 P y r o l y s i s p f P y r a z o l i n e s 5 • P h o t o l y s i s o f P y r a z o l i n e s 4 0 O b j e c t o f t h e P r e s e n t R e s e a r c h 4 2 II. R E S U L T S A N D D I S C U S S I O N 1. P R E P A R A T I O N W O R K T h e S y n t h e s i s o f 1 - P y r a z o l i n e s 4 4 . 2 . K I N E T I C M E A S U R E M E N T S C a l c u l a t i o n o f t h e R a t e C o n s t a n t s a n d A c t i v a t i o n P a r a m e t e r s 6 4 3 . P R O D U C T A N A L Y S I S 81 4 . D I S C U S S I O N O F R E S U L T S 8 8 S u b s t i t u e n t E f f e c t s o n P y r o l y s i s R a t e s a n d P r o d u c t D i s t r i b u t i o n 88 T h e T r a n s i t i o n S t a t e f o r P y r a z o l i n e P y r o l y s i s 9 5 i ) . E f f e c t o f D e u t e r i u m S u b s t i t u t i o n a t C - 5 9 5 i i ) . S o l v e n t E f f e c t s o n P y r o l y s i s R a t e s 99 i i i ) . E f f e c t o f D e u t e r i u m S u b s t i t u t i o n a t C - 4 102 V P a g e 5. S U G G E S T I O N S F O R F U T U K E R E S E A R C H 118 I I I . E X P E R I M E N T A L G e n e r a l S t a t e m e n t 121 N - N i t r o s o - N - m e t h y l u r e a 122 N - N i t r o s o - N - e t h y l u r e a 122 D i a z o m e t h a n e a n d d i a z o e t h a n e 122 D i d e u t e r i o d i a z o m e t h a n e 122 1 - M e t h y l - 3 - c y a n o - 1 - p y r a z o l i n e (98) 1 2 3 3 - M e t h y l - 3 - c y a n o - 1 - p y r a z o l i n e - 5 - 5 - d ^ (99) 1 2 3 P r o d u c t s f r o m t h e d e c o m p o s i t i o n o f 3 - m e t h y l - 3 - c y a n o - ' 1 - p y r a z o l i n e (98) 1 2 4 3 - M e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (95) 1 2 5 3 - M e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e - 5 , 5 - d £ (97) 126 3 - M e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (42) 126 C i s - a n d t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e ( 4 3 a n d 44) 127 C i s - a n d t r a n s - 3, 5 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1-p y r a z o l i n e (5 a n d 6) 127 C i s - 3, 4 - d i m e t h y l - 3- c a r b o m e t h o x y - 1- p y r a z o l i n e (3) 128 C i s - a n d t r a n s - 2 - b r o m o - 2 - b u t e n e 129 M e t h y l A n g e l a t e ' (2) 130 T r a n s - 3, 4 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1- p y r a z o l i n e (4) 130 " 3 - V i n y l - 1 - p y r a z o l i n e (55) 131 / v i T r i m e t h y l c< - p h o s p h o n o p r o p i o n a t e (102) 131 M e t h y l c i s - a n d t r a n s - 2 - m e t h y l - 2 - p e n t e n o a t e (60 a n d 59) 132 C i s - 3 - m e t h y l - 4 - e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (84) 133 T r a n s - 3 - m e t h y l - 4 - e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (85) ^ 1 3 3 3, 5, 5 - T r i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (100) 1 3 4 A c e t o n e a z i n e 1 3 4 A c e t o n e h y d r a z o h e 1 3 4 3, 5, 5 - T r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (101) 135 C h a r a c t e r i z a t i o n o f t h e p r o d u c t s f r o m t h e p y r o l y s i s o f 3, 5, 5 - t r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (101 ) 136 M e t h y l m e t h a c r y l a t e - 3 , 3 - d 2 (115) 139 (a) W i t t i g r e a c t i o n 139 (b) M o d i f i e d W i t t i g r e a c t i o n 141 (c) T h e M a n n i c h r e a c t i o n 142 3 - M e t h y l - 3 - c a r b o m e t h o x y - l - p y r a z o l i n e - 4 , 4 - d ^ (96) 146 P r o d u c t s f r o m t h e t h e r m a l d e c o m p o s i t i o n o f 3 - m e t h y l -3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e - 4 , 4 - d ^ (96) 147 K i n e t i c s 148 P r o d u c t A n a l y s i s 1 5 3 B I B L I O G R A P H Y 158 v i i L I S T O F T A B L E S T a b l e P a g e I . 1 - P y r a z o l i n e s 4 4 I I . T h e S u m m a r y o f t h e R a t e C o n s t a n t s a n d t h e A c t i v a t i o n P a r a m e t e r s i n t h e P y r o l y s i s o f 1 - P y r a z o l i n e s 66 I I I . P r o d u c t C o m p o s i t i o n s f o r t h e P y r o l y s i s o f 3 - M e t h y l - 3 -c a r b o m e t h o x y - 1 - p y r a z o l i n e ( 9 5 ) , 3 - M e t h y l - 3 -c a r b o m e t h o x y - l - p y r a z o l i n e - 4 , 4 - d , ( 9 6 ) , a n d 3 -M e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o H n e - 5 , 5 - d ^ (97) 82 I V . 1 P r o d u c t C o m p o s i t i o n s f o r t h e P y r o l y s i s o f 3 - M e t h y l 3 - a c e t y l - 1 - p y r a z o l i n e (42) 8 3 V . P r o d u c t C o m p o s i t i o n s f o r t h e P y r o l y s i s o f 3, 5, 5 -T r i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (100 ) 8 3 V I . P r o d u c t C o m p o s i t i o n s f o r t h e P y r o l y s i s o f 3, 5, 5 -T r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (101) 8 4 V I I . P r o d u c t C o m p o s i t i o n s f o r t h e P y r o l y s i s o f c i s -a n d t r a n s - 3, 4 - D i m e t h y l - 3 - c a r b o m e t h o x y - 1-p y r a z o l i n e (_3 a n d 4) 8 4 V I I I . E f f e c t o f T e m p e r a t u r e o n P r o d u c t D i s t r i b u t i o n s f o r t h e P y r o l y s i s o f 3 - m e t h y l - 3 - c a r b o m e t h o x y - 1 -v p y r a z o l i n e (95) 8 5 v i i i L I S T O F F I G U R E S P a g e F i g u r e I . M e c h a n i s m s o f 1 - p y r a z o l i n e f o r m a t i o n 3 I I . P o s s i b l e m e c h a n i s m s f o r t h e p y r o l y s i s o f 1 - p y r a z o l i n e s 7 I I I . I o n i c m e c h a n i s m f o r t h e p y r o l y s i s o f 3, 4 - d i m e t h y l -3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s 10 I V . F r e e - r a d i c a l m e c h a n i s m o f p y r o l y s i s o f 3, 5 - d i a r y l -1 - p y r a z o l i n e s 14 V . P r o d u c t s f r o m t h e p y r o l y s i s o f 3 - m e t h y l - 3 - a c e t y l -1 - p y r a z o l i n e V I . P r o d u c t s f r o m t h e p y r o l y s i s o f 3, 5 - d i m e t h y l - 3 - a c e t y l -1 - p y r a z o l i n e s V I I . P r o d u c t s f r o m t h e p y r o l y s i s o f 3, 5 - d i m e t h y l - 3 -c a r b o m e t h o x y - 1 - p y r a z o l i n e s 2 0 V I I I . P y r o l y s i s o f 4 - m e t h y l - l - p y r a z o l i n e - 4 - d - ^ 2 4 I X . I n t e r m e d i a t e s f o r t h e p y r o l y s i s o f c i s - a n d t r a n s -3, 5 - d i m e t h y l - 1 - p y r a z o l i n e s 26 X . P y r o l y s i s o f c i s - a n d t r a n s - 4 - d e u t e r i o - 3 - m e t h y l - 1 -p y r a z o l i n e s 2 8 X I . T h e s y m m e t r i c (S) a n d a n t i s y m m e t r i c ( A ) T \ - t y p e m o l e c u l a r o r b i t a l s i n t r . m e t h y l e n e X I I . T h e e l e c t r o n i c s t r u c t u r e o f t r i m e t h y l e n e . X I I I . P y r o l y s i s p r o d u c t s f r o m c i s - a n d t r a n s - 3 - m e t h y l - 4 -e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s 34 X I V . T h e n . r n . r . s p e c t r u m o f 3 - m e t h y l - 3 - c a r b o m e t h o x y -1 - p y r a z o l i n e (95) 55 Page F i g u r e X V . T h e n. m. r. s p e c t r u m of 3 - m ethyl-3-carbomethoxy-1 - p y r a z o l i n e - 5 , 5 - d 2 (97) 56 X V I . P o s s i b l e p r e p a r a t i v e scheme f o r m e t h y l m e t h a c r y l a t e -3- d 57 1 X V I I . P r e p a r a t i o n of m e t h y l m e t h a c r y l a t e - 3 , 3-d^ by the M a n n i c h r e a c t i o n 60 X V I I I . The n. m. r. s p e c t r u m of 3-methyl- 3-carbomethoxy-1 - p y r a z o l i n e - 4 , 4 - d 2 (96) 62 X I X . P r o d u c t s f r o m the p y r o l y s i s of 9_5 and 96. 63 X X . R a t e p l o t s f o r the p y r o l y s i s of 3 - m e t h y l - 3-carbomethoxy-1 - p y r a z o l i n e (95) and 3 - m e t h y l - 3 - c a r b o m e t h o x y - 1 -p y r a z o l i n e - 4 , 4 - d 2 (96) i n n - b u t y l phthalate. 71 X X I . R a t e p l o t s f o r the p y r o l y s i s of 3 - m e t h y l - 3 - c y a n o - 1 -p y r a z o l i n e (98) and 3 - m e t h y l - 3 - c y a n o - 1 - p y r a z o l i n e -5, 5-d 2, (99) i n n - b u t y l phthalate 72 X X I I . R a t e p l o t s f o r the p y r o l y s i s of 3, 5, 5 - t r i m e t h y l - 3 -c a r b o m e t h o x y - 1 - p y r a z o l i n e (100) i n n - b u t y l phthalate and i n f o r m a m i d e 7 3 X X I I I . R a t e p l o t s f o r the p y r o l y s i s of 3, 5, 5 - t r i m e t h y l - 3 -a c e t y l - 1 - p y r a z o l i n e (101) i n n - b u t y l phthalate and i n f o r m a m i d e 74 X X I V . R a t e p l o t s f o r the p y r o l y s i s of c i s - and t r a n s -3, 4-d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s (3 and 4) i n n - b u t y l phthalate 75 X X V . R a t e p l o t s f o r the p y r o l y s i s of c i s - and t r a n s - , 3 - m e t h y l -4- e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s (84 and 85) i n n - b u t y l phthalate 76 X X V I . C-3 and C-5 s u b s t i t u e n t e f f e c t s on the r e l a t i v e r a t e s of p y r o l y s i s of 1 - p y r a z o l i n e s 89 X Page F i g u r e X X V I I . X X V I I I . The effect of 4 - a l k y l s u b s t i t u t i o n on the r a t e s of 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s K i n e t i c d e u t e r i u m i s o t o p e e f f e c t s i n the p y r o l y s i s of 1 - p y r a z o l i n e s X X I X . T r a n s i t i o n s t a t e s f o r o l e f i n f o r m a t i o n X X X . K i n e t i c s a p p a r a t u s 93 107 110 149 x i A C K N O W L E D G M E N T S I w i s h t o e x p r e s s m y s i n c e r e g r a t i t u d e t o D r . D . E . M c G r e e r f o r h i s c o n s t a n t i n t e r e s t a n d e n c o u r a g e m e n t d u r i n g t h e c o u r s e o f t h e r e s e a r c h a n d ' t h e p r e p a r a t i o n o f t h i s t h e s i s . I a m i n d e b t e d t o M r s . A . B r e w s t e r , M i s s C . B u r f i t t , a n d M r . R . B u r t o n f o r t h e N . M . R . s p e c t r a , a n d t o M r . P . B o r d a f o r t h e m i c r o a n a l y s e s . F i n a l l y , I w i s h t o t h a n k t h e N a t i o n a l R e s e a r c h C o u n c i l o f C a n a d a f o r t h e a w a r d o f s t u d e n t s h i p s f o r t h e p e r i o d f r o m 1 9 6 5 - 1 9 6 8 . I. INTRODUCTION The a d d i t i o n of a d i a z o a l k a n e to £~>. c x ^ - u n s a t u r a t e d e s t e r , k e -tone, o r n i t r i l e to f o r m 1 - p y r a z o l i n e s and the p y r o l y s i s of these 1-pyra-z o l i n e s to f o r m c y c l o p r o p a n e s and o l e f i n s have been known f o r some t i m e (1-3). T h i s sequence of r e a c t i o n s has p r o v e d to be a convenient route f o r the s y n t h e s i s of c y c l o p r o p a n e d e r i v a t i v e s and of oC^sS- and j~>^-un-s a t u r a t e d o l e f i n s (4-6). c y c l o p r o p a n e s + o l e f i n s R .= H, a l k y l Y = CO zR, COR, CN The m e c h a n i s m of the p y r o l y s i s of 1 - p y r a z o l i n e s has been under debate f o r many y e a r s and r e c e n t l y a c o n s i d e r a b l e amount of w o r k has been done to c l a r i f y the m e c h a n i s m , o r m e c h a n i s m s , i n v o l v e d . The r e s u l t s of t h i s r e c e n t w o r k and the m e c h a n i s m s p r o p o s e d w i l l be d i s c u s s e d a f t e r the e a r l i e r w o r k on 1 - p y r a z o l i n e s has been s u m m a r i z e d . P r e p a r a t i o n of P y r a z o l i n e s T h e m e c h a n i s m of the a d d i t i o n of a d i a z o a l k a n e to an c<^3--un-s a t u r a t e d c a r b o n y l compound has been suggested, by H u i s g e n and - 2 -c o w o r k e r s (7-9), to be a one-step m u l t i p l e - c e n t e r a d d i t i o n r a t h e r than a t w o - s t e p i o n i c m e c h a n i s m p r o p o s e d e a r l i e r (10, 11). T h e i r a r g u m e n t s a r e based- on both k i n e t i c and s y n t h e t i c r e s u l t s . R a t e c o n s t a n t s w e r e m e a s u r e d (7) f o r the a d d i t i o n of d i a z o a l k a n e s to o l e f i n s to f o r m p y r a -zolones. The r a t e constants w e r e l a r g e l y independent of the d i e l e c t r i c c onstant of the s o l v e n t and w e r e g r e a t l y i n f l u e n c e d by s t e r i c f a c t o r s . L a r g e n e g a t i v e e n t r o p i e s of a c t i v a t i o n w e r e o b s e r v e d . H ence the l e s s i o n i c and m o r e s t e r i c a l l y r e s t r i c t e d p o l y c e n t e r a d d i t i o n m e c h a n i s m i s f a v o u r e d . The r e a c t i o n of 1, 3-di p o l e s w i t h c i s and t r a n s o l e f i n s p r o -duced i s o m e r i c p y r a z o l i n e s (8) by a s t e r e o s e l e c t i v e c o n c e r t e d c i s a d d i -t i o n . The r e c e n t f i n d i n g s of L e d w i t h and P a r r y (12) a l s o support con-c e r t e d _cis a d d i t i o n . T h e s e w o r k e r s s t u d i e d the k i n e t i c s of the r e a c t i o n s betv/een d i a z o m e t h a n e or diazoethane and m e t h y l a c r y l a t e o r m e t h y l m e t h a c r y l a t e and found that the r e a c t i o n p a r a m e t e r s w e r e not i n f l u e n c e d by a change of s o l v e n t and the e n t r o p y of a c t i v a t i o n f o r the a d d i t i o n was l a r g e and n e g a t i v e . O v e r b e r g e r and c o w o r k e r s (13), however, p r e p a r e d a m i x t u r e of c i s - and t r a n s - 3 , 5-bis ( p - a n i s y l ) - 1 - p y r a z o l i n e s by r e a c t i n g j>-methoxy-s t y r e n e w i t h p_-methoxyphenyldiazomethane. The f o r m a t i o n of the c i s i s o m e r was r a t i o n a l i z e d by p r o p o s i n g a t w o - s t e p m e c h a n i s m f o r the a d d i -t i o n . H o wever, the c o n c e r t e d m e c h a n i s m wo u l d a l s o give a m i x t u r e of c i s and t r a n s i s o m e r s . The two m e c h a n i s m s p r o p o s e d f o r p y r a z o l i n e f o r m a t i o n a r e s h o w n i n F i g u r e I . • 2 R R v — c \ R Y + RCHN2 o n e - s t e p t w o - s t e p —t. R" N , R RV R>V 1* •N R Y R = H, a l k y l , a r y l Y =• C0 2CH 3, COCH3, CN, N 0 2 F I G U R E I - M e c h a n i s m s o f 1 - p y r a z o l i n e f o r m a t i o n . T h e c i s a d d i t i o n o f d i a z o m e t h a n e w i t h t h e f o r m a t i o n o f a s i n g l e p y r a z o l i n e p r o d u c t i s i l l u s t r a t e d b y t h e a d d i t i o n t o m e t h y l t i g l a t e (1) a n d m e t h y l a n g e l a t e (_2) t o g i v e c i s - a n d t r a n s - 3, 4 - d i m e t h y l - 3 - c a r b o m e t h o x y -1 - p y r a z o l i n e s (3 a n d 4) (14) r e s p e c t i v e l y . CH, H ' C 0 2 C H - 3 + CH2.N2 CH. N CH, C 0 2 C H 3 H- ' C H 3 "CQ2CH3 + CH2N2 H -> C H -N N CH3 CO^ CH, - 4 -T h i s f e a t u r e of the p y r a z o l i n e s y n t h e s i s p r o v i d e s a means to o b t a i n i n g i s o m e r i c p y r a z o l i n e s d i f f e r i n g o n ly i n t h e i r c o n f i g u r a t i o n at the C-4 p o s i t i o n l i k e _3 and _4. S e v e r a l other i s o m e r i c p y r a z o l i n e s have been p r e p a r e d as m i x t u r e s and t h e i r s e p a r a t i o n into p a i r s of g e o m e t r i c i s o -m e r s has been a c h i e v e d by d i s t i l l a t i o n , v a p o u r - p h a s e c h r o m a t o g r a p h y , and c r y s t a l l i z a t i o n . The c i s - and t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o m e t h o x y -1 - p y r a z o l i n e s (_5 and _6) w e r e s e p a r a t e d by d i s t i l l a t i o n (15), c i s - and t r a n s -3, 5 - d i m e t h y l - 1 - p y r a z o l i n e (_7 and _8) w e r e s e p a r a t e d by v a p o u r - p h a s e c h r o m a t o g r a p h y (16), and c i s - and t r a n s - 3 , 5-bis (p_~anisyl)- 1 - p y r a z o l i n e (9 and 20) w e r e s e p a r a t e d by c r y s t a l l i z a t i o n (13). C H C H 5 6 7 8 C 6 H 4 O C H 3 - p C,H O C H -6 4 3 9 10 5 -l i t h e 3 - p o s i t i o n of the 3 - s u b s t i t u t e d pyra.zoli_ie i s s u b s t i t u t e d by hydrogen, t a u t o m e r i z a t i o n can o c c i r due to the i n f l u e n c e of the sub-s t i t u e n t . G e n e r a l l y , t h i s o c c u r s when the 3- s u b s t i t u e n t i s s t r o n g l y e l e c t r o n w i t h d r a w i n g . F o r example, the a d d i t i o n of d iazomethane to m e t h y l a c r y l a t e g i v e s 3 - c a r b o m e t h o x y - 2 - p y r a z o l i n e (11) (3), w h i c h i s m o r e s t a b l e -- due to c o n j u g a t i o n -- than the 3 - c a r b o m e t h o x y - 1 - p y r a -z o l i n e (12). C H 2 = C H C 0 2 C H 3 + C H 2 N 2 Y C O C H 2 3 N C O C H i f 2 : N •N l H 12 11 S u b s t i t u t i o n of the 3-hydrogen by other groups leads to 1 - p y r a z o l i n e s w h i c h ca n be t a u t o m e r i z e d to 5 - p y r a z o l i n e s o n l y by t r e a t m e n t w i t h a c i d o r base. P y r o l y s i s of P y r a z o l i n e s v o n A u w e r s and K o n i g (3) s t u d i e d the s t e r e o c h e m i s t r y of the f o r m a t i o n of c y c l o p r o p a n e s by the p r e p a r a t i o n and subsequent decompo-s i t i o n of p y r a z o l i n e s and c o n c l u d e d that when the i n t e r m e d i a t e p y r a z o l i n e s a r e 1 - p y r a z o l i n e s , the c y c l o p r o p a n e s f o r m e d r e t a i n the g e o m e t r y of the i n i t i a l o l e f i n . A g e n e r a l s t e r e o s p e c i f i c i t y i n the d e c o m p o s i t i o n of 1-p y r a z o l i n e s was t h e r e f o r e a s s u m e d to be v a l i d f o r some t i m e (3, 4, 5, 17a-c), H o w e v e r , i n l a t e r w o r k by Jones and T a i (18a-b), they conclude that "the - 6 -r e a c t i o r i s , at best, p a r t i a l l y s t e r e o s p e c i f i c w i t h r e s p e c t to the c a r b o n -c a r b o n bo.id between the number t h r e e and f o u r m e m b e r s of the h e t e r o -c y c l i c ring''. T h e i r r e s u l t s w i t h two i s o m e r i c 1-pyrazolines i n d i c a t e d that the c y c l o p r o p a n e f o r m a t i o n does not p r o c e e d e n t i r e l y t h r o u g h a com-mon i n t e r m e d i a t e (18b). The r e s u l t s of V a n A u k e n and R i n e h a r t (14) and the e a r l i e r r e s u l t s of M c G r e e r et _al. (19, 20, 21), on the d e c o m p o s i t i o n of 1 - p y r a z o l i n e s d e m o n s t r a t e d that the a n a l y t i c a l t e c h n i q u e of v o n A u w e r s was d e f e c t i v e and that t h e r e i s often c o n s i d e r a b l e r a n d o m i z a t i o n of s t e r e o -c h e m i s t r y i n the c y c l o p r o p a n e p r o d u c t s . E a r l y s u g g e s t i o n s f o r the m e c h a n i s m of p y r o l y s i s of 1-pyra-z o l i n e s i n c l u d e d i o n i c ( 11, 22, 23) and b i r a d i c a l (24, 25) pathways. T h e s e w e r e based on the r a t h e r l i m i t e d i n f o r m a t i o n o b t a i n a b l e f r o m the product d i s t r i b u t i o n s . O l e f i n f o r m a t i o n was a t t r i b u t e d e i t h e r to h y d r i d e or p r o -ton s h i f t s i n n i t r o g e n - c o n t a i n i n g o r n i t r o g e n - f r e e i n t e r m e d i a t e s (11), or to r e a r r a n g e m e n t of b i r a d i c a l i n t e r m e d i a t e s (24). It was o b s e r v e d (22) that an i o n i c pathway mi g h t w e l l be the case w h e r e the 3- and 5 - s u b s t i -tuents of an u n s y m m e t r i c a l l y s u b s t i t u t e d 1 - p y r a z o l i n e a r e able to de-l o c a l i z e a p o s i t i v e or n e g a t i v e c h a r g e . P r o p o s e d m e c h a n i s m s f o r the p y r o l y s i s of 1 - p y r a z o l i n e s a r e shown i n F i g u r e II. Step (a) i n v o l v e s c o m p l e t e l o s s of n i t r o g e n to g i v e the z w i t t e r i o n (14), w h i c h p r e s u m a b l y c o u l d be s t a b i l i z e d by d e l o c a l i z a t i o n of the p o s i t i v e and n e g a t i v e c h a r g e s by s u b s t i t u e n t s on C-3 and C-5. R i n g c l o s u r e i n 14 g i v e s c y c l o p r o p a n e (15) and a h y d r i d e s h i f t g i v e s the - u n s a t u r a t e d e s t e r H v / R C — C . R \ CO R 2 N N H - / R :o R 2 H ,R > — ^ R \ / N C O R CH 2 15 13 14 R N R c = c N CH' CO R 3 2 proton shift R CH = C-C-H 2 I X C O R R 2 16 17 A R H C. CO R 2 2 1\T — N — N 15 18 17 H yR / H H \ H / \ R N / 19 , N RCHCH CHR 2 20 H R .H R 21 H / R C CH R H 2 22 FIGURE II - Possible mechanism s for the pyrolysis of 1-pyrazolines. - 8 -(16). F o r m a t i o n of the / ^ ^ ' . u n s a t u r a t e d o l e f i n (17) i s p o s s i b l e by a C(4)-C(3) o r o t o n s h i f t . If the c a r b o n - n i t r o g e n bonds i n 1_3 do not b r e a k s i m u l t a n e o u s l y a d i a z o n i u m ien i n t e r m e d i a t e (18) c o u l d be f o r m e d as i n step (b). L o s s of n i t r o g e n f r o m s p e c i e s JJ3 c o n c e r t e d w i t h r i n g c l o s u r e v / i l l give c y c l o -propane (15), w h e r e a s l o s s of n i t r o g e n c o n c e r t e d w i t h h y d r i d e m i g r a t i o n g i v e s J_6 and w i t h p r o t o n m i g r a t i o n g i v e s 17. Step(c) i l l u s t r a t e s f o r m a t i o n of a b i r a d i c a l i n t e r m e d i a t e (20) f o r m e d w i t h 19 by s i m u l t a n e o u s b r e a k i n g of both c a r b o n - n i t r o g e n bonds. R i n g c l o s u r e i n s p e c i e s 20 g i v e s c y c l o p r o p a n e (21) and r e a r r a n g e m e n t g i v e s olefin. (22). It i s p o s s i b l e that the r a d i c a l pathway m i g h t i n v o l v e a b i r a d i c a l s p e c i e s analogous to the d i a z o n i u m i o n 18; but t h i s was con-s i d e r e d u n l i k e l y s i n c e i n azo compounds a p p a r e n t l y both c a r b o n - n i t r o g e n bonds b r e a k s i m u l t a n e o u s l y (26, 27). ( T h i s i s not a l w a y s the case as w i l l be d i s c u s s e d l a t e r ) . F r o m the r e s u l t s i n the e a r l i e r l i t e r a t u r e i t a p p e a r s that no d e f i n i t e c o n c l u s i o n s c o u l d be d r a w n about the m e c h a n i s m of the p y r o l y s i s of 1 - p y r a z o l i n e s . M o r e r e c e n t m e c h a n i s t i c d e s c r i p t i o n s of the p y r o l y s i s r e a c t i o n have been made on the r e s u l t s of c a r e f u l product a n a l y s i s and k i n e t i c s t u d i e s . V a n A u k e n and R i n e h a r t (14) i n v e s t i g a t e d the s t e r e o c h e m i s t r y of the t h e r m a l and p h o t o l y t i c d e c o m p o s i t i o n of two i s o m e r i c 1 - p y r a z o l i n e s . - 9 -The p y r o l y s i s of t r a n s - 3 , 4-dimethyl--3-car bomethoxy- 1 - p y r a z o l i n e (4) gi v e s m e t h y l 2, 3-dimethyl-3-butenoate (2 3), t r a n s - 1, 2 - d i m e t h y l - 1-c a r b o m e t h o x y c y c l o p r o p a n e (24), c i s - 1, 2- d i m e t h y l - 1 - c a r b o m e t h o x y c y c l o -propane ( 2 5 ) , and m e t h y l , 2, 3-dimethyl-2->utenoate (26) i n the r a t i o 0. 15: 1.22:1:00:1. 16. P y r o l y s i s of the c i s - p y r a z o l i n e (_3) gave the same com-pounds i n the r a t i o 0.24:0.70:1. 00:3. 73. The p y r o l y s i s of the s e p y r a -z o l i n e s p r o c e e d s w i t h only a s l i g h t degree of s t e r e o s e l e c t i v i t y : 1.22:1.00 i n favovir of the t r a n s - c y c l o p r o p a n e 24 f r o m the t r a n s - p y r a z o l i n e 4 and 1. 00:0. 70 i n f a v o u r of the c i s - c y c l o p r o p a n e 25 f r o m the c i s - p y r a z o l i n e _3. T h e s e a u t h o r s e x p l a i n e d the r e s u l t s by an e l a b o r a t i o n of the i o n i c m e c h a n i s m d i s c u s s e d above. The p r o p o s e d m e c h a n i s m i s shown i n F i g u r e III. T o account f o r the f a c t that the i s o m e r i c c y c l o p r o p a n e s a r e f o r m e d i n a l m o s t e q u a l amounts they p o s t u l a t e that r o t a t i o n about the f o r m e r C(3)-C(4) bond must take p l a c e i n e i t h e r i n t e r m e d i a t e _27 or 28 b e f o r e c y c l i z a t i o n to c y c l o p r o p a n e o c c u r s . It was expe c t e d that the z w i t t e r i c n 28 and i t s s i n g l e t d i r a d i c a l r e s o n a n c e f o r m 2 9 s h o u l d c y c l i z e i m m e d i a t e l y , that i s , b e f o r e r o t a t i o n c o u l d o c c u r . The s m a l l s t e r e o -s e l e c t i v i t y o b s e r v e d was e x p l a i n e d by the s u g g e s t i o n that step (c), l o s s of n i t r o g e n i n going f r o m 27 to 28, i s s l i g h t l y f a s t e r than r o t a t i o n i n 27. Some b a r r i e r to r o t a t i o n i s p r o v i d e d i n that i t i n v o l v e s c o n s e c u t i v e ec-l i p s e d i n t e r a c t i o n s of m e t h y l - c a r b o m e t h o x y and m e t h y l e n e d i a z o n i u m -m e t h y l . The ene r g y b a r r i e r f o r r o t a t i o n i n 27 was t h e r e f o r e e s t i m a t e d -IO-C H C O C H 2 3 C H 0  N _3 ( m e t h y l s c i s ) o r 4 ( m e t h y l s t r a n s ) H C O C H CH CH. N 2 27 - N H C H ,CO, C z C H 3 CH, 28 H C H ; C 0 2 C H 3 C H , CH, 29 .CH H 7 C = C — C H 3 | X C O C H 3 C H 3 23 C H JCB. C O C H 2 3 24 H C H 25 .CO C H 2 3 C H C H C H 3 X C — C y C H / 3 C 0 2 C H 3 26 F I G U R E III - I o n i c m e c h a n i s m f o r the p y r o l y s i s of 3, 4-d i m e t h y l - 3-carbomethoxy- 1 - p y r a z o l i n e s . to be g r e a t e r than the e n e r g y of a c t i v a t i o n f o r step (c). T h e r e a r e two o b s e r v a t i o n s w h i c h a r e not i n f a v o u r of the p r o -p o s e d i n t e r m e d i a t e 27. (i) The r a t i o s of c y c l o p r o p a n e to o l e f i n f o r the p y r o l y s i s of the two p y r a z o l i n e s a r e d i f f e r e n t ; the r a t i o i s 1. 70:3. 97 f o r the c i s - p y r a z o l i n e 3 and 2. 22:1. 31 f o r the t r a n s - p y r a z o l i n e 4. - 11 -T h i s s i g n i f i c a n t d i f f e r e n c e i n p r o d u c t d i s t r i b u t i o n cannot be e x p l a i n e d by an i n t e r m e d i a t e s u c h as 27, w h i c h w o u l d be the same i n t e r m e d i a t e f o r both p y r a z o l i n e s . (ii ) If the l i f e t i m e of i n t e r m e d i a t e 27 i s s u f f i c i e n t l y l o n g to p e r -m i t r o t a t i o n s , then one w o u l d expect r e v e r s a l of step (a.) w h i c h w o u l d give some p y r a z o l i n e w i t h i n v e r s i o n of g e o m e t r y at C-3. However, i t was shown that the p a r t i a l p y r o l y s i s of c i s - 3 , 4 - d i m e t h y l - 3-carbomethoxy- 1 - p y r a z o l i n e (3) g i v e s no r e a r r a n g e m e n t i n the r e c o v e r e d p y r a z o l i n e s a m p l e (14). It a p p e a r e d that f u r t h e r e x a m i n a t i o n was n e c e s s a r y to t e s t the v a l i d i t y of t h i s i o n i c m e c h a n i s m f o r the p y r o l y s i s of 1 - p y r a z o l i n e s . E a r l y e v i d e n c e f o r a d i r a d i c a l i n t e r m e d i a t e upon p y r o l y s i s of a p y r a z o l i n e s y s t e m i n the gas phase and i n s o l u t i o n has been p r e s e n t e d by C o h e n and c o w o r k e r s (28) and O v e r b e r g e r and c o w o r k e r s (13, 29, 30), r e s p e c t i v e l y . C o h e n conducted a k i n e t i c i n v e s t i g a t i o n on 2, 3 - d i a z a b i c y c l o [2,2, f]-2~heptene (30). The gas phase d e c o m p o s i t i o n r e a c t i o n showed f i r s t - o r der k i n e t i c s w i t h an a c t i v a t i o n energy, E a = 37. 3 K c a l / m o l e , and an e n t r o p y of a c t i v a t i o n , AS^ = 8. 7 e. u. 30 31 - 12 -The a u t h o r s c o m p a r e d t h e s e v a l u e s w i t h those found f o r the a c y c l i c ana-l o g of 30, a z o - b i s - 2 - p r o p a n e , w h i c h shows a h i g h e r a c t i v a t i o n energv, E a - 40. 9 K c a l / m o l e . A t 250 the r a t e constant f o r the d e c o m p o s i t i o n of the c i s - a z o compound 30 i s about 430 t i m e s l a r g e r than that f o r the t r a n s a c y c l i c analog. The r a t e d i f f e r e n c e m a y be due to the m o r e f a v o u r a b l e e n e r g y of a c t i v a t i o n of 30, w h i c h c o u l d a r i s e f r o m r e l i e f of s t r a i n i n the b i c y c l i c s t r u c t u r e . The e n t r o p y of a c t i v a t i o n was h i g h enough, when c o m p a r e d to v a l u e s f o r a l i p h a t i c azo compounds, to be c o n s i s t e n t w i t h the s i m u l t a n e o u s r u p t u r e of the two C-N bonds i n the t r a n s i t i o n state to f o r m a d i r a d i c a l i n t e r m e d i a t e _31. A m o l e c u l a r o r f o u r - c e n t e r type of r e a c t i o n i n w h i c h the new C-C bond i s f o r m e d s i m u l -t a n e o u s l y w i t h r u p t u r e of the two C-N bonds was c o n s i d e r e d u n l i k e l y , O v e r b e r g e r and c o w o r k e r s p r e p a r e d a s e r i e s of 3, 5 - d i a r y l sub-s t i t u t e d 1 - p y r a z o l i n e s and d e t e r m i n e d the s t e r e o c h e m i s t r y of the p r o d u c t s and r a t e s of t h e r m a l d e c o m p o s i t i o n (13, 2 9 , 30). The p y r o l y s i s of t r a n s -3, 5 - d i p h e n y l - 1 - p y r a z o l i n e (32) and t r a n s - 3, 5-bis (p_- c h l o r o p h e n y l ) - 1 -p y r a z o l i n e (33) was r e p o r t e d ( 2 9 ) to give only the c o r r e s p o n d i n g t r a n s - 1 , 2 - d i a r y l c y c l o p r o p a n e s . E l e c t r o n s p i n r e s o n a n c e s t u d i e s of the photo-l y t i c d e c o m p o s i t i o n of _32 i n d i c a t e d the p r e s e n c e of a f r e e r a d i c a l and the p h o t o l y t i c d e c o m p o s i t i o n of _32 at 15° gave only t r a n s - 1, 2 - d i p h e n y l c y c l o -propane. T h e s e r e s u l t s p r o m p t e d the a u t h o r s to suggest a f r e e - r a d i c a l m e c h a n i s m f o r the t h e r m a l d e c o m p o s i t i o n of 3 3 5 - d i a r y l - 1 - p y r a z o l i n e s . T h e s t e r e o s p e c i f i c d e c o m p o s i t i o n of _32 and _33 was r a t i o n a l i z e d i n t e r m s - 1 3 -of f a s t c o u p l i n g of the i n t e r m e d i a t e b i r a d i c a l s . P r o d u c t s t u d i e s c u the b a s e - c a t a l y z e d t h e r m a l d e c o m p o s i t i o n of the c o r r e s p o n d i n g 2 - p y r a z o -l i n e s i n d i c a t e d a l a c k of s t e r e o s p e c i f i c i t y i n the c y c l o p r o p a n e p r o d u c t s , w h i c h c o u l d be a r e s u l t of n o n s t e r e o s e l e c t i v e i s o m e r i z a t i o n of the 2-p y r a z o l i n e s to the 1 - p y r a z o l i n e s . A l a t e r r e e x a m i n a t i o n (30) of the t h e r m a l and p h o t o l y t i c decom-p o s i t i o n of t r a n s - 3, 5 - d i p h e n y l - 1 - p y r a z o l i n e (32) showed that the r e a c t i o n s w e r e not c o m p l e t e l y s t e r e o s p e c i f i c . D e c o m p o s i t i o n of 32 at 80° i n r e -f l u x i n g benzene gave a prod u c t c o n s i s t i n g of 8 9 % t r a n s - 1, 2 - d i p h e n y l -c y c l o p r o p a n e (34) and 1 1 % eds- 1, 2 - d i p h e n y l c y c l o p r o p a n e (J35). P h o t o l y s i s of 32 gave 8 8 % 34 and 1 2 % 35. PhHCT ^ C H P h \\y o r P h A P h A P h \ _ / r e f l u x i n > V _ \ + <LS/. P h 32 34 35 The t h e r m a l and p h o t o l y t i c d e c o m p o s i t i o n of c i s - and t r a n s - 3, 5-b i s (_p_-anisyl)- 1 - p y r a z o l i n e s (9 and 10) gave i n t e r e s t i n g r e s u l t s (13). H \ / C H 2 \ / H A A A C A r A A r A r p-CH O C , H 4 \ / C 6 H 4 O C H v p > + \ N — N A r c i s t r a n s c i s (9) t h e r m a l 4 3 . 0 % 57. 0% p h o t o l y t i c 5 7 . 2 % 4 2 . 8 % t r a n s (JL0) t h e r m a l 6.7% 9 3 . 3 % p h o t o l y t i c 0.7% 99. 3% - 1 4 -T h e f o r m a t i o n of c i s - c y c l o p r o p a n e s by t h e r m a l d e c o m p o s i t i o n of the t r a n s - p y r a z o l i n e s i n d i c a t e s that some r o t a t i o n m u s t o c c u r i n the b i -r a d i c a l i n t e r m e d i a t e b e f o r e c o u p l i n g . The f o r m a t i o n of r e l a t i v e l y l a r g e amounts of t r a n s - c y c l o p r o p a n e f r o m _9 i n d i c a t e s that t h e r e i s c o n s i d e r a b l e r o t a t i o n a r o u n d the C-C bonds i n the b i r a d i c a l . O v e r b e r g e r ' s f r e e -r a d i c a l pathway f o r p y r a z o l i n e d e c o m p o s i t i o n i s d e p i c t e d i n F i g u r e IV. H C H / A r 2 . N - N M A r - C C x C H A r 2 C c Ax/ X C H / \ r 2 A r A r H H W C H N A r 2 o l e f i n s H A r C H . _H \ A r .H H A r A r H A r F I G U R E IV - F r e e - r a d i c a l m e c h a n i s m of p y r o l y s i s of 3, 5 - d i a r y l - 1 - p y r a z o l i n e s . The c i s - p y r a z o l i n e 9^  was found to decompose at a f a s t e r r a t e than the t r a n s - p y r a z o l i n e s w i t h a c o n c o m i t a n t l y s m a l l e r a c t i v a t i o n e n e r g y ( 1 3 ) . A c c o r d i n g to O v e r b e r g e r s t h i s r e f l e c t s the g r e a t e r s t r a i n of the C-N bond and the i n c r e a s e d s t e r i c h i n d e r a n c e of the two a r y l s u b s t i t u e n t s . The - 15 -d e c r e a s e d s t a b i l i t y of the r i n g , plus the f a c t that the c i s - c y c l o p r o p a n e i s the l e s s s t a b l e i s o m e r , suggests that vhe b i r a d i c a l f r o m the c i s - 1 - p y r a -z o l i n e w o u l d p o s s e s s s u f f i c i e n t e n e r g y to have f r e e r o t a t i o n a round the C-C bond b e f o r e c o u p l i n g . The k i n e t i c s t u d i e s on the 3, 5 - d i a r y l - 1 - p y r a z o l i n e s i n d i c a t e d that e l e c t r o n i c c o n t r i b u t i o n s had l i t t l e e f f e c t on the r e s u l t s s i n c e the r a t e s and a c t i v a t i o n e n e r g i e s f o r the t r a n s - p y r a z o l i n e s , w h e r e the a r y l groups w e r e phenyl,_p-chlorophenyl, o r p_~methoxyphenyl w e r e e s s e n t i a l l y the same. M c G r e e r et _al. (15, 31, 32) have done a c o n s i d e r a b l e amount of w o r k i n t h i s l a b o r a t o r y c o n c e r n i n g the p o s s i b i l i t y of an i o n i c i n t e r m e d i a t e i n the t h e r m a l d e c o m p o s i t i o n of 1 - p y r a z o l i n e s . If a r i n g - o p e n e d d i a -z o n i u m i o n s u c h as _27 i s f o r m e d as an i n t e r m e d i a t e , as was suggested by V a n A u k e n and R i n e h a r t (14), t h e r e s h o u l d be a b u i l d u p of p o s i t i v e c h a r g e at C-5 of the p y r a z o l i n e i n the t r a n s i t i o n state. A t y p i c a l c a r b o n i u m i o n r e a r r a n g e m e n t s u c h as m i g r a t i o n of an a l k y l group f r o m C-4 to C-5 w o u l d i n d i c a t e s u c h a c h a r g e development on C-5. A c c o r d i n g l y , a s e r i e s of 4, 4 - d i a l k y l - 3-cyano- 3-carbomethoxy- 1 - p y r a z o l i n e s (36) w e r e p r e p a r e d and s u b j e c t e d to p y r o l y s i s under v a r i o u s c o n d i t i o n s (31). A l k y l m i g r a -t i o n f r o m C-4 to C-5 of the p y r a z o l i n e to give C.^ £ - u n s a t u r a t e d e s t e r s (38) was i n deed o b s e r v e d . A n o t h e r f a c t o r s u g g e s t i n g s t r u c t u r e _37 as i n t e r m e d i a t e was the i n c r e a s e i n the r a t e of d e c o m p o s i t i o n of two 4, 4 - d i a l k y l - 3 - c y a n o - 3 -- 16 -C O C H R C O C H R C O C H 2 3 \ / 2 3 \ / 2 3 > R/ ^ C N ^ / ^ C N \ + R 36 37 38 c a r b o m e t h o x y - 1 - p y r a z o l i n e s w i t h i n c r e a s i n g s o l v e n t p o l a r i t y . S u c h a r a t e i n c r e a s e w o u l d be e x p e c t e d i f - t h e t r a n s i t i o n s t a t e f o r t h e p y r o l y s i s w e r e m o r e p o l a r t h a n t h e s t a r t i n g m a t e r i a l . T h e p r o d u c t c o m p o s i t i o n f o r 4 , 4 - d i m e t h y l - 3 - c y a n o - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (39) w a s f o u n d t o b e s o l v e n t d e p e n d e n t . C O z C H 3 C O z C H 3 x / C 0 2 C H 3 ^ ^ C O ^ C H ^ C N \ / C N — ' C N / C N 39 m e t h y l c i s e t h y l c i s h e a t - 3 9 % 3 9 % 2 2 % b e n z e n e 38 2 8 3 4 t e t r a c h l o r o e t h y l e n e 57 5 38 H o w e v e r , s t r u c t u r e 37 , t h r o u g h r o t a t i o n a b o u t t h e s i n g l e b o n d s , w o u l d be e x p e c t e d t o g ive a m a r l y 5 0 : 5 0 m i x t u r e o f t h e o l e f i n s . T h e r e s u l t s w e r e e x p l a i n e d b y a s s u m i n g t h a t t h e m e t h y l g r o u p m i g r a t e s c o n c e r t e d w i t h n i t r o g e n l o s s f r o m t h e p y r a z o l i n e . S i m i l a r r e s u l t s w e r e f o u n d b y H a m e l i n a n d C a r r i e ( 1 0 0 , 101) i n t h e p y r o l y s i s o f 4 - a l k y l a n d 4 - a r y l s u b -s t i t u t e d 3 - c y a n o - 3 - c a r b o e t h o x y - 1 - p y r a z o l i n e s . I t a p p e a r s t h a t t h e c o n -f o r m a t i o n o f t h e s t a r t i n g 1 - p y r a z o l i n e , a s w e l l a s s o l v e n t a n d e l e c t r o n i c - }.7 -e f f e c t s , a r e i m p o r t a n t f a c t o r s i n th.^ t h e r m a l d e c o m p o s i t i o n r e a c t i o n . T h i s was i l l u s t r a t e d by the f o r m a t i o n of d i h y d r o f u r a n d e r i v a t i v e s , 40 and 41, d u r i n g the d e c o m p o s i t i o n of 3 - m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (42) and c i s - and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e s (43 and 44) r e s p e c t i v e l y (32, 33). T h e p r o d u c t s obtained by p y r o l y s i s of t h e s e p y r a -z o l i n e s a r e shown i n F i g u r e s V and VI, r e s p e c t i v e l y . ~{^~COCH 3 _A_ .N C O C H . C O C H . 46 C O C H . 42 45 C O C H 48 47 DC ^O 40 F I G U R E V - P r o d u c t s f r o m the p y r o l y s i s of 3-methyl- 3 - a c e t y l - 1 - p y r a z o l i n e . - C O C H , 43 N 44 f N C O C H 49 C O C H 3 /\ /""COCH 50 C O C H 51 52 'COCH. / C H 3 C H Q C H = C H C H 3 "-COCH. 53 F I G U R E V I - P r o d u c t s f r o m the p y r o l y s i s of 3, 5-d i m e t h y l - 3 - a . c e t y l - 1 - p y r a z o l i n e s . 41 - 18 -The f o r m a t i o n of the d i h y d r o f u r a n d e r i v a t i v e s can be e x p l a i n e d by a s -su m i n g an i n t e r m e d i a t e i s f o r m e d w i t i - n e g a t i v e c h a r g e b u i l t up on the C-3 of the pyra.zoline s y s t e m , that i s , an i o n i c i n t e r m e d i a t e , 54, s i m i l a r to 2/7 and 37. D e l o c a l i z a t i o n of the n e g a t i / e c h a r g e into the c a r b o n y l oxygen w i l l a l l o w r i n g c l o s u r e to oxygen. , C O C H 3 N • 1^ ^ 3 -£> P R O D U C T S 54 In the p y r o l y s i s of c i s - and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e s (43 and 44) under v a r i o u s c o n d i t i o n s , the c i s i s o m e r _43 y i e l d e d the d i -h y d r o f u r a n p r o d u c t _41 w h i l e the t r a n s i s o m e r _44 gave l i t t l e o r no 41. F r e e r o t a t i o n a r o u n d the C(3)-C(4) bond i n an i n t e r m e d i a t e l i k e 54 w o u l d a l l o w both i s o m e r s to give the same amount of d i h y d r o f u r a n p r o d u c t . S i n c e t h i s i s not the case, the f o r m a t i o n of the d i h y d r o f u r a n p r o d u c t was c o n s i d e r e d p r e d e t e r m i n e d by the s t e r i c f a c t o r s p r e s e n t i n the o r i g i n a l p y r a z o l i n e (32, 33). F o r example, the s t e r i c i n t e r a c t i o n of C-3 and C-5 m e t h y l groups i n c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (43) w o u l d be ex p e c t e d to f o r c e the c a r b o n y l group under the r i n g i n a p o s i t i o n f a v o u r a b l e f o r r i n g c l o s u r e to oxygen. Othe r d e t a i l s of the p r o d u c t d i s t r i b u t i o n s f o r 43 and _44 cannot be e x p l a i n e d by an i n t e r m e d i a t e l i k e 54. A s i m i l a r type of r e a c t i o n was r e c e n t l y o b s e r v e d by C r a w f o r d and C a m e r o n (34) i n the - 19 -p y r o l y s i s o f 3 - v i n y l - 1 - p y r a z o l i n e (55). a n d 3 - i s o p r o p e n y l - 3 - m e t h y l - 1 -p y r a z o l i n e ( 5 6 ) . 9 7 % 3% 5 6 a 5 6 b I n t h e c o n f o r m e r s 5 5 b a n d 5 6 b t h e m e t h y l e n e c a r b o n s a r e i n a f a v o u r a b l e p o s i t i o n f o r c l o s u r e t o C - 5 t o f o r m c y c l o p e n t e n e s . R e s u l t s o b t a i n e d f o r t h e p y r o l y s i s o f c i s - a n d t r a n s - 3 , 5 - d i -m e t h y l - 3 - c a r b o m e t h o x y - . 1 - p y r a z o l i n e s (5 a n d _6) i n d i c a t e t h a t t h e f o r m a -t i o n o f t h e d i h y d r o f u r a n d e r i v a t i v e 4 1 f r o m c i s - 3, 5 - d i m e t h y l - 3 - a c e t y l - 1 -p y r a z o l i n e (43) o c c u r s a t t h e e x p e n s e o f t h e t r a n s - c y c l o p r o p a n e 50 ( 1 5 , 3 3 ) . P y r o l y s i s o f J> a n d _6 g i v e s a m i x t u r e o f c y c l o p r o p a n e a n d o l e f i n p r o d u c t s ( F i g u r e V I I ) . - 20 -5 I I 2 3 N /• N 6 N C 0 2 C H 3 A -c-57 C 0 2 C H 3 59 C O C H , / \ / C H 2 3 V 2 3 58 C 0 2 C H 3 60 C 0 2 C H 3 61 F I G U R E VII - P roduc t s f r o m the p y r o l y s i s of 3, 5-dimethyl~ 3 -ca rbome thoxy-1 -py razo l ines . The product composi t ions for the p y r o l y s i s of _5 and 6 are s i m i l a r to those for the p y r o l y s i s of _43 and _44 in two respec ts . F i r s t , ^3_olefin f o r m a -t ion is essent ia l ly s te reospeci f ic w i t h c i s olefins being fo rmed f r o m the c i s py razo l ines , that i s , J>1 f r o m _43 and _6_0 f r o m _5, and t rans olefins being fo rmed f r o m the t rans py razo l ines , that i s , _52 f r o m _14 and _59 f r o m _6. Second, the cyclopropane wi th the methyls t rans (58) i s the p r e d o m i -nant cyclopropane f r o m the _c is -pyrazol ine 5 and the cyclopropanes wi th the methyls c is (57 and 49) are the predominant cyclopropanes f r o m the tr_ans-pyrazolines, _6 and 44 r e spec t ive ly . Cyc lopropane format ion is not as s te reospec i f ic as olef in format ion and requ i res i n v e r s i o n at ei ther - 2 1 -C - 3 o r C - 5 d u r i n g r i n g c l o s u r e . P y r o l y s i s o f _5 a n d _6 i n s o l v e n t s o f i n -c r e a s i n g d i e l e c t r i c c o n s t a n t r a i s e s t h e p r o p o r t i o n o f o l e f i n s i n t h e p r o -d u c t b u t a t t h e s a m e t i m e , s l i g h t l y d e c r e a s e s t h e r a t e o f d e c o m p o s i t i o n ( 1 5 ) . T h i s s u g g e s t s t h a t t h e t r a n s i t i o n s t a t e m i g h t b e l e s s . p o l a r t h a n t h o s t a r t i n g m a t e r i a l . T h e m e c h a n i s m p r o p o s e d b y V a n A u k e n a n d R i n e h a r t (14) w a s d i s c o u n t e d f o r t h e r e a s o n s d i s c u s s e d a b o v e ( p . 1 0 ) . P a r t i a l p y -r o l y s i s o f t r a n s - 3, 5 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (6) g a v e n o c i s i s o m e r i n t h e r e c o v e r e d p y r a z o l i n e s a m p l e a n d t h e p r o d u c t a n a l y s e s f r o m p a i r s o f i s o m e r i c p y r a z o l i n e s , _5 a n d _6; 43 a n d 4 4 , s h o w d i f f e r e n c e s w h i c h c a n n o t b e e x p l a i n e d b y a n i n t e r m e d i a t e l i k e 6 2 . Y •Y Y = a c e t y l o r c a r b o m e t h o x y 62 E s t i m a t i o n s o f t h e d e g r e e o f f o l d i n g i n c i s - a n d t r a n s - 3 , 5 - d i -m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s (5 a n d _6) i n d i c a t e t h a t t h e p r e -f e r r e d n o n p l a n a r c o n f o r m a t i o n s a r e 63 a n d _6_4 r e s p e c t i v e l y ( 1 5 ) . H H C Q 2 C H 3 H 6 3 6 4 - 22 -The s t e r e o s p e c i f i c o l e f i n f o r m a t i o n o b s e r v e d can be e x p l a i n e d by h y d r o g e n m i g r a t i o n c o n c e r t e d w i t h n i t r o g e n e l i m i n a t i o n , w h e r e the m i g r a t i n g C-4 h y d r o g e n i s t r a n s to the l e a v i n g n i t r o g e n ( t h i s i s the C-4 h y d r o g e n c i s to the c a r b o m e t h o x y group i n jS3 and t r a n s to the c a r b o m e t h o x y group i n 64). M i g r a t i o n to C-5 g i v e s the * * } ^ - u n s a t u r a t e d o l e f i n s and m i g r a t i o n to C-3 g i v e s the t r a n s /^<J-ester 61. A s i m i l a r c o n c e r t e d h y d r o g e n m i g r a t i o n can be v i s i i a l i z e d f o r the o l e f i n - f o r m i n g step d u r i n g the p y r o l y s i s of c i s -and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e s (43 and 44). T h e f o r m a t i o n of c y c l o p r o p a n e s p r o b a b l y o c c u r s t h r o u g h a s l i g h t l y d i f f e r e n t t r a n s i t i o n state ( perhaps l e s s polar) s i n c e the c y c l o -p ropane to o l e f i n r a t i o d e c r e a s e s w i t h i n c r e a s i n g s o l v e n t p o l a r i t y . A c o n c e r t e d p r o c e s s was c o n s i d e r e d m o s t l i k e l y , b e c a use the e n e r g y of the t r a n s i t i o n state f o r t h i s w o u l d d i f f e r o n l y s l i g h t l y f r o m that f o r the o l e f i n -f o r m i n g r e a c t i o n . M c G r e e r _et a l . (15) have d e s c r i b e d two p o s s i b i l i t i e s f o r n i t r o g e n e l i m i n a t i o n . (i) L o s s of n i t r o g e n i n the plane of the t h r e e c a r b o n atoms w o u l d f o r m two p - o r b i t a l s at C-3 and C-5 o r i e n t e d t o w a r d s each other w h i c h c o u l d couple to g i v e p r o d u c t of r e t a i n e d con-f i g u r a t i o n . (ii) L o s s of n i t r o g e n p e r p e n d i c u l a r to the p l a n e of atoms 3, 4, and 5 w o u l d give two p - o r b i t a l s at C-3 and C-5 r o u g h l y p a r a l l e l to e ach o t h e r . S t e r i c i n t e r f e r e n c e between the C-3 and C-5 s u b s t i t u e n t s w o u l d r e s u l t i n i n v e r s i o n at one of t h e s e c e n t e r s . A f u r t h e r e x a m p l e of s t e r e o s p e c i f i c o l e f i n f o r m a t i o n w i l l be d i s -c u s s e d a f t e r the p e r t i n e n t d e t a i l s of w o r k done by C r a w f o r d and c o w o r k e r s on 1 - p y r a z o l i n e s have been g i v e n . T h e s e w o r k e r s have s t u d i e d the py-r o l y s i s of 1 - p y r a z o l i n e s i n the gas phase and have a c c u m u l a t e d con-s i d e r a b l e e v i d e n c e f o r a 1, 3 - d i r a d i c a l o r t r i m e t h y l e n e type of i n t e r m e d i a t e i n the d e c o m p o s i t i o n r e a c t i o n (16, 34-39). A s e r i e s of m e t h y l s u b s t i t u t e d 1 - p y r a z o l i n e s w e r e p r e p a r e d (16, 36) and the k i n e t i c s and p r o d u c t s of p y r o l y s i s subsequently d e s c r i b e d (35, 36). E x c e l l e n t f i r s t - o r d e r k i n e t i c s f o r the t h e r m a l d e c o m p o s i t i o n s w e r e o b s e r v e d . A g e n e r a l d e c r e a s e i n the a c t i v a t i o n e n e r g y upon m e t h y l s u b s t i t u t i o n on the 3- and 5 - p o s i t i o n i n d i c a t e d that both c a r b o n - n i t r o g e n bonds a r e c l e a v e d i n the t r a n s i t i o n state. The f a c t that c i s - and t r a n s -3, 5 - d i m e t h y l - 1 - p y r a z o l i n e (7 and _8) a r e not i n t e r c o n v e r t e d d u r i n g t h e i r p y r o l y s i s m a k e s an i n t e r m e d i a t e s u c h as _65 u n l i k e l y . f a s t slow 1>, A + N N — N N = N ' * 2 _65 F u r t h e r e v i d e n c e f o r s i m u l t a n e o u s c l e a v a g e of the C - N bonds i n the t r a n s -s i t i o n state, even i n an u n s y m m e t r i c a l p y r a z o l i n e , i s i n d i c a t e d by a k i n e t i c i s o t o p e e f f e c t of k /k = 1,21 f o r 3 - v i n y l - 1 - p y r a z o l i n e (55) and 3 - v i n y l -H" D 1 - p y r a z o l i n e - 5 , 5-d^ (34). However, t h e r e m a y be u n e q u a l s t r e t c h i n g of - 2 4 -t h e C - N b o n d s i n g o i n g f r o m t h e s t a r t i n g m a t e r i a l t o t r a n s i t i o n s t a t e . ( 4 0 ) . K i n e t i c s t u d i e s o n 4 - m e t h y l - l - p y r a z o l ' n e - 4 - d ^ (66) s h o w e d t h a t t h e r a t e c o n s t a n t i s e s s e n t i a l l y i d e n t i c a l to t h a t o f t h e n o n - d e u t e r a t e d c o m p o u n d (67) b u t t h a t t h e p r o d u c t r a t i o s a r e c h a n g e a . C H 3 H (-D) C H . N = N 67 H 66 D D = 1. 07 H (D) 5 2 . 3% 6 6 . 0% C H , C H . C H 3 ( D ) 4 7 . 7% 3 4 . 0% T h e s m a l l e f f e c t o f d e u t e r i u m s u b s t i t u t i o n o n t h e r a t e o f d e c o m p o s i t i o n o f 66 i n d i c a t e s t h a t f o r m a t i o n o f 2 - m e t h y l p r o p e n e b y a d e u t e r i u m s h i f t m u s t o c c u r a f t e r t h e r a t e - d e t e r m i n i n g s t e p . T h e r e s u l t s w e r e e x p l a i n e d b y t h e s c h e m e i l l u s t r a t e d i n F i g u r e V I I I . C H i n t e r m e d i a t e - N . -N — N C H , *> C H — C — C H 2 D C H D k 2 / k 3 • = 4 7 . 7 / 5 2 . 3 a n d k 2 / k 3 = 3 4 . 0 / 6 6 . 0 ; H H D D t h e n k 2 k 3 / k 2 k 3 = 1 . 8 0 . H D D H F I G U R E • V I I I - P y r o l y s i s o f 4 - m e t h y l - l - p y r a z o l i n e - 4 - d ^ . - 2 5 -A s s u m i n g t h a t k 3 /l^-i, = 1;'Q, t h a t i s , r i n g c l o s u r e i s u n a f f e c t e d b y I I D d e u t e r i u m s t i b s t i t u t i o n , t h e m a g n i t u d e o f k 2 / k 2 i s c a l c u l a t e d f r o m t h e H D p r o d u c t p r o p o r t i o n s ( F i g u r e VIII) t o b e 1. 8 0 . C a l c u l a t i o n s i n v o l v i n g o l e f i n a n d c y c l o p r o p a n e f o r m a t i o n b y s e p a r a t e p a t h s ( s e e D i s c u s s i o n ) i n -d i c a t e t h a t s u c h a s c h e m e f o r _66 a n d _67 i s h i g h l y i m p r o b a b l e . It w a s t h e r e f o r e c o n c l u d e d t h a t a c o m m o n n i t r o g e n - f r e e i n t e r m e d i a t e i s f o r m e d a f t e r t h e r a t e - d e t e r m i n i n g s t e p . T h e g e o m e t r y o f t h e t r a n s i t i o n s t a t e i s r e v e a l e d b y t h e r e l a t i v e r a t e s f o r t h e f o l l o w i n g p y r a z o l i n e s . N = N N = N N — N 6 8 . 67 69 R e l r a t e 1 . 0 0 0 . 97 0 . 0 0 7 9 T h e 4 , 4 - d i m e t h y l - 1 - p y r a z o l i n e ( 6 9 ) . h a s 1 / 1 2 7 t h e r a t e o f 6 8 , w h e r e a s t h e i n t r o d u c t i o n o f o n e m e t h y l g r o u p a t C - 4 h a s l i t t l e e f f e c t ( 6 7 ) . T h e g e o m e t r y o f t h e p y r a z o l i n e s , a s i n f e r r e d f r o m n . m . r . s p e c t r o s c o p y ( 1 5 , 16) , a p p e a r s t o b e s i m i l a r t o t h a t o f c y c l o p e n t e n e a n d h a s t h e f o l d e d a r r a n g e m e n t 7 0 , w i t h a n a n g l e b e t w e e n t h e t w o p l a n e s o f a p p r o x i m a t e l y o .155 . P r e s u m a b l y , t h i s a n g l e d e c r e a s e s a s t h e c a r b o n - n i t r o g e n b o n d s l e n g t h e n t o a p p r o a c h t h e t r a n s i t i o n s t a t e 7 1 . I n 6 9 , t h e s e c o n d m e t h y l - 26 -group i s c i s to the d e p a r t i n g n i t r o g e n and a l a r g e s t e r i c c o m p r e s s i o n i s p r e s e n t i n the t r a n s i t i o n s t a t e . R R H V / C \ / H + N 2 Y 9 H H 70_ 71 72 T h e r e i s s t r o n g e vidence that the t e r m i n a l m e t h y l e n e s i n the i n t e r m e d i a t e 72 a r e p l a n a r . P y r o l y s i s of c i s - and t r a n s - 3 , 5 - d i m e t h y l -1 - p y r a z c l i n e s (7_and_8) c a n l e a d to the i n t e r m e d i a t e s shown i n F i g u r e I X . CHr^ N c c H H \ / •> CH ,C CH 3 c c I I H H 7 (In) H H - N \ / // ^ C H 3 X y C v / 3 H CH— 1—i N J C 3 CH 3 H CH 8 8 (In) In 7 (In) and 8 (In) t h e r e a r e p - o r b i t a l s on C-3 and C-5 perpen-d i c u l a r to the plane.. F I G U R E I X - I n t e r m e d i a t e s f o r the p y r o l y s i s of c i s -and t r a n s - 3 , 5 - d i m e t h y l - 1-pyrazolines„ - 27 -M i g r a t i o n of a C-4 h y d r o g e n to e i t h e r C-3 or C-5 i n 7 (In) can give o n l y the o b s e r v e d t r a n s - 2 - p e n t e n e w h e r e a s m i g r a t i o n of a C-4 h y d r o g e n i n 8(In) can give two r e s u l t s : m i g r a t i o n to C-3 g i v e s t r a n s - 2 - p e n t e n e and t o C-5 g i v e s g i v e s c i s - 2 - p e n t e n e . W h i l e these r e s u l t s cannot r u l e out an o l e f i n - f o r m i n g m e c h a n i s m i n v o l v i n g h y d r o g e n m i g r a t i o n c o n c e r t e d w i t h n i t r o g e n l o s s as p r o p o s e d by M c G r e e r et a l . (15), the l a c k of an a p p r e c i a b l e k i n e t i c i s o t o p e e f f e c t f o r _66 and 67 and the r e s u l t s obtained f o r c i s - and t r a n s - 4 - d e u t e r i o - 3-methyl- 1 - p y r a z o l i n e s (7 3 and 74) (39) m a k e c o n c e r t e d h y d r o g e n m i g r a t i o n i m p r o b a b l e i n these p y r a z o l i n e s y s -t e m s . The p r o p o s e d i n t e r m e d i a t e (75) f o r the p y r o l y s i s of 3-methyl-1-p y r a z o l i n e has. a plane of s y m m e t r y t h r o u g h the f o u r c a r b o n atoms. 3.7% B o t h 7 3 and 74 a r e capable of p r o d u c i n g the d e u t e r a t e d i n t e r m e d i a t e 76, and i f 76 has a s u f f i c i e n t l i f e t i m e to become c o m p l e t e l y f r e e of n i t r o g e n the p r o d u c t r a t i o s s h o u l d be independent of the i n i t i a l s t e r e o c h e m i s t r y . T h i s was indeed o b s e r v e d ( F i g u r e X) (39). The p e r c e n t a g e s g i v e n i n - 28 -Figure X are the values predicted assuming a value of -k^/k.^ = 2. 0 in the product-determining step. The agreement with the observed values was excellent. The results do not allow for the possibility of a con-certed migration of only that hydrogen transoid to the leaving nitrogen since only four of the six possible olefin products would be accounted for from each pyrazoline and hence the predicted yields would differ from those actually observed. D 1.4% H D 74 94. 9% FIGURE X Pyrolysis of cis- and trans- 4-deuterio 3-methyl- 1-pyrazolines. - 2 9 -T h e s t e r e o c h e m i c a l r e s u l t s of c y c l o p r o p a n e f o r m a t i o n f r o m the p y r o l y s i s of c i s - and t r a n s - 3 , 5 - d i m e t h y l - 1 - p y r a z o l i n e s (7 and 8) a r e s i m i l a r to'those found by M c G r e e r _et _al. (15, 32) d u r i n g the gas phase p y r o l y s i s of 3, 5 - d i s u b s t i t u t e d p y r a z o l i n e s i n that i n v e r s i o n of the s t e r e o -c h e m i s t r y of the parent p y r a z o l i n e i s p r e d o m i n a n t (35). H o w e v e r , the t h e r m o l y s i s of c i s - and t r a n s - 3, 4-dim e t h y l - 1 - p y r a z o l i n e s (77 and 78) 7 and 8 • Vl__V V _ \ + o l e f t n c i s t r a n s 7 (c i s ) > 3 3 . 2 % 66. 1% 8 (trans) >• 7 2 . 6 % 25.-4% g i v e s c y c l o p r o p a n e p r o d u c t s w h i c h w e r e f o r m e d n o n - s t e r e o s p e c i f i c a l l y about the C(3)-C(4) bond of the p y r a z o l i n e (38). T h a t _77 and _78 give •77-and 78 * + V _ \ + o l e f e l v c i s t r a n s •N 77 -> 4 5 . 4 % 3 3 . 0 % 2 1 . 5 % 78 •> 4 6 . 0 % 2 1 . 8 % 3 2 . 1 % - 30 -d i s t i n c t l y d i f f e r e n t i n t e r m e d i a t e s i n t h e p y r o l y s i s r e a c t i o n i s d e m o n -s t r a t e d b y t h e f a c t t h a t t h e 5, 5 ~ d i d e u t t r i o d e r i v a t i v e s o f 77 a n d 7 8 g a v e 79 a n d 80 r e s p e c t i v e l y . C H , ^ / C D ^ H C H , . C H , / C = C ^ z 3 ^ c = c ^ 6 H C H 3 H C D 2 H 79 80 C r a w f o r d a n d M i s h r a (35) h a v e s u g g e s t e d t h a t t h e r e i s s o m e f o r m o f i n t e r a c t i o n b e t w e e n t h e t w o t e r m i n a l m e t h y l e n e s i n t h e i r p r o p o s e d i n -2 t e r m e d i a t e s . T h e p r o x i m i t y o f t h e t w o s p c a r b o n s c o u l d i n d e e d a l l o w s o m e p n - p n b o n d i n g t o f o r m s p e c i e s 8 1 , a " i f - c y c l o p r o p a n e " . T h e i r c a l c u l a t i o n s i n d i c a t e t h a t i n t e r a c t i o n o f t h e p - o r b i t a l s d o e s n o t a l l o w t h e " d i r a d i c a l " t o b e a p a i r o f f r e e l y r o t a t i n g r a d i c a l s a n d s u g g e s t s a b o n d i n g e n e r g y o f 8 - 1 2 k c a l m o l e - ' ' ' . T h i s s p e c i e s w o u l d a p p e a r t o be a s a t i s f a c -t o r y i n t e r m e d i a t e w h i c h t h e n h a s a n a c t i v a t i o n e n e r g y f o r c o n v e r s i o n t o c y c l o p r o p a n e a n d o l e f i n . H o f f m a n n ( 4 1 , 42) h a s m a d e a d e t a i l e d t h e o r e t i c a l s t u d y o f t r i -m e t h y l e n e . E x t e n d e d . H u c k e l c a l c u l a t i o n s o n t h e CH2CH2CH2 s e r i e s . - 31 -gave the e n e r g y ( r e l a t i v e to c y c l o p r o p a n e ) as a f u n c t i o n of the C C C angle and r o t a t i o n of the t e r m i n a l m e t h y l e n e groups. Two m i n i m a w e r e ob-s e r v e d on the g r o u n d c o n f i g u r a t i o n p o t e n t i a l s u r f a c e . One of t h e s e c o r -r e s p o n d s to opened c y c l o p r o p a n e and the other to the t r i m e t h y l e n e i n t e r -m e d i a t e w h e r e the t e r m i n a l m e t h y l e n e s a r e c o p l a n a r w i t h the t h r e e -c a r b o n c h a i n . A c o n s i d e r a t i o n of the e l e c t r o n i c s t r u c t u r e of the g r o u n d state of t r i m e t h y l e n e c a n h e l p to r a t i o n a l i z e the s t e r e o s p e c i f i c i t y o b s e r v e d i n t h e c y c l o p r o p a n e f o r m a t i o n f r o m some 1 - p y r a z o l i n e s . The m o l e c u l a r o r b i t a l s f o r m e d f r o m the c o m b i n a t i o n of the t e r m i n a l 2 P z o r b i t a l s a r e shown i n F i g u r e X I . T\-type m o l e c u l a r o r b i t a l s i n t r i m e t h y l e n e . S p e c i e s 82 and 83 c o r r e s p o n d to the " TT - c y c l o p r o p a n e " and " T C n - c y c l o -• g u p r o p a n e " i n t e r m e d i a t e s , r e s p e c t i v e l y , p r o p o s e d by C r a w f o r d and M i s h r a (35). H o f f m a n n has shown (42) that at l a r g e C C C a n g l e s the m i x i n g of the c e n t r a l m e t h y l e n e group ( h y p e r c o n j u g a t i o n i n e f f e c t ) , d e s t a b i l i z i n g the S l e v e l , d o m i n a t e s ( F i g u r e XII), w h i l e at s m a l l angles the d i r e c t 1, 3-- 32 -i n t e r a c t i o n s t a b i l i z i n g the S l e v e l w i n s out. s — A - H F I G U R E X I I - The e l e c t r o n i c s t r u c t u r e of t r i m e t h y l e n e . The t r i m e t h y l e n e i n t e r m e d i a t e l i e s i n the f o r m e r r e g i o n and i t i s apparent that a s p e c i e s w i t h two e l e c t r o n s i n the A l e v e l ( F i g u r e XII) should c l o s e to a c y c l o p r o p a n e i n a c o n r o t a t o r y m anner. The c o n r o t a t o r y c l o s u r e i s u s e f u l t o r a t i o n a l i z e the o b s e r v e d p r e f e r e n c e s f o r i n v e r s i o n of s t e r e o c h e m i s t r y i n the 3, 5 - d i s u b s t i t u t e d p y r a z o l i n e to c y c l o p r o p a n e p y r o l y s i s s t u d i e d by C r a w f o r d and by M c G r e e r . The e n e r g y d i f f e r e n c e between the S and A l e v e l s i s s m a l l enough to a l l o w an e q u i -l i b r i u m p o p u l a t i o n of the S l e v e l . P r e s u m a b l y , a s p e c i e s i n the S l e v e l w o u l d c l o s e to a c y c l o p r o p a n e i n a d i s r o t a t o r y m anner. T h i s can e x p l a i n the c y c l o p r o p a n e p r o d u c t s w i t h r e t a i n e d g e o m e t r y . c o n r o t a t i o n d i s r o t a t i o n - 33 -The r e s u l t s of O v e r b e r g e r et a l . (13, 29,30), however, cannot be r e a d i l y e x p l a i n e d i n the above m a n n e r s i n c e i n two c a s e s t h e r e was a h i g h degree of r e t e n t i o n of the g e o m e t r y of the i n i t i a l p y r a z o l i n e i n the c y c l o p r o p a n e p r o d u c t s . It was shown above that the f o r m a t i o n of o l e f i n s d u r i n g p y r o l y s i s of the p y r a z o l i n e s s t u d i e d by C r a w f o r d cannot be s u c c e s s f u l l y d e s c r i b e d by a c o n c e r t e d h y d r o g e n m i g r a t i o n as p r o p o s e d by M c G r e e r . S i m i l a r l y , the t r i m e t h y l e n e o r "TT-cyclopropane" i n t e r m e d i a t e pathway of C r a w f o r d does not a l l o w a s a t i s f a c t o r y e x p l a n a t i o n f o r the r e s u l t s d e s c r i b e d below. A n i m p o r t a n t e x a m p l e of s t e r e o s p e c i f i c o l e f i n f o r m a t i o n i n 1-p y r a z o l i n e p y r o l y s i s i s g i v e n by M c G r e e r and Wu (43, 44). P y r o l y s i s of the g e o m e t r i c a l l y i s o m e r i c c i s - and t r a n s - 3 - m e t h y l - 4 - e t h y l - 3 - c a r b o -m e t h o x y - 1 - p y r a z o l i n e s (84 and 85) ( F i g u r e XIII) gave c y c l o p r o p a n e p r o -ducts of m i x e d s t e r e o c h e m i s t r y , but p r e d o m i n a n t l y w i t h r e t e n t i o n of the s t e r e o c h e m i s t r y p r e s e n t i n the s t a r t i n g p y r a z o l i n e . E a c h p y r a z o l i n e gave s t e r e o s p e c i f i c a l l y a d i f f e r e n t c N j ^ - u n s a t u r a t e d e s t e r product. - 34 -C H 3 G H 2 N C H , - C 0 2 C H 3 ~v_/ C Q 2 C H 3 + ft* C 0 2 C H 3 -I- e s t e r t r ans (85) neat c i s t r a n s • c i s * t r a n s 31 9 0 56 4 11 72 13 0 4 F I G U R E X I I I - P y r o l y s i s p r o d u c t s f r o m c i s - and t r a n s -3-m e t h y l - 4 - e t h y l - 3 - carbomethoxy- 1 - p y r a z o l i n e s . The r e s u l t s a r e s i m i l a r to those found by V a n A u k e n and R i n e h a r t (14) f o r c i s - and t r a n s - 3, 4 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s (_3 and _4) s i n c e the c i s p y r a z o l i n e s give m o r e ^ ^ - u n s a t u r a t e d e s t e r than the t r a n s p y r a z o l i n e s . H o w e v e r , the C-4 e t h y l p y r a z o l i n e s g i v e a somewhat h i g h e r p r o p o r t i o n of the c y c l o p r o p a n e p r o d u c t and a g r e a t e r t e n d e n c y t o w a r d s t e r e o s p e c i f i c c o n v e r s i o n of p y r a z o l i n e i n t o c y c l o p r o p a n e . F r o m the C H 3 C H 2 C O - C H - . H C H 3 84 C H 3 C H 2 H C 0 2 C H 3 85 * G e o m e t r i c a l i s o m e r s of o l e f i n s a r e d e s c r i b e d as c i s o r t r a n s a c c o r -ding to whether the c a r b o n s of the f\\n'damental c h a i n a r e on the same si d e ( c i s ) o r o p p o s i t e sides- (trans)- of the plane p e r p e n d i c u l a r and p a r a l l e l to the C-C double bond. - 35 -n . m . r . s p e c t r a o f 8 4 a n d 8 5 , t h e p r e f e r r e d c o n f o r m a t i o n s o f t h e p y r a z o -l i n e s w e r e s h o w n t o h a v e t h e C - 4 h y d r o g e n in. t h e p s e u d o a x i a l p o s i t i o n a n d t h e C - 4 e t h y l g r o u p i n t h e p s e u d o e q u a t o r i a l p o s i t i o n . T h e s t e r e o -s p e c i f i c o l e f i n f o r m a t i o n w a s a t t r i b u t e d t o c o n c e r t e d m i g r a t i o n o f t h e h y d r o g e n f r o m C - 4 t o C - 5 o n t h e s i d e o f t h e m o l e c t i l e t r a n s t o t h e l e a v i n g n i t r o g e n , a s p r o p o s e d e a r l i e r f o r o l e f i n f o r m a t i o n d u r i n g t h e p y r o l y s i s o f J5 a n d _6. T h e t r a n s i t i o n s t a t e s f o r _8_4 a n d _8_5 w e r e t h u s p r o p o s e d t o b e 86 a n d 8 7 , r e s p e c t i v e l y . O n e m i g h t e x p e c t t h a t l o s s o f n i t r o g e n w o u l d - o c c u r m o r e e a s i l y f r o m t h e s i d e c i s t o t h e h y d r o g e n o n C - 4 , s i n c e t h a t i s t h e p r e f e r r e d c o n f o r m a t i o n i n 8 4 a n d 8 5 . It v / a s s u g g e s t e d (43) t h a t t h e a d v a n t a g e g a i n e d b y t h e c o n -c e r t e d m i g r a t i o n o f h y d r o g e n i s s u f f i c i e n t t o o v e r c o m e t h e a d v e r s e s t e r i c f a c t o r s p r e s e n t i n t r a n s i t i o n s t a t e s _86 a n d 8 7 . T h e a t t e m p t e d a p p l i c a t i o n o f t h e " J I T - c y c l o p r o p a n e " ( t r i m e t h y l e n e ) i n t e r m e d i a t e m e c h a n i s m t o t h i s p y r a z o l i n e s y s t e m i s a s f o l l o w s . ( i) L o s s o f n i t r o g e n f r o m _84 a n d 8_5 o n t h e s i d e c i s t o t h e h y -d r o g e n a t C - 4 ( t h e l e s s h i n d e r e d s i d e ) w o u l d g i v e t h e t w o - 36 -" " f t - c y c l o p r o p a n e " i n t e r m e d i a t e s _88 a n d 8 9 , r e s p e c t i v e l y . C H , C H , N H 3 2 H / C O z C H 3 C H 3 C H 2 v ^ H H H C O C H 2 3 8 8 89 H o w e v e r , t h e s e i n t e r m e d i a t e s c a n n o t g i v e t h e c o r r e c t o l e f i n p r o d u c t s , s i n c e j88 w o u l d l e a d t o t h e c i s ^ ^ - u n s a t u r a t e d e s t e r a n d £>9_ w o u l d g i v e t h e t r a n s - u n s a t u r a t e d e s t e r , ( i i ) I f t h e f o r m a t i o n o f t h e " f t - c y c l o p r o p a n e " i n t e r m e d i a t e s p r o -c e e d e d t h r o u g h t r a n s i t i o n s t a t e s s i m i l a r t o _86 a n d 87 ( w h i c h a c t u a l l y a r i s e f r o m c o n f o r m a t i o n a l i n v e r s i o n o f 8 4 a n d 8 5 ) , t h a t i s , l o s s o f n i t r o g e n t r a n s t o t h e h y d r o g e n o n C - 4 , t h e n 8 4 w o u l d g i v e 9j) a n d _85 w u u l d g i v e 9_1. T h e s e i n t e r m e d i a t e s H C H 2 C H 3 H , C H 2 C H 3 H H r C ° 2 C H 3 H C 0 2 C H 3 9 0 9 1 l e a d t o t h e c o r r e c t o l e f i n p r o d u c t s . T h e a r r o w s i n jMD a n d 9JL i n d i c a t e t h e m o d e o f c o n r o t a t i o n w h i c h g i v e s r i s e t o t h e - 37 -geometry found in the predominant cyclopropane products. Conrotation in the opposite sense (counterclockwise) w i l l give the minor cyclopropane product. This mechanism has two disagreeable features: (1) loss of nitrogen from the side cis to the ethyl group is sterically unfav our able, especially without the "pushing" assistance of concerted hydrogen mi-gration; (2) the question of why one mode of conrotation is favoured over the other is not easily answered. The concerted hydrogen migration mechanism appears to be more reasonable since for the C-4 methyl and C-4 ethyl pyrazolines, _3 and 4; 84 and 85, there is a correlation between the proportion of olefin found in the product and the preferred conformation of the pyrazolines (43). Thus, pyrazoline _3 (giving 70% olefin) appears to have the highest equilibrium concentration of the conformation having the C-4 hydrogen in the pseudo equatorial position whereas pyrazoline 85 (giving only 17% olefin) is ex-pected to have the lowest population of the conformation with the C-4 hydrogen in the pseudo equatorial position. Recent stereochemical investigations of the pyrolysis of the 2, 3-diazabicyclo [j2. 2. l j -2-heptene system have been made by Roth and Martin (45) and by A l l r e d and Smith (46). Gas phase pyrolysis of exo-5, 6-dideuterio-2, 3-diazabicyclo [2.2. l j -2-heptene (92) gave a 1:3 mixture of cis- and trans-2, 3-dideuterio-bicy clo 2. 1.0 pentanes (45). - 38 -c i s t r a n s 2 5 % 75-% T h e p r e d o m i n a n t i n v e r s i o n o f s t e r e o c h e m i s t r y i n t h e p r o d u c t s w a s a t t r i -b u t e d t o c o n c e r t e d e l i m i n a t i o n o f n i t r o g e n w i t h a c c o m p a n y i n g b a c k - s i d e p - o r b i t a l o v e r l a p i n t h e t r a n s i t i o n s t a t e . A s i m i l a r n e t i n v e r s i o n o f s t e r e o c h e m i s t r y i n t h e p r o d u c t s w a s C H s O e x o : 37% 6 3 % e n d o 6% 9 4 % 9 4 (endo) . o b s e r v e d ' b y A l l r e d a n d S m i t h d u r i n g t h e t h e r m o l y s i s o f e x o - a n d e n d o - 5 -m e t h o x y - 2 , 3 - d i a z a b i c y c l o [2. 2. l ] -2- h e p t e n e ( 9 3 a n d 94) ( 4 6 ) . H o w e v e r , t h e s e a u t h o r s a t t r i b u t e d i n v e r s i o n t o t h e f o r m a t i o n o f s t r u c t u r a l l y i n v e r t e d p y r a m i d a l d i r a d i c a l s . T h e i n v e r s i o n w a s c o n s i d e r e d t o b e a c o n s e q u e n c e o f r e c o i l f r o m e n e r g y r e l e a s e d b y C - N b o n d b r e a k i n g . R i n g c l o s u r e b e -f o r e c o m p l e t e e q u i l i b r a t i o n a c c o u n t s f o r t h e e x c e s s p r o d u c t o f i n v e r t e d s t r u c t u r e . 9 3 9 4 t r a n s c i s i f 0 T h i s d i r a d i c a l s c h e m e i s i n a c c o r d w i t h t h e d i r a d i c a l m e c h a n i s m p r o p o s e d b y C o h e n (28) f o r t h e p y r o l y s i s o f 2 , 3 - d i a z a b i c y c l o [ 2 . 2 . l ] - 2 - h e p t e n e ( 3 0 ) . O b v i o u s l y , n o o n e m e c h a n i s t i c s c h e m e w i l l c o m p l e t e l y e x p l a i n t h e m a n y a n d v a r i e d r e s u l t s r e v i e w e d a b o v e . T h e c o r r e c t d e s c r i p t i o n , w h e t h e r d i r a d i c a l , d i p o l a r , o r m o r e l i k e l y s o m e w h e r e b e t w e e n t h e s e t w o e x t r e m e s , m a y d e p e n d o n t h e s u b s t i t u e n t s a n d t h e p h a s e o f t h e r e a c t i o n . - 40 -P h o t o l y s i s o f P y r a z o l i n e s A b r i e f s u m m a r y o f t h e r e s u l t s o b t a i n e d u p o n p h o t o l y t i c d e c o m -p o s i t i o n o f 1 - p y r a z o l i n e s w i l l b e p r e s e n t e d i n t h i s s e c t i o n . V a n A u k e n a n d R i n e h a r t (14) o b s e r v e d t h a t p h o t o l y s i s o f J3 a n d 4 g a v e c y c l o p r o p a n e p r o d u c t s w i t h t h e s a m e s t e r e o c h e m i s t r y a s t h e s t a r t i n g p y r a z o l i n e a n d a l s o g a v e s t e r e o s p e c i f i c a l l y t h e ^ ^ - u n s a t u r a t e d e s t e r c o r r e s p o n d i n g t o t h e l o s s o f t h e e l e m e n t s o f C H ^ N . , . ~ C 0 2 C H 3 N / / N 6 3 - 7 6 % V_7 A C 0 2 C H 3 2 5 % C 0 2 C H 3 • C H . C 0 2 C H 3 C H . 7 2 % + , C 0 2 C H 3 ^ 2 5 % S i m i l a r r e s u l t s w e r e f o u n d f o r t h e p h o t o l y s i s o f c i s - a n d t r a n s -3 - m e t h . y l ~ 4 - e t h . y l ~ 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s ( 8 4 a n d 85) ( 4 3 ) . T h e s e r e s u l t s c a n b e e x p l a i n e d b y a m o l e c u l a r m e c h a n i s m w i t h b o n d i n g b e t w e e n C - 3 a n d C - 5 t a k i n g p l a c e c o n c e r t e d w i t h n i t r o g e n e l i m i n a t i o n , f o r e x a m p l e : w C H H C H C O C H 2 3 C 0 2 C H 3 - 41 -R e g e n e r a t i o n of the parent <*-JP-unsaturated e s t e r can o c c u r i n a s i m i l a r m a n n e r i n w h i c h the C ( 3 ) - N and C(4)-0(5) bonds a r e b r e a k i n g i n the t r a n -s i t i o n s t a t e 3 f o r e x a m p l e : 4 3 T h e g r e a t e r s t e r e o s p e c i f i c i t y i n the f o r m a t i o n of c y c l o p r o p a n e s d u r i n g p h o t o l y s i s of 1 - p y r a z o l i n e s a l s o extends to c i s - and t r a n s - 3, 5-d i m e t h y l - 3 -carbomethoxy- 1 - p y r a z o l i n e s (_5 and _6) (15) and to c i s - and t r a n s - 3 , 5 - d i r n e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e s (43 and 44) ( 3 2 ) ^ a l t h o u g h i n t h e s e c a s e s t h e r e was g e n e r a l l y o n l y a 3:1 r a t i o of r e t a i n e d to i n v e r t e d s t e r e o c h e m i s t r y . S c h e i n e r (47) has r e c e n t l y o b s e r v e d that p h o t o d e c o m p o s i t i o n of g e o m e t r i c a l l y i s o m e r i c t r i a z o l i n e s a l s o g i v e s p r e d o m i n a n t r e t e n t i o n of H H 3 0* ' t r a n s ; 2 2 % 6 6 % 1 2 % ' t r a n s - 42 -g e o m e t r y i n the a z i r i d i n e p r o d u c t s . However, S c h e i n e r e x p l a i n e d these, r e s u l t s by p r o p o s i n g that s i n g l e t e x c i t e d state 1, 3 - d i r a d i c a l i n t e r m e d i a t e s a r e f o r m e d w h i c h then undergo r i n g c l o s u r e m o r e r a p i d l y t h a n bond r o t a -t i o n . Support f o r t h i s m e c h a n i s m can be derived f r o m the o b s e r v a t i o n that the above i s o m e r i c t r i a z o l i n e s g i ve e s s e n t i a l l y i d e n t i c a l p r o d u c t d i s -t r i b u t i o n s , u nder p h o t o s e n s i t i z e d d e c o m p o s i t i o n (47). The p r o p o s e d t r i -p l e t state 1, 3 - d i r a d i c a l i n t e r m e d i a t e s m u s t undergo s p i n i n v e r s i o n b e f o r e r i n g c l o s u r e ; hence i f s p i n i n v e r s i o n i s s l o w e r t h a n C - b o n d r o t a t i o n a r o t a t i o n a l e q u i l i b r i u m c o u l d be a t t a i n e d . A p p a r e n t l y , m o r e data on p h o t o d e c o m p o s i t i o n of 1 - p y r a z o l i n e s , p a r t i c u l a r l y 3, 5 - d i s u b s t i t u t e d 1 - p y r a z o l i n e s , a r e needed. It w o u l d c e r t a i n l y be i n t e r e s t i n g to see i f p h o t o s e n s i t i z e d d e c o m p o s i t i o n of i s o -m e r i c 1 - p y r a z o l i n e s g i v e s r e s u l t s s i m i l a r to those found f o r i s o m e r i c t r i a z o l i n e s . O b j e c t of the P r e s e n t R e s e a r c h The above r e v i e w on the r e s u l t s o b t a i n e d f o r the p y r o l y s i s of 1 - p y r a z o l i n e s shows that t h e r e a r e p r o b a b l y two d i s t i n c t pathways p r e -sent. The f i r s t can be c o n s i d e r e d to be e s s e n t i a l l y , o r p a r t i a l l y , f r e e r a d i c a l , that i s , a 1, 3 - d i r a d i c a l or, w h e r e t h e r e i s 1, 3 - i n t e r a c t i o n , a " T I - c y c l o p r o p a n e " i n t e r m e d i a t e a p p e a r s to be r e a s o n a b l y e s t a b l i s h e d . -O T h i s m e c h a n i s m can be o p e r a t i v e e i t h e r i n the gas phase or i n s o l u t i o n . The n a t u r e of the s u b s t i t u e n t s i s an i m p o r t a n t g o v e r n i n g f e a t u r e . When e l e c t r o n - w i t h d r a w i n g g r o u p s a r e p r e s e n t a s e c o n d m e c h a n i s m a p p e a r s t o b e o p e r a t i v e . A l t h o u g h t h e r e i s g o o d e v i d e n c e t h a t a n i o n i c i n t e r m e -d i a t e i s u n l i k e l y , o t h e r o b s e r v a t i o n s d i s c u s s e d a b o v e i n d i c a t e t h a t t h e r e m u s t b e a p a r t i a l l y i o n i c s p e c i e s s o m e w h e r e a l o n g t h e r e a c t i o n c o o r d i n a t e T h i s r e s e a r c h w a s c o n d u c t e d m a i n l y o n v a r i o u s s u b s t i t u t e d 3 -m e t h y l - 3 - c a r b o m e t h o x y ( o r 3 - a c e t y l ) - 1 - p y r a z o l i n e s . C r a w f o r d h a s c o m p a r e d t h e r a t e s o f g a s p h a s e t h e r m a l d e c o m p o s i t i o n o f i s o m e r i c a l k y l s u b s t i t u t e d I - p y r a z o l i n e s a n d h a s d e r i v e d a c o n s i d e r a b l e a m o u n t o f u s e -f u l i n f o r m a t i o n . I t w a s h o p e d t h a t a s i m i l a r k i n e t i c s t u d y o f t h e 3 - c a r b o -m e t h o x y - a n d 3 - a c e t y l - 1 - p y r a z o l i n e s w o u l d g i v e r e s u l t s w h i c h c o u l d be u s e d i n a m e c h a n i s t i c d e s c r i p t i o n o f t h e d e c o m p o s i t i o n r e a c t i o n . C r a w f o r d ' s s u c c e s s f u l u s e o f d e u t e r i u m s u b s t i t u t e d p y r a z o l i n e s p r o m p t e d u s t o a p p l y t h i s t e c h n i q u e t o o u r p y r a z o l i n e s y s t e m . T h e d e u -t e r i u m k i n e t i c i s o t o p e e f f e c t h a s b e e n i n v e s t i g a t e d i n a g r e a t n u m b e r o f o r g a n i c r e a c t i o n s ( 4 8 , 4 9 ) . S i n c e t h e f o r m a t i o n o f o l e f i n i n t h e p y r a z o l i n e p y r o l y s i s i s t h o u g h t t o o c c u r b y a c o n c e r t e d h y d r o g e n t r a n s f e r (a t l e a s t f o r t h e p y r a z o l i n e s s t u d i e d b y M c G r e e r ) , i t a p p e a r e d l o g i c a l t o s e e i f t h e r e i s a k i n e t i c d e u t e r i u m i s o t o p e e f f e c t f o r a C - 4 d e u t e r i u m s u b s t i -t u t e d p y r a z o l i n e . T h e e f f e c t o f s o l v e n t p o l a r i t y o n t h e r a t e o f d e c o m p o s i t i o n a n d p r o d u c t d i s t r i b u t i o n w i l l a l s o b e f u r t h e r e x p l o r e d . - 44 -II. R E S U L T S A N L D I S C U S S I O N I I - 1 P R E P A R A T I O N W O R K The S y n t h e s i s of l-Pyrazo1in.es The 1 - p y r a z o l i n e s p r e p a r e d f o r the p r e s e n t i n v e s t i g a t i o n a r e l i s t e d i n T a b l e I. A l l of t h e s e compounds v/ere p r e p a r e d by the a d d i t i o n of"a d i a z o a l k a n e to the a p p r o p r i a t e a c t i v a t e d o l e f i n . T A B L E I 1 - P y r a z o l i n e s 1 - P y r a z o l i n e X R l R 2 R 3 R 4 R 5 R e f e r e n c e 95 C 0 2 C H 3 C H 3 H H H H 50 96 C 0 2 C H 3 C H 3 D D H H t h i s w o r k 97 CO2CH3 C H 3 H H D D t h i s w o r k 98 C N C H 3 : H H H H 50 99 C N C H 3 H H D D t h i s w o r k 55 C H C H 2 H H H H H 34 42 COCH3 C H 3 H H H H 32 5 C 0 2 C H 3 C H 3 : H H H C H 3 15 6 C 0 2 C H 3 C H 3 H H C H 3 H 15 43 C O C H 3 C H 3 H H H C H 3 32 44 C O C H 3 C H 3 H H C H 3 H 32 100 C 0 2 C H 3 C H 3 H H C H 3 C H 3 51 101 C O C H 3 C H 3 H H C H 3 C H 3 t h i s w o r k 3 C 0 2 C H 3 C H 3 H C H 3 H H 14 4 C Q 2 C H 3 C H 3 C H 3 H H H 14 84 C 0 2 C H 3 C H 3 H C H 2 C H 3 H H 43 "85 C 0 2 C H 3 C H 3 C H 2 C H 3 H H H 43 - 45 -A d d i t i o n of diazoethane to m e t h y l m e t h a c r y l a t e o r methyl- i-so-p r o p e n y l ketone g i v e s m i x t u r e s of _5 and _6 or 43 and _44 r e s p e c t i v e l y . T h e r a t i o of c i s to t r a n s i n the m i x t u r e s i s a l w a y s about 40:60. The g r e a t e r amount of the t r a n s i s o m e r r e f l e c t s the s t e r i c r e q u i r e m e n t s of the a d d i t i o n r e a c t i o n (32), S e p a r a t i o n of the m i x t u r e s into p a i r s of geo-m e t r i c a l l y i s o m e r i c p y r a z o l i n e s was a c h i e v e d by s p i n n i n g - b a n d c o l u m n d i s t i l l a t i o n under r e d u c e d p r e s s u r e . The c i s : t r a n s r a t i o s in-the d i s t i l -l a t i o n f r a c t i o n s w e r e e s t i m a t e d by i n t e g r a t i o n of the n. m. r . r e s o n a n c e s f o r the c a r b o m e t h o x y h y d r o g e n s and the a c e t y l m e t h y l h y d r o g e n s . C H 3 _ T ^ 5^3. T.- - C0 2CH_3 r f-- C 0 2 C H 3 C H j ^IST 6. 33T C H ^ N 6 . 2 7 T T C H 3 C H 3 > N „ 3 , N ~ o c _ _ 3 C O C H . I j f ^ C O C H .C H 3 C H 3 ^ N 7 7 . 7 8 f 7.65T 43 44 The best s a m p l e s ob t a i n e d f o r the 3, 5 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a -z o l i n e s c o n t a i n e d 9 8 % c i s (5) and 9 9 % t r a n s (6) ; l i k e w i s e the best s a m p l e s of the 3, 5 - d i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e s c o n t a i n e d 9 1 % c i s (43) and 9 2 % t r a n s (44). The s y n t h e s i s of p y r a z o l i n e s i s o m e r i c at the C-4 p o s i t i o n r e q u i r e s both of the i s o m e r s of the s t a r t i n g o l e f i n . Thus, c i s - and t r a n s - 3 , 4-- 46 -d i m e t h y l - 3-carbomethoxy- 1-pyrazolones (_3 and 4) w e r e p r e p a r e d by the, a d d i t i o n of di a z o m e t h a n e to m e t h y l t i g l a t e (1) • and m e t h y l angelate (2) r e s p e c t i v e l y (page 3). S i m i l a r l y , the a d d i t i o n of diazomethane to m e t h y l c i s - and t r a n s - 2 - m e t h y l - 2 - p e n t e n o a t e (60 and 59) gave t r a n s - and c i s - 3 -m e t h y l - 4 - e t h y l - 3-carbomethoxy- 1 - p y r a z o l i n e s (85 and 84) r e s p e c t i v e l y . C 0 2 C H 3 C H 3 C H 2 V _ ^ / C 0 2 C H 3 H C H 3 60 C H 0 C H „ C H „ 3 2\ / 3 H + C H 2 N 2 85 N C H. C Q 2 C H 3 + C H 2 N 2 CH. 59 N 84 C Q 2 C H 3 In the o r i g i n a l p r e p a r a t i o n (43) of _84 and _85 the s t a r t i n g o l e f i n s w e r e ob-t a i n e d f r o m the d e c o m p o s i t i o n of the c i s - and t r a n s - 3, 5 - d i m e t h y l - 3 - c a r -b o m e t h o x y - 1 - p y r a z o l i n e s (_5 and _6, F i g u r e V I I ) . However, i t was found that the two e s t e r s _6_0 and 59, w e r e m o s t c o n v e n i e n t l y s y n t h e s i z e d by means of the m o d i f i e d W i t t i g r e a c t i o n (52). O t * ( C H O ) P - C H 102 C 0 2 C H 3 •CH O N a H _^  ( C H 3 Q ) 2 P - C ^ t / C ° 2 C H 3 CH. C H 3 C H 2 C H O C H 3 C H 2 C ( H ) = C ( C H 3 ) C 0 2 C H 3 4 2 % c i s and 58% t r a n s - 47 -The, c i s : t r a n s r a t i o i n the o l e f i n p r o d u c t depends on m a ny f a c t o r s . In p a r t i c u l a r , f o r t h i s r e a c t i o n the c o n d i t i o n s w e r e m o d e r a t e (no r e f l u x i n g a f t e r the p r o p i o n a l d e h y d e addition) so that an a p p r e c i a b l e amount of the l e s s s t a b l e c i s i s o m e r was o b t a i n e d . T h e 5, 5 - d i m e t h y l sxtbstituted 1 - p y r a z o l i n e s , 100 and 101, w e r e s y n t h e s i z e d by r e a c t i o n of m e t h y l m e t h a c r y l a t e and m e t h y l i s o p r o p e n y l ketone at -25° w i t h d i a z o i s o p r o p a n e w h i c h was p r e p a r e d , i n s i t u , by o x i -d i z i n g acetone h y d r a z o n e w i t h s i l v e r o x i d e (51). A g 2 0 (CH 3) 2C.=NNH_ ( C H 3 ) 2 C N 2 ( C H 3 ) 2 C N 2 101 P y r a z o l i n e 100 has been r e p o r t e d p r e v i o u s l y (51, 5 3) but the n. m. r . spec-t r u m was d e t e r m i n e d a g a i n to p r o v i d e a c o m p a r i s o n f o r the n. m, r . spec-t r u m of "101. The n. m. r. s p e c t r u m of 3, 5, 5 - t r i m e t h y l - 3 - a c e t y l - 1 -p y r a z o l i n e (101) shows the a c e t y l m e t h y l at 7. 6 8 f and the n o n - e q u i v a -l e n t C-5 m e t h y l s at 8. 58t" and 8. 7 6 t . The two h y d r o g e n s on C-4 show an A B s i g n a l w i t h a p a i r of doublets at 7. 90 aiad 8.92 V , J = 13. 4 Hz, - 48 -The a n i s o t r o p y of the -~N=N- group a f f e c t s the C-4 hy d r o g e n s u n e q u a l l y as a r e s u l t of f o l d i n g of the f i v e - m e m b e r ed r i n g . The h y d r o g e n t r a n s to the a c e t y l group i s f o l d e d t o w a r d s and above, the -N=N- group, g i v i n g i t a g r e a t e r s h i e l d i n g than the h y d r o g e n c i s to the a c e t y l group. 8. 92--C 7. 9 0 t C O C H . 101 T h i s r e s u l t i s s i m i l a r to that o b s e r v e d f o r c i s - 3, 5 - d i m e t h y l - 3 - a c e t y l - 1 -p y r a z o l i n e (43) (32, 33). 7. 5 7 t H •H 9. 301 COCH-.43 P y r o l y s i s of 3, 5, 5 - t r i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (100) was r e p o r t e d to give only m e t h y l 1, 2, 2 - t r i m e t h y l c y c l o p r o p a n e - 1 - c a r b o x y -l a t e (10 3) and m e t h y l t r a n s - 2 , 4 -dimethyl-2-pentenoate (104) i n the r a t i o of 84: 16 (51). However, i t was found i n t h i s w o r k that a s m a l l amount of m e t h y l c i s - 2 , 4 - d i m ethyl-2-pentenoate (105) i s f o r m e d as w e l l . N C 0 2 C H 3 __A_ + C O C H ' 2 3 100 C 0 2 C H 3 103 104 105 C O C H J 2 3 - 49 -T h e c i s i s o m e r 105 w a s i d e n t i f i e d b y c o m p a r i s o n o f t h e v . p . c . r e t e n t i o n t i m e ( p e a k e n h a n c e m e n t ) w i t h a p u r e s a m p l e p r e p a r e d b y t h e W i t t i g r e a c -t i o n ( 5 1 ) , P y r o l y s i s o f 10 1 g a v e a m i x t u r e o f s i x p r o d u c t s , f o u r o f w h i c h w e r e c h a r a c t e r i z e d . T w o m i n o r c o m p o n e n t s c o u l d n o t b e p u r i f i e d b y v . p . c . I t i s p o s s i b l e t h a t o n e o f t h e s e c o m p o n e n t s c o r r e s p o n d s t o t h e d i h y d r o f u r a n d e r i v a t i v e 1 1 0 , w h i c h w o u l d a r i s e b y r i n g c l o s u r e t o o x y g e n . T h i s w a s s h o w n t o b e a c h a r a c t e r i s t i c o f t h e 3 - a c e t y l p y r a z o l i n e s 42 a n d 4 3 ( F i g u r e s V a n d V I ) . A l t h o u g h t h e p r e f e r r e d c o n f o r m a t i o n o f 101 p l a c e s t h e a c e t y l g r o u p b e l o w t h e f o u r a t o m p l a n e o f t h e r i n g , , f a v o u r a b l e f o r r i n g c l o s u r e t o o x y g e n a s i n 4 3 , t h e r e m a y b e a s t e r i c r e p u l s i o n o f a p p r o a c h o f t h e a c e t y l o x y g e n b y t h e s e c o n d m e t h y l o n c a r b o n f i v e . H e n c e f o r m a t i o n o f 110 i s 109 108 110 50 -unfavourable. ' " The s t r u c t u r e of 1, 2, 2 - t r i m e t h y l - 1-acetylcyclopropane (106) was d e t e r m i n e d by its n. m. r . s p e c t r u m which shows three singlets at 8. 60, 8. 82, and 9.051" for the r i n g methyls. The two hydrogens on C - 4 f o r m an A B s y s t e m and show a pair of doublets at 8. 64^ and 9 .75^ with J =4.5 Hz. T h i s cyclopropane i s e x t r e m e l y l a b i l e and under the p y r a z o l i n e p y r o l y s i s conditions is p a r t i a l l y converted to the YJb -unsaturated ketone 107. The strticture of 3, 5-dimethyl-5-hexen -2-one (107) was e s t a b l i s h e d by its i n f r a r e d andn.m. r. s p e c t r a . Ketone 107 shows ab s o r p t i o n at 1700 (unconjugated ketone), 1643 (double bond), and 890 cm" ^ (CH 2=). The n.m. r. s p e c t r u m of 107 showed peaks at 5. 30t (multiplet), 7. 15-8. 15f (complex multiplet), 7 .95 r (singlet), 8.30^ (doublet, J = 1.0 Hz), and 8.96t: (doublet, J = 7.0 Hz) due r e s p e c t i v e l y to the t e r m i n a l methylene group, the C - 3 and C - 4 hydrogens, the a c e t y l m e t h y l group, the C - 5 m e t h y l group, and the C - 3 m e t h y l group ( s p l i t by the C- 3 hydrogens). The t h e r m a l r e a r r a n g e m e n t of cis_- 2-alkyl- 1 -acetyl and 1 -carbomethoxy c y c l o p r o -panes to the Y £ -unsaturated ketones and e s t e r s has r e c e n t l y been investigated by M c G r e e r . a n d C h i u (51, 53). T h e i r m e c h a n i s m for this- rearrangement, inv o l v i n g a 1, 5-hydrogen t r a n s f e r to the oxygen atom f r o m the c i s a.lkyl group, can be applied to the 106—»• 1.07 r e -arrangement o b s e r v e d here. - 51- -106 C H C H . O H 107 T h u s c o m p o u n d 107 d o e s n o t a r i s e d i r e c t l y f r o m t h e t h e r m a l d e c o m p o s i -t i o n o f t h e p y r a z o l i n e 1 0 1 . T h e s t r u c t u r e s o f t h e c i s - a n d t r a n s - 3 , 5 - d i m e t h y l - 3 - h e x e n - 2 -o n e s ( 1 0 8 a n d 109) w e r e e s t a b l i s h e d b y t h e i r n . m . r . s p e c t r a . . T h e C - 4 h y d r o g e n o f t h e c i s i s o m e r a p p e a r s a t h i g h e r f i e l d ( 0 . 8 8 1 ' ) t h a n t h a t o f t h e t r a n s i s o m e r b e c a u s e t h e l a t t e r i s d e s h i e l d e d b y t h e a n i s o t r o p i c c a r -b o n y l g r o u p , w h i c h i s c i s t o i t . O n t h e o t h e r h a n d , t h e C - 4 m e t h i n e h y d r o g e n o f t h e c i s i s o m e r i s a t l o w e r f i e l d ( 0 . Z3X ) t h a n t h a t o f t h e t r a n s i s o m e r a s i t i s d e s h i e l d e d b y t h e c a r b o n y l g r o u p . T h e r e a c t i o n o f 1, 3 - b u t a d i e n e w i t h d i a z o m e t h a n e g a v e 3 - v i n y l -1 - p y r a z o l i n e (55) ( 3 4 ) . + C H 2 N 2 ST r 55 - 52 -A l t h o u g h t h i s p y r a z o l i n e i s s o m e w h a t d i f f e r e n t f r o m t h e o t h e r s i n T a b l e I, t h a t i s , t h e C = C g r o u p i s n o t a s e l e c t r o n - w i t h d r a w i n g a s a c a r b o n y l g r o u p a n d t h e r e i s n o C - 3 a l k y l s u b s t i t u e n t , i t was o f i n t e r e s t t o c o m p a r e t h e k i n e t i c s o f l i q u i d - p h a s e d e c o m p o s i t i o n w i t h t h o s e f o u n d f o r t h e g a s - p h a s e d e c o m p o s i t i o n ( 3 4 ) . T h e r e s u l t s w i l l b e d i s c u s s e d l a t e r . T h e a d d i t i o n o f d i a z o m e t h a n e t o m e t h a c r y l o n i t r i l e a t 0 ° g i v e s 3 - m e t h y l - 3 - c y a n o - 1 - p y r a z o l i n e ( 9 8 ) . / C H 3 CH 2=C + CH 2N 2 — • . _ N \ C N L ^ N N 9 8 D e c o m p o s i t i o n o f 98> g i v e s 1 - m e t h y l - 1 - c y a n o c y c l o p r o p a n e (111) a n d o l e f i n p r o d u c t s . - C H . 3 9 8 > \ + o l e f i n s C N 111 T h e p r e p a r a t i o n . o f 1.11 w a s e m p l o y e d b y G o t k i s a n d C l o k e (6) b u t t h e p y r a -z o l i n e w a s n o t i s o l a t e d i n a p u r e s t a t e . T h e n . m . r . s p e c t r u m o f 98 s h o w s t h e s a m e g e n e r a l f e a t u r e s f o u n d i n t h e n . m . r . s p e c t r a o f _9_5 a n d 4 2 . T h e n o n - e q u i v a l e n t C - 4 h y d r o g e n s a n d t h e C - 5 h y d r o g e n s f o r m a n A B X ^ s y s t e m i n a l l t h r e e p y r a z o l i n e s . T h e e q u i v a l e n c e o f t h e C - 5 h y d r o g e n s i n d i c a t e s t h a t t h e r e i s a n e q u i l i b r a t i o n o f t h e t w o e q u a l l y p o p u l a t e d c o n f o r m a t i o n s i n a l i t h r e e c a s e s . - 5 3 -X = CN, C O C H 3 C O z C H 3 The p y r o l y s i s of 9_8 gave a m i x t u r e of s i x p r o d u c t s , o n l y t h r e e of w h i c h c o u l d be p o s i t i v e l y i d e n t i f i e d . T h e n. m. r . s p e c t r u m of 1-m e t h y l - 1 - c y a n o c y c l o p r o p a n e (111) showed an A ^ B 2 s y s t e m s i g n a l at 8. 75 to 9. 4 7 f f o r the c y c l o p r o p a n e h y d r o g e n s . T h e low f i e l d p o r t i o n of the s i g n a l a r i s e s f r o m the h y d r o g e n s w h i c h a r e on the same si d e of the r i n g as the a n i s o t r o p i c cyano group and a r e thus d e s h i e l d e d . The two o l e f i n i c p r o d u c t s i d e n t i f i e d a r e the c/^jS-unsaturated n i t r i l e s , a n g e l o n i -t r i l e (112) and t i g l o n i t r i l e (113). C N . N / N / ~ \ ~ ~ ^ C N 112 113 The g e o m e t r i c a l a s s i g n m e n t s f o r 112 and 113 a r e b a s e d on the n. m. r . s p e c t r a . F o r 113 the o l e f i n i c h y d r o g e n i s c i s to the cyano groixp and hence i s d e s h i e l d e d a n d a p p e a r s at a l o w e r f i e l d than i n 112. P y r a z o l i n e s w i t h d e u t e r i u m atoms at the C-5 p o s i t i o n w e r e p r e -p a r e d by the a d d i t i o n of d i d e u t e r i o d i a z o m e t h a n e to the a p p r o p r i a t e o l e f i n s . - 5 4 -T h e d i d e u t e r i o d i a z o m e t h a n e w a s p r e p a r e d b y a s i m p l e b a s e c a t a l y s e d e x c h a n g e r e a c t i o n . K 2 C ° 3 C H 2 N 2 + D 2 Q > C D 2 N 2 + H 2 0 C D 2 N 2 / C H 3  2 C O z C H 3 _ _ ^ C H 3 N 99 D ' C H . N 9 7 N C O C H i N 2 3 T h e n . m . r . s p e c t r a o f t h e C - 5 d e u t e r a t e d p y r a z o l i n e s i n d i c a t e d t h e e x -t e n t o f d e u t e r i u m s u b s t i t u t i o n . T h e n . m . r . s p e c t r u m o f 3 - m e t h y l - 3 -c y a n o - 1 - p y r a z o l i n e - 5 , 5 - d 2 (99) i s c o n s i d e r a b l y d i f f e r e n t f r o m t h a t f o r 9 8 . T h e t r i p l e t a t 5 . 3 2 1 f o r t h e C - 5 h y d r o g e n s h a s v i r t u a l l y d i s a p -p e a r e d a n d t h e A B X 2 s i g n a l f o r t h e C - 4 h y d r o g e n s i s s i m p l i f i e d t o a n A B s i g n a l , J e r n = 1 3 . 4 H z . T h e n . m . r . s p e c t r u m o f 9j> a n d 9_7 a r e g i v e n i n F i g u r e s X I V a n d X V r e s p e c t i v e l y . T h e e f f e c t o f d e u t e r i u m s u b s t i t u t i o n a t t h e C - 5 p o s i t i o n i s t h e s a m e a s d e s c r i b e d a b o v e . T h e t r i p l e t a t 5 . 4 3 f : s h o w n b y 9J> h a s d i s a p p e a r e d a n d t h e C - 4 h y d r o g e n s g i v e a n A B s y s t e m s i g n a l , J = 13 H z . T h e p r e p a r a t i o n o f a 1 - p y r a z o l i n e w i t h d e u t e r i u m s u b s t i t u t i o n a t rrrrrrra ii:!- "i i '• !.\.\ : ' i \ : I U.i j ; i i i ! ' i ! !• i . ! i ' i ; ; ; •: !• I i i I • • ; j i 'I : , j 'j r; :i1iM':.i|ii!li . l > . : i : ' . M , !!•• ; : - i ! ' ; ! i i ! i ! M J H J i i ; i i ; ; i ! ! ' • ! i ; i I.!'! ! i h . : -V i U U 1 : ; ! - ! M l ! i :•! 1 M ; i-i ! ! i ' ! 1 .Ml. r . . j- i i i.H i : . ! M i u J ; i •: • : ; ' i I i • ; < ^ ! ' 1 i I I 1 i ! • ! ! ; i.i ! . i ; i i i ! : i < i • i-.'.''.i-|'.!.i ! i ;H:i i T i T i T i i i i - f i -I i. -; r;-r m : i i i l l . 1"! !• ! ' ' ' Hi j ' . i ! ; ;-.;. !..!. i •i riT. • i i i : ; i i i i i 1 i : ; •!•; i i i i i i i i ' : i M.l : ij.'.i.i !.-.!..! !.!.;..! i ! 1 u i i i !•! i i M : i i i. 1 ; i i i i " f i r MA i i i •li ! i •! .i i i i i •i-i ! i !'.-i ;.' jY i' I', i i-i • i i i i i i i i i F I G U R E X I V - The n . m . r . spec t rum of 3 -methyl -3-carbomethoxy -1 - py r az oline ( 9 5 ) . - 57 -the C-4 position proved to be more difficult. In the early stages of this research it.was hoped that stereospecifically deuterated methyl metha-crylate could be prepared by the scheme illustrated in Figure XVI. H B r 1) L i H £ 0 2 H HC=CCH 3 + DBr — > ^ = c > NC=C D "CH 3 2) CO z D "CH 3 .3) H 3Q C H 2 N 2 H CO-CHo V . c D CEU FIGURE XVI - Possible preparative scheme for methyl methacrylate-3-d^. However, t r i a l additions of hydrogen bromide to methylacetylene under a wide variety of conditions did not give suitable yields of the desired 2-bromo-2-propene. Indeed, Griesbaum et al. reported that the addition of hydrogen bromide to methylacetylene can give extremely complex pro-duct mixtures (54). Consequently, this method was abandoned and the results that were obtained are not reported in this work. It is interes-ting to note that several groups of v/orkers are currently investigating the best conditions for obtaining the stereospecific trans addition of hydrogen halides and other acids to acetylenes' (55, 56, 57). Another possible route to deuterated methyl methacrylate is the Wittig reaction (58). House and Rasmus son (59) employed this reaction - 58 -i n t h e p r e p a r a t i o n o f m e t h y l t i g l a t e (J.) a n d m e t h y l a n g e l a t e ( 2 ) . © ( C 6 H - ) - P C H 2 C H 3 e B r C 6 H 5 L i ( C 6 H 5 ) 3 P = C H C H 3 O n C H 3 C C 0 2 C H 3 \ / \ \ / + \ C 0 2 C H 3 C O z C H 3 2 1 % o v e r a l l y i e l d P o m e r a n t z [60) d e m o n s t r a t e d t h a t t h e m e t h y l h y d r o g e n s o f m e t h y l t r i -p h e n y l p h o s p h o n i u m b r o m i d e c o u l d b e e x c h a n g e d w i t h d e u t e r i u m a t o m s t o f o r m t r i d e u t e r i o m e t h y l t r i p h e n y l p h o . s p h o n i u m b r o m i d e ( 1 1 4 ) . ( C 6 H 5 ) 3 P C H 3 B e r D z O / N a O D ( C 6 H 5 ) 3 ? C D 3 B e r 1 1 4 H e n c e t h e s c h e m e b e l o w w a s t e s t e d a s a s y n t h e s i s o f m e t h y l m e t h a c r y -l a t e - 3 j 3 - d 2 . ( G 6 H 5 ) 3 P C D 3 B e r 1 1 4 C 6 H 5 L i ( C 6 H 5 ) 3 P = C D 2 C H 3 C C 0 2 C H 3 C H 3 G D 2 = C C 0 2 C H 3 1 1 5 - 59 -T r i a l preparations using methyltriphenylphosphonium bromide gave ap-proximately 10-15% yields of methyl methacrylate. However, when the deuterated phosphonium salt 114 was employed some difficulty was found in the reaction sequence. Although further t r i a l experiments would pro-bably point out the best conditions, the reaction was not further tested since it-appeared that the yields would be low in any case (59). Another route tested was the modified Wittig reaction (52). The reaction scheme tested is illustrated below. O O f / C H . NaH CH, (CH O) PCH b (CH-OKP-C© C 0 2 C H 3 5 L C O z C H 3 ( C H 2 0 ) n / C H 3 CH 2= C 3 C 0 2 C H 3 The best yield of methyl methacrylate obtained was 18% although there may have been some lost due to polymerization. Since the preparation of methyl methacrylate-3, 3-d2 (115) by this scheme would necessitate the use of paraformaldehyde-d (an expensive compound) it was thought that 21 a reaction giving better yields of methyl methacrylate should be tested. In 1924, Mannich and Ritsert (6l) prepared ethyl methacrylate in about 60% yield by the condensation of ethyl diethylammonium malonate and formaldehyde. This Mannich reaction was employed by Kourim and c Vacek (62) to prepare methyl methacrylate-3, 3-d2 (115) (Figure XVII). - 60 ( C 2 H 5 ) 2 N H G D z O + C H 3 C H C 0 2 C H 3 > C D 2 = C Q 2 H / C ° 2 C H 3 H . 116 115 F I G U R E X V I I - P r e p a r a t i o n o f m e t h y l m e t h a c r y l a t e - 3 , 3 - d 2 b y t h e M a n n i c h r e a c t i o n . T h e a b o v e a u t h o r s h o w e v e r d i d n o t d e s c r i b e t h e r e a c t i o n c o n d i t i o n s o r t h e s o u r c e o f t h e f o r m a l d e h y d e - d ^ . M e t h y l h y d r o g e n m e t h y l m a l o n a t e (116) w a s s y n t h e s i z e d f r o m m e t h y l m a l o n a t e . C 0 2 . C H . 3 2) C H 3 I C 0 2 C H 3 C Q 2 C H 3 1) N a / M e O H > H C C H C Q 2 C H 3 K O H / M e O H C 0 2 H H C C H -C 0 2 C H 3 116 A l t h o u g h t h e r e w a s s o m e d i f f i c u l t y d u e t o t h e s e e m i n g l y l o w r e a c t i v i t y o f t h e C D 2 0 u s e d i n t h e r e a c t i o n , m e t h y l m e t h a c r y l a t e - 3 , 3 - d 2 (115) w a s f i n a l l y o b t a i n e d b y t h e M a n n i c h r e a c t i o n ( F i g u r e X V I I ) . T h e n . m . r . s p e c t r u m o f t h e s a m p l e o f 115 i n d i c a t e d t h a t d e u -t e r i u m s u b s t i t u t i o n w a s v i r t u a l l y 9 9 % c o m p l e t e . T h i s w a s e x p e c t e d s i n c e t h e r e a p p e a r e d t o b e n o p o s s i b i l i t y o f i s o t o p e e x c h a n g e i n t h i s r e a c t i o n . T h e n ; m . r . s p e c t r u m s h o w e d t w o s i n g l e t s o f e q u a l i n t e n s i t y a t 6 . 30 f - 61 . a n d 8. 10 *C d u e t o t h e e s t e r m e t h y l h y d r o g e n s a n d t h e C - 2 m e t h y l h y d r -g e n s r e s p e c t i v e l y . T h e r e w e r e n o p e a k s i n t h e l o w f i e l d r e g i o n f r o m 3 . 9 - 4 . 5 X \ / h e r e t h e m e t h y l e n e h y d r o g e n s o f m e t h y l m e t h a c r y l a t e a p p e a r . T h e m e t h y l m e t h a c r y l a t e - 3 , 3 - d w a s r e a c t e d w i t h d i a z o m e t h a n e t o g i v e 3 - m e t h y l - 3 - c a r b o m e t h o x y - l - p y r a z o l i n e - 4 , 4 - d ( 9 6 ) . / C H C D 2 = C 3 + C H 2 N 2 C 0 2 C H 3 D D N 96 ,CH ^ C 0 2 C H 3 T h e i n f r a r e d s p e c t r u m o f _96 s h o w e d a w e a k b a n d a t 2 1 5 0 c m * ' d u e t o c a r -b o n - d e u t e r i u m s t r e t c h i n g . T h e n . m . r . s p e c t r u m o f 96 i s s h o w n i n F i g u r e X V I I I . T h e s i g n a l f o r t h e C - 5 h y d r o g e n s i s c o l l a p s e d t o a b r o a d s i n g l e t a t 5 . 46 X. b e c a u s e o f t h e d e u t e r i u m s u b s t i t u t i o n a t C - 4 . M c G r e e r jej: al. (20) h a v e s h o w n t h a t t h e p y r o l y s i s o f 3 - m e t h y l -3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (95) g i v e s m e t h y l 2 - m e t h y l - 3 - b u t e n o a t e ( 1 1 7 ) , m e t h y l 1 - m e t h y l c y c l o p r o p a n e c a r b o x y l a t e ( 1 1 8 ) , m e t h y l a n g e l a t e (2 ) , a n d m e t h y l t i g l a t e (_1). T h e d e c o m p o s i t i o n p r o d u c t s f r o m 9 5 a n d t h o s e e x p e c t e d f r o m 9_6 a r e s h o w n i n F i g u r e X I X . I i i i i i i i i i i i I i i i i I i i i i I i i i i i i i i i i i i i i i i i i i i i i i i i i i i i r 5 6 7 8 9 ^ F I G U R E X V I I I - The n. m. r. spectrum of 3-methyl-3-carbomethoxy-l-pyrazoline-4, 4-d (96). f N ' 9 5 C O C H 2 3 A 6 3 C 0 2 C H 3 A 117 + , C 0 2 C H 3 < C 0 2 C H ; 1 1 8 v__/ + — \ C O z C H 3 D — D A 9 6 ' C 0 2 C H 3 -> D > 119 • D C 0 2 C H 3 D, + D 120 C O C H 2 3 C H 2 D N / C 0 2 C H 3 + C H 2 D \ _ _ / 121 N C O z C H 3 122 F I G U R E X I X - P r o d u c t s f r o m t h e p y r o l y s i s o f 9 5 a n d 9 6 . . T h e p o s i t i o n a n d d e g r e e o f d e u t e r i u m s u b s t i t u t i o n i n 120 a n d 122 w e r e d e t e r m i n e d b y n . m . r . ( s e e E x p e r i m e n t a l ) . T h e n . m . r . s p e c t r u m o f 122 i n d i c a t e d t h a t d e u t e r i u m s u b s t i t u t i o n i s i n d e e d a s d e p i c t e d i n F i g u r e X I X . H e n c e t h e f o r m a t i o n o f o l e f i n p r o d u c t s f r o m p y r a z o l i n e 9 6 a r i s e s f r o m C - 4 d e u t e r i u m m i g r a t i o n t o e i t h e r C - 3 t o g i v e t h e d e u t e r a t e d (^Y - u n s a t u r a t e d e s t e r 119 o r t o C - 5 t o g i v e t h e d e u t e r a t e d ^ - u n s a t u r a t e d e s t e r s 121 a n d 1 2 2 . I I - 2 K I N E T I C M E A S U R E M E N T S C a l c u l a t i o n of the Rate C o n s t a n t s and A c t i v a t i o n P a r a m e t e r s P r e v i o u s w o r k by Snyder (50) has shown that the d e c o m p o s i t i o n of 1 - p y r a z o l i n e s f o l l o w s f i r s t o r d e r k i n e t i c s . The rate e x p r e s s i o n f o r a f i r s t o r d e r d e c o m p o s i t i o n r e a c t i o n i s the f o l l o w i n g , k = 2- 3 0 3 l o g _ _ _ • ' ' I t a G - x where k = the f i r s t o r d e r r a t e constant; a Q = i n i t i a l c o n c e n t r a t i o n of the r e a c t a n t and x = amount of r e a c t a n t w h i c h h a s de c o m p o s e d i n t i m e i n t e r v a l t, l e a v i n g a Q - x u n r e a c t e d . One m o l e of 1 - p y r a z o l i n e gives one m o l e of n i t r o g e n gas upon c o m p l e t e d e c o m p o s i t i o n , hence the concen-t r a t i o n changes w i t h t i m e a r e m o s t c o n v e n i e n t l y f o l l o w e d by m e a s u r i n g the r a t e of f o r m a t i o n of n i t r o g e n . E x p r e s s i o n 1_ now becomes k = 2« 3 0 3 l o g ... 2 t Veo - -Vt . ~ • where "Voo = the v o l u m e of n i t r o g e n , at s t a n d a r d t e m p e r a t u r e and p r e s -s u r e , e q u i v a l e n t to the i n i t i a l c o n c e n t r a t i o n of the p y r a z o l i n e and Vj- = the v o l u m e of n i t r o g e n , at S. T„ P. , e q u i v a l e n t to the amount of p y r a z o l i n e d e c o m p o s e d i n t i m e i n t e r v a l t, l e a v i n g - V^ . s t i l l u n r e a c t e d . A g r a p h i c a l p l o t of the quantity l o g (Vco / V „ - Vj.) v e r s u s t w i l l r e s u l t i n a s t r a i g h t l i n e . The slope of the l i n e m u l t i p l i e d by 2. 303 w i l l be e q u a l to the r a t e constant. - 65 -A least squares method of fitting the straight lines was tested and the results compared to those obtained by a graphical plot. For runs where a good straight line was produced there proved to be no real ad-vantage in using the least squares analysis. The slopes obtained by the two procedures were essentially identical. In some runs where the more volatile solvent, formamide, was employed and where very volatile pro-ducts were formed, e.g., in the decomposition of vinyl-1-pyrazoline, the graphical plots were more advantageous since the slight deviations after 60% completion could be avoided. For these reasons, a l l rate con-stants were obtained from the best straight lines drawn through the graphical plots. The results of the kinetic studies are summarized in Table II, and some typical first order rate plots are shown in Figures XX-XXV. The activation parameters were obtained from the Eyring equation, 3 k - i _ 3 Z - A l I # / R T „ A S # / R r, c / e where kg = Boltzmann's constant, h = Planck's constant, andAH^and A s ^ a r e the enthalpy and entropy of activation respectively. The loga-rithm form of equation _3 is W k - 10 319 1 / AH# \ AS# 4 l 0 g T ~ - 1 0 ' 3 1 9 "T" (.4. 574 I + 47574" ~ ± A plot of log (k/T) vs. 1/T gave a straight line whose slope multiplied T A B L E I I The Summary of the Rate Constants and the Activation Parameters  in the Pyrolysis of 1-Pyrazolines Compound f 95 CO CH N 2 3 Solvent Run Temp. kxl04 No. o c sec"--'-Tetralin 45-6 a 109.4 1.28 50 114. 0 2. 00 47 119.5 3. 87 51 123. 4 5. 10 48-9 ' 126. 0 6.69 Calc. 127. 0 7. 31 Ref. 50 125.9 7. 17 n-Butyl 77 107. 3 0.662 ' phthalate 78 116. 1 1. 75 Avg. of 10 runs 127. 0 5.63+0.20 Nitro- 59-60 113. 3 0. 824 benzene 57-8 121. 3 2.03 52-3 126. 1 3. 35 54-56 131. 3 5.99 Calc. 127. 0 3. 81 Formamide 163-4 127. 0 2.54+0.12 167-8 "£51 A S # Kcal/mole e.u. 30. 0 1.5 o Os 32. 4 7.0 33. 8 9.7 D f - C 0 2 C H 3 n-Butyl-phthalate 165-6 127. 0 4. 15+0.10 96 Formamide 169-170 127.0 • 2. 39+0.0 5 T A B L E I I (cont'd) 'Compound Solvent Run No. Temp. k x l O 4 •1 sec Kcal/mole e. u. N •C0 2CH 3 97 n-Butyl phthalate Formamide 144-146 Corrected c 173 127. 0 127. 0 127. 0, 5. 04+0. 10 4.62+0. 10 2. 17+0. 05 C "f^-CN 98 n-Butyl- 79-82, 132 109. 4 7. 34+0. 20 phthalate 85 99.7 2. 58 30. 3 6. 0 86 89. 25 0. 765 Tetralin Ref. 50 109.5 7. 68 E a=30 Kcal/mole Formamide 114-115 109.4 4. 03 116 89.25 0. 385 31.4 7. 6 n-Butyl 133-135 109. 4 5. 95+0. 10 phthalate n-Butyl- 121-22 128. 1 4. 16 phthalate 123 118.0 1^37 33.4 8.7 M 124 107.9 0. 418 SN 55 Gas phase Ref. 34 128.0 9. 11 31.4 4.7 T A B L E II (cont'd) Compound Solvent Run No. Temp. ° C k x l O 4 sec" l A H # A S # Kcal/mole e.u. [ ^-COCHo n-Butyl-phthalate Tetralin 103-104 105 107 Ref. 50 127. 0 117. 0 106. 8. 125.9 9.61 3. 46 1. 18 8.20 30. 6 3.6 E a=29 Kcal/mole 42 Formamide 159-160 174 127. 0. 106. 5 13. 7 1. 83 28. 9 0.1 J --/-CO CH 1 2 3 n-Butyl-phthalate 111 • 112 113 109.4 99.7 89.75 6. 77 2. 63 0. 857 28. 3 0.6 / / r f - c o z C H 3 N 1 n-Butyl-phthalate 108 109 110 109.4 99. 7 89. 75 8. 48 3. 17 1. 03 28. 9 2.5 ) ^-COCH„ N / 44 n-Butyl-phthalate 117 118 119 109.4 99.7 89. 8 17. 0 6. 47 2. 22 27.9 1.2 J f-COCH, 43 n-Butyl-phthalate 120 109.4 13. 6 T A B L E II (cont'd) Compound Solvent Run Temp. k x l O 4 A.H# AS# ' No. ° C sec"''' kcal/mole e.u. 100 f ,N C Q 2 C H 3 phthalate. n-Butyl- 149-151 109. 4 4.26+0. 10 Formamide 155-156 109. 4 2. 90+0. 10 / n-Butyl- 152-154 109. 4 8. 89+0. 20 "p-COCH 3 phthalate 175 89. 9. 1. 09 29. 1 3.1 101 Formamide 157--158 109. 4 20. 1+0.6 161-162 89. 7 2. 87+0. 05 26. 6 -1.9 n-Butyl- 99-100 147. 4 13.1 ~ C 0 2 C H 3 phthalate 101 137. 1 4. 60 33. 8 7.9 /N 102 127. 1 1. 61 V 3 CO CH n-Butyl 94- 96 157.2 5. 11 2 3 phthalate 147-148 147.4 1. 59 38. 7 15.6 /N 98 137. 0 0. 533 4 n-Butyl- 125-126, -CO zCH 3 phthalate 131 147. 4 5.64 v ^ 127, 130 137. 2 1. 81 38. 1 16.4 SN' g 4 128 127. 0 0. 529 ON T A B L E I I ( c o n t ' d ) C o m p o u n d S o l v e n t R u n T e m p . k x l O 4 AH# AS^ . N o . . ° C s e c " K c a l / m o l e e . u . C 0 2 C H 3 n - B u t y l - 1 3 9 - 1 4 0 1 5 7 . 2 2 . 9 1 p h t h a l a t e 1 3 6 , 138 1 4 7 . 4 1 . 0 3 3 7 . 6 1 2 . 0 85 W h e r e t w o o r m o r e r u n s w e r e m a d e a t t h e s a m e t e m p e r a t u r e k i s t h e m e a n v a l u e . ^ E r r o r l i m i t s a r e e x p r e s s e d a s e i t h e r t h e s t a n d a r d d e v i a t i o n f r o m t h e m e a n o r t h e a v e r a g e d e v i a t i o n f r o m t h e m e a n . c V a l u e o f k c o r r e c t e d t o a c c o u n t f o r i n c o m p l e t e d e u t e r a t i o n , s e e R e f e r e n c e 6 6 . 0 . 6 0 . 5 0 . 4 C 0 2 C H . 0 . 3 0 . 2 1 2 7 . 0 e D. CH D" rco2cH3 0 .1 0 0 F I G U R E X X -1 0 1 5 2 0 2 5 3 0 3 5 t i m e ( m i n ) R a t e p l o t s f o r t h e p y r o l y s i s o f 3 - m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (95) a n d 3 - m e t h y l - 3 - c a r b o m e t h o x y - l - p y r a z o l i n e - 4 , 4 - d ^ (96) i n n - b u t y l p h t h a l a t e 4 0 Um<2 (min) X X I - R a t e P l o t s f o r t h e pyrolysis of 3-methyl-3-cyano-1-pyrazoline (98) and 3-methyl-3-cyano-l-pyrazoline-5, 5-d 2 (_99) in n-butyl phthalate. 0 . 6 0 . 5 0 . 4 ^ 3 0 . 3 o 0 . 2 0.1 0 0 n - b u t y l p h t h a l a t e 1 0 9 . 4 1 0 2 0 f o r m a m i d e C H 3 i C H 3 3 0 4 0 t i m e ( m i n ) 5 0 6 0 7 0 8 0 F I G U R E X X I I - R a t e p l o t s f o r t h e p y r o l y s i s o f 3, 5, 5 - t r i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (100) i n n - b u t y l p h t h a l a t e a n d i n f o r m a m i d e . 0 5 1 0 1 5 2 0 2 5 3 0 t ime (min) FIGURE X X I I I - Rate plots for the pyrolysis of 3, 5, 5-trimethyl-3-acetyl-1-pyrazoline (10 1) in n-butyl phthalate and in formamide. t ime (min) F I G U R E X X I V - R a t e p l o t s f o r t h e p y r o l y s i s o f c i s - a n d t r a n s - 3, 4 - d i m e t h y l -3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s (_3 a n d _4) i n n - b u t y l p h t h a l a t e . t i m e (min) FIGURE XXV - Rate plots for the pyrolysis of c i s - and trans-3-methyl-4-ethyl-3-carbomethoxy-1-pyrazolines (84 and 85) in n-butyl phthalate. - 77 -b y 4 . 5 7 4 g a v e A H . S u b s t i t u t i n g t h i s A H * b a c k i n t o e q u a t i o n 4 g a v e AS^. T h e v a l u e s o f A H # a n d A S ^ a r e . g i v e n i n T a b l e I I . T h e r e a r e s e v e r a l f a c t o r s w h i c h w i l l a f f e c t t h e a c c u r a c y o f t h e r a t e c o n s t a n t ; : a n d a c t i v a t i o n p a r a m e t e r s o b t a i n e d . T h e e r r o r s o f m e a s u r e m e n t o f t i m e a n d o f t h e i n i t i a l a m o u n t o f p y r a z o l i n e ( V c ^ ) a r e v e r y s m a l l ( < 1 % ) „ S e v e r a l g r o u p s o f w o r k e r s h a v e s h o w n ( 6 3 , 64) t h a t t h o r o u g h a g i t a t i o n o f t h e r e a c t i o n s o l u t i o n i s n e c e s s a r y w h e n v o l u m e t r i c m e a s u r e m e n t s o f a n e v o l v e d g a s a r e t o b e m a d e . T h e r a t e o f a g i t a t i o n o f t h e s o l u t i o n s h o u l d b e s u f f i c i e n t l y h i g h s o t h a t t h e r a t e o f e s c a p e o f n i t r o g e n f r o m t h e s o l u t i o n i s n o t r a t e d e t e r m i n i n g . T h e m a g n e t i c s t i r -r i n g e m p l o y e d i n t h i s w o r k g a v e t h o r o u g h a n d r e p r o d u c i b l e a g i t a t i o n o f t h e r e a c t i o n s o l u t i o n a s d e m o n s t r a t e d b y t h e g o o d r e p r o d u c i b i l i t y o f t h e k i n e t i c r e s u l t s . T h e t e m p e r a t u r e o f t h e o i l b a t h w a s k e p t t o w i t h i n j K > . 0 5 ° . H o w e v e r , t h e a c c u r a c y o f t h e t e m p e r a t u r e r e a d i n g s i s d e c r e a s e d w h e n s t e m c o r r e c t i o n s a r e n e c e s s a r y . T h e t e m p e r a t u r e s a r e c o n s i d e r e d a c c u r a t e t o _+0. 1 ° o r b e t t e r . F r o m e q u a t i o n 4 , t h i s t e m p e r a t u r e v a r i a -t i o n c o r r e s p o n d s t o a n e r r o r ' o f a b o u t 1-2% i n t h e r a t e c o n s t a n t . W i t h t h e o t h e r f a c t o r s i n c l u d e d t h e a v e r a g e e r r o r i n t h e r a t e c o n s t a n t s w i l l b e c l o s e t o _+3%. T h e m a x i m u m e r r o r i n t h e v a l u e s f o r A H ^ i s e s t i m a t e d t o b e a b o u t + 5 % . A s m a l l v a r i a t i o n i n t h e v a l u e f o r A H r e s u l t s i n a r e l a -t i v e l y , l a r g e v a r i a t i o n i n t h e v a l u e f o r A S ^ , H e n c e t h e e r r o r i n t h e v a l u e s f o r As^ g i v e n i n T a b l e I I c a n b e a s g r e a t a s _+2-4 e . u . - 78 -T h e f o l l o w i n g c h e c k s w e r e m a d e t o s h o w t h a t a l a r g e c h a n g e i n t h e c o n c e n t r a t i o n o f t h e p y r a z o l i n e d i d n o t a f f e c t t h e r a t e o f d e c o m p o s i -t i o n . ( i) T h e r a t e o f p y r o l y s i s o f 3 - m e t h y l - 3 - c a r b o m e t h o x y - 1 -p y r a z o l i n e (95) w a s d e t e r m i n e d a t 1 2 7 . 0 ° i n n - b u t y l p h t h a -l a t e b y t h e u s u a l p r o c e d u r e . H o w e v e r , t h e s t a n d a r d s o l u -t i o n o f p y r a z o l i n e w a s p r e p a r e d s o t h a t Vca ( c a l c . ) e q t i a l e d 6 0 . 2 3 m l , i . e. , t h e c o n c e n t r a t i o n o f p y r a z o l i n e w a s i n -c r e a s e d a p p r o x i m a t e l y 5 0 % . T h e r a t e c o n s t a n t o b t a i n e d w a s 5 . 9 3 x 1 0 ~ 4 s e c " ' ' ' , r e a s o n a b l y c o m p a r a b l e t o t h e a v e r a g e v a l u e o f 5 . 6 3 x 1 0 " 4 s e c " ' ' o b t a i n e d w h e n t h e u s u a l c o n c e n t r a t i o n w a s e m p l o y e d , ( i i ) T h e r a t e o f p y r o l y s i s o f 3 - m e t h y l - 3 - c y a n o - 1 - p y r a z o l i n e (98) w a s d e t e r m i n e d a t 1 0 9 . 4 ° i n t h e u s u a l m a n n e r w i t h t h e e x -c e p t i o n t h a t 100 m l o f s o l v e n t w a s u s e d ; h e n c e t h e p y r a -z o l i n e c o n c e n t r a t i o n w a s d e c r e a s e d b y 5 0 % ( R u n n o . 8 0 ) . T h e r a t e c o n s t a n t o b t a i n e d , 7 . 4 0 x 1 0 ~ 4 s e c - ' ' ' , w a s i n g o o d a g r e e m e n t w i t h t h e v a l u e s o b t a i n e d f r o m r u n s m a d e at t h e n o r m a l c o n c e n t r a t i o n s a n d i s i n c l u d e d i n t h e a v e r a g e d v a l u e g i v e n i n T a b l e I I . T h e r e a c t i o n s y s t e m w a s f l u s h e d w i t h p u r i f i e d n i t r o g e n g a s b e -f o r e c o m m e n c i n g a r u n s o t h e s o l v e n t w o u l d b e s a t u r a t e d a n d t h e s y s t e m w o u l d b e f r e e o f o x y g e n . H o w e v e r , o n e r x m w a s m a d e ( 9 5 i n n - b u t y l - 79 -phthalate at 127. 0 ) i n w h i c h the s o l v e n t and s y s t e m w e r e not f l u s h e d w i t h n i t r o g e n . .The r a t e constant a g r e e d w i t h the.values obtained by the u s u a l p r o c e d u r e , i n d i c a t i n g that the p r e s e n c e of oxygen has no a p p r e c i a b l e ef-f e c t on the r a t e of d e c o m p o s i t i o n . F l u s h i n g w i t h n i t r o g e n gas s t i l l ap-p e a r e d n e c e s s a r y because the a g r e e m e n t between ( c a l c . ) and V M (obs.) i s o n l y 9 7 - 9 8 % when the s o l v e n t has not been s a t u r a t e d . It was o b s e r v e d that the plots of l o g (V©^  /Voo - V )^ v s . t i m e f a i l to go t h r o u g h the o r i g i n as e x p e c t e d f o r a f i r s t o r d e r k i n e t i c s plot. S n yder (50) a l s o o b s e r v e d t h i s r e s u l t and suggested that s e v e r a l f a c t o r s may c o n t r i b u t e . The r e a c t i o n may have an i n d u c t i o n p e r i o d . A c t u a l l y i t a p p e a r s as i f a s l i g h t v o l u m e s h r i n k a g e i n the s y s t e m o c c u r s at the be-g i n n i n g of a r u n . T h i s may be due to a s l i g h t a b s o r p t i o n of n i t r o g e n by the s o l u t i o n of p y r a z o l i n e i n t r o d u c e d at the s t a r t of the r u n . The perhaps m o s t s i g n i f i c a n t i n d i c a t i o n that the r a t e constants a r e r e l i a b l e v a l u e s i s the f a c t that t h e r e i s quite r e a s o n a b l e agreement between the r a t e constants g i v e n h e r e and those found by Snyder (50). F o r example, f o r the d e c o m p o s i t i o n of 9 5 i n t e t r a l i n at 1 2 6 . 0 ° the r a t e / - 4 - 1 constant found i n t h i s w o r k i s 6 . 69 x 10 sec , c o m p a r e d to Snyder's v a l u e of 7 . 17 x 1 0 ~ 4 sec f o r the d e c o m p o s i t i o n of _9_8 i n n - b u t y l phtha-o - 4 1 l a t e at 1 0 9 . 4 the r a t e constant i s 7 . 34 x 10 sec , c o m p a r e d to 7 . 68 x 1 0 " 4 s e c " 1 found f o r 98 i n t e t r a l i n at 1 0 9 . 5 ° (50). In the l a t t e r c o m p a r i s o n t h e r e may be a s o l v e n t effect d i f f e r e n c e but t h i s i s expected to be v e r y s m a l l i n the case of p y r a z o l i n e 9 8 . The a g r e e m e n t i s good - 80 -d e s p i t e the f a c t that quite d i f f e r e n t m e a s u r i n g methods w e r e employed. Snyder u s e d c a r b o n d i o x i d e to f l u s h the n i t r o g e n gas f r o m t h e r e a c t i o n v e s s e l . The gas v o l u m e s w e r e m e a s u r e d o v e r a p o t a s s i u m h y d r o x i d e s o l u t i o n w h i c h a b s o r b e d the c a r b o n d i o x i d e . That t e c h n i q u e was not e m p l o y e d i n t h i s w o r k s i n c e a d i r e c t m e a s u r e m e n t of n i t r o g e n o v e r m e r c u r y a p p e a r e d to be m o r e convenient. - 81 -II - 3 PRODUCT ANALYSIS With the exception of 3, 5, 5-trimethyl-3-acetyl-1-pyrazoline (101) and 3-methyl-3-cyano-1-pyrazoline (98), the identification and percentage composition of the thermal decomposition products of the 1-pyrazolines used in this work has been discussed in the literature (14, 15, 19, 20, 21, 31, 32, 43). McGreer and workers (15, 32) have studied the effect of various solvents on the product distribution for cis- and trans- 3, 5- dimethyl- 3- carbomethoxy- 1-pyrazolines (_5and_6), cis- and trans-3, 5-dimethyl-3-acetyl-1-pyrazolines (43 and 44), and 3-methyl-3-acetyl-1-pyrazoline (42). One feature of their results was the in-crease in olefin formation, particularly the trans ^-unsaturated ester or ketone, with an increase in solvent polarity. Preliminary product distribution studies in formamide showed a large increase in olefin formation and-it was hoped that this could be re-lated to the kinetic results. Solutions and neat samples of the pyrazolines in sealed ampoules were heated to the appropriate temperatures in an oil. bath. Recovery of, the reaction products from solvent and in some cases, unreacted pyrazoline, was achieved by bulb - t o s b u l b distillation under re-duced pressure. The product distribution for 3-methyl-3-carbomethoxy-l-pyrazoline-4, 4- d^ (96) was obtained by recovering the products from the solution remaining after the kinetic runs. The product distributions obtained are given in Tables III--VI11. T A B L E I I I Product Compositions for the Pyrolysis of 3-Methyl-3-car borne thoxy-1-pyrazoline (95), 3-Methyl-3-carbomethoxy- 1-pyrazoline-4,4-d., (96), and 3-Methyl-3-carbomethoxy- 1-pyrazoline-5, 5-d ? (97) D 2 D 2 Sample Reaction Conditions Z\ c* s trans 117 118 2 1 Neat* at 120° 5 65 15 15 •C0 2CH 3 N e a t a t 1 2 7 o 4. 6+0.4 66. 8+0. 9 12. 2+0. 7 16.4+1.2 ^ N 127° in n-butylphthalate 4. 1+0. 5 68.9+0. 8 14.7+0. 6 12. 3+0.6 127° in formamide 2. 7+0. 3 44. 5+0. 3 15. 4+0. 3 37.4+0.3 95_ . 127° in tetralin 4.2 . 7 2 . 6 • 13.3 9.9 127° in nitrobenzene 4.4 72.5 13.0 10.1 -f~COzCU3 Neat at 127° 2. 8+0.2 77. 8+0. 6 8.9+0. 3 10. 5+0.5 N 127° in n-butylphthalate 2. 0+0. 3 78. 2+1. 2 9. 6+0. 6 10.2+0.8 y 127° in formamide 1. 5+0.2 61.0+0. 7 11. 3+0. 8 26.2+0.6 'N 96 97 -f-COzCU3 Neat at 127° 5.4+0. 3 63. 8+0. 6 14. 6+0. 5 16.2+0.5 Reference 20. - 83 -T A B L E IV Product Compositions for the Pyrolysis of 3-Methyl-3-acetyl-1-pyrazoline {42) <*,/3 Reaction Conditions A trans cis 45 46 47 48 40 Neat* at 120° 65 14 14 4 3 125° in n-butylphthalate 67 10 16 3 4 125° in formamide 45 47 8 0 0 12 3° in formamide: 6 min 44. 8 42. 3 11.4 0 1. 5 10 min 43. 8 41.9 12. 5 0 1.8 * Reference 32. T A B L E V Product Compositions fo r the Pyrolysis of 3, 5, 5-Trimethyl- 3-carbomethoxy- 1-pyrazoline (100) Reaction Conditions A 103 C I S 105 trans 104 Neat* at 90-100° 83. 8 0 16. 2 Neat at 113° 82. 6 3.0 14.4 113° in n-butylphthalate 87. 7 3.6 8. 7 113° in formamide 42. 0 6.5 51. 5 ^Reference 51; the products were distilled before analysis so that any cis- c<;(3 formed might have isomerized to the trans isomer. - 8 4 -T A B L E V I P r o d u c t C o m p o s i t i o n s f o r t h e P y r o l y s i s o f 3, 5, 5 - T r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (101) R e a c t i o n C o n d i t i o n s A T o t a l o f c i s t r a n s U n k n o w n 106 107 108 109 P r o d u c t s N e a t a t 1 0 9 ° 68 9 9 14 t r a c e 1 0 0 ° i n n - b u t y l p h t h a l a t e 6 6 . 5 9 . 5 9 . 5 9 . 8 4 . 7 1 0 0 ° i n f o r m a m i d e 1 7 . 6 6 . 8 5 . 7 6 6 . 0 3 . 9 '"' 107 i s t h e t h e r m a l r e a r r a n g e m e n t p r o d u c t o f 106 ; n o t a d i r e c t p r o d u c t f r o m p y r a z o l i n e d e c o m p o s i t i o n . T A B L E V I I P r o d u c t C o m p o s i t i o n s f o r t h e P y r o l y s i s o f c i s - a n d t r a n s - 3, 4 - D i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e s (3 a n d 4) S a m p l e R e a c t i o n C o n d i t i o n s 2 3 A CIS 2 5 t r a n s 2 4 26 CIS (3) N e a t * a t 1 5 5 - 1 6 5 ° N e a t a t 1 5 5 ° 1 5 5 ° i n n - b u t y l p h t h a l a t e 1 5 5 ° i n f o r m a m i d e 4 4 3 3 18 2 1 22 19 12 17 17 6 66 58 58 72 t r a n s N e a t * a t 155 (4) 155 i n n - b u t y l p h t h a l a t e 1 5 5 ° i n f o r m a m i d e 4 4 2 2 8 29 2 4 35 4 2 11 33 2 5 63 ' ' R e f e r e n c e 14 . - 85 -TABLE V I I I Effect of Temperature on Product Distributions for the Pyrolysis of 3-methyl- 3- carbomethoxy- 1-pyrazoline (95) Reaction Conditions Time of Pyrolysis ft* 117 A 118 cis 2 trans 1 Neat at 112° 8 hrs 4. 7 67. 0 12. 7 15. 6 Neat at 127° 3 hrs 4.6 66. 8 12.2 16.4 Neat at 157° 20 min 4. 3 70. 7 12. 6 12.4 Vapour Phase at 200° 4 85 7 4 Reference 20. There are several important features in these results. The formation of the trans cx^jS-unsaturated products is highly favoured in the polar solvent formamide. For pyrazolines _3 and 4 (Table VII) there is only one °<j^ -unsaturated product (26), but here again it is the pre-dominant product upon pyrolysis in formamide. The percentages given in Tables I I I - V I I I have not been corrected for the thermal isomeriza-tion of cis °<^ /3 -unsaturated esters or ketones to give the trans isomers. However, this isomerization is slow (even in formamide), especially for the cis ^j/S -esters. For example, when methyl angelate (_2) was heated in formamide solvent at 127° for 6 hours the recovered mixture consisted of 98. 3% methyl angelate and 1. 7% methyl tiglate (1). The cis - K6 -o ^ p - k e t o n e s a r e s o m e w h a t m o r e l a b i l e . T h u s , c i s - 3 - m e t h y l - 3 - p e n t e n -2 - o n e (47) i n f o r m a m i d e s o l v e n t a t 1 2 5 ° f o r t w o h o u r s g i v e s a m i x t u r e c o n s i s t i n g o f 8 2 . 6% c i s (47) a n d 1 7 . 4% t r a n s ( 4 6 ) . H e n c e i n f o r m a m i d e s o l v e n t t h e p r e d o m i n a n t f o r m a t i o n o f t h e t r a n s ° < ; / 3 - u n s a t u r a t e d p r o d u c t s a r i s e s a t t h e e x p e n s e o f c y c l o p r o p a n e p r o d u c t . T h e e f f e c t o f d e u t e r i u m s u b s t i t u t i o n o n p r o d u c t d i s t r i b u t i o n i s s h o w n i n T a b l e I I I . A s e x p e c t e d , d e u t e r i u m s u b s t i t u t i o n a t t h e C - 4 p o s i t i o n (96) d e c r e a s e s t h e e x t e n t o f o l e f i n f o r m a t i o n . D e u t e r i u m s u b -s t i t u t i o n a t t h e C - 5 p o s i t i o n (97) s l i g h t l y d e c r e a s e s t h e e x t e n t o f c y c l o -p r o p a n e f o r m a t i o n . T h e s e r e s u l t s w i l l b e d i s c u s s e d l a t e r i n d e t a i l i n c o n j u n c t i o n w i t h t h e k i n e t i c r e s u l t s . T a b l e I V s h o w s t h a t t h e p r o d u c t d i s t r i b u t i o n r e m a i n e d c o n s t a n t d u r i n g d i f f e r e n t e x t e n t s o f t h e p y r o l y s i s o f _42 i n f o r m a m i d e . T h e o n l y m a j o r d i f f e r e n c e f r o m c o m p l e t e p y r o l y s i s i s i n t h e c i s t o t r a n s ^j/S-u n s a t u r a t e d k e t o n e r a t i o ( 4 7 : 4 6 ) . H o w e v e r , i t w a s m e n t i o n e d a b o v e t h a t t h e c i s i s o m e r _47 i s o m e r i z e s t o t h e t r a n s i s o m e r 46 u n d e r t h e p y r o l y s i s c o n d i t i o n s . H e n c e f o r t h e s h o r t e r p y r o l y s i s t i m e s o f 6 a n d 10 m i n t h e a m o u n t o f c i s o l e f i n w i l l be 2 0 - 3 0 % g r e a t e r t h a n t h a t f o r t h e 3 h o u r p e r i o d o f p y r o l y s i s . It i s e x p e c t e d t h a t t h i s l a c k o f v a r i a t i o n o f p r o d u c t d i s t r i b u t i o n f o r d i f f e r e n t e x t e n t s o f p y r o l y s i s w i l l b e g e n e r a l f o r a l l o f t h e p y r a z o l i n e s . F r o m T a b l e V I I I , i t i s a p p a r e n t t h a t t h e t e m p e r a t u r e d o e s n o t h a v e a n y a p p r e c i a b l e e f f e c t o n t h e p r o d u c t c o m p o s i t i o n w i t h i n t h e r a n g e - 87 -of t e m p e r a t u r e studied. The t i m e s of p y r o l y s i s given i n T a b l e V I I I were t h o s ^ estimated to give complete p y r o l y s i s at the p a r t i c u l a r tem-pe r a t u r e . T h e r e i s a 3 to 4% i n c r e a s e in c yclopropane f o r m a t i o n at 157°, appearL'.g at the expense of the t r a n s °<j/S-ester _1. T h i s i s not a t e m p e r a t u r e effect but a c t u a l l y indicates that some of the p y r a z o l i n e must be decomposing i n the vapour phase at that t e m p e r a t u r e . Vapour-phase p y r o l y s i s i n c r e a s e s cyclopropane f o r m a t i o n and also d e c r e a s e s the amount of _1 r e l a t i v e to 2_ (20). The effect of going f r o m vapour phase to solution phase i s thus i n the same d i r e c t i o n as going f r o m a l e s s polar to a m o r e polar solvent. A w o r d should be s a i d c o n c e r n i n g the a c c u r a c y of the percen-tages given in T a b l e s I I I - V I I I . The analyses in this w ork are con-s i d e r e d m o r e r e l i a b l e than those p r e v i o u s l y done since a d i s c integrator was employed i n peak a r e a m e a s u r e m e n t s . In T a b l e I I I the e r r o r l i m i t s a r e given as standard deviations f o r at l e a s t four m e a s u r e m e n t s . M o r e attention was paid to e r r o r s for p y r a z o l i n e s 95 and 9_6 since r e l i a b l e pro-duct d i s t r i b u t i o n s were r e q u i r e d for the e s t i m a t i o n of isotope effects. - 88 -II - 4 DISCUSSION OF RESULTS Substituent Effects on Pyrolysis Rates and Product Distribution Previous work by Snyder (50) illustrated several important sub-stituent effects an the rates of pyrolysis of 1-pyrazolines. The rate of nitrogen evolution was increased by the substitution of a carboxyl group at position 3 by an aceto or cyano group, and by the substitution of an alkyl group at position 5. The rate of pyrolysis was decreased by substi-tution of a methyl group at position 4. No explanation was given for the above results and in some cases, the decompositions were carried out on mixtures of isomeric pyrazolines. The same results were found hi this work. However, the results are more informative since the effect of changing the stereochemistry of the substituents was also studied. To facilitate a comparison with a stan-dard pyrazoline (95), relative rates for a number of C-3 and C-5 substi-tuted pyrazolines are given in Figure XXVI. The numbers given here represent relative rates (k(pyrazoline) /k(9_5)) at 109.4° in n-butyl phthalate solvent. In order to compare the rates with pyrazoline 9_5 it was neces-sary to calculate the rate constants for 9j> and 42_ in n-butyl phthalate at 109.4°. Using the rate constants and activation parameters in Table II, -4 1 -4 the rate constants obtained are 0. 830 x 10 sec" for 95 and 1. 55 x 10 sec" 1 for 42. Thus the value of k(42)/k(95) is 1.87. N 1. 00 C 0 2 C H 3 9 5 N • C 0 2 C H 3 8. 16 N " C 0 2 C H 3 1 0 . 2 X O ? C H , 100 5 . 13 - C O C H . N 1. 87 4 2 1 6 . 4 N • C O C H . 4 3 N 2 0 . 2 C O C H . 4 4 - C O C H , 101 . 1 0 . 7 N •N 8. 8 5 • C N 9 8 1 0 9 . 4 ° i n n - b u t y l p h t h a l a t e F I G U R E X X V I - C - 3 a n d C - 5 s u b s t i t u e n t e f f e c t s o n t h e r e l a t i v e r a t e s o f p y r o l y s i s o f 1 - p y r a z o l i n e s . C h a n g i n g t h e e l e c t r o n - w i t h d r a w i n g s u b s t i t u e n t a t C - 3 h a s a l a r g e e f f e c t o n t h e r a t e o f p y r o l y s i s . T h e r a t e ' i n c r e a s e i n g o i n g f r o m 9 5 t o 42 t o 9 8 c o r r e l a t e s r o u g h l y w i t h t h e i n c r e a s i n g e l e c t r o n - w i t h d r a w i n g a b i l i t y - 90 -of the C-3 s u b s t i t u e n t (65). A l t h o u g h t h i s a p p e a r s to s u p p o r t the f o r m a -t i o n of a n e g a t i v e c h a r g e at the C-3 p o s i t i o n i n the t r a n s i t i o n state, other r e s u l t s d i s c u s s e d l a t e r i n d i c a t e that a p o l a r t r a n s i t i o n state o r pathway i s u n l i k e l y . The t w o f o l d r a t e i n c r e a s e upon s u b s t i t u t i o n of the c a r b o m e t h o x y group by an a c e t y l g r o up i s m a i n t a i n e d even upon s u b s t i t u t i o n of m e thyl(s) at the C-5 p o s i t i o n , f o r example, _5 c o m p a r e d to _43; 100 c o m p a r e d to 101. T h i s s uggests that t h e r e i s no e l e c t r o n i c G(3)-C(5) i n t e r a c t i o n i n the t r a n -s i t i o n state f o r p y r a z o l i n e p y r o l y s i s . T h e r e i s an eight to t e n f o l d r a t e i n c r e a s e upon s u b s t i t u t i o n of a m e t h y l group at the C-5 p o s i t i o n ( F i g u r e X X V I ) . C o n c u r r e n t w i t h the r a t e i n c r e a s e i s a s m a l l enthalpy of a c t i v a t i o n d e c r e a s e ( T a b l e II) i n d i c a t i n g that the C ( 5 ) - N bond i s s l i g h t l y weakened by m e t h y l s u b s t i t u t i o n at C-5. T h e r e a r e l a r g e d i f f e r e n c e s i n the p r o d i t c t d i s t r i b u t i o n s f o r the i s o m e r i c p y r a z o l i n e s , _5 and_6; _43 and 44 (15, 32). However, the s t e r e o c h e m i s t r y of the C-5 m e t h y l group has v e r y l i t t l e e f f e c t on the p y r o l y s i s r a t e s , the t r a n s i s o m e r s , 6 and 44, d e c o m p o s i n g only s l i g h t l y f a s t e r than the c i s i s o m e r s , 5 and 43. P r e s u m a b l y on a p p r o a c h i n g the t r a n s i t i o n states f o r the c i s i s o m e r s the f o l d i n g of the p y r a z o l i n e r i n g c a u s e s an i n c r e a s e i n the m e t h y l - m e t h y l no.n-bonded i n t e r a c t i o n s , m a k i n g the t r a n s i t i o n state s l i g h t l y l e s s f a v o u r a b l e and thus d e c r e a s i n g the:rate. One of the m a j o r d i f f e r e n c e s i n the p r o d u c t d i s t r i b u t i o n s f o r _43 and 44 i s that _43 g i v e s the d i h y d r o f u r a n d e r i v a t i v e 41 w h e r e a s 44 does not. In c y c l o h e x a n e at 12 5°, 41 f o r m s 3 4 % of the p r o d u c t (32).' However, the v e r y s m a l l r a t e - 91 -d i f f e r e n c e b e t w e e n 43 a n d _44 i n d i c a t e s t h a t t h e r a t e o f f o r m a t i o n o f 41 ( i f f o r m e d d u r i n g t h e l o s s o f n i t r o g e n ) m u s t b e c o m p a r a b l e t o t h e r a v e o f f o r m a t i o n o f c y c l o p r o p a n e a n d o l e f i n p r o d u c t s . S u b s t i t u t i o n o f a s e c o n d m e t h y l g r o u p a t t h e C - 5 p o s i t i o n (100 a r d 101) d e c r e a s e s t h e p y r o l y s i s r a t e b y a f a c t o r o f t w o w h e n c o m p a r e d t o t h e t r a n s p y r a z o l i n e s _6 a n d _44 ( F i g u r e X X V I ) . T h i s i n d i c a t e s t h a t r e a c h i n g t h e t r a n s i t i o n s t a t e i s m o r e s t e r i c a l l y h i n d e r e d t h a n f o r p y r a z o l i n e s w i t h a s i n g l e C - 5 m e t h y l g r o u p . S i m i l a . r s u b s t i t u e n t e f f e c t s w e r e f o u n d b y C r a w f o r d a n d M i s h r a (35) f o r t h e p y r o l y s i s o f m e t h y l s u b s t i t u t e d 1 - p y r a z o l i n e s i n t h e g a s p h a s e . P y r a -z o l i n e 124 d e c o m p o s e s s l i g h t l y f a s t e r t h a n 123 b u t t h e r a t e o f p y r o l y s i s o f 125 i s a b o u t t w i c e a s s l o w a s f o r 124. A p p a r e n t l y t h e s a m e s t e r i c e f f e c t s N = N N = N N = N 123 124 125 i n 125 a r e o p e r a t i v e i n p y r a z o l i n e s 100 a n d 101. T h e c h a n g e i n o l e f i n f o r m a t i o n w i t h s u b s t i t u t i o n o f m e t h y l g r o u p s a t t h e C - 5 p o s i t i o n i s w o r t h y o f c o m m e n t . W e s h a l l f o c u s o u r a t t e n t i o n t o t h e 3 - c a r b o m e t h o x y p y r a z o l i n e s s i n c e t h e 3 - a c e t y l p y r a z o l i n e s b e h a v e s i m i l a r l y . N e a t p h a s e p y r o l y s i s o f 3 - m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (95) g i v e s e q u a l m i x t u r e s o f c i s a n d t r a n s ^ j ^ - e s t e r s J2 a n d J . ( T a b l e I I I ) . H o w e v e r , t h e c i s - a n d t r a n s - 3 , 5 - d i m e t h y l - 3-r c a r b o m e t h o x y - 1 - p y r a z o l i n e s - 9 2 -(_5 a n d _6) each , g i v e o n l y o n e ^ P - e s t e r ( 1 5 ) , 5 g i v i n g t h e c i s c < J y S _ e s t e r (60) a n d _6 g i v i n g t h e t r a n s ^jfi-ester (59) ( F i g u r e V I I ) . I n p y r a z o l i n e 9 5 c o n f o r m a t i o n a l i n v e r s i o n o f t h e r i n g a l l o w s e i t h e r C - 4 h y d r o g e n t o m i -g r a t e t o C - 5 o n t h e s i d e o f t h e m o l e c u l e t r a n s t o t h e l e a v i n g n i t r o g e n t o g i v e b o t h o l e f i n s . P y r a z o l i n e s J5 a n d _6 p o p u l a t e t h e c o n f o r m a t i o n s 63 a n d 6 4 r e s p e c t i v e l y , w h i c h g i v e r i s e t o s t e r e o s p e c i f i c o l e f i n f o r m a t i o n . T h i s c o n f o r m a t i o n a l r i g i d i t y w a s e x p e c t e d t o b e c a r r i e d o v e r t o 3, 5, 5 - t r i m e t h y l -3 — c a r b o m e t h o x y - 1 - p y r a z o l i n e (100) b u t t h i s p y r a z o l i n e f o r m s s o m e c i s - e s t e r ( 105 ) ( T a b l e V ) . S i m i l a r l y , t h e a c e t y l a n a l o g , 1 0 1 , g i v e s a p p r o x i m a t e l y e q u a l a m o u n t s o f c i s a n d t r a n s $ - k e t o n e s ( T a b l e V I ) . T h e s e r e s u l t s i n d i c a t e t h a t t h e r e m u s t b e c o n f o r m a t i o n a l i n v e r s i o n i n t h e s e p y r a z o l i n e s t o a l l o w m i g r a t i o n o f e i t h e r C - 4 h y d r o g e n , f o r e x a m p l e : / C O z C H 3 T h e r a t e c o n s t a n t s f o u n d f o r t h e C - 4 a l k y l s u b s t i t u t e d 1 - p y r a z o -l i n e s a r e c o m p a r e d w i t h t h a t o f 3 - m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (95) i n F i g u r e X X V I I , S i n c e t h e t e m p e r a t u r e s r e q u i r e d f o r t h e p y r o l y s i s o f t h e C - 4 a l k y l p y r a z o l i n e s w e r e a b o v e t h e r a n g e f o r 9 5 , t h e r a t e f o r _9_5 i n n - b u t y l p h t h a l a t e a t 1 4 7 . 4 ° w a s e x t r a p o l a t e d f r o m t h e d a t a f o r t h e 1 0 7 -o 127 r a n g e g i v e n i n T a b l e I I . T h e r a t e c o n s t a n t o b t a i n e d i s - 9 3 -4 2 . 9 x 1 0 " 4 s e c " 1 . . V N -C0 2CH 3 9 5 4 2 . 9 ( c a l c . ) " ' C 0 2 C H 3 , 1 3 . 1 N N - C 0 2 C H 3 V 1. 5 9 C H 3 C H 2 ^ 4 N - C 0 2 C H 3 8 4 5. 6 4 C H X H A 3 2' T-CO 2CH 3 N N 1 . 0 3 8 5 1 4 7 . 4 i n n - b u t y l phthalate * 4 i 1 0 k ( s e c " 1 ) F I G U R E X X V I I - The e f f e c t of 4 - a l k y l s u b s t i t u t i o n on the r a t e s of d e c o m p o s i t i o n of 3 - c a r b o m e t h o x y -1 - p y r a z o l i n e s . F i g u r e X X V I I shows that 4 - a l k y l s u b s t i t u t i o n d e c r e a s e s the r a t e of p y r o l y s i s c o m p a r e d to 9 5 , however, the r a t e d e c r e a s e depends not o n l y on the s i z e of the a l k y l group but a l s o on the s t e r e o c h e m i s t r y of the sub-s t i t u e n t s on the r i n g . S i n c e p y r a z o l i n e 3 g i v e s about 7 0 % t o t a l o l e f i n - 94 -(23 and 26), ( T a b l e VII) and p y r a z o l i i e 84_ gi v e s about 6 0 % t o t a l o l e f i n ( F i g u r e X I I I ) , the t r a n s i t i o n states m u s t r e s e m b l e 126 w h e r e the C-4 h y d r o g e n t r a n s to the l e a v i n g n i t r o g e n m i g r a t e s to e i t h e r C-3 o r C-5 ( m a i n l y to C-5). In 126 the C-4 a l k y l g r o ^ p i s c i s to the l e a v i n g n i t r o g e n 126 and thus the d e c r e a s e d r a t e s f o r the c i s p y r a z o l i n e s , _3 and 84, may be at-t r i b u t e d to s t e r i c c o m p r e s s i o n i n the t r a n s i t i o n s t a t e . The f a c t that the r a t e of p y r o l y s i s of _84 i s 2. 3 t i m e s s l o w e r than _3 s u p p o r t s t h i s a rgument s i n c e the C-4 e t h y l group i n _84 i s s l i g h t l y b u l k i e r than the C-4 m e t h y l g roup i n _3. It i s not c l e a r why the r a t e s of p y r o l y s i s of the t r a n s p y r a z o l i n e s , j4.and_8J>, a r e so m u c h l o w e r than the c i s p y r a z o l i n e s , _3 and 84. S i n c e the t r a n s p y r a z o l i n e s give l e s s o l e f i n , 1 7 % from_85 ( F i g u r e X I I I ) and 3 7 % f r o m 4 ( T a b l e V I I ) , a t r a n s i t i o n state r e s e m b l i n g 126 a p p e a r s to be l e s s i m p o r t a n t . Indeed, i f the m a j o r t r a n s i t i o n state f o r p y r o l y s i s r e s e m b l e d 127 we m i g h t even expect the r a t e s f o r 4 and 8_5 to be g r e a t e r t han f o r _3 and _8_4 s i n c e t h e r e w o u l d not be the same s t e r i c c o m p r e s s i o n due to an - 95 -alkyl group cis to the leaving nitrogen. Y " W C H \ ~ * N Y = - C H 3 ' - C H 2 C H 3 C . 0 2 C H 3 127 Obviously, steric factors greatly influence the pyrolysis reaction and must be accounted for in a complete mechanistic description. The Transition State for Pyrazoline Pyrolysis •i) Effect of Deuterium Substitution at C-5 The description of the transition state for the pyrazoline pyrolysis must begin with a discussion on the degree of breaking of the carbon-nitro-gen bonds. In particular, does one carbon-nitrogen bond break before the other to give a nitrogen containing intermediate, for example, 128—• 129; ^ C Q 2 C H 3 ^ C O z C H . 3 R — " / N R-N / ^ N 2 I-I i+i 128 129 or, is there simultaneous rupture of both carbon-nitrogen bonds as found by Crawford and workers? Seltzer has made a detailed study of the pyrolysis of acyclic azo - 96 -compounds. K i n e t i c s t u d i e s on the p y r o l y s i s of azobis-c*-phenylethane (130) (66), .cX-phenylethylazo-2-propane (131). (40), cx-phenylethylazome-thane (132) (67), and t h e i r ex.-deuterium d e r i v a t i v e s have shown that f o r 130 both c a r b o n - n i t r o g e n bonds a r e b r e a k i n g e q u a l l y i n the t r a n s i t i o n state, f o r 131 both c a r b o n - n i t r o g e n bonds a r e b r e a k i n g s i m u l t a n e o u s l y but to a d i f f e r e n t degree, and f o r 132 on l y the <X-phenylethyl c a r b o n -n i t r o g e n bond i s b r e a k i n g i n the t r a n s i t i o n state. T h e s e r e s u l t s have been r e c e n t l y c o r r e l a t e d w i t h p r i m a r y n i t r o g e n i s o t o p e e f f e c t s (97). H 3 C X / C H 3 H 3 C ^ / C H 3 H .CH-N^N-CH / C H - N = N - C H / C H - N = N > C H , V 0 0 ^ C H 3 if 5 130 131 132 It was suggested (15): that the c y c l i c azo compounds m i g h t behave i n a s i m i l a r m a nner. Thus the u n s y m m e t r i c a l 1 - p y r a z o l i n e s w o u l d be exp e c t e d to behave somewhat l i k e 131 and 132. However, the C-3 and C-5 s u b s t i t u t i o n e f f e c t s on the p y r o l y s i s r a t e s , d i s c u s s e d above, s t r o n g l y suggest that both C-N bonds a r e b r e a k i n g i n the t r a n s i t i o n state. S e l t z e r r e p o r t e d that the s e c o n d a r y o(.-deuterium i s o t o p e e f f e c t i n the r a d i c a l d e c o m p o s i t i o n of azobis-<x-phenylethane- cA^c^-d^ i n e t h y l b e n -zene at 105° i s k /k = 1.27 (66). S i n c e t h i s e f fect i s a p p r o x i m a t e l y H D t w i c e as l a r g e as those e n c o u n t e r e d i n other " u n i m o l e c u l a r " r e a c t i o n s , i t was t a k e n as evi d e n c e f o r both C-N bonds b r e a k i n g s i m u l t a n e o u s l y i n the t r a n s i t i o n state of the r a t e - c o n t r o l l i n g step. - 97 -H 3 C C H 3 H 3 C C H 3 . I . slow . i 0— C - N = N - C — 0 * 0 — C - - - N = N - - - C — 0 I I I | H ( D ) H(D) H(D) . H(D) A c o m p i l a t i o n of s e c o n d a r y <x-deuterium i s o t o p e e f f e c t s f o r r e a c t i o n s w h i c h i n v o l v e a r a t e - c o n t r o l l i n g u n i m o l e c u l a r bond s c i s s i o n showed that the avera.ge v a l u e was 1. 12 at 105° (66). T h i s v a l u e i s f o r one d e u t e r i u m a t o m at the r e a c t i o n c e n t e r . If two atoms of d e u t e r i u m a r e at the r e a c -t i o n c e n t e r the e f f e c t i s about t w i c e as l a r g e . F o r example, f o r the a c e t o l y s i s of b e n z y l - o c - d 2 - t o s y l a t e (133) the o v e r a l l i s o t o p e e f f e c t at 105° i s about 1. 20. C 6 H 5 C D 2 O T o s ^ C 6 H 5 C D 2 O T o s 133 F o r C-5 d e u t e r i u m s u b s t i t u t e d p y r a z o l i n e s a v a l u e of k ^ / k ^ = 1. 24 w o u l d be exp e c t e d i f the C ( 5 ) - N bond was being c l e a v e d i n the t r a n s i -t i o n state. T h e r a t e c o n s t a n t s o b t a i n e d f o r two C-5 d e u t e r i u m s u b s t i t u t e d 1 - p y r a z o l i n e s , 97 and 99» a r e g i v e n i n T a b l e I L along w i t h the r a t e con-stants f o r the n a t u r a l compounds, -95 and 98 r e s p e c t i v e l y . - 9 8 -"T-.CO CH I T~CO CH } 23 ° 2C72 3N NT 9 5 9 7 o I n n - b u t y l p h t h a l a t e at 127 : = k (95) / k ( 9 7 ) = 5 . 6 3 / 4 . 62 = 1. 22 +0. 0 5 I n f o r m a m i d e a t 1 2 7 ° : k H / k D = k (95) / k (_97). = 2 . 5 4 / 2 . 17 = 1. 17 +0. 0 5 ~Y~CN ( T;*CN 98 99 I n n - b u t y l p h t h a l a t e a t 1 0 9 . 4 ° : k H / k D = k {98) / k ( 9 9 ) = 7 . 3 4 / 5 . 9 5 = 1. 2 3 +0 . 0 5 T h e a b o v e s e c o n d a r y c x ~ d e u t e r i u m i s o t o p e e f f e c t s c o r r e s p o n d t o a t r a n s i -t i o n s t a t e w h e r e t h e C ( 5 ) - N b o n d i s b r e a k i n g . C o u p l e d w i t h t h e C - 3 s u b -s t i t u e n t e f f e c t s i t i s b b v i o \ x s t h a t t r a n s i t i o n s t a t e s o r i n t e r m e d i a t e s r e s e m -b l i n g _1_29_ a r e n o t f o r m e d . T h e s e c o n d a r y f X - d e u t e r i u m i s o t o p e e f f e c t i n f o r m a m i d e s o l v e n t , a l t h o u g h s l i g h t l y s m a l l e r t h a n t h e v a l u e s i n t h e l e s s p o l a r n - b u t y l p h t h a l a t e , i n d i c a t e s a c o n s i d e r a b l e d e g r e e o f C ( 5 ) - N b o n d b r e a k a g e i n t h e t r a n s i t i o n s t a t e d e s p i t e t h e f a c t t h a t a n i n t e r m e d i a t e s u c h a s 1 29 w o u l d b e f a v o u r e d i n a p o l a r s o l v e n t . C r a w f o r d ' s g r o u p f o u n d s i m i l a r s e c o n d a r y k i n e t i c i s o t o p e e f f e c t s - 99 -for a number of oC-deuterated 1-pyrazolines (34, 38, 68). For example, k^/k-p = 1. 55 (corrected to 105°) for the pyrolysis of 1-pyrazoline-3, 3, 5, 5-d 4 (134) (68). N=N 134 This large effect is expected if both carbon-nitrogen bonds are undergoing simultaneous cleavage in the transition state. The effect of o%- deuterium substitution on the product distribution is small. Table I I I shows that the neat pyrolysis of 97 at 127° gives a slightly smaller amount of cyclopropane than for the pyrolysis of the natural compound 95. If the C-5 deuterium substitution affects the C-4 to C-5 hydrogen transfer we would expect a change in the amount of ester products (2^and_l). A slight increase is observed. However, there is also a small increase in the amount of /^V-ester (117). This involves a C-4 to C-3 hydrogen transfer, which should not be affected by C-5 deu-terium substitution. These factors suggest that the effect of deuterium substitution at C-5 is to slightly decrease the rate of cyclopropane for-mation. ii) Solvent Effects on Pyrolysis Rates Solvent effects, on decomposition rates should yield information - 100 -on the p o l a r i t y of the t r a n s i t i o n state c o m p a r e d to the s t a r t i n g compound, A p r e l i m i n a r y study (15) of s o l v e n t e f f e c t s on the p y r o l y s i s of c i s - and trans-3, 5-dimethyl-3-carbomethoxy- 1-pyrazolines (_5 and _6) showed that the p o l a r i t y of the s o l v e n t has l i t t l e e f f e c t c n the r a t e of decomposition,, T h e h a l f - l i f e f o r the t h e r m a l d e c o m p o s i t i o n of a m i x t u r e of 5 and 6 was found to i n c r e a s e s l i g h t l y w i t h an i n c r e a s e i n s o l v e n t p o l a r i t y , f o r example, the r a t e i n t e t r a l i n was about 3 t i m e s the r a t e i n f o r m a m i d e . S i m i l a r s o l v e n t e f f e c t s on s i m i l a r p y r a z o l i n e s have been o b s e r v e d i n the k i n e t i c s t u d i e s r e p o r t e d h e r e . T h e r a t e of p y r o l y s i s of 3-methyl-3-carbo-m e t h o x y - 1 - p y r a z o l i n e (95) d e c r e a s e s upon going f r o m t e t r a l i n s o l v e n t to f o r m a m i d e s o l v e n t ( T a b l e I I ) , the r a t e i n t e t r a l i n (at 127.0°) i s about 3 t i m e s the r a t e i n f o r m a m i d e . R a t e s i n n - b u t y l phthalate and f o r m a m i d e w e r e c o m p a r e d f o r other p y r a z o l i n e s ( T a b l e I I ) . F o r 3-methyl-3-cyano-1-pyrazoline (98) and 3, 5, 5 -trimethyl-3-carbomethoxy-1-pyrazoline (100) t h e r e i s a s m a l l ( l e s s than twofold) r a t e d e c r e a s e upon going to the m o r e p o l a r s o l v e n t . P e r h a p s s u r p r i s i n g l y , f o r the 3-acetyl p y r a z o l i n e s , 42 and 101, t h e r e i s a r a t e i n c r e a s e upon going f r o m n - b u t y l phthalate to f o r m a m i d e . However, the e f f e c t i s s t i l l s m a l l and m a y r e f l e c t some f o r m of i n t e r a c t i o n of the s o l v e n t w i t h the c a r b o n y l m o i e t y . The l o w e r v a l u e s of A H ^ and AS^ i n f o r m a m i d e f o r 42 and 101 support t h i s . T h e i m p o r t a n t f e a t u r e i s that w h i l e the p r o d u c t d i s t r i b u t i o n s a r e s e v e r e l y changed upon going f r o m n - b u t y l phthalate to f o r m a m i d e - - a d r a s t i c p o l a r i t y m e r ease -- t h e r e a r e only s m a l l e f f e c t s on the p y r o l y s i s - 101 -r a t e s . T h i s suggests that t h e r e i s l i t t l e o r no development of c h a r g e i n the t r a n s i t i o n s tates f o r p y r o l y s i s of the p y r a z o l i n e s i n T a b l e I. However, ther« m i g h t be s u f f i c i e n t p o l a r i t y d evelopment in the m o l e c u l e a f t e r the t r a n s i t i o n state to make the p r o d u c t s s e n s i t i v e to the so l v e n t used. T h i c c a n e x p l a i n the p r e d o m i n a n t f o r m a t i o n of otfe-unsaturated e s t e r and ketone p r o d u c t s i n f o r m a m i d e s o l u t i o n . A l d e r and L e f f l e r (69) s t u d i e d the e f f e c t of s o l v e n t on the r a d i c a l d e c o m p o s i t i o n of p h e n y l a z o t r i p h e n y l m e t h a n e . T h e s m a l l e f f e c t on the r a t e s w as a t t r i b u t e d to l a r g e but c o m p e n s a t i n g changes i n enthalpy and e n t r o p y of a c t i v a t i o n . T h e y c o n c l u d e d t h e r e f o r e that the i n s e n s i t i v i t y of the r a t e t o changes i n s o l v e n t i s not n e c e s s a r i l y due to the absence of s t r o n g i n t e r -a c t i o n s between the s o l v e n t and e i t h e r the s t a r t i n g o r t r a n s i t i o n s t a t e s . T h e r e s u l t s f o r p y r a z o l i n e d e c o m p o s i t i o n s found h e r e a r e s i m i l a r and may i n d i c a t e some f r e e r a d i c a l d e velopment i n the t r a n s i t i o n state. In the absence of l a r g e i n t e r a c t i o n s w i t h the solvent, i t i s ex-pect e d that the r a t e of an u n i m o l e c u l a r d e c o m p o s i t i o n i n the gas phase w i l l be v e r y l i t t l e d i f f e r e n t f r o m the r a t e i n s o l u t i o n (70). The gas-phase p y r o l y s i s of 3 - v i n y l - 1 - p y r a z o l i n e (55) h a s been s t u d i e d by C r a w f o r d and C a m e r o n (34). The r a t e constant at 128.0° i s 9. 11 x 1 0 " 4 s e c " 1 . P y r a -z o l i n e _55 was p y r o l y z e d i n n - b u t y l phthalate s o l v e n t and the r a t e constant at 128. 1° was found to be 4. 16 x 1 0 " 4 s e c " 1 ( T a b l e I I ) . T he decompo-s i t i o n i s 2. 2 t i m e s f a s t e r i n the gas phase. A p p a r e n t l y t h e r e i s l i t t l e d i f -f e r e n c e i n the m e c h a n i s m of the gas-phase and the l i q u i d - p h a s e p y r o l y s i s - 102 -of 55. The e f f e c t of phase change on the r a t e of p y r o l y s i s of _55 i s of the same o r d e r as found i n the change f r o m n o n p o l a r to h i g h l y p o l a r s o l v e n t s f o r the 3-carbomethoxy and 3-cyano- 1 - p y r a z o l i n e s . T h e r e f o r e , t h e r e m u s t be some s i m i l a r i t y between C r a w f o r d ' s t r i m e t h y l e n e m e c h a n i s m and the m e c h a n i s m f o r the p y r a z o l i n e s s t u d i e d h e r e . L i k e l y m o s t of t h i s s i m i -l a r i t y i s the l a c k of c h a r g e d e v e l o p m e n t on C-3 and C-5 i n the t r a n s i t i o n s t a t e s . The t r i m e t h y l e n e i n t e r m e d i a t e pathway was d i s c o u n t e d f o r the 3- ' c a r b o m e t h o x y and 3 - a c e t y l p y r a z o l i n e s f o r the r e a s o n s d i s c u s s e d i n the I n t r o d u c t i o n . T h e a l t e r n a t e pathway i s the c o n c e r t e d o r m o l e c u l a r de-c o m p o s i t i o n , p r e v i o u s l y s u g g ested by M c G r e e r (15,43). . H e r e , s e p a r a t e pathways a r e c o n s i d e r e d f o r o l e f i n and c y c l o p r o p a n e f o r m a t i o n . A g a i n , a c o n c e r t e d p r o c e s s w o u l d be e x p e c t e d to show l i t t l e s o l v e n t effect on the r a t e (7, 8, 71). H owever, i n t e r a c t i o n s w i t h the solvent, a f t e r c a r b o n -n i t r o g e n bond b r e a k a g e i s advanced, c o u l d a f f e c t the p r o d u c t d i s t r i b u t i o n . i i i ) E f f e c t of D e u t e r i u m S u b s t i t u t i o n at C-4 In the l i t e r a t u r e t h e r e a r e s e v e r a l e x a m p l e s of n o n p o l a r r e a c t i o n s i n v o l v i n g c a r b o n - c a r b o n bond c l e a v a g e i n w h i c h the bond c l e a v a g e i s sug-g e s t e d to be a s s i s t e d by p a r t i a l h y d r o g e n bonding, o r even by a l k y l bonding or p a r t i c i p a t i o n . S t e e l et_a]_. (72) s t u d i e d the i s o m e r i z a t i o n of s m a l l - r i n g compounds to o l e f i n s i n o r d e r to d e t e r m i n e i f the p r o c e s s was c o n c e r t e d o r s t e p w i s e . The i s o m e r i z a t i o n of b i c y c l o [2. l . O J pentane (135) to c y c l o p e n t e n e ( m a j o r product) and 1, 4-pentadiene ( m i n o r product) was - 103 -suggested to be a s t e p w i s e p r o c e s s s i n c e the a c t i v a t i o n e n e r g i e s found f o r each r e a c t i o n a r e not l e s s t h an the c a r b o n - c a r b o n bond d i s s o c i a t i o n energy. T h us the t r a n s i t i o n state 136 w h e r e c a r b o n - c a r b o n bond c l e a v a g e i s as-s i s t e d by the c o n c e r t e d m i g r a t i o n of a m e t h y l e n e h y d r o g e n was c o n s i d e r e d u n l i k e l y . T h i s i s i n c o n t r a s t w i t h the e a r l i e r r e p o r t of H a l b e r s t a d t and G h e s i c k (98) w h e r e a c o n c e r t e d m e c h a n i s m was suggested f o r the p y r o -l y s i s of 135. c o m p a r e d by L a n g r i s h and P r i t c h a r d (73). D e s p i t e the f a c t that h y d r o g e n s do not t r a n s f e r i n the r e a c t i o n , B l a d e s (74) has suggested that the k i n e t i c i s o t o p e e f f e c t found f o r the c y c l o b u t a n e p y r o l y s i s i n d i c a t e s "a t r a n s i t i o n state i n w h i c h the c a r b o n - c a r b o n bond s p l i t i s a s s i s t e d by the p a r t i a l bon-ding of one h y d r o g e n to i t s n e i g h b o u r i n g c a r b o n atom". In the same paper, B l a d e s r e p o r t e d the h y d r o g e n i s o t o p e effect i n the p y r o l y s i s of c y c l o p r o -pane and c y c l o p r o p a n e - d ^ . The h i g h p r e s s u r e v a l u e of k p r / k . ^ was 1. 98 o at 482 . A n argument .was put f o r w a r d to support an a c t i v a t e d c o m p l e x 137 136 The r a t e s of p y r o l y s i s of c y c l o b u t a n e and c y c l o b u t a n e - d w e r e - 1 0 4 -i n w h i c h o n e o f t h e h y d r o g e n s i s w e a k l y b o n d e d t o i t s o r i g i n a l c a r b o n a t o m a n d t o i t s u l t i m a t e a c c e p t o r . I f t h e h y d r o g e n i s b r i d g e d b e t w e e n t h e t w o 137 c a r b o n a t o m s a s i n 137 s o a s t o p r o v i d e a s s i s t a n c e t o t h e C - C b o n d r u p -t u r e , t h e n a c o n t i n u i n g o n t o t h e s e c o n d c a r b o n w i l l l e a d t o p r o p e n e a s s h o w n a b o v e . T h e t r a n s i t i o n s t a t e 137 w a s f o u n d t o b e c o n s i s t e n t w i t h t h e r e -s u l t s o b t a i n e d b y S e t s e r a n d R a b i n o v i t c h ( 7 5 ) f o r t h e t h e r m a l u n i m o l e c u l a r i s o m e r i z a t i o n o f m e t h y l c y c l o p r o p a n e ( 1 3 8 ) . T h e s t r u c t u r a l i s o m e r i z a t i o n o f m e t h y l c y c l o p r o p a n e f o l l o w s t h e k i n e t i c s c h e m e C H b 138 T h e o v e r a l l r a t e c o n s t a n t , k g , f o r m e t h y l c y c l o p r o p a n e i s o m e r i z a t i o n i s t h e s u m o f t h e i n d i v i d u a l b u t e n e f o r m a t i o n r a t e s a n d w a s d e t e r m i n e d b y t h e r a t e o f d i s a p p e a r a n c e o f m e t h y l c y c l o p r o p a n e . I n t e r m o l e c u l a r i s o t o p e e f f e c t s w e r e o b t a i n e d b y a c o m p a r i s o n o f t h e c o r r e s p o n d i n g r a t e c o n s t a n t s k i " i s o b u t e n e ( a - p - b s h i f t ) -> t r a n s - 2 - b u t e n e ( b - » b s h i f t ) k c > c i s - 2 - b u t e n e (b— >b s h i f t ) k b -fr- 1 - b u t e n e ( b - s - a s h i f t ) - 105 -( i n d i c a t e d b y p r i m e s ) f o u n d f o r m e t h / l c y c l o p r o p a n e - d _ (1 39) . a 139 T h e o v e r a l l i n t e r m o l e c u l a r i s o t o p e e f f e c t , k g / k ' s , w a s 1. 3 6 . T h e c o r -r e c t e d i n t e r m o l e c \ T l a r i s o t o p i c r a t i o s f o r 1 - b u t e n e a n d 2 - b u t e n e f o r m a t i o n a r e k t j r / k ' ' t D = l - 5 9 > k c H . / k ' c D = l ' 4 1 » o r a n a v e r a g e o f 1. 50 , a n d k ^ / k ^ E , = 2 . 3 6 . S e t s e r a r id R a b i n o v i t c h s u g g e s t e d t h a t s i n c e t h e s e r a t i o s a r e l a r g e l y p r i m a r y , i n t h e a c t i v a t e d c o m p l e x e s f o r s t r u c t u r a l i s o m e r i z a t i o n t o 1 - b u t e n e a n d 2 - b u t e n e t h e b r e a k i n g o f t h e m i g r a t i n g C - D b o n d m u s t p l a y a n i m p o i - t a n t r o l e . T h e a u t h o r s f u r t h e r i n d i c a t e t h a t a t r a n s i t i o n s t a t e s u c h a s 137 w h e r e o n e C - C b o n d i s c o m p l e t e l y o r v i r t u a l l y b r o k e n a n d a n H i s b o n d e d b e t w e e n t w o c a r b o n a t o m s i s c o n s i s t e n t w i t h t h e i r o b s e r v a t i o n s . I s o t o p i c l a b e l l i n g t o d i s t i n g u i s h b e t w e e n a t w o - s t e p o r c o n c e r t e d m e c h a n i s m h a s b e e n a p p l i e d t o t h e C u r t i u s , H o f m a n n , a n d L o s s e n r e a r -r a n g e m e n t s ( 7 6 ) . L a r g e c a r b o n - 1 4 k i n e t i c i s o t o p e e f f e c t s i n d i c a t e s t h a t m i g r a t i o n o f t h e r e a r r a n g i n g g r o u p i s c o n c e r t e d w i t h r u p t u r e o f t h e n i t r o g e n - X b o n d ( 1 4 0 ) , w h e r e X i s m o l e c u l a r n i t r o g e n f o r t h e C u r t i u s r e a r -r a n g e m e n t . - 106 -O II / ~ \ \ - + s l o w + R ^ N - N = N » N , + R - N - C = O « - > R - N = C = O U 2 140 T o s u m m a r i z e , t h e r e a r e a m p l e r e s u l t s i n t h e l i t e r a t u r e w i t h ' w h i c h t h e r e s u l t s f o u n d f o r t h e C - 4 d e u t e r a t e d p y r a z o l i n e _9_6 c a n b e c o m -p a r e d . T h e r e s u l t s o b t a i n e d f o r t h e p y r o l y s i s o f 96 i n t h e l o w p o l a r i t y -s o l v e n t , n - b u t y l p h t h a l a t e , w i l l b e d i s c u s s e d f i r s t . I n t h i s s o l v e n t t h e o v e r a l l d e u t e r i u m k i n e t i c i s o t o p e e f f e c t , k p ^ / k p j - ) (k (95) / k ( 9 6 ) i n n - b u t y l p h t h a l a t e ) , i s c a l c u l a t e d t o b e 1. 36 _+ 0 . 0 6 . k p H / k p D = 5 . 6 3 / 4 . 15 = 1. 36 + 0.06 H e r e , k p j j i s t h e r a t e c o n s t a n t f o r p y r o l y s i s o f t h e n a t u r a l c o m p o u n d 95 a n d k p j j i s t h e r a t e c o n s t a n t f o r t h e d e u t e r a t e d c o m p o u n d 9 6 . T h e e f f e c t o f C - 4 d e u t e r i u m s u b s t i t u t i o n o n t h e p r o d u c t d i s t r i b u -t i o n i s s h o w n i n T a b l e I I I . C y c l o p r o p a n e f o r m a t i o n r i s e s t o 7 8 . 2 % d u e t o t h e d e c r e a s e i n f o r m a t i o n o f t h e o l e f i n p r o d u c t s 117 , 2, a n d _1. T h e r e a r e s e v e r a l p o i n t s a b o u t t h e m a g n i t u d e o f k p j ^ / k p - Q w h i c h s h o u l d b e m e n t i o n e d . T h e m a g n i t u d e o f t h e e f f e c t i s s i m i l a r t o t h a t f o u n d b y S e t s e r a n d R a b i n o v i t c h (75) f o r t h e s t r u c t u r a l i s o m e r i z a t i o n o f m e t h y l -c y c l o p r o p a n e a n d m e t h y l c y c l o p r o p a n e - d ^ w h e r e a s i m i l a r n u m b e r o f d i f -f e r e n t p r o d u c t s a r e f o r m e d . T h e v a l u e o f k p ^ / k p j ) i s l a r g e r t h a n t h a t - 107 -found by Crawford and coworkers (35, 39, 68) for a number of C-4 deu-terium substituted pyrazolines (Figure X X V I I I ) . (D)H C H 3 H(D) (D)H H (D)H H(D) C H 3 N=N N=N N=N N=N k H / k D = 1.07. _ k H / k D = 1.07 k H / k D = 1.05 k H / k D = 1.12. (35) (39) (68) (68) FIGURE X X V I I I - Kinetic deuterium isotope effects in the pyrolysis of 1-pyrazolines. Seltzer and Hamilton (77) have determined the secondary y3-deuterium isotope effect in the thermal decomposition of azobis-oV-phenylethane (130). ¥ ¥ ¥ ¥ 0— C-N=N-C — 0 0—C-N=N-C — 0 C H 3 C H 3 C D 3 C D 3 130 A comparison of the rates of thermal decomposition of the azo-d^ and the azo-d^ compound gave a value of k^/k^ = 1. 018 per D atom. It is ap-parent that the larger overall kinetic isotope effect found for 96 cannot be mainly secondary in nature. While the value of kpj-[/ kpyj * s smaller than what might be expected - 108 -f o r a p r i m a r y i s o t o p e e f f e c t , s a y c l o s e t o 2, T a b l e I I I s h o w s t h a t c n l y 2 0 t o 3 0 % o l e f i n i s f o r m e d . T h u s i f t h e h y d r o g e n m i g r a t i o n c o n c e r t e d w : t h n i t r o g e n l o s s i s o n l y a f f e c t i n g t h e o l e f i n f o r m a t i o n t h e d e u t e r i u m e f f e c t o n t h e o v e r a l l r ,a te o f p y r o l y s i s w i l l b e f a i r l y s m a l l . T h e o b s e r v e d o v e r a l l i s o t o p e e f f e c t a n d t h e p r o d u c t d i s t r i b u t i o n s a r e u s e d b e l o w t o s h o w t h a t c y c l o p r o p a n e a n d o l e f i n f o r m a t i o n c a n o c c u r b y s e p a r a t e p a t h w a y s . T h e s e p a r a t e p a t h w a y a p p r o a c h c y c l o p r o p a n e f-~ - N , •N f N C 0 2 C H 3 9 5 H . 96 D 2 g i v e s r i s e t o t h e k i n e t i c s c h e m e -c» o l e f i n s k = k + k p H o H c H . . 5 k p D = k o D + k c D ... 6 w h e r e a n d k ^ a r e t h e o b s e r v e d r a t e c o n s t a n t s f o r t h e p y r o l y s i s o f _95 a n d 9j> r e s p e c t i v e l y ; k Q - Q a n d a r e t h e r a t e c o n s t a n t s f o r o l e f i n f o r m a t i o n a n d c y c l o p r o p a n e f o r m a t i o n , r e s p e c t i v e l y , f r o m t h e n a t u r a l p y r a z o l i n e 9 5 ; a n d k a n d k _ a r e t h e r a t e c o n s t a n t s f o r C J •.— o D c D o l e f i n f o r m a t i o n a n d c y c l o p r o p a n e f o r m a t i o n , r e s p e c t i v e l y , f r o m t h e d e u t e r a t e d p y r a z o l i n e 9_6. R e a r r a n g e m e n t o f e q u a t i o n s 5 - 109 -and _6 a r d s u b s t i t u t i o n of the o b s e r v e d p r o d u c t r a t i o s into t h e s e equations g i v e s k p H / k o H = 1 + ( k c H / k o r j ) = 1 + (68.9/31.1) = 3.215 k p D / k o D = 1 + ( k c D / k o D ) = 1 + (78. 2/21. 8) = 4. 587 T h u s ( k p H k o D ) / ( k p D k o H ) = 0.7009 B u t t h i s i s e q u i v a l e n t to ( k p H / k p D ) ( k o D / k o H ) = 0 ' 7 0 0 9 S u b s t i t u t i n g the o b s e r v e d v a l u e f o r k T T / k „ w e o b t a i n to p H pD k o D / k o H = 0. 7009/1. 36 = 0. 515 T h e r e f o r e k o H / k o D = X ' 9 4 ± 0 ' 1 0 T h e d e u t e r i u m i s o t o p e effect, k Q^. / k ^ - 1. 94, on the o l e f i n f o r m i n g r e a c t i o n i s l a r g e l y p r i m a r y . T h e r e w i l l be a s m a l l s e c o n d a r y i s o t o p e e f f e c t due to the C-4 d e u t e r i u m a t om w h i c h does not m i g r a t e f o r a p a r t i -c u l a r o l e f i n f o r m a t i o n but t h i s e f f e c t i s e x p e c t e d to be s m a l l ( <5%) (49). The above c a l c u l a t i o n s d i d not account f o r the f a c t that t h e r e a r e two deu-t e r i u m a toms on C-4. However, a s t a t i s t i c a l c o r r e c t i v e f a c t o r i s not n e c e s s a r y s i n c e f o r ^ p ' - e s t e r f o r m a t i o n o n l y m i g r a t i o n of that C-4 h y d r o g e n w h i c h i s t r a n s to the l e a v i n g n i t r o g e n w i l l g i v e r i s e to the c o r r e c t - 110 -o l e f i n p r o d u c t . T h e magnitude of ^  j^/k p ^ s c o m p a r a b l e to the v a l u e s g i v e n e a r l i e r f o r c y c l o p r o p a n e p y r o l y s i s and thus s u p p o r t s the e a r l i e r sugges-t i o n s (15, 43) that i n the t r a n s i t i o n state f o r o l e f i n f o r m a t i o n the b r e a k a g e of the C ( 4 ) - h y d r o g e n bond p l a y s an i m p o r t a n t r o l e . S i n c e i t was shown above that c a r b o n - n i t r o g e n b r e a k a g e i s als o , i m p o r t a n t i n the t r a n s i t i o n state, the b r e a k a g e of the c a r b o n - h y d r o g e n bond m u s t be c o n c e r t e d w i t h the b r e a k a g e of the c a r b o n - n i t r o g e n bond. In t h i s way, p a r t i a l bonding of the m i g r a t i n g h y d r o g e n to the C-5 p o s i t i o n can a s s i s t i n the c a r b o n -n i t r o g e n bond c l e a v a g e . The m o s t p r o b a b l e t r a n s i t i o n states a r e shown i n F i g u r e X X I X . H H F I G U R E X X I X - T r a n s i t i o n s tates f o r o l e f i n f o r m a t i o n . - I l l -A s o m e w h a t s i m i l a r i s o t o p e e f f e c t w a s f o u n d b y W i n s t e i n a n d T a k a h a s h i (78) i n t h e a c e t o l y s i s o f 3 - m e t h y l - 2 - b u t y l p - t o l u e n e s u l f o n a t e ( 1 4 1 ) . T h e y r e p o r t e d t h a t /S - d e u t e r a t . ' o n r e t a r d s t h e r a t e o f t h e s o l v o -l y s i s b y m o r e t h a n a f a c t o r o f t w o . T h u s t h e r e a p p e a r s t o b e a s s i s t a n c e H (D) H C . I . C I T H C v / + \ / C H 3 \ 1 / 3 3 \ / \ / 3 (-) ,C—C * s> 3 , C —cC + O T o s H 3 C I H H C H O T o s 141 t o s o l v o l y s i s b y / S - h y d r o g e n m i g r a t i o n . A c r i t i c a l c o m p a r i s o n w i t h t h e p y r a . z o l i n e s y s t e m i s d i f f i c u l t b e c a u s e o f t h e d i f f e r e n c e s i n t h e t w o r e a c -t i o n s y s t e m s . H o w e v e r , t h e a u t h o r s a b o v e e s t i m a t e d t h a t t h e r a t i o o f k^ /k ( w h e r e k A i s t h e r a t e c o n s t a n t f o r a n c h i m e r i c a l l y a s s i s t e d s o l -v o l y s i s a n d k g i s t h e r a t e c o n s t a n t f o r a n c h i m e r i c a l l y u n a s s i s t e d s o l -v o l y s i s ) i s a b o u t 6 f o r t h e n a t u r a l c o m p o u n d a n d a b o u t 3 f o r t h e d e u t e r a t e d c o m p o u n d . W e c a n c o m p a r e t h e s e v a l u e s t o ^ 0 j j / ^ c f j = 0 . 4 5 1 a n d / k = 0 . 2 7 9 f o u n d f o r p y r a z o l i n e s 9 5 a n d 96 r e s p e c t i v e l y . T h u s , o D ' c D — ~ -i n t h e a b o v e s o l v o l y s i s r e a c t i o n /3 - h y d r o g e n p a r t i c i p a t i o n o c c u r s t o a g r e a t e r e x t e n t t h a n i n t h e p y r a z o l i n e s y s t e m . T h i s c a n a c c o u n t f o r t h e m u c h l a r g e r r a t e r e t a r d a t i o n u p o n /3 - d e u t e r a t i o n . S o m e i n f o r m a t i o n a b o u t t h e c y c l o p r o p a n e f o r m i n g r e a c t i o n i s o b t a i n e d b y u s i n g e q u a t i o n s 5_ a n d _6. A g a i n , r e a r r a n g e m e n t o f t h e s e e q u a t i o n s a n d s u b s t i t u t i o n o f t h e o b s e r v e d p r o d u c t r a t i o s g i v e s - 112 -kP H / k c H = 1 + < k oH / k cH> = 1 + ( 3 L 1/68. 9) = 1.451 k p D / k c D = 1 + ^ o D ^ c D 1 = 1 + (21-8/78. 2) = 1.279 Thus ( k P h k c D ) / ( k P D k c H ^ = 1 ' 1 3 5 T h i s i s equivalent to (V/V ( k c D / k c H ) = 1.135 and substi tuting the observed value for k T T / k n w e obtain b pH pD k c D / k c H = 1. 135/1.36 = 0.835 There fo re k c H / k c D = 1.20 + 0. 10 T h i s i m p l i e s that subst i tut ion of deuter ium for hydrogen at C-4 decreases the rate constant, k , by 2 0 % . The above resu l t i s quite different f r o m that found by C r a w f o r d and M i s h r a (35) for 4-methyl- l - p y r a z o l i n e-4 - d ^ (66). H 3 C ^ / H (D) N = N .66. D 67 H - 113 -W h e n t h e y c a l c u l a t e d t h e i s o t o p e e f f e c t o n t h e r a t e o f c y c l o p r o p a n e f o r m a -t i o n , k ^ , u s i n g t h e s e p a r a t e p a t h w a y s c h e m e ( e q u a t i o n s _5 a n d 6) , t h e v a l u e f o u n d f o r k ^ / k . , ^ w a s 0 . 8 4 , i m p l y i n g t h a t k ^ i s i n c r e a s e d 19% b y C - 4 d e u t e r i u m s u b s t i t u t i o n , a h i g h l y i m p r o b a b l e s i t u a t i o n . T h i s l e d t o t h e i r c o n c l u s i o n t h a t a c o m m o n i n t e r m e d i a t e i s f o r m e d ( 3 5 ) . T h e v a l u e o f k ^/k^ f o r _95 a n d 9_6 i n d i c a t e s t h a t t h e r e i s a s e c o n d a r y d e u t e r i u m k i n e t i c i s o t o p e e f f e c t o n t h e c y c l o p r o p a n e f o r m i n g r e a c t i o n . T h i s m a y a r i s e i n t h e m a n n e r d e s c r i b e d b y C r a w f o r d (68)-, w h o o b s e r v e d t h a t d e u t e r i u m s u b s t i t u t i o n a t t h e 4 p o s i t i o n o f p y r a z o l i n e s s l o w s d o w n t h e r a t e a t w h i c h t h e t r i m e t h y l e n e i n t e r m e d i a t e c y c l i z e s t o c y c l o p r o p a n e . T h e r e i s a h y p e r c o n j u g a t i v e i n t e r a c t i o n p l a y i n g a r o l e i n s t a b i l i z a t i o n o f t h e t r i m e t h y l e n e s p e c i e s ( F i g u r e XII) (42) a n d C r a w f o r d (68) s u g g e s t e d t h a t t h i s h y p e r c o n j u g a t i v e i n t e r a c t i o n m i g h t g i v e r i s e t o t h e e n h a n c e d /9 - d e u t e r i u m i s o t o p e e f f e c t s . A n e x p l a n a t i o n n o t i n v o l v i n g a t r i m e t h y l e n e s p e c i e s i s o f f e r e d b e l o w . It i s w e l l a c c e p t e d t h a t t h e C - H b o n d s i n c y c l o p r o p a n e s a r e 2 3 c l o s e r t o s p h y b r i d i z a t i o n t h a n s p ( 9 9 ) . A w e l l e s t a b l i s h e d r u l e i s t h a t 3 2 i n a t r a n s i t i o n s t a t e f r o m t h e s p t o t h e s p s t a t e , H c o m p o u n d s w i l l r e a c t f a s t e r t h a n D o r T c o m p o u n d s ( 7 9 ) . T h u s t h e c o n v e r s i o n o f t h e s p 3 2 C ( 4 ) - H b o n d s i n p y r a z o l i n e _9_5 t o s p C - H b o n d s i n t h e c y c l o p r o p a n e p r o -d u c t 118 c o u l d a c c o u n t f o r t h e o b s e r v e d d e u t e r i u m i s o t o p e e f f e c t o n t h e c y c l o p r o p a n e f o r m i n g r e a c t i o n . T h e p y r o l y s i s o f 9 5 a n d _9_6 i n f o r m a m i d e g a v e r e s u l t s q u i t e - 1 1 4 -d i f f e r e n t f r o m t h o s e i n n - b u t y l p h t h a l a t e . I n f o r m a m i d e s o l v e n t t h e o v e r a l l d e u t e r i u m k i n e t i c i s o t o p e e f f e c t , k ^ ^ j / k (^ (95) / k ( 9 6 ) i n f o r m a -m i d e ) , i s c a l c u l a t e d t o b e 1. 06 + 0 . 0 5 . T h e e f f e c t o f C - 4 d e u t e r i u m s u b s t i t u t i o n o n p r o d u c t d i s t r i b u t i o n f o r 95 a n d 9 6 i n f o r m a m i d e i s g i v e n i n T a b l e I I I . A g a i n c y c l o p r o p a n e f o r m a -t i o n i s f a v o u r e d u p o n C - 4 d e u t e r a t i o n . H o w e v e r , t h e c o n c u r r e n t d e -c r e a s e i n o l e f i n f o r m a t i o n , p a r t i c u l a r l y t h e t r a n s e s t e r , i s m o r e n o t i c e a b l e t h a n i n n - b u t y l p h t h a l a t e b e c a u s e f o r m a m i d e s o l v e n t f a v o u r s t h e f o r m a t i o n o f o l e f i n s . S i n c e m o r e o l e f i n i s f o r m e d i n t h i s s o l v e n t i t w a s e x p e c t e d t h a t t h e e f f e c t o f fi - d e u t e r a t i o n o n t h e r a t e o f d e c o m -p o s i t i o n w o u l d b e g r e a t e r t h a n i n n - b u t y l p h t h a l a t e i f t h e m e c h a n i s m s w e r e s i m i l a r i n e a c h s o l v e n t . H o w e v e r , t h e v e r y s m a l l o v e r a l l i s o t o p e e f f e c t i n f o r m a m i d e , 1. 0 6 , i n d i c a t e s t h a t C - 4 t o C - 5 h y d r o g e n m i g r a t i o n c a n -n o t b e c o n c e r t e d w i t h t h e b r e a k i n g o f t h e C ( 5 ) - N b o n d . O n e p o s s i b l e e x p l a n a t i o n i s t h a t a n i t r o g e n - f r e e i n t e r m e d i a t e i s f o r m e d . T h i s i n t e r m e d i a t e m a y r e s e m b l e a t r i m e t h y l e n e o r c y c l o -p r o p a n e " s p e c i e s . I f a n i n t e r m e d i a t e i s f o r m e d t h e f o l l o w i n g k i n e t i c s c h e m e s w i l l a p p l y . k / k p H p D = 2 . 5 4 / 2 . 39 = 1. 06 + 0 . 05 - 115 -k _ o l e f i n s k o D P D r i 9 6 1> I n t e r m e d i a t e - d 9 I - I N 2 c y c l o p r o p a n e T h e r a t e s o f f o r m a t i o n o f o l e f i n s a n d c y c l o p r o p a n e s w i l l b e i n d e p e n d e n t o f t h e r a t e s o f d e c o m p o s i t i o n o f t h e p y r a z o l i n e s a n d t h e i s o t o p e e f f e c t o n t h e o l e f i n - f o r m i n g s t e p c a n b e e s t i m a t e d f r o m t h e o b s e r v e d p r o d u c t d i s t r i -b u t i o n s . T h u s k / k = 5 5 . 5 / 4 4 . 5 a n d k _ / k ~ = 3 9 . 0/61 . 0 o H c H o D c D a n d t h e r e f o r e ( k o H / k o D ) { k c D / k c H } = ( 5 5 . 5 / 4 4 . 5) ( 6 1 . 0 / 3 9 . 0) = 1. 9 5 C r a w f o r d (68) h a s s h o w n t h a t t h e r a t e o f r i n g c l o s u r e o f a t r i m e t h y l e n e t y p e o f i n t e r m e d i a t e t o a c y c l o p r o p a n e i s a f f e c t e d b y d e u t e r i u m s u b s t i t u -t i o n a n d t h u s w e c a n a s s u m e k c p ^ / k c £ ) = 1. 1 3 . T h e r e f o r e , t h e d e u t e r i u m i s o t o p e e f f e c t o n t h e o l e f i n f o r m i n g s t e p i s k o H / k o D = 2 . 2 T h e m a g n i t u d e o f t h i s i s o t o p i c r a t i o i s o f t h e s a m e o r d e r f o u n d b y C r a w f o r d f o r o l e f i n f o r m a t i o n f r o m C - 4 d e u t e r a t e d p y r a z o l i n e s ( 3 5 , 3 9 , 6 8 ) . - 116 -T h e n i t r o g e n - f r e e i n t e r m e d i a t e s w h i c h c o u l d be f o r m e d f r o m 95 a r e ^42 and, 143 f o r m e d f r o m c o n f o r m a t i o n s 95a and 95b r e s p e c t i v e l y . I n t e r m e d i a t e 142 w o u l d g i v e the c i s cXjA-ester (2) and 143 w o u l d give the t r a n s o< 3/3-ester (_1). 95b 143 1 In a h i g h l y p o l a r s o l v e n t s u c h as f o r m a m i d e c o n f o r m a t i o n 95b w o u l d be f a v o u r e d s i n c e the c a r b o m e t h o x y group i s i n the e q u a t o r i a l p o s i t i o n and i s d i r e c t e d away f r o m the r i n g . In p a r t i c u l a r t h i s w o u l d a l l o w r o o m f o r i n -t e r a c t i o n of the s o l v e n t w i t h the c a r b o m e t h o x y m o i e t y . The p r e d o m i n a n t f o r m a t i o n of the t r a n s o l e f i n _1 i n f o r m a m i d e s o l v e n t c o u l d thus be a t t r i -b uted to the e f f e c t of s o l v e n t on the c o n f o r m a t i o n a l e q u i l i b r i u m i n the s t a r t i n g p y r a z o l i n e . T h e p y r o l y s i s r e a c t i o n s i n f o r m a m i d e appear anomalous i n that - 1 1 7 -d e u t e r i u m substitution at C - 4 has v e r y l i t t l e effect on the rate of decom-pos i t i o n despite the fact that f o r m a m i d e fav o u r s o l e f i n f o r m a t i o n . It i s i n t e r e s t i n g to note that the decomposition of 95 in nitrobenzene (Table III) gives e s s e n t i a l l y the same product d i s t r i b u t i o n as found f o r the decomposi-tio n i n n-butyl phthalate. However, the k i n e t i c r e s u l t s f o r _9J> (Table II) show that the p y r o l y s i s rate constant d e c r e a s e s i n a somewhat r e g u l a r manner with i n c r e a s i n g solvent p o l a r i t y . C e r t a i n l y f u r t h e r work on the p y r o l y s i s r e a c t i o n i n the f o r m a m i d e s y s t e m appears to be j u s t i f i e d . - 118 -II - 5 SUGGESTIONS FOR FUTURE RESEARCH The overall kinetic deuterium isotope effect found for the decom-position of 3-methyl-3-carbomethoxy-1-pyrazoline (95) and 3-methyl-3-carbomethoxy-1-pyrazoline-4, 4-d^ (96) in n-butyl phthalate solvent, while small, indicates that migration of a C-4 hydrogen to C-5 is concerted with breaking of the C(5)-N bond during olefin formation. A larger overall, isotope effect might be found for a pyrazoline which gives considerably more olefin than 9j>. The cis 4-alkyl substituted pyrazolines _3 and _84 give 70% olefin and 60% olefin respectively (14 and 43). CCLCH ] ~ f-CO CH 2 3 1 2 3 N TST 3 84 The C-4 hydrogen of pyrazoline _3 can be substituted by deuterium by the following synthetic scheme. CH NaOH X H / 3 - / 3 0 P-C-H : 0 P = C C 0 2 C H 3 C 0 2 C H 3 CH CDO .3 C H 3 ^ /C0 2CH 3 C H 3 x 3 ,c=c N C=C^ T>' C H 3 D N C Q 2 C H 4% 96% - 119 -The total yield of the unsaturated esters for the natural compounds is re-ported to be 90% (59). Addition of diazomethane would lead to cis - 3, 4-dimethyl- 3-carbomethoxy- l-pyrazoline-4-d^ (144). CH ,CH D-3\ / .3 ,C=C + CH N —c-D CO CH 2 2 2 3 CO CH 2 3 144 On the basis of the results found in this work it is anticipated that the rate of decomposition of the natural compound _3 w i l l be at least 1. 5 times faster than the rate for 144. The stereochemistry of olefin forma-tion in the decomposition of _3 could be observed since the C-4 deuterium atom provides a label. On the basis of the results of McGreer and Wu C O z C H 3 145 CH D. /CH + 2 3 C H ^ CO CH 3 2 3 146 (43) it is expected that no 146 w i l l be formed. Generalizations about the pyrazoline decompositions appear to be - 3 20 -difficult to make. However, it shotld be possible, with the information now available, to predict with fair accuracy the effect of a particular sub-stituent on the stereochemistry and the i ate of the pyrolysis of a large number of 1-pyrazolines. - 121 -I I I . E X P E R I M E N T A L G e n e r a l Statement . B o i l i n g points a r e u n c o r r e c t e d . B o i l i n g p o ints w e r e d e t e r m i n e d by the m i c r o i n v e r t e d c a p i l l a r y method. I n f r a r e d s p e c t r a w e r e m e a s u r e d w i t h a P e r k i n - E l m e r M o d e l 21 s p e c t r o p h o t o m e t e r . A l l s p e c t r a w e r e m e a s u r e d on l i q u i d f i l m s between s o d i u m c h l o r i d e p l a t e s . 60 M H z n u c l e a r m a g n e t i c r e s o n a n c e s p e c t r a w e r e r e c o r d e d on e i t h e r a V a r i a n A s s o c i a t e s M o d e l A-60 s p e c t r o m e t e r or a J e o l c o M o d e l C-60 s p e c t r o m e t e r by M r s . A. B r e w s t e r , M i s s C. B u r f i t t , and M i s s P. Watson. 100 M H z n u c l e a r .magnetic r e s o n a n c e s p e c t r a w e r e r e c o r d e d on a V a r i a n A s s o c i a t e s M o d e l HR-100 s p e c t r o m e t e r by M r . R. B u r t o n . M o s t s p e c t r a w e r e r u n as 3 0 % v/v s o l u t i o n s i n c a r b o n t e t r a c h l o r i d e c o n t a i n i n g t e t r a m e t h y l s i l a n e as an i n t e r n a l r e f e r e n c e . T h e v a p o u r - p h a s e c h r o m a t o g r a p h y u n i t s u s e d w e r e an A e r o g r a p h M o d e l A - 9 0 - P and an A e r o g r a p h M o d e l A - 9 0 - P 3 . T h e e l e m e n t a l m i c r o a n a l y s e s w e r e p e r f o r m e d by D r . A. B e r n h a r d t of G e r m a n y and by M r . P. B o r d a of t h i s department. A l l p y r a z o l i n e s a m p l e s w e r e s t o r e d at 0° i n the d a r k u n t i l r e -q u i r e d . - 122 -N - N i t r o s o - N - m e t h y l u r e a N - N i t r o s o - N - m e t h y l u r e a was p r e p a r e d by the p r o c e d u r e g i v e n i n O r g a n i c S y n t h e s e s (80). N - N i t r o s o - N - e t h y l u r e a N - N i t r o s o - N - e t h y l u r e a was p r e p a r e d by the p r o c e d u r e g i v e n by C h i u (33). D i a z o m e t h a n e and diazoethane i D i a z o m e t h a n e and diazoethane w e r e p r e p a r e d f r o m N - n i t r o s o - N -m e t h y l u r e a and N - n i t r o s o - N - e t h y l u r e a r e s p e c t i v e l y , a c c o r d i n g to the p r o c e d u r e g i v e n by C h i u (33). D i d e u t e r i o d i a z o m e t h a n e D i d e u t e r i o d i a z o m e t h a n e was p r e p a r e d by m o d i f i c a t i o n of a p r o -c e d u r e g i v e n by C r a w f o r d (34). To an e t h e r e a l s o l u t i o n of d i a z o m e t h a n e (prepa.red f r o m 50 g of N - n i t r o s o - N - m e t h y l urea) was added a s o l u t i o n of 2 g of K2CO3 i n 50 m l of D 2 0 (MSD). The m i x t u r e was s t i r r e d f o r 12 h o u r s at 0°. T h e aqueous l a y e r was r e m o v e d and a f r e s h s o l u t i o n of 2 g of r ^ C O ^ i n 50 m l of D^O was added. The m i x t u r e was s t i r r e d f o r another 12 h o u r s at 0°; t h e n the aqueous l a y e r w a s r e m o v e d and the pale y e l l o w e t h e r e a l s o l u t i o n d r i e d o v e r s o d i u m sulphate f o r s e v e r a l h o u r s . The s o l u t i o n was f i l t e r e d and u s e d i m m e d i a t e l y ^ The y i e l d s w e r e gene-r a l l y low b e cause m u c h d i a z o m e t h a n e was l o s t d u r i n g the exchange. F o r one p r e p a r a t i o n a s h o r t e r exchange t i m e was a l l o w e d but the amount of - 123 -d e u t e r i u m s u b s t i t u t i o n dropped. 3 - M e t h y l - Z - cyano - 1 - py r az o l i n e (9,8) T h i s p y r a z o l i n e was p r e p a r e d a c c o r d i n g to S n y d e r (50). To an i c e - c o l d w e l l s t i r r e d s o l u t i o n of d i a z o m e t h a n e i n ether was added d r o p w i s e o v e r a p e r i o d of one hour 15 g of m e t h a c r y l o n i t r i l e (K & K ) . A t the end of the a d d i t i o n the solution'was pale y e l l o w i n c o l o u r i n d i c a t i n g a slight, ex-c e s s of d i a z o m e t h a n e . The s o l u t i o n was c o n c e n t r a t e d on the r o t a r y eva-p o r a t o r and the c r u d e p y r a z o l i n e d i s t i l l e d u n d e r r e d u c e d p r e s s u r e to give .13. 5 g of c l e a r l i q u i d ; b. p. 42-45° (0.2-0. 3 mm), n 2 ^ 4 1. 4509 ( l i t . (50) b. p. 45-46 (0. 3 mm), n ^ 1.4518). The. i n f r a r e d s p e c t r u m had bands at 2213 cm"' (m) and 1559 cm"' (s) due to c a r b o n - n i t r o g e n t r i p l e bond s t r e t c h i n g and n i t r o g e n - n i t r o g e n double bond s t r e t c h i n g r e s p e c t i v e l y . T h e n.m. r . s p e c t r u m showed a t r i p l e t at 5. 32 ^ " w i t h J = 7. 5 H z due to the C-5 h y d r o g e n s , a m u l t i p l e t (4 t r i p l e t s ) at 7. 7-8. 6 1 1 due to the C-4 h y d r o g e n s , and a s i n g l e t at 8. 39 t r due to the C-3 m e t h y l h y d r o g e n s . The f o u r t r i p l e t s f o r the C-4 protons a r e the A B p a r t of an A B X s y s t e m and appear at 7. 80, 8. 02, 8. 20, and 8. 4 2 1 w i t h J = 7.6, 7. 6, 7. 2, and 7. 4 H z r e s p e c t i v e l y . The geminaT c o u p l i n g constant (J^-g) i s 13.0 Hz. 3 - M e t h y l - 3-cyano- 1 - p y r a z o l i n e - 5 , 5 - d 2 (99) T h i s compound was p r e p a r e d i n the same m a n n e r as that of 98, except that d i d e u t e r i o d i a z o m e t h a n e was used. The i n f r a r e d s p e c t r u m showed a b r o a d weak band at 2200 cm" ' due to c a r b o n - d e i i t e r i u m - 124 -s t r e t c h i n g . The n. m. r . s p e c t r u m i n d i c a t e d that d e u t e r i u m s u b s t i t u t i o n on C-5 was at l e a s t 9 5%. T h e n o r m a l t r i p l e t at 5. 32 t h a s v i r t u a l l y -d i s a p p e a r e d . The c o m p l e x s i g n a l f o r the C-4 h y d r o g e n s fotmd i n the n. m. r . s p e c t r u m of _98 i s r e d u c e d to an A B quartet, J = 13. 4- Hz, w i t h b r o a d l i n e s due to h y d r o g e n - d e u t e r i u m c o u p l i n g . P r o d u c t s f r o m the d e c o m p o s i t i o n of 3-me t h y l - 3 - c y a n o - 1 -p y r a z o l i n e (98) ' A 10 g s a m p l e of 98 i n a r o u n d - b o t t o m f l a s k equipped w i t h a con-d e n s e r w a s heated to 90-120° f o r 4. 5 h o u r s . The r e s u l t i n g product m i x -t u r e (7. 3 g, 99%) was s e p a r a t e d by v a p o u r - p h a s e c h r o m a t o g r a p h y em-p l o y i n g a 20' x 3/8" d i d e c y l p h t h a l a t e c o l u m n at 140° w i t h a h e l i u m flow of 50 m l per m i n . S i x peaks w e r e o b s e r v e d , A, B, C, D, E, and F, i n the r a t i o of 2%, 80%, 9%, 5%, 3%, and 0. 3% w i t h r e t e n t i o n t i m e s of 26. 0, 30.0, 40.0 43. 0, 55.0, and 63.0 m i n . r e s p e c t i v e l y . C omponent A: i n s u f f i c i e n t m a t e r i a l f o r b o i l i n g point, e t c . , it was a s s i g n e d the s t r u c t u r e of a n g e l o n i t r i l e (112) ( c i s - 2 - m e t h y l - 2- b u t e n o n i t r i l e ) on the b a s i s of the n. m. r . s p e c t r u m w h i c h showed peaks at 3. 78 V ( m u l t i -plet) f o r the o l e f i n i c C-3 h y d r o g e n and 8. 0 5 1 (two m u l t i p l e t s ) f o r the C-3 m e t h y l h y d r o g e n s . The. l a t t e r s i g n a l i s p a r t l y h i d d e n by the s i n g l e t at 8. 13 f o r the C-2 m e t h y l h y d r o g e n s . The n. m. r . s p e c t r u m i s s i m i l a r to that found f o r m e t h y l angelate (2). n 25 Component B: b. p. 128 , n ^ 1.4115, i t w a s a s s i g n e d the s t r u c -o t u r e of 1 - m e t h y l - 1 - c y a n o c y c l o p r o p a n e (111) ( l i t . (6), b. p. 127-127.5 , 20 -1 n^ 1. 41407). It showed an i n f r a r e d band at 22 50 c m c h a r a c t e r i s t i c o f the C=N s t r e t c h i n g v i b r a t i o n . The n. m. r . s p e c t r u m showed peaks at - 125 -8. 66 f (sing l e t ) f o r the C- 1 m e t h y l h y d r o g e n s and 8. 75-9. 47 *iZ (>' 2 B 2 m u l t i p l e t ) f o r the c y c l o p r o p a n e h y d r o g e n s . Component C: b. p. 137°, i t was a s s i g n e d the s t r u c t u r e of t i -g l o n i t r i l e (113) ( t r a n s - 2 - m e t h y l - 2 - b u t e n o n i t r i l e ) ( l i t . (81), b. p. 73° at 90 mm, I.R. : 2222 cm" 1, V (C=N); 1646 cm" 1, V (C=C) ). The i n f r a -r e d s p e c t r u m a g r e e d w i t h the r e p o r t e d s p e c t r u m (81). T h e n. m. r . spec-t r u m showed peaks at 3. 58 '£ ( q u a r t e d of quartets) f o r the C-3 o l e f i n i c h y drogen, 8. 15 t (sing l e t ) f o r the C-2 m e t h y l h y d r o g e n s , and 8 . 2 5 ^ ( m u l t i p l e t , p a r t l y h i d d e n by the. s i g n a l at 8. 15 t ) f o r the C-3 m e t h y l h y d r o -gens. T h e s p e c t r u m i s s i m i l a r to that found f o r m e t h y l t i g l a t e (1). A n a l . C a l d . f o r C ? H 4 N : C, 74. 03; H, 8. 70: N, 17.26. Found: G, 73. 93; H, 8.74; N, 17.13. The g e o m e t r i c a l a s s i g n m e n t s f o r 112 and 113 a r e r e a s o n a b l e s i n c e f o r 113 the o l e f i n i c h y d r o g e n i s c i s to the cyano group and hence i s de-s h i e l d e d and a p p e a r s at a l o w e r f i e l d t h a n i n 112. C o m p o n e n t s D, E, and F: t h e s e c o u l d not be a s s i g n e d s t r u c t u r e s w i t h the l i m i t e d data that w e r e obtained. 3 - M e t h y l - 3-carbomethoxy- 1 - p y r a z o l i n e (95)_ T h i s compound was p r e p a r e d (50) by adding m e t h y l m e t h a c r y l a t e t o a s t i r r e d e t h e r e a l s o l u t i o n of d i a z o m e t h a n e u n t i l the y e l l o w c o l o u r of d i a z o m e t h a n e d i s a p p e a r e d . T h e r e a c t i o n t i m e was about 1 hour. Con-c e n t r a t i o n of the e t h e r e a l s o l u t i o n and d i s t i l l a t i o n of the r e s i d u e under r e -duced p r e s s u r e gave a c l e a r c o l o u r l e s s l i q u i d ; b. p. 46-48° (0. 75 mm), - 126 -n 2} 5 1 . 4 5 3 0 ( l i t . (50) b . p . 4 5 - 4 6 ° ( 1 . 0 m m ) , n ^ 4 1 . 4 5 3 5 ) . T h e n . m . r . s p e c t r u m ( F i g u r e X I V ) w a s c o n s i s t e n t w i t h t h e s t r u c t u r e a n d c o n f i r m e d t h e p u r i t y o f t h e s a m p l e . 3 - M e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l o n e - 5 , 5 - d g (JLZ) T h i s c o m p o u n d w a s p r e p a r e d i n t h e s a m e m a n n e r a s t h a t o f 9 5 e x c e p t t h a t d i d e u t e r i o d i a z o m e t h a n e w a s u s e d . T h e f i r s t p r e p a r a t i o n o f 97 g a v e a g o o d y i e l d o f a s a m p l e w h i c h w a s 6 1 % s u b s t i t u t e d b y d e u t e r i u m a s d e t e r m i n e d b y i n t e g r a t i o n o f t h e n . m . r . s p e c t r u m . T h i s s a m p l e w a s u s e d f o r k i n e t i c r u n s i n n - b u t y l p h t h a l a t e s o l v e n t . L a t e r p r e p a r a t i o n s f o r p r o -d u c t d i s t r i b u t i o n a n d k i n e t i c r u n s i n f o r m a m i d e g a v e l o w e r y i e l d s o f s a m p l e s w h i c h w e r e v i r t u a l l y 9 9 % d e u t e r i u m s u b s t i t u t e d a t t h e C - 5 p o s i t i o n . T h e n. m . r . s p e c t r u m ( F i g u r e X V ) o f 9 7 , 9 9 % - d 2 , s h o w e d p e a k s o f e s t e r m e t h y l h y d r o g e n s a t 6 . 30 t ( s i n g l e t ) , C - 3 m e t h y l h y d r o g e n s a t 8. 52 t ( s i n g l e t ) , a n d C - 4 h y d r o g e n s a t 7 . 9 8 t ( d o u b l e t ) a n d 8.65T2- ( d o u b l e t ) . T h e C - 4 h y d r o g e n s i n t h e d e u t e r a t e d p y r a z o l i n e g i v e a n A B s y s t e m s i g n a l , J = 13 H z . T h e p e a k s a r e b r o a d d u e t o H D c o u p l i n g . T h e e x t e n t o f d e u t e r i u m s u b s t i t u -t i o n i s s h o w n b y t h e c o m p l e t e d i s a p p e a r a n c e o f t h e t r i p l e t a t 5 . 4 3 f s h o w n b y t h e n o n - d e u t e r a t e d p y r a z o l i n e . T h e i n f r a r e d s p e c t r u m o f _9_7 h a s a w e a k b a n d a t 2 1 6 0 c m " ' w h i c h c a n b e a t t r i b u t e d t o c a r b o n - d e u t e r i u m s t r e t c h i n g . 3 - M e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (42) A f r e s h l y p r e p a r e d s a m p l e o f m e t h y l i s o p r o p e n y l k e t o n e , p u r i f i e d a c c o r d i n g t o M c G r e e r _et a l . ( 3 2 ) , w a s r e a c t e d w i t h d i a z o m e t h a n e i n e t h e r - 127 -at r o o m t e m p e r a t u r e . The s o l u t i o n was c o n c e n t r a t e d and the r e s u l t i n g o i l d i s t i l l e d to give a c l e a r c o l o u r l e s s l i q u i d ; b. p. 46-49° (1. 5 mm) ( l i t . (32) b. p. 45° (0. 3 mm) ). The n.m. r. s p e c t r u m showed peaks of C-5 h y d r o g e n s at 5.47 x: ( t r i p l e t w i t h J = 8 Hz), a c e t y l m e t h y l h y d r o -gens at 7. 7 4 1 ( s i n g l e t ) , C-4 h y d r o g e n s at 7. 89-8. 9 0 1 ( m u l t i p l e t ) , and C-3 m e t h y l h y d r o g e n s at 8. 5 5 1 ( s i n g l e t ) . C i s - and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (43 and 44) A m i x t u r e of c i s - and t r a n s - 3, 5 - d i m e t h y l - 3 - a c e t y l - 1-pyrazo-l i n e s was p r e p a r e d f r o m e t h e r e a l diazoethane and m e t h y l i s o p r o p e n y l ketone a c c o r d i n g to the p r o c e d u r e of M c G r e e r et a l . (32). The n.m. r. s p e c t r u m , b a s e d on the a c e t y l r e s o n a n c e s , showed t h i s to be a m i x t u r e of 4 0 % c i s and 6 0 % t r a n s . T h e c i s - and t r a n s - p y r a z o l i n e m i x t u r e was s e p a r a t e d by d i s t i l -l a t i o n t h r o u g h a N e s t e r and F a u s t 60 c m by 8 m m spinning-band s t i l l . o The b o i l i n g point v a r i e d f r o m 36-40 at 0. 15 mm. The c i s : t r a n s r a t i o i n e a c h f r a c t i o n was d e t e r m i n e d by the p r o p o r t i o n of the a c e t y l r e s o n a n c e s i n the n. m. r . s p e c t r u m at 7. 78.t and 7. 65 t r e s p e c t i v e l y . B y r e -peated d i s t i l l a t i o n s s a m p l e s c o n t a i n i n g 9 1 % c i s (43) and 9 2 % t r a n s (44) w e r e obtained. C i s - and t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (_5 and .6) A m i x t u r e of c i s - and t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 -p y r a z o l i n e s was p r e p a r e d f r o m diazoethane and m e t h y l m e t h a c r y l a t e (15). - 128 -Th e p r o p o r t i o n of i s o m e r s was 4 0 % c i s and 6 0 % t r a n s as d e t e r m i n e d by the i n t e n s i t y of the c a r b o m e t h o x y r e s o n a n c e s i n the n,m,r, s p e c t r u m at 6. 3 3 1 and 6 e 27X. r e s p e c t i v e l y . T h i s m i x t u r e was. s u b j e c t e d to f r a c t i o n a l d i s -t i l l a t i o n as d e s c r i b e d f o r the s e p a r a t i o n of c i s - and t r a n s - 3 , 5 - d i m e t h y l -3 - a c e t y l - 1 - p y r a z o l i n e t o gi v e c i s - and t r a n s -3, 5 - d i m e t h y l - 3 - c a r b o m e t h o x y -1 - p y r a z o l i n e (5 and _6) of 9 8 % and 9 9 % p u r i t y r e s p e c t i v e l y . The b o i l i n g point d u r i n g the s e p a r a t i o n v a r i e d f r o m 56-62° (0. 1-0. 3 mm). .Cis-3, 4 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (_3) T h i s p y r a z o l i n e was p r e p a r e d by the method of V a n A u k e n and R i n e h a r t (14). A n e t h e r e a l s o l u t i o n of dia z o m e t h a n e was added s l o w l y to an i c e - c o l d s o l u t i o n of 12. 9 g of t i g l i c a c i d ( C o l u m b i a Chem.) i n 75 m l of et h e r . V i g o r o u s e v o l u t i o n of n i t r o g e n gas took p l a c e u n t i l the y e l l o w c o l o u r of d i a z o m e t h a n e p e r s i s t e d , i n d i c a t i n g that c o m p l e t e e s t e r i f i c a t i o n had oc-c u r r e d . T h e r e m a i n d e r of the d i a z o m e t h a n e s o l u t i o n was added and the y e l l o w s o l u t i o n l e f t to stand at r o o m temperatxxre f o r 6 days. A f t e r t h i s t i m e , the e x c e s s d i a z o m e t h a n e was d e s t r o y e d by c a r e f u l a d d i t i o n of f o r m i c a c i d . T he e t h e r e a l , s o l u t i o n was w a s h e d w i t h s a t u r a t e d N a H C O ^ s o l u t i o n , w a t e r , and f i n a l l y d r i e d o v e r MgSO^. C o n c e n t r a t i o n by r o t a r y e v a p o r a -t i o n l e f t a c o l o u r l e s s o i l y l i q u i d w h i c h was d i s t i l l e d t h r o u g h the s p i n n i n g -band c o l u m n to give 12. 2 g of c i s - 3 , 4 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a -z o l i n e ; b. p. 55° (0. 3 mm), n 2 5 1.4550 ( l i t . (14) b. p. 98-101° (11 mm), 25 n n 1. 4546). The n. m. r . s p e c t r u m w a s i d e n t i c a l to that r e p o r t e d i n the - 129 -l i t e r a t u r e (14). C i s - and Jrxan.s.-2-bromo-2-butene A m i x t u r e of c i s - and t r a n s - 2 - b r o m o - 2 - b u t e n e w a s p r e p a r e d by the m ethod of D r e i d i n g and P r a t t (82). To a heated w e l l - s t i r r e d m i x t u r e of 500 g (2. 3 mole) of 2, 3-dibromobutane and 300 m l of ethylene g l y c o l i n a t h r e e - n e c k e d 2 - l i t r e f l a s k equipped w i t h a 5-inch V i g r e u x c o l u m n was added s l o w l y a s o l u t i o n of 157 g (2. 75 mole) of reage n t K O H i n 500 m l of ethylene g l y c o l . The t e m p e r a t u r e of the r e a c t i o n m i x t u r e was r a i s e d u n t i l the 2-bromo-2-butenes, along w i t h some water, d i s t i l l e d . T he v a p o u r t e m p e r a t u r e was m a i n t a i n e d at about 83°. The a d d i t i o n of base took about 1-1/2 h o u r s . The h e a t i n g was con t i n u e d u n t i l no m o r e of the same d i s t i l l a t e was obtained. The c r u d e 2-bromo-2-butenes w e r e s e p a r a t e d f r o m the w a t e r and d r i e d o v e r C a C l ^ . The y i e l d was 248 g ( 8 0 % ) . T h e m i x t u r e of c i s - and t r a n s - 2 - b r o m o - 2 - b u t e n e was f r a c t i o n a l l y d i s t i l l e d t h r o u g h a N e s t e r and F a u s t 45 c m by 6 m m spinning-band s t i l l at a t m o s p h e r i c p r e s s u r e . T h e f r a c t i o n s b o i l i n g at 82. 0-86. 0° w e r e com-b i n e d (65 g) and r e d i s t i l l e d t h r o u g h a s h o r t V i g r e u x c o l u m n to g i v e 45 g of t r a n s ~ 2 - b r o m o - 2 - b u t e n e ; b. p. 83. 5-86. 0°, n 2 5 1.4540 ( l i t . (59) o 25 5 b.p. 39-41.5 (133-137 mm), n D * 1. 4552). The n. m. r. s p e c t r u m c o n f i r m e d the s t r u c t u r e and i n d i c a t e d that the s a m p l e had o n l y about 5% c i s i m p u r i t y p r e s e n t . T h e n, m. r . s p e c t r u m showed peaks at 4. 35 f (qua r t e t of q u a r t e t s w i t h J g e r n = 6. 5 H z and J c ^ s = 1. 5 Hz), 7. 7 8 t - 130 -( u n r e s o l v e d m u l t i p l e t ) , and 8. 3 3 t (doublet of q u a r t e t s w i t h J g e m = 6. 5 H z ^ d J t r a n s = 1.0. H z ) . M e t h y l A n g e l a t e (2) A n g e l i c a c i d was p r e p a r e d f r o m t r a n S " 2 - b r o m o - 2 - b u t e n e by the m e t h o d of H o use and R a s m u s s o n (59). F r o m 45 g (0. 33 mole) of the b r o m o b u t e n e was obtained 14. 0 g (41%) of c r u d e a n g e l i c a c i d . The an-g e l i c a c i d was e s t e r i f i e d by r e a c t i o n w i t h d i a z o m e t h a n e to g i v e 9. 0 g of m e t h y l angelate; b. p. 126-128°, n 2 0 1.4329 ( l i t . (83) b. p. 127.6-127.8°, n 2 ^ 1.4321). The p u r i t y of the s a m p l e was c o n f i r m e d by W P . C. The n. m. r. s p e c t r u m of the s a m p l e was i d e n t i c a l to that r e -p o r t e d i n the l i t e r a t u r e (84). Trans-3, 4 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (.4) T h i s p y r a z o l i n e was p r e p a r e d a c c o r d i n g to V a n A u k e n and R i n e -h a r t (14). To a s o l u t i o n of 8. 9 g (0. 08 mole) of m e t h y l angelate i n ether was added a l a r g e e x c e s s of d i a z o m e t h a n e i n ether. ; T h e s o l u t i o n was l e f t to stand at r o o m t e m p e r a t u r e f o r one week. The extent of the a d d i t i o n was f o l l o w e d by V. P. C. F r e s h e t h e r e a l d i a z o m e t h a n e was added as r e q u i r e d to m a i n t a i n an e x c e s s of that reagent. The r e a c t i o n s o l u t i o n was then d r i e d o v e r MgSO^, f i l t e r e d , and c o n c e n t r a t e d to an o i l y l i q u i d w h i c h was d i s t i l l e d vinder r e d u c e d p r e s s \ i r e to g i v e 8. 3 g (69%) of trans»-3, 4-d i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (4); b. p. 47-50° ( 0 . 1 m m ) , n 2 / 1.4521 ( l i t . (14) b. p. 54-55°,' n 2 ) 5 1. 4509). The n. m. r. s p e c t r u m - 131 -was i d e n t i c a l to that r e p o r t e d i n the l i t e r a t u r e (14). 3 - V i n y l - 1 - p y r a z o l i n e (55) 3 - V i n y l - 1 - p y r a z o l i n e was p r e p a r e d by the p r o c e d u r e of C r a w f o r d and C a m e r o n (34). 1, 3-Butadiene (14 g) was d i s t i l l e d i nto 300 m l of ether c o o l e d to 0°. To t h i s s o l u t i o n was added an e x c e s s of diazomethane i n e t h e r . T h e m i x t u r e was kept at 0° f o r two days and at r o o m t e m p e r a -t u r e f o r one day. The s o l u t i o n was d r i e d o v e r N a 2 S 0 4 and the ether eva-p o r a t e d to l e a v e an o r a n g e - y e l l o w o i l (11 g). D i s t i l l a t i o n under r e d u c e d p r e s s u r e gave 3 - v i n y l - 1 - p y r a z o l i n e (55); b.p. 69-72° (12 mm), n 2 ^ 1.4678 ( l i t . (34) b.p. 72-75° (40 mm), n 2 5 1. 4665). T h e p y r a z o l i n e i s a c o l o u r l e s s l i q u i d w h i c h c o l o u r s r a p i d l y upon e x p o s u r e to a i r . T h e n. m. r . s p e c t r u m (neat sample) was i d e n t i c a l to that r e p o r t e d (34). T r i m e t h y l es... phos phono p r o p i o n a t e (102) T r i m e t h y l C \ - p h o s phono pr opionate (102) was p r e p a r e d by means of the M i c h a e l i s - A r b u z o v r e a c t i o n (85). A m i x t u r e of 72 g (0. 58 mole) of t r i m e t h y l phosphite (Eastman) and 67 g (0. 4 mole) of m e t h y l c A - b r o m o -p r o p i o n a t e ( A l d r i c h ) , i n a r o u n d bottom f l a s k equipped w i t h a w a t e r con-d e n s e r whose top was connected to a d r y i c e / a c e t o n e c o o l e d t r a p , was heated s l o w l y to 110° at w h i c h t i m e m e t h y l b r o m i d e began to condense. T h e r e a c t i o n was t e r m i n a t e d a f t e r t h r e e h o u r s , when the r e a c t i o n t e m -p e r a t u r e r e a c h e d 155°. The r e s u l t i n g s o l u t i o n was f r a c t i o n a t e d under r e -duced'" p r e s s u r e to give t r i m e t h y l os-phos phonopr opionate (102); b.p. - 132 -75-90° fO. 1 m m ) , n 2 0 l.-4344 ( l i t . (51) b. p. 82-84° ( 0 . 1 m m ) ) . M e t h y l c i s - and t r a n s - 2 - m e t h y l - 2 - p e n t e n o a t e (J^O and 59) A m i x t u r e of m e t h y l c i s - and t r a n s - 2 - m e t h y l - 2 - p e n t e n o a t e was p r e p a r e d by the m o d i f i e d W i t t i g r e a c t i o n (52). To a s l u r r y of 4 9 % s o d i u m h y d r i d e (11 g, 0. 224 mole) i n 200 m l of d r y 1, 2-dimethoxyethane m a i n -t a i n e d at 15° was added d r o p w i s e i n 1 h r t r i m e t h y l o\-phos phono p r o p i o n a t e (43 g, 0. 22 m o l e ) . A f t e r the a d d i t i o n the g r e y s o l u t i o n was s t i r r e d f o r 1 h r at r o o m t e m p e r a t u r e and f o r 5 m i n at 35°. The s o l u t i o n was c o o l e d to 15° and f r e s h l y d i s t i l l e d p r o p i o n a l d e h y d e (13 g, 0.22 mole) was added d r o p w i s e w i t h i n 20 m i n w i t h r a p i d s t i r r i n g . D u r i n g the a d d i t i o n a gummy p r e c i p i t a t e a p p eared. The m i x t u r e was w a r m e d to r o o m t e m p e r a t u r e and s t i r r e d v i g o r o u s l y f o r 15 m i n . Ice (300 g) was added w i t h s t i r r i n g . T h e m i x t u r e w a s e x t r a c t e d w i t h f i v e 100-ml p o r t i o n s of e t h e r . T h e e t h e r e a l s o l u t i o n s w e r e then c o m b i n e d and w a s h e d w i t h two 1 00-ml p o r t i o n s of w a t e r to r e m o v e 1, 2-dimethoxyethane. The e t h e r s o l u t i o n was f i n a l l y d r i e d o v e r s o d i u m sulphate and c o n c e n t r a t e d . The r e s i d u e (48 g) was d i s t i l l e d to g i v e 14 g (50%) of product, b. p. 130-152°. A n a l y s i s by v a p o u r - p h a s e c h r o m a t o g r a p h y i n d i c a t e d that the m i x t u r e c o n t a i n e d 4 2 % m e t h y l c i s - 2 - m e t h y l - 2 - p e t e n o a t e (60) and 5 8 % m e t h y l t r a n s - 2 - m e t h y l - 2 -pentenoate (59). S e p a r a t i o n of t h i s m i x t u r e was a c h i e v e d by d i s t i l l a t i o n t h r o u g h a-N e s t e r and F a u s t a n n u l a r T e f l o n s p i n n i n g - b a n d c o l u m n . F r a c t i o n s - 133 -c o n t a i n i n g t h e c i s i s o m e r w e r e c o l l e c t e d b e t w e e n 1 3 4 - 1 4 7 ( 7 6 0 m m ) a n d f r a c t i o n s c o n t a i n i n g t h e t r a n s i s o m e r w e r e c o l l e c t e d b e t w e e n 1 4 7 - 1 5 2 ° ( 7 6 0 m m ) . C a r e f u l m o n i t o r i n g o f t h e d i s t i l l a t e b y V . P . C . g a v e f r a c t i o n s w h i c h w e r e 99'7? p u r e c i s o r t r a n s . O t h e r f r a c t i o n s w e r e p u r i f i e d b y V. P . C . T h e f i n a l s a m p l e s o f t h e u n s a t u r a t e d e s t e r s w e r e i n a p u r e s t a t e a s i n d i c a t e d b y V . P . C . a n d n . m . r . T h e n . m . r . s p e c t r a w e r e i d e n t i c a l t o t h o s e p r e v i o u s l y r e p o r t e d ( 1 4 , 2 1 ) . Cis- 3 - m e t h y l - 4 - e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (,84) T h e p y r a z o l i n e w a s p r e p a r e d b y a d d i n g a n e x c e s s o f d i a z o -m e t h a n e t o a n e t h e r s o l u t i o n o f 4 . 7 5 g o f m e t h y l - t r a n s - 2 - m e t h y l - 2 -p e n t e n o a t e ( 5 9 ) . A f t e r s t a n d i n g f o r 7 d a y s a t r o o m t e m p e r a t u r e t h e e t h e r w a s r e m o v e d t o l e a v e 6 . 2 g o f c r u d e p y r a z o l i n e , w h i c h w a s p u r i f i e d b y d i s t i l l a t i o n t o g i v e c i s - 3 - m e t h y l - 4 - e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e ; b . p . 6 5 - 6 6 ° ( 0 . 1 m m ) , n 2 0 1. 4 5 8 0 ( l i t . (43) b . p . 7 0 - 7 5 ° ( 0 . 22 m m ) , n ^ 1. 4 5 6 5 ) . T h e n . m . r . s p e c t r u m was i d e n t i c a l t o t h a t r e p o r t e d b y M c G r e e r a n d W u ( 4 3 ) . T r a n s - 3 - m e t h y l - 4 - e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (J35) T h i s p y r a z o l i n e w a s p r e p a r e d f r o m 4 . 31 g o f m e t h y l c i s - 2 - m e t h y l -2 - p e n t e n o a t e (60) b y t h e s a m e p r o c e d u r e a s g i v e n a b o v e . T h e c r u d e p y r a -z o l i n e ( 6 . 2 2 g) w a s d i s t i l l e d t o g i v e t r a n s - 3 - m e t h y l - 4 - e t h y l - 3 - c a r b o -m e t h o x y - 1 - p y r a z o l i n e ( J S 5 ) ; b . p . 6 0 - 6 3 ° ( 0 . 1 m m ) , n 2 0 1. 4 5 5 9 ( l i t . 2 1 (43) n n 1. 4 5 3 5 ) . T h e n . m . r . s p e c t r u m w a s i d e n t i c a l t o t h a t r e p o r t e d - 134 -p r e v i o u s l y (43). 3, 5, 5 - T r i m e t h y l - 3-carbomethoxy- 1 - p y r a z o l i n e (100) T h e s a m p l e u s e d i n t h i s w o r k was p r e p a r e d by N . C h i u by adding m e t h y l m e t h a c r y l a t e to an e t h e r e a l s o l u t i o n of d i a z o i s o p r o p a n e . (The p r o -c e d u r e w i l l be d e s c r i b e d i n the s e c t i o n on the p r e p a r a t i o n of 3, 5, 5 - t r i ~ m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e ) . The p y r a z o l i n e was p u r i f i e d by d i s t i l l a -t i o n , b. p. 54-56° (0. 1 mm). The n.m. r. s p e c t r u m showed peaks at 6. 2 8 f ( s i n g l e t of m e t h y l e s t e r ) , 8. 04 and 8. 8 0 t (two doublets f o r the C-4 h y d r o g e n s w h i c h f o r m an A B s y s t e m , J = 13.0 Hz), 8.46 and 8. 6 0 ^ (•singlets f o r the m e t h y l groups on C-5), and 8. 6 4 1 ( s i n g l e t f o r the C-3 m e t h y l ) . , A c e t o n e a z i n e H y d r a z i n e h y d r a t e (50 g, 1.0 mole) was added to acetone (117 g, 2. 0 mole) c o o l e d to 0°. The m i x t u r e was w a r m e d on a s t e a m bath f o r 5 h r . A f t e r b e i n g c o o l e d to r o o m t e m p e r a t u r e , anhydrous p o t a s s i u m c a r -bonate (40 g) was added and the l o w e r aqueous l a y e r s e p a r a t e d , A f u r t h e r 20 g of p o t a s s i u m c a r b o n a t e w e r e added to h e l p s e p a r a t e the aqueous l a y e r . T h e p r o d u c t was d r i e d o v e r p o t a s s i u m c a r b o n a t e and f r a c t i o n a l l y d i s t i l l e d at a t m o s p h e r i c p r e s s u r e to g i v e acetone a z i n e (82. 5 g, 7 4 % ) ; b. p. 130-132° ( l i t . (86) b. p. 129-132°). A c e t o n e h y d r a z o n e A m i x t u r e of acetone a z i n e (82. 5 g 0. 74 mole) and h y d r a z i n e - 135 -h y d r a t e -'37 g, 0. 74 mole) was heated at 110 f o r 17 h r . F r a c t i o n a l d i s -o 25 t i l l a t i o n gave acetone h y d r a z o n e (69 g); b. p. 120-122 , n~ 1. 4588 ( l i t . (87) b. p. 115-120°). 3, 5, 5 - T r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (101) The p r o c e d u r e g i v e n by M c G r e e r and C h i u (53) f o r the p r e p a r a -t i o n of 3, 5, 5 - t r i m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e (100) was adapted to p r e p a r e 3, 5, 5 - t r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (101). To a v i g o r o u s l y s t i r r e d s u s p e n s i o n of s i l v e r oxide (69. 6 g, 0. 3 mole) i n anhydrous ether (300 ml) c o o l e d to -60° was added acetone h y d r a z o n e (21. 6 g, 0. 3 mole) and then m e t h y l i s o p r o p e n y l ketone (17. 1 g, 0. 2 m o l e ) . A f t e r the a d d i t i -t i o n s the m i x t u r e was a l l o w e d to come s l o w l y to -25° and s t i r r e d at that t e m p e r a t u r e f o r 30 m i n . The c o o l i n g bath was r e m o v e d and the r e a c t i o n m i x t u r e w a r m e d to r o o m t e m p e r a t u r e . The b l a c k p r e c i p i t a t e was f i l -t e r e d off and the ether r e m o v e d by r o t a r y e v a p o r a t i o n to l e a v e a s l i g h t l y y e l l o w c o l o u r e d o i l (22. 5 g). Two d i s t i l l a t i o n s u nder r e d u c e d p r e s s u r e , the s econd d i s t i l l a t i o n t h r o u g h a N e s t e r and F a u s t s t a i n l e s s s t e e l s p i n n i n g -band column, gave pure 3, 5, 5 - t r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e ; b. p. 44-45° (0.5 mm), n ^ 1.4492. T h e n . m. r . s p e c t r u m showed peaks at 7 . 6 8 t ( s i n g l e t f o r a c e t y l m e t h y l ) , 7.90 and 8 . 9 2 t (two doublets f o r the C-4 h y d r o g e n s w h i c h f o r m an A B s y s t e m , J = 13. 4 Hz), 8. 4 5 1 ( s i n g l e t f o r the C-3 m e t h y l ) , and 8. 58 and 8. 76t:. ( s i n g l e t s f o r the m e t h y l groups on C-5). I n f r a r e d bands found at 1705 c m " ' and 1547 c m " 1 w e r e due to c a r b o n y l and n i t r o g e n - n i t r o g e n double bond s t r e t c h i n g r e s p e c t i v e l y . - 136 -A n a l . C a l c d . f o r C g H j ^ O : . C, 62. 30; H, 9.15; N, 18.17. Found: C, 62.27; H, 9.29; N, 18.13. C h a r a c t e r i z a t i o n of the p r o d u c t s f r o m the p y r o l y s i s of  3, 5, 5 - t r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (101) A 10 m l s a m p l e of the p y r a z o l i n e was heated to 90-100° i n a s m a l l d i s t i l l a t i o n a p p a r a t u s i n an o i l bath. E v o l u t i o n of n i t r o g e n began at 90° and was v i g o r o u s at 100°. D i s t i l l a t i o n y i e l d e d a c o l o u r l e s s p r o d u c t m i x t u r e b o i l i n g up.to 160°. F o u r components w e r e i s o l a t e d by v a p o u r - p h a s e c h r o -m a t o g r a p h y u s i n g a 10' x 1/4" d i i s o d e c y l p h t h a l a t e c o l u m n at 140° w i t h a h e l i u m f l o w of 50 m l per m i n u t e . The b o i l i n g point, r e f r a c t i v e index, and r e t e n t i o n t i m e i n the v a p o u r - p h a s e c h r o m a t o g r a m a r e g i v e n f o r e a c h com-pound. The r e l a t i v e p r o p o r t i o n s of t h e s e p r o d u c t s a r e g i v e n i n T a b l e V I . C i s - 3 , 5-dimethyl-3-hexen-2-one (10 8): b.p. 148°, n 2^ 0 1.4360, and 18. 5 m i n u t e s . The i n f r a r e d s p e c t r u m showed a b s o r p t i o n s at 1687 c m " ' ( s) and 1621 cm" * (s) i n d i c a t i v e of an - u n s a t u r a t e d ke-tone (88) . The n. m. r. s p e c t r u m showed peaks of v i n y l h y d r o g e n at 4. 63t: (two q u a r t e t s due to c o u p l i n g w i t h the C-5 hydrogen, J = 9. 8 Hz, and w i t h the C-3 m e t h y l , J = 1. 5 H z ) , m e t h i n e h y d r o g e n at 7. 10 'C ( m u l t i p l e t ) , a c e t y l m e t h y l h y d r o g e n s at 7 . 8 5 f ( s i n g l e t ) , v i n y l m e t h y l h y d r o g e n s at 8. 1 4 t (doublet w i t h J = 1. 5 Hz), and a l k y l m e t h y l h y d r o g e n s at 9. 0 6 t : (doublet due to c o u p l i n g w i t h C-5 hydrogen, J = 6. 5 H z ) . The geo-m e t r i c a s s i g n m e n t i s d i s c u s s e d below. A n a l . C a l c d . f o r C 8 H 1 4 0 : C, 76.14; H, 11.18. Found: - 137 -C, 75. 89; K, 11. 37. o ?0 Trans-3, 5-dimethyl-3-hexen~2-one (109): b.p. 159.5 , 1,-"4458 (lit. (89) b.p. 55. 2-56.4° (13 mm) ) and 28. 4 minutes. The infrared spectrum showed absorptions at 1657 cm"' (s) and 1633 cm"' (s) indicative of an ^/^-unsaturated ketone. The n.m. r. spectrum showed signals of vinyl hydrogen at 3. 75t: (two quartets due to coupling with the C-5 hydrogen, J = 9. 0 Hz, and with the C-3 methyl, J = 1. 2 Hz), methine hydrogen at 7. 33 tr (complex multiplet), acetyl methyl hydrogens at 7. 82TT (singlet), vinyl methyl hydrogens at 8. 31 (doublet, J = 1.2 Hz), and alkyl methyl hydrogens at 8. 95tr (doublet, J = 7.0 Hz). 'The geometric assignments for the cis- and trans-3, 5-dimethyl-3-hexen-2-one (108 and 109) were based on the lower chemical shift of the vinyl proton in 109. In 109 the vinyl proton is cis to the carbonyl group and is deshielded due to the anistropy of the carbonyl group (90). The carbonyl group also affects the position of the signal for the C-5 hydrogen. In 108 the C-5 hydrogen signal is shifted downfield because the hydrogen is closer to the carbonyl group than in 109. Anal. Calcd. for C g H 1 4 0 : C, 76.14; H, 11.18. Found: C, 75. 95; H, 10.91. 1, 2, 2-Trimethyl- 1-acetylcyclopropane (106): 20. 4 minutes. This compound could be obtained only 95% pure because rearrangement to give a Y}6 -unsaturated ketone (described below) occurred during - 138 -i s o l a t i o n p r o c e d u r e s . The i n f r a r e d s p e c t r u m showed a b s o r p t i o n at 1685 cm" ' ( s) i n d i c a t i v e of a c a r b o n y l group conjugated w i t h a c y c l o p r o p a n e r i n g (88). The n. m. r . s p e c t r u m showed s i g n a l s of a c e t y l m e t h y l h y d r o -gens at 7. 92 ( s i n g l e t ) , C- 1 m e t h y l h y d r o g e n s at 8. 60 tr ( s i n g l e t ) , C-2 m e t h y l h y d r o g e n s at 8. 8 2 1 and 9. 0 5 1 ( s i n g l e t s ) , and c y c l o p r o p a n e h y d r o g e n s at 8. 6 4 T and 9 . 7 5 t (two doublets, the C-3 hydroge n s f o r -m i n g an A B s y s t e m w i t h A = 66. 4 H z and J = 4. 5 H z ) . AJJ A B S m a l l s a m p l e s of 106 s e a l e d into g l a s s tubes w e r e heated i n an o i l b ath to 150°. A s a m p l e was r e m o v e d h o u r l y and a n a l y z e d by v a p o u r - p h a s e c h r o m a t o g r a p h y . A f t e r two h o u r s the p r o d u c t was a 50:50 m i x t u r e of 1, 2, 2 - t r i m e t h y l - 1 - a c e t y l c y c l o p r o p a n e (106) and 3, 5-dimethyl-5-hexen-2-one (107). T h i s r e s u l t c o n f i r m s the s t r u c t u r e f o r 106 suggested by the i n f r a r e d and n. m. r , s p e c t r a . 3, 5-Dimethyl-5-hexen-2-one (107): b.p. 151.0°, n 2 0 1.4311, — _ . = _ D and 24.0 m i n u t e s . The i n f r a r e d s p e c t r u m had bands at 3060 cm"' (s, t e r m i n a l m e t h y l e n e ^ ^ Q C H ^ ) , 1700 c m " 1 (s, non-conjugated c a r b o n y l V C — O ) , 1643 c m " 1 (m, ^ C = C ) , and 890 c m " 1 (s, t e r m i n a l methy-lene <£CH). The n. m. r . s p e c t r u m showed s i g n a l s of t e r m i n a l m e t h y l e n e h y d r o g e n s at 5. 30"K ( m u l t i p l e t ) , C-3 and C-4 hydrogen s at 7. 15-8. 15 "tr ( c o m p l e x m u l t i p l e t ) , a c e t y l m e t h y l h y d r o g e n s at 7.95 "C ( s i n g l e t ) , C-5 • m e t h y l h y d r o g e n s at 8. 30"V (doublet w i t h J = 1.0 Hz), and C-3 m e t h y l h y d r o g e n s at 8.961: (doublet w i t h J = 7.0 H z ) . A n a l , C a l c d . f o r C 8 H 1 4 0 : C, 76,14; H, 11.18. Found: - 139 -C, 76.42; H, 11.08. . U n i d e n t i f i e d p r o d u c t s : When the o r i g i n a l p r o d u c t m i x t u r e r e s u l -t i n g f r o m the p y r o l y s i s of 3, 5, 5 - t r i m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (10 1) was a n a l y z e d on a d i e t h y l e n e g l y c o l s u c c i n a t e c o l u m n a s m a l l peak a p p e a r e d between the peaks f o r 106 and 107. It was not p o s s i b l e to c o l l e c t any of t h i s compound f o r i d e n t i f i c a t i o n . A s m a l l peak at 7, 8 m i n u t e s on the d i i s o d e c y l p h t h a l a t e c o l u m n c h r o m a t o g r a m c o u l d not be i d e n t i f i e d as t h e r e was i n s u f f i c i e n t m a t e r i a l c o l l e c t e d . M e t h y l m e t h a c r y l a t e - 3 , 3-d 2 (115) S e v e r a l r o u t e s to d e u t e r a t e d m e t h y l m e t h a c r y l a t e w e r e e x p l o r e d . T h e p r o c e d u r e f i n a l l y u s e d was the M a n n i c h r e a c t i o n (.61). The e x p e r i -m e n t a l d e t a i l s of v a r i o u s t r i a l p r e p a r a t i o n s of m e t h y l m e t h a c r y l a t e a r e g i v e n below. (a) W i t t i g r e a c t i o n (i) P r e p a r a t i o n of m e t h y l m e t h a c r y l a t e T h e p r o c e d u r e of H ouse and R a s m u s s o n (59) f o r the s y n t h e s i s of m e t h y l t i g l a t e and m e t h y l angelate was adapted w i t h some m o d i -f i c a t i o n s . A n e t h e r e a l s o l u t i o n (80 ml) c o n t a i n i n g 0. 1 m o l e of p h e n y l l i t h i u m was added w i t h s t i r r i n g i n a n i t r o g e n a t m o s p h e r e to a s u s p e n s i o n of 35. 7 g (0. 10 mole) of m e t h y l t r i p h e n y l p h o s p h o n i u m b r o m i d e i n 200 m l of e t h e r . A f t e r the a d d i t i o n was c o m p l e t e (15 minutes) the r e s u l t i n g d a r k r e d s o l u t i o n was s t i r r e d f o r 2 h o u r s . A s o l u t i o n of f r e s h l y d i s t i l l e d m e t h y l p y r u v a t e - 140 -(10. 2 g, 0. 10 mole) i n 10 m l of ether was t h e n added w i t h i n 5 m i n u t e s . "The s o l u t i o n b ecame a l m o s t c o l o u r l e s s and a p a l e y e l l o w p r e c i p i t a t e s e p a r a t e d . T h e pasty r e a c t i o n m i x t u r e was r e f l u x e d o v e r n i g h t w i t h s t i r -r i n g . The b\ilk of the ether was d i s t i l l e d f r o m the m i x t u r e and 200 m l of t e t r a h y d r o f u r a n was added. The r e s u l t i n g m i x t u r e was r e f l u x e d f o r 38 h r u nder a n i t r o g e n a t m o s p h e r e and then c o n c e n t r a t e d to about 100 m l by d i s t i l l a t i o n of the t e t r a h y d r o f u r a n t h r o u g h a 30-cm V i g r e u x c o l u m n . Th e r e a c t i o n m i x t u r e was d i l u t e d w i t h ether and the e t h e r e a l s o l u t i o n was s e p a r a t e d f r o m an orange c o l o u r e d s o l i d . F r a c t i o n a l d i s t i l l a t i o n of the e t h e r e a l s o l u t i o n t h r o u g h a N e s t e r and F a u s t s t a i n l e s s s t e e l s p i n n i n g -band c o l u m n gave a f r a c t i o n w i t h b. p. 65-92° w e i g h i n g 2. 6 g. V. P. C. i n d i c a t e d that t h i s f r a c t i o n was a 50:50 m i x t u r e of t e t r a h y d r o f u r a n and m e t h y m e t h a c r y l a t e . T h u s the y i e l d of m e t h y l m e t h a c r y l a t e was at l e a s t 1. 3 g ( 1 3 % ) . (ii ) M e t h y l - d ^ _ t r i p h e n y l p h o s p h o n i u m b r o m i d e (114) The h y d r o g e n - d e u t e r i u m exchange was a c h i e v e d by f o l l o w i n g the p r o c e d u r e of P o m e r a n t z (60). M e t h y l t r i p h e n y l p h o s p h o n i u m b r o m i d e (40 g, 0. 112 mole) was d i s s o l v e d i n 50 m l (a 2 2 - f o l d m o l a r e x c e s s ) of d e u t e r i u m o x i d e (SIC, 99. 8% D); 1. 0 g of 4 0 % N a O D i n D z O was added and the s o l u t i o n w a r m e d to 50° f o r 1 h r . The D2O-H2O was r e m o v e d on the r o t a r y e v a p o r a t o r . Two a d d i t i o n a l exchanges w i t h an 1 8 - f o l d m o l a r e x c e s s of D^O w e r e c a r r i e d out and the d e u t e r a t e d s a l t w a s f i n a l l y d r i e d u n d e r v a c u u m o v e r P^C^. The n. m. r. s p e c t r u m of m e t h y l - d , - t r i p h e n y l -- 141 -p h o s p h o n i u m b r o m i d e (114) (50 m g i n 0. 5 m l D2Q, e x t e r n a l T M S standard) shows o n l y a c o m p l e x s i g n a l at 2. 4-2. 8 1£ due to the a r o m a t i c h y d r o g e n s . T h e n. m. r. s p e c t r u m of the n o n - d e u t e r a t e d s a l t shows s i g n a l s of a r o -m a t i c h y d r o g e n s at 2. 4-2. 8 t ( c o m p l e x m u l t i p l e t ) and of m e t h y l h y d r o g e n s at 7. 23 t (doublet due to c o u p l i n g w i t h phosphorus, ^p-^ = '3. 5 H z ) . The d e u t e r i u m s u b s t i t u t i o n i n 114 i s t h e r e f o r e v i r t u a l l y 9 9 % c o m p l e t e . ( i i i ) A t t e m p t e d p r e p a r a t i o n of M e t h y l m e t h a c r y l a t e - 3 , 3-d„ The W i t t i g r e a c t i o n d e s c r i b e d above i n p a r t (i) was r e p e a t e d u s i n g m e t h y l - d ^ - t r i p h e n y l p h o s p h o n i u m b r o m i d e (114). The p r o -c e d u r e was the same except that the r e a c t i o n m i x t u r e was r e f l u x e d f o r o n l y one hour a f t e r the m e t h y l p y r u v a t e a d d i t i o n . Upon a d d i t i o n of f r e s h l y d i s t i l l e d t e t r a h y d r o f u r a n a t h i c k y e l l o w l u m p f o r m e d i n the r e a c t i o n m i x -t u r e . The s o l i d was e v e n t u a l l y d i s p e r s e d and the r e a c t i o n m i x t u r e r e -f l u x e d f o r 7 days. A n a l y s i s of the r e a c t i o n m i x t u r e by v a p o u r - p h a s e c h r o m a t o g r a p h y i n d i c a t e d that only a t r a c e of m e t h y l m e t h a c r y l a t e was p r e s e n t . A t t e m p t s to i s o l a t e the m e t h y l m e t h a c r y l a t e i n a p u r e state w e r e u n s u c c e s s f u l . T h i s r e a c t i o n was not e x p l o r e d f u r t h e r b e c ause of d i f f i c u l t i e s i n i s o l a t i n g the p r o d u c t and the f a c t that the y i e l d , even under o p t i m u m con-d i t i o n s (59), w o u l d s t i l l r e m a i n at only 15-20%. (b) M o d i f i e d W i t t i g r e a c t i o n (i) P r e p a r a t i o n of m e t h y l m e t h a c r y l a t e - 142 -The p r o c e d u r e f o r the p r e p a r a t i o n of e t h y l «A-n-b u t y l a c r y l a t e g i v e n by W a d s o r t h and E m m o n s (52) was m o d i f i e d . T r i -m e t h y l o C-phosphonopropionate (19. 6 g, 0. 1 mole) was added d r o p w i s e at 15° to a s l u r r y of 4 9 % s o d i u m h y d r i d e (4. 8 g, 0. 1 mole) i n 150 m l of d r y 1, 2-dimethoxyethane. The s o l u t i o n was s t i r r e d f o r 1 h o u r at r o o m t e m -p e r a t u r e . A s l u r r y of p a r a f o r m a l d e h y d e (3. 0 g, 0. 1 mole) i n 1, 2 - d i -m ethoxyethane was added at 20° o v e r a p e r i o d of 3/4 h r d u r i n g w h i c h t i m e a gummy p r e c i p i t a t e appeared. The m i x t u r e was s t i r r e d at r o o m t e m -p e r a t u r e f o r 1 h r and then t a k e n up i n 300 m l of w a t e r . The aqueous l a y e r was e x t r a c t e d w i t h t h r e e 100-ml p o r t i o n s of ether and the ether s o l u -t i o n t h e n e x t r a c t e d w i t h t h r e e 100-ml p o r t i o n s of w a t e r . A t r a c e of h y d r o -quinone (to i n h i b i t p o l y m e r i z a t i o n ) was added to the ether s o l u t i o n w h i c h was d r i e d o v e r s o d i u m sulphate and f r a c t i o n a l l y d i s t i l l e d t h r o u g h a s t a i n -l e s s s t e e l s p i n n i n g - b a n d c o l u m n . T h e y i e l d of m e t h y l m e t h a c r y l a t e was 1.8 g ( 1 8 % ) . (c) The M a n n i c h r e a c t i o n (i) D i m e t h y l m e t h y l m a l o n a t e D i m e t h y l m e t h y l m a l o n a t e was p r e p a r e d f r o m d i -m e t h y l m a l o n a t e by m o d i f i c a t i o n of a p r o c e d u r e g i v e n by V o g e l (91) f o r the p r e p a r a t i o n of d i e t h y l n - b u t y l m a l o n a t e . S o d i u m m e t a l (11. 5 g, 0. 5 mole) was added to 500 m l of d r y m e t h a n o l i n a 500 m l t h r e e - n e c k e d f l a s k equipped w i t h a d r o p p i n g funnel, c ondenser, C a C l ^ d r y i n g tube, a n d m a g -n e t i c s t i r r i n g . T he s o l u t i o n was w a r m e d to 50° a f t e r the a d d i t i o n and - 1 4 3 -t h e n c o o l e d t o r o o m t e m p e r a t u r e . F r e s h l y d i s t i l l e d d i m e t h y l m a l o n a t e ( 6 6 g, 0. 5 m o l e ) w a s a d d e d w i t h s t i r r i n g . T o t h e s o l u t i o n o f t h e e n o l a t e w a s a d d e d m e t h y l i o d i d e ( 7 5 g, 0 . 53 m o l e ) o v e r a p e r i o d o f o n e h o u r . T h e s o l u t i o n w s r e f l u x e d f o r 1 - 1 / 2 h r ( n e u t r a l t o l i t m u s ) a n d c o n c e n -t r a t e d b y d i s t i l l i n g o f f 4 0 0 m l o f m e t h a n o l . W a t e r ( 2 0 0 m l ) w a s a d d e d t o t h e r e s i d u e a n d t h e m i x t u r e e x t r a c t e d w i t h t h r e e 1 0 0 - m l p o r t i o n s o f e t h e r , T h e c o m b i n e d e t h e r e x t r a c t s w e r e d r i e d o v e r s o d i u m s u l p h a t e a n d c o n -c e n t r a t e d . U n c h a n g e d d i m e t h y l m a l o n a t e w a s r e m o v e d f r o m t h e c r u d e p r o d u c t b y s e l e c t i v e h y d r o l y s i s ( 9 2 ) . T h e c r u d e e s t e r w a s s h a k e n w i t h z c o l d s o l u t i o n o f 2 . 5 g N a O H i n 15 m l w a t e r f o r e x a c t l y o n e m i n u t e . T h e b o t t o m a q u e o u s l a y e r w a s s e p a r a t e d , t h e e s t e r w a s h e d w i t h d i l u t e H C 1 , d r i e d q u i c k l y o v e r c a l c i u m c h l o r i d e , a n d f i l t e r e d t h r o u g h a g l a s s w o o l p l u T h e d i m e t h y l m e t h y l m a l o n a t e ( 5 3 g , 73%) w a s d i s t i l l e d u n d e r r e d u c e d p r e s u r e ; b . p . 7 3 - 7 4 ° ( 1 5 m m ) ( l i t . (93) b . p . 1 7 2 - 1 7 5 ° ) . T h e n . m . r . s p e c t r u m s h o w e d p e a k s f o r e s t e r m e t h y l h y d r o g e n s a t 6.29"^' ( s i n g l e t ) , C - 2 h y d r o g e n a t 6 . 58 2' ( q u a r t e t w i t h J = 6. 7 H z ) , a n d a l k y l m e t h y l h y d r o g e n s a t 8 . 6 5 X ( d o u b l e t w i t h J = 6 . 7 H z ) . ( i i ) M e t h y l h y d r o g e n m e t h y l m a l o n a t e (116) D i m e t h y l m e t h y l m a l o n a t e w a s p a r t i a l l y h y d r o l y z e d a c c o r d i n g t o t h e p r o c e d u r e o f S n y d e r ( 5 0 ) . T o a s o l u t i o n o f K O H ( 2 1 . 8 g 0. 39 m o l e ) i n m e t h a n o l ( 3 0 0 m l ) w a s a d d e d d i m e t h y l m e t h y l m a l o n a t e (57 g, 0. 39 m o l e ) . T h e s o l u t i o n w a s s t i r r e d a t r o o m t e m p e r a t u r e f o r 32 h r . A f t e r t h i s t i m e t h e s o l u t i o n w a s p o u r e d i n t o a n e v a p o r a t i n g d i s h a n d - 144 -heated on a s t e a m bath u n t i l the m e t h a n o l was r e m o v e d . The concen-t r a t e d l i q u o r was d i s t r i b u t e d between w a t e r and c h l o r o f o r m to r e m o v e unchanged d i m e t h y l m e t h y l m a l o n a t e . The aqueous l a y e r w a s s e p a r a t e d , c o o l e d to 0°, and a c i d i f i e d w i t h c o n c e n t r a t e d HC1 (congo r e d ) . The aqueous s o l u t i o n was e x t r a c t e d w i t h t h r e e 100-ml p o r t i o n s of ether and the c o m b i n e d ether e x t r a c t s d r i e d o v e r s o d i u m sulphate. C o n c e n t r a t i o n of the ether s o l u t i o n gave an o i l y r e s i d u e w h i c h , a f t e r d r y i n g o v e r n i g h t i n v a c u o o v e r ^ 2 ^ 5 ' w e i g h e d 35.0 g ( 6 8 % ) . D i s t i l l a t i o n under r e d u c e d p r e s s u r e gave p u r e m e t h y l h y d r o g e n m e t h y l m a l o n a t e ; b.p. 78-80° (0.2 mm), n ^ 1. 4262 ( l i t . (93) b.p. 131° (16 m m ) ) . T h e n . m . r . s p e c t r u m showed s i g n a l s of a c i d h y d r o g e n at -0. 5 to -1.01' ( s i n g l e t , p o s i t i o n of the peak depending on the c o n c e n t r a t i o n of the s o l u t i o n ) , e s t e r m e t h y l h y d r o g e n s at 6. 2 5 f ( s i n g l e t ) , C-2 h y d r o g e n at 6. 50ir (quartet w i t h J = 6, 5 Hz), and a l k y l m e t h y l h y d r o g e n s at 8. 58V (doublet w i t h J = 6. 5 H z ) . ( i i i ) T he p r e p a r a t i o n of m e t h y l m e t h a c r y l a t e and m e t h y l m e t h a c r y l a t e - 3 , Z-d^ T r i a l p r e p a r a t i o n s of m e t h y l m e t h a c r y l a t e f o l l o w i n g the p r o c e d u r e of M a n n i c h and R i t s e r t (61) w e r e c a r r i e d out under v a r i o u s c o n d i t i o n s . A t y p i c a l e x p e r i m e n t u s i n g f o r m a l d e h y d e i n the 3 7 % aqueous s o l u t i o n f o r m i s d e s c r i b e d below. M e t h y l h y d r o g e n m e t h y l m a l o n a t e (6. 6 g, 0. 05 mole) was n e u t r a -l i z e d by d r o p w i s e a d d i t i o n of d i e t h y l a m i n e (3. 65 g, 0.05 mole) at 0°. T o 145 -t h i s c o l d s t i r r e d s o l u t i o n v/as added 4. 05 g (0. 05 m o l e H^CO) of 3 7 % f o r m a l d e h y d e s o l u t i o n . Upon w a r m i n g the c l e a r s o l u t i o n t o r o o m t e m -p e r a t u r e gas e v o l u t i o n became v i g o r o u s . A f t e r four h o u r s a second l a y e r began t o f o r m . The m i x t u r e w a s a l l o w e d to stand o v e r n i g h t at r o o m t e m p e r a t u r e . The c l e a r upper l a y e r was s e p a r a t e d and d r i e d o v e r s o d i u m sulphate f o r s e v e r a l h o u r s . D i s t i l l a t i o n t h r o u g h a t h r e e - i n c h V i g r e u x c o l u m n gave a f r a c t i o n w i t h b. p. 93- 105°. V. P. C. showed that t h i s f r a c t i o n was 9 7 % m e t h y l m e t h a c r y l a t e . The y i e l d w a s 2. 6 g ( 5 2 % ) . In other t r i a l p r e p a r a t i o n s , s o l i d p a r a f o r m a l d e h y d e was used. T h i s was added to the. a c i d base m i x t u r e as a s l u r r y i n 3-5 m l of w a t e r . The y i e l d of m e t h y l m e t h a c r y l a t e u s i n g the s o l i d f o r m a l d e h y d e was 3 0 - 3 5 % P a r a f o r m a l d e h y d e - d 2 was a v a i l a b l e f r o m M e r c k , Sharp, and Dohme. Y i e l d s of m e t h y l m e t h a c r y l a t e - 3 , 3-d., w e r e e x t r e m e l y low. T h i c o u l d p o s s i b l y be a t t r i b u t e d to the l o w e r s o l u b i l i t y of the ( C D ^ O ^ com-p a r e d to the ( C H 2 C * ) n w h i c h was u s e d i n the t r i a l p r e p a r a t i o n s . F r o m e x p e r i m e n t s u s i n g a t o t a l of 6. 0 g of p a r a f o r m a l d e h y d e - d 2 only 200-250 ^A! of m e t h y l m e t h a c r y l a t e - 3 , 3-d^ was obtained. S i n c e poor y i e l d s w e r e obtained u s i n g s o l i d p a r a f o r m a l d e h y d e - d 2 a r e q u e s t was made to M S D to supply an aqueous s o l u t i o n of f o r m a l d e h y d e d 2 . A 3 0 % s o l u t i o n of f o r m a l d e h y d e - d ^ was obtained. T h i s was u s e d i n the M a n n i c h r e a c t i o n as d e s c r i b e d above. The v o l u m e of upper l a y e r o b t a i n e d w a s quite s m a l l , i n d i c a t i n g that y i e l d s w e r e s t i l l low. The - 146 -m e t h y l m e t h a c r y l a t e - 3 , 3-d-> (115) was i s o l a t e d i n a pure state by p r e p a r a -t i v e v a p o u r - p h a s e c h r o m a t o g r a p h y . The t o t a l y i e l d ( f r o m 3. 0 g of CD^O) was ctbout 1. 2 g ( 1 2 % ) . The y i e l d was low because the s o l u t i o n of f o r -m a l d e h y d e - d ^ p r o b a b l y c o n t a i n e d a l a r g e amount of d i s s o l v e d p a r a f o r -m a l d e h y d e - d 2 , w h i c h a p p e a r s to be l e s s r e a c t i v e than the n o n - p o l y m e r i z e d f o r m . The n. m. r . s p e c t r u m of m e t h y l m e t h a c r y l a t e - 3 , 3-d^ (115) showed two singlets of e q u a l i n t e n s i t y at 6. 3 0 f and 8. 10X w h i c h w e r e a s s i g n e d to the e s t e r m e t h y l h y d r o g e n s and the a l l y l i c m e t h y l h y d r o g e n s r e s p e c t i v e l y . The c o m p l e t e absence of a b s o r p t i o n i n the low f i e l d r e g i o n f r o m 3.9-4. 5 1" i n d i c a t e s that d e u t e r i u m s u b s t i t u t i o n i s at l e a s t 99%. 3 - M e t h y l - 3 - c a r b o m e t h o x y - l - p y r a z o l i n e - 4 , 4-d? (96) One m l of m e t h y l m e t h a c r y l a t e - 3 , 3-d (115) was added to a l a r g e e x c e s s of d i a z o m e t h a n e i n ether and the- s o l u t i o n l e f t to stand at r o o m t e m -p e r a t u r e f o r two h o u r s . The y e l l o w s o l u t i o n was then c a r e f u l l y concen-t r a t e d on the r o t a r y e v a p o r a t o r to a v o l u m e of 3 m l . The r e s u l t i n g c l e a r c o l o u r l e s s s o l u t i o n was t r a n s f e r r e d to a b u l b - t o - b u l b d i s t i l l a t i o n a p p a r a t u s and d i s t i l l e d u nder r e d u c e d p r e s s u r e to give a p p r o x i m a t e l y 900 / A I of 3 - m e t h y l - 3 - c a r b o m e t h o x y - l - p y r a z o l i n e - 4 , 4-d 2; b.p. 50° (0.3 mm). T h e i n f r a r e d s p e c t r v i m showed bands at 2150 c m - 1 (w) and 1547 cm"' (m) due to c a r b o n - d e u t e r i u m bond s t r e t c h i n g and n i t r o g e n - n i t r o g e n double bond s t r e t c h i n g r e s p e c t i v e l y . The n. m. r. s p e c t r u m ( F i g u r e X V I I I ) showed s i g n a l s of C-5 h y d r o g e n s at 5. 46 t r ( b r o a d s i n g l e t ) , e s t e r m e t h y l h y d r o g e n s - 147 -at 6. 30 T ( s i n g l e t ) , and C-3 m e t h y l h y d r o g e n s at 8. 5 2 f ( s i n g l e t ) . The s i g n a l f o r the e q u i v a l e n t C-5 h y d r o g e n s i s broadened because of c o u p l i n g w i t h the d e u t e r i u m s on C-4. P r o d u c t s f r o m the t h e r m a l d e c o m p o s i t i o n of 3-methyl- 3-c a r b o m e t h o x y - l - p y r a z o l i n e - 4 , 4 - d 2 (96) A f t e r v a p o u r - p h a s e c h r o m a t o g r a p h i c a n a l y s i s of the d e c o m p o s i -t i o n p r o d u c t s was completed, t h e r e was enough p r o d u c t m i x t u r e l e f t f o r i s o l a t i o n and n. m. r . i d e n t i f i c a t i o n of some of the d e u t e r a t e d p r o d u c t s . T h e p r o d u c t m i x t u r e was s e p a r a t e d on a 10' x 1/4" d i i s o d e c y l p h t h a l a t e c o l u m n at 100° w i t h h e l i u m f l o w r a t e of 50 m l per m i n u t e t o give two p u r e compounds. The other two compounds c o u l d not be obtained i n s u f f i c i e n t amounts f o r s p e c t r a l a n a l y s i s . M e t h y l J i r ^ n s - 2 - m e t h y l - 2 - b u t e n o a t e - 3 , 4 - d 2 (122): The n. m. r. s p e c t r u m showed s i g n a l s of e s t e r m e t h y l h y d r o g e n s at 6. 3 7T ( s i n g l e t ) and o v e r l a p p i n g s i g n a l s of C-2 m e t h y l h y d r o g e n s at 8. 2 3 f (singlet) and G-4 h y d r o g e n s at 8. 15-8. 40 f ( b r o a d s i n g l e t ? ) . The r a t i o of i n t e g r a l s f o r the two a r e a s of s i g n a l s was 3:5. A c o m p a r i s o n w i t h the n. m. r , s p e c t r u m of m e t h y l t i g l a t e (84) c o n f i r m e d the p o s i t i o n s of the two d e u t e r i u m atoms i n 122. M e t h y l 1-methyl- 1 - c y c l o p r o p a n e c a r b o x y l a t e - 2 , 2-d? (_120): The i n f r a r e d s p e c t r u m showed a weak band at 2210 cm"' (l^C-D) and a s t r o n g band at 1720 c m " ' (l/ ;C==0, e s t e r c a r b o n y l conjugated to the c y c l o p r o p a n e r i n g ) . The n. m, r. s p e c t r u m showed peaks of e s t e r m e t h y l h y d r o g e n s at - 148 -6. 39 f ( s i n g l e t ) , C- 1 m e t h y l h y d r o g e n s at 8. 75 f ( s i n g l e t ) , and c y c l o -p ropane h y d r o g e n s at 8. 9 0 t and 9.42 T ( b r o a d s i n g l e t s ) . The r a t i o of i n t e g r a l s f o r the f o u r s i g n a l s o b s e r v e d was 3:3:1:1, w h i c h a g r e e s w i t h the a s s i g n e d s t r u c t u r e . The expec t e d A B p a t t e r n f o r the c y c l o p r o p a n e h y d r o g e n s i s not c l e a r l y o b s e r v e d due to c o u p l i n g w i t h the d e u t e r i u m atoms. K i n e t i c s T h e r a t e s of d e c o m p o s i t i o n of the 1 - p y r a z o l i n e s w e r e d e t e r -m i n e d by v o l u m e t r i c m e a s u r e m e n t of the r a t e of f o r m a t i o n of n i t r o g e n . T h e a p p a r a t u s u s e d f o r the k i n e t i c d e t e r m i n a t i o n s i s shown i n F i g u r e X X X . The d e s i g n i s s i m i l a r to that of P e t e r s o n et a l . (94) w i t h m o d i -f i c a t i o n s made w h e r e r e q u i r e d . T h e h e a t i n g bath E c o n s i s t e d of a 4 l i t r e s t a i n l e s s s t e e l b e a k e r set i n s i d e a l a r g e s o l v e n t c a n and w e l l i n s u -l a t e d w i t h g l a s s w o o l . T h e heat exchange m e d i u m was Dow C o r n i n g s i l i -cone f l u i d (DC-550). A l a r g e f l e x i b l e c o i l e d h e a t i n g u n i t p r o v i d e d a con-stant heat input and a s m a l l e r h e a t i n g u n i t was c o n t r o l l e d by a t h e r m o -r e g u l a t o r and r e l a y c i r c u i t . The t e m p e r a t u r e c o n t r o l was to w i t h i n _+0. 05°. T h e contents of the r e a c t i o n f l a s k A w e r e s t i r r e d by an a i r -d r i v e n m a g n e t i c s t i r r e r D ( B r o m w e l l ) . The f i l t e r e d a i r s u p p l y was r e g u -l a t e d by means of a s c r e w c l a m p to p r o v i d e a constant s t i r r i n g speed. The co n n e c t i o n s between the c o n d e n s e r F and the m e a s u r i n g b u r e t I c o n s i s t e d of c a p i l l a r y t u b i n g to r e d u c e e r r o r s due to f l u c t u a t i n g r o o m t e m p e r a t u r e . A constant t e m p e r a t u r e w a t e r pump J was e m p l o y e d to s t a b i l i z e the - 1 4 9 -J A . R e a c t i o n V e s s e l B . N i t r o g e n I n l e t C. S a m p l e I n l e t D . M a g n e t i c S t i r r e r E . O i l B a t h F . C o n d e n s e r G . C a p i l l a r y T u b i n g H . W a t e r J a c k e t J. K . L. M . B u r e t C o n s t a n t T e m p e r a t u r e W a t e r P u m p T h r e e - w a y S t o p c o c k T h r e e - w a y S t o p c o c k U - t u b e m a n o m e t e r N . B u b b l e r F I G U R E X X X K i n e t i c s A p p a r a t u s - 150 -t e m p e r a t u r e i n t h e w a t e r j a c k e t s o f t h e m e a s u r i n g b u r e t a n d t h e c o n d e n s e r . T h e e v o l v e d n i t r o g e n w a s m e a s u r e d o v e r m e r c u r y . A u - t u b e m a n o m e t e r f i l l e d w i t h n - b u t y l p h t h a l a t e w a s a t t a c h e d t o t h e b u r e t t o e n s u r e t h a t t h e p r e s s u r e i n s i d e t h e a p p a r a t u s w a s e q u a l t o t h e a t m o s p h e r i c p r e s s u r e w h e n a r e a d i n g w a s t a k e n . T i m e w a s r e c o r d e d b y a n e l e c t r i c c h r o n o m e t e r ( L a b - C h r o n ) . T h e t w o t h e r m o m e t e r s u s e d , o n e i n t h e 0 - 1 0 0 ° r a n g e a n d t h e o t h e r i n t h e 1 0 0 - 2 0 0 ° r a n g e , w e r e c a l i b r a t e d a g a i n s t a N . B . S . c a l i -b r a t e d t h e r m o m e t e r . T h e s o l v e n t s u s e d f o r t h e k i n e t i c s w e r e p u r i f i e d a s f o l l o w s . T e t r a l i n ( r e a g e n t g r a d e ) w a s d r i e d o v e r c a l c i u m c h l o r i d e f o r 2 4 h r s a n d d i s t i l l e d t w i c e u n d e r r e d u c e d p r e s s u r e ; b . p . 4 6 ° ( 3 - 4 m m ) , n 2 4 1 . 5 3 9 6 ( l i t . (95) n 2 5 1. 5 3 9 1 9 ) . N i t r o b e n z e n e ( r e a g e n t g r a d e ) w a s w a s h e d w i t h d i l u t e H ^ S O ^ , N a H C O g s o l u t i o n , a n d f i n a l l y w i t h w a t e r . A f t e r d r y i n g o v e r c a l c i u m c h l o r i d e t h e n i t r o b e n z e n e w a s d i s t i l l e d t w i c e u n d e r r e d u c e d p r e s s u r e ; b . p . 6 7 ° (2 m m ) , n 2 ^ 0 1. 5 5 2 5 ( l i t . (96) n 2 0 1. 5 5 2 9 ) . D i - n - b u t y l p h t h a l a t e ( r e a g e n t g r a d e ) w a s d i s t i l l e d t w i c e u n d e r r e d u c e d p r e s s u r e ; b . p . 1 5 7 ° ( 0 . 5 m m ) . F o r m a m i d e ( E a s t m a n W h i t e L a b e l ) w a s d i s t i l l e d t w i c e u n d e r r e d u c e d p r e s s u r e ; b . p . 6 2 - 6 5 ° (2 m m ) , n 2 5 1 . 4 4 5 4 ( l i t . (96) n 2 2 ' 7 D D . 1. 4 4 5 3 ) . T h e g e n e r a l p r o c e d u r e f o r a r u n i s a s f o l l o w s . A s t a n d a r d s o l u -t i o n o f t h e p y r a z o l i n e w a s m a d e u p i n a f i v e o r t e n m l v o l u m e t r i c f l a s k . - 151 -One m l of the s o l u t i o n c o n t a i n e d enough p y r a z o l i n e to give a f i n a l n/trogen v o l u m e of 40-45 m l . When the o i l bath was at the r e q u i r e d t e m p e r a t u r e the r e a c t i o n f l a s k A, c h a r g e d w i t h 50 m l of solvent, was i m m e r s e d and s t i r r i n g was commenced. S t o p c o c k s K and L w e r e set so that expanding a i r and n i t r o g e n c o u l d escape t h r o u g h the b u b b l e r N, A steady s t r e a m of p u r i f i e d n i t r o g e n was p a s s e d t h r o u g h s t o p c o c k B into the s y s t e m f o r 30 m i n . S t o p c o c k B was then c l o s e d and the s y s t e m a l l o w e d to e q u i l i -b r a t e f o r 30 m i n . A t the end of t h i s p e r i o d the m e r c u r y l e v e l w a s set to z e r o and L v/as c l o s e d f r o m N. S t o p c o c k C was opened, 1. 00 m l of the p y r a z o l i n e s o l u t i o n was q u i c k l y i n j e c t e d , and C c l o s e d a g a i n c o n c u r r e n t w i t h the c h r o n o m e t e r b e i n g s t a r t e d . The f r e q u e n c y of the v o l u m e r e a d i n g s depended on the h a l f - l i f e of the d e c o m p o s i t i o n . About twenty r e a d i n g s w e r e t a k e n f o r each r u n . T h e a t m o s p h e r i c p r e s s u r e was r e c o r d e d p e r i o d i c a l l y d u r i n g a r u n . R e a c t i o n s w e r e g e n e r a l l y f o l l o w e d to 7 0 - 8 0 % c o m p l e t i o n . S e v e r a l r u n s w e r e t a k e n to c o m p l e t i o n (nine o r t e n h a l f - l i v e s ) to c h e c k the a p p a r a t u s . F o r n - b u t y l phthalate s o l v e n t r u n s , the o b s e r v e d Voo was w i t h i n 9 9 - 1 0 1 % of the c a l c u l a t e d ( s t o i c h i o m e t r i c ) Voo . The a g r e e m e n t between the o b s e r v e d V«> and c a l c u l a t e d Voo f o r the m o r e v o l a t i l e s o l -v e n t s was not as good. It i s f o r t h i s r e a s o n that m o s t of the r u n s w e r e c a r r i e d out i n n - b u t y l phthalate. A f t e r e a c h r u n the v o l u m e r e a d i n g s w e r e c o r r e c t e d to s t a n d a r d t e m p e r a t u r e and p r e s s i i r e to g i v e V , . and the r a t e c o n s t a n t d e t e r m i n e d as d e s c r i b e d above. M o s t of the k i n e t i c r u n s gave good s t r a i g h t l i n e p l o t s to - 1 5 2 -70% c o m p l e t i o n . W h e r e s l i g h t d e v i a t i o n s f r o m l i n e a r i t y o c c u r r e d they w e r e a t t r i b u t e d to s o l v e n t v a p o u r e f f e c t s . It was n e c e s s a r y to m o d i f y the k i n e t i c p r o c e d u r e s l i g h t l y when the r u n s f o r 3 - m e t h y l - 3 - c a r b o m e t h o x y l - 1 - p y r a z o l i n e - 4 , 4-d^  ( 9 6 ) w e r e made s i n c e t h e r e was i n s u f f i c i e n t p y r a z o l i n e to make up s t a n d a r d s o l u t i o n s . W hen t h i s p y r a z o l i n e was d e c o m p o s e d i n n - b u t y l phthalate the p r o c e d u r e was as f o l l o w s . A 2 4 0 - 2 6 0 IAI s a m p l e of the p y r a z o l i n e was d i s s o l v e d i n one m l of n - b u t y l phthalate. M o s t of t h i s s o l u t i o n was i n j e c t e d into the r e a c t i o n f l a s k when the r u n was commenced. The d e c o m p o s i t i o n was f o l -l o w e d to t e n h a l f - l i v e s and the o b s e r v e d was u s e d to c a l c u l a t e k. T h i s p r o c e d u r e c o u l d not be e m p l o y e d f o r r u n s i n f o r m a m i d e s i n c e the a g r e e m e n t between c a l c u l a t e d Voo and o b s e r v e d Vo^ > i s not good due to so l v e n t v a p o u r p r e s s u r e . T h e a r m of the r e a c t i o n f l a s k h o l d i n g s t o p c o c k C was s h o r t e n e d so that the s t o p c o c k was r e m o v e d . A r u b b e r s e ptum stopper c l o s e d the tube. When the r u n i n f o r m a m i d e was to be s t a r t e d a 2 4 0 - 2 5 0 /J.1 s a m p l e of the p y r a z o l i n e was t a k e n up into a 2 5 0 /xl s y r i n g e . T h e s y r i n g e and p y r a z o l i n e w e r e then weighed on an a n a l y t i c a l balance. T o c o m m e n c e the r u n the p y r a z o l i n e was i n j e c t e d t h r o u g h the septum stopper into the f l a s k . R e w e i g h i n g the empty s y r i n g e gave the amount of p y r a z o l i n e t r a n s f e r r e d to the f l a s k . T h i s p r o c e d u r e was a l s o f o l l o w e d f o r the d e c o m p o s i t i o n of 3 - m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e - 5 , 5 - d ^ ( 9 7 ) i n f o r m a m i d e , r u n no. 1 7 3 . T r i a l r u n s w i t h the n a t u r a l compounds i n d i c a t e d that the above - 1 5 3 -procedu.~e changes gave r a t e c o n s t a n t s c o m p a r a b l e t o t h o s e obtained f r o m r u n s p e r f o r m e d i n the u s u a l m anner. P r o d u c t A n a l y s i s S o l u t i o n s c o n s i s t i n g of 1 2 0 - 1 5 0 ^ml of p y r a z o l i n e and one m l of s o l v e n t w e r e s e a l e d i n t o f i v e m l a m p o u l e s equipped w i t h b r e a k - s e a l s . The a m p o u l e s w e r e heated at the d e s i r e d t e m p e r a t u r e i n an o i l bath f o r s e v e r a l hour s. The t e m p e r a t u r e and t i m e r e q u i r e d f o r c o m p l e t e decom-p o s i t i o n of each p y r a z o l i n e i s g i v e n i n d e t a i l below. The ampoules w e r e t h e n c o o l e d and opened, and the contents t r a n s f e r r e d to a b u l b - t o - b u l b d i s t i l l a t i o n a p p a r a t u s w h e r e the p r o d u c t s w e r e ob t a i n e d f r e e of s o l v e n t by v a c u u m d i s t i l l a t i o n . The p r o d u c t m i x t u r e s w e r e a n a l y z e d by v a p o u r -phase c h r o m a t o g r a p h y . The c h r o m a t o g r a p h i c u n i t u s e d was e i t h e r an A e r o g r a p h M o d e l A - 9 0 - P or an A e r o g r a p h A-90-P3, both equipped w i t h a t h e r m a l c o n d u c t i v i t y d e t e c t o r . T h e c o l u m n s and a n a l y s i s c o n d i t i o n s w e r e d i f f e r e n t f o r each p y r a z o l i n e p r o d u c t m i x t u r e and a r e g i v e n below. C h r o m a t o g r a x n s w e r e r e c o r d e d on a H o n e y w e l l M o d e l E l e c t r o n i c 15 g r a p h i c r e c o r d e r and w e r e c o n v e r t e d to d i g i t a l data by peak a r e a d e t e r m i n a t i o n u s i n g a d i s c c h a r t i n t e g r a t o r . It was a s s u m e d that the r e s p o n s e of the d e t e c t o r to a l l of the compounds was the same. D e c o m p o s i t i o n of neat p y r a z o l i n e was c a r r i e d out by h e a t i n g a 4 0 - 1 0 0 JULI s a m p l e of the p y r a z o l i n e i n a one o r f i v e m l ampoule. The contents of the ampoule w e r e a n a l y z e d d i r e c t l y when the d e c o m p o s i t i o n - 154 -was c o m p l e t e d . When p r o d u c t a n a l y s i s f o r 3-methyl- 3-carbomethoxy- 1-pyrazo-l i n e - 4 , 4 - d . , (96) was d e t e r m i n e d i t was n e c e s s a r y to r e c o v e r the p r o d u c t s f r o m the s o l u t i o n s r e m a i n i n g a f t e r the k i n e t i c r u n s . T h i s was a c c o m -p l i s h e d i n the f o l l o w i n g manner. A f t e r the r u n was c o m p l e t e d the r e a c t i o n f l a s k was a l l o w e d to c o o l w i t h the c o n d e n s e r s t i l l a ttached. A few m l of so l v e n t w e r e r i n s e d down the c o n d e n s e r into the r e a c t i o n f l a s k to c a r r y down any prod u c t w h i c h m a y have condensed i n the c o i l s . T he r e a c t i o n f l a s k was then connected to a D r y Ic e / a c e t o n e c o o l e d t r a p on a v a c u u m l i n e and the p r o d u c t s r e m o v e d f r o m the s o l v e n t by pumping f o r two h o u r s . T h e p r o d u c t m i x t u r e i n the t r a p was then a n a l y z e d . (i) D e c o m p o s i t i o n of 3 - m e t h y l - 3 - c a r b o m e t h o x y - 1 - p y r a z o l i n e i (95), 3 - m e t h y l - 3 - c a r b o m e t h o x y - l - p y r a z o l i n e - 4 , 4 -d 2 (96), and 3-methyl- 3-carbomethoxy- 1 - p y r a z o l i n e - 5 , 5 -d 2 (97). S o l u t i o n s and neat s a m p l e s of 3 - m e t h y l - 3 - c a r b o -methoxy- 1 - p y r a z o l i n e and the d e u t e r a t e d analogs w e r e heated to 127° f o r t h r e e h o u r s . The V . P . C , a n a l y s i s e m p l o y e d a 10' x 1/4" d i i s o d e c y l -p h t h a l a t e c o l u m n at 100° w i t h h e l i u m f l o w of 50 m l per m i n . T h e r e s u l t s a r e g i v e n i n T a b l e III. D e c o m p o s i t i o n i n f o r m a m i d e s o l u t i o n gave a r e l a t i v e l y l a r g e p e r -centage of m e t h y l t i g l a t e (_1). A t e s t was made to see i f some of t h i s a r o s e f r o m t h e r m a l i s o m e r i z a t i o n of the c i s i s o m e r , m e t h y l angelate (2). - 155 -M e t h y l angelate (100 y.1) and f o r m a m i d e (1 ml) w e r e s e a l e d i n t o a 5 m l ampoule and heated at 127° f o r 6 h o u r s . The r e s u l t i n g o l e f i n m i x t u r e w a s r e m o v e d f r o m the so l v e n t by the u s u a l p r o c e d t i r e and a n a l y z e d by V . P . C . (same c o n d i t i o n s ) . The m i x t u r e c o n s i s t e d of 98. 3 % of m e t h y l angelate ( s t a r t i n g m a t e r i a l ) and 1. 7% of m e t h y l t i g l a t e . P y r a z o l i n e _9_5 was a l s o p y r o l y z e d at t e m p e r a t u r e s of 112° and 157° f o r 8 h r and 20 m i n p e r i o d s r e s p e c t i v e l y . The r e s u l t s a r e g i v e n i n T a b l e V I I I . (i i ) D e c o m p o s i t i o n of 3 - m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e (42) S o l u t i o n s of 3 - m e t h y l - 3 - a c e t y l - 1 - p y r a z o l i n e w e r e he a t e d t o 125° f o r 3 h o u r s . The p r o d u c t m i x t u r e s w e r e a n a l y z e d on a 20' x 1/4" d i e t h y l e n e g l y c o l s u c c i n a t e c o l u m n (DEGS) at 152° w i t h h e l i u m f l o w of 60 m l per m i n . The r e s u l t s a r e g i v e n i n T a b l e IV. F o r p a r t i a l d e c o m p o s i t i o n i n f o r m a m i d e , the s o l u t i o n s w e r e heated to 12 3° f o r 6 and 10 m i n u t e i n t e r v a l s and then i m m e d i a t e l y c o o l e d i n i c e - c o l d w a t e r . The p r o d u c t s w e r e r e m o v e d f r o m u n r e a c t e d p y r a z o l i n e and s o l v e n t i n the u s u a l m a n n e r . The r e s u l t s g i v e n i n T a b l e IV have not been c o r r e c t e d f o r the t h e r m a l i s o m e r i z a t i o n of c i s - 3-methyl- 3-penten-2-one (47) to t r a n s - 3-methyl-3-penten-2-one (46). The extent of t h i s i s o m e r i z a t i o n w a s r o u g h l y e s t i m a t e d i n the f o l l o w i n g m anner. A s o l u t i o n c o n s i s t i n g of 5 ^J. of c_is_- 3-m e t h y l - 3 - p e n t e n-2-one and 10 pX of f o r m a m i d e s e a l e d i n t o a 1 m l ampoule - 156 -was heated to 125° f o r 2 hovirs. A n a l y s i s by V. P.C. showed that the m i x t u r e was 82. 6% c i s and 17. 4% t r a n s . ( i i i ) D e c o m p o s i t i o n of 3, 5, 5 - t r i m e t h y l - 3 - c a r b o m e t h o x y - 1 -p y r a z o l i n e (100) S o l u t i o n s and neat s a m p l e s of 3, 5, 5 - t r i m e t h y l - 3 -c a r b o m e t h o x y - 1 - p y r a z o l i n e w e r e heated to 113° f o r 4 h o u r s . The p r o -duct m i x t u r e s w e r e a n a l y z e d on a 20' x 1/4" D E G S c o l u m n at 127° w i t h a h e l i u m f l o w of 45 m l per m i n u t e . T h e r e s u l t s a r e given i n T a b l e V. The p r o d u c t s w e r e i d e n t i f i e d by c o m p a r i s o n of the r e t e n t i o n t i m e s w i t h s t a n d a r d s a m p l e s p r e p a r e d by N. C h i u of t h i s l a b o r a t o r y (51). (iv) D e c o m p o s i t i o n of 3, 5, 5 - t r i m e t h y l - 3 - a c e t y l - 1 -p y r a z o l i n e (101) S o l u t i o n s and neat s a m p l e s of 3, 5, 5 - t r i m e t h y l - 3 -a c e t y l - 1 - p y r a z o l i n e w e r e heated to 100° f o r 3-1/2 h o u r s . P r o d u c t m i x -t u r e s w e r e a n a l y z e d on a 20' x 1/4" D E G S c o l u m n at 140° w i t h h e l i u m f l o w of 30 m l per m i n . The r e s u l t s a r e g i v e n i n T a b l e V I . (v) D e c o m p o s i t i o n of t r a n s - 3 , 4 - d i m e t h y l - 3-carbomethoxy -1 - p y r a z o l i n e (4) S o l u t i o n s of t r a n s - 3 , 4 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 -p y r a z o l i n e w e r e heated to 155° f o r 5-1/2 h o t i r s j . T he p r o d u c t m i x t u r e s w e r e a n a l y z e d on a 10' x 1/4" Dow C o r n i n g - 5 5 0 (DC-550) c o l u m n at 115° - 157 -w i t h a h e l i u m f l o w of 50 m l per m i n . T h e r e s u l t s a r e g i v e n i n T a b l e V I I . (vi) D e c o m p o s i t i o n of c i s - 3, 4 - d i m e t h y l - 3 - c a r b o m e t h o x y - 1 -p y r a z o l i n e (_3) S o l u t i o n s and neat s a m p l e s of c i s - 3, 4 - d i m e t h y l - 3 -c a r b o m e t h o x y - 1 - p y r a z o l i n e w e r e h e a t e d to 155° f o r 6 h o u r s . The p r o -duct m i x t u r e s w e r e a n a l y z e d on a 10' x 1/4" DC-550 c o l u m n at 115° w i t h a h e l i u m f l o w of 50 m l per m i n . T h e r e s u l t s a r e g i v e n i n T a b l e V I I . - 158 -B I B L I O G R A x ^ H Y 1. E . B u c h n e r a n d H . D e s s a u e r , B e r . , _26, 2 5 8 ( 1 8 9 3 ) . 2 . K . v o n A u w e r s a n d J . K o n i g , A n n . , 4 9 6 , 2 7 ( 1 9 3 2 ) . 3 . K . v o n A u w e r s a n d J . K o n i g , i b i d . , 4 9 6 , 2 5 2 ( 1 9 3 2 ) . 4 . J . V a n A l p h e n , R e c . t r a v . c h i m . , _62, 3 3 4 ( 1 9 4 3 ) . 5 . T . L . J a c o b s i n R . C . E l d e r f i e l d e d . , " H e t e r o c y c l i c C o m p o u n d s " , V o l . 5, J o h n W i l e y a n d S o n s , N e w Y o r k , 1 9 5 7 , C h a p t e r 2 . . 6. D . G o t k i s a n d J . B . C l o k e , J . A m . C h e m . S o c . , _56, 2 7 1 0 ( 1 9 3 4 ) . 7. R . H u i s g e n , H . S t a n g l , H . J . S t u r m , a n d H . W a g e n h o f e r , A n g e w . C h e m . , _73, 170 ( 1 9 6 1 ) . 8 . R . H u i s g e n , P r o c . C h e m . S o c , 3 5 7 ( 1 9 6 1 ) . 9 . R . H u i s g e n , A n g e w . C h e m . , I n t e r n a t . E d n . , _2, 6 3 3 ( 1 9 6 3 ) . 1 0 . B . E i s t e r t i n " N e w e r M e t h o d s o f P r e p a r a t i v e O r g a n i c C h e m i s t r y " , f i r s t A m e r i c a n E d i t i o n , I n t e r s c i e n c e P u b l i s h e r s , N e w Y o r k , 1 9 4 8 , p p . 5 5 1 - 5 5 6 . 1 1 . W . G . Y o u n g , L . J , A n d r e w s , S . L . L i n d e n b a u m , a n d S . J . C r i s t o l , J . A m . C h e m . S o c , _66, 8 1 0 ( 1 9 4 4 ) . 1 2 . A . L e d w i t h a n d D . P a r r y , J . C h e m . S o c . , 1 4 0 8 ( 1 9 6 6 } . 1 3 . C . G . O v e r b e r g e r , N . W e i n s h e h k e r , a n d J . - . P . A n s e l m e , J . A m . C h e m . S o c . , _ 8 7 , 4 1 1 9 ( 1 9 6 5 ) . 1 4 . T . V , V a n A u k e n a n d K . L . R i n e h a r t , J r . , J . A m . C h e m . S o c , _84, 3 7 3 6 ( 1 9 6 2 ) . 1 5 . D . E . M c G r e e r , N . W . K . C h i u , M . G . V i n j e , a n d K . C . K . W o n g , C a n . J . C h e m . , 4 3 , 1 4 0 7 ( 1 9 6 5 ) . 1 6 . R . J . C r a w f o r d , A . M i s h r a , a n d R . J . D u m m e l , J . A m . C h e m . S o c . , 8 8 , 3 9 5 9 ( 1 9 6 6 ) . - 159 -1 7 . a) W . M . J o n e s , J . A m . C h e m . S o c . , _80, 6 6 8 7 ( 1 9 5 8 ) . b) W . M . J o n e s , i b i d . , 8 1 , 5 1 5 3 ( 1 9 5 9 ) . c ) W . M . J o n e s , i b i d . , 8 2 , 3 1 3 6 ( 1 9 6 0 ) . 1 8 . a) W . M . J o n e s a n d W . T . T a i , J . O r g . C h e m . , 2 7 , 1 0 3 0 ( 1 9 5 2 ) . b) W . M . J o n e s a n d W . T . T a i , i b i d . , 2 7, 1 3 2 4 ( 1 9 6 2 ) . 1 9 . D . E . M c G r e e r , i b i d . , 2_5, 8 5 2 ( I 9 6 0 ) . 2 0 . D . E . M c G r e e r , W . W a i , a n d G . C a r m i c h a e l , C a n . J . C h e m . , 3 8 , 2 4 1 0 ( I 9 6 0 ) . 2 1 . D . E . M c G r e e r , P . M o r r i s , a n d G . C a r m i c h a e l , C a n . J . C h e m . , 4 1 , 726 ( 1 9 6 3 ) . 2 2 . H . M . W a l b o r s k y a n d C . G . P i t t , J . A m . C h e m . S o c . , _84, 4 8 3 1 ( 1 9 6 2 ) . 2 3 . D . E . M c G r e e r , P h . D . T h e s i s , U n i v e r s i t y o f I l l i n o i s , 1 9 5 9 . 2 4 . S . G . B e e c h , J . H . T u r n b u l l , a n d W . W i l s o n , J . C h e m . S o c , 4 6 8 6 ( 1 9 5 2 ) . 2 5 . W . I . A w a d , S . M . A b d e l , R . O m r a n , a n d M . S o b h y , J . O r g . C h e m . , 2 6 , 4 1 2 6 ( 1 9 6 1 ) . 2 6 . S . G . C o h e n a n d C . H . W a n g , J . A m . C h e m . S o c . , _77, 3 6 2 8 ( 1 9 5 5 ) . 2 7 . C . G . O v e r b e r g e r a n d A . V . D i G i u l i o , i b i d . , 8 1 , 2 1 5 4 ( 1 9 5 9 ) . 2 8 . S . G . C o h e n , R . - Z a n d , a n d C . S t e e l , i b i d . , 8 3 , 2 8 9 5 ( 1 9 6 1 ) . 2 9 . C . G . O v e r b e r g e r a n d J . - P . A n s e l m e , i b i d . , 8 6 , 6 5 8 ( 1 9 6 4 ) . 3 0 . C . G . O v e r b e r g e r , R . E . Z a n g a r o , a n d J . T - P . A n s e l m e , J . O r g . C h e m . , 3_L» 2 0 4 6 ( 1 9 6 6 ) . 3 1 . D . E . M c G r e e r , R . S . M c D a n i e l , a n d M . G . V i n j e , C a n . J . C h e m . , 4 3 , 1 3 8 9 ( 1 9 6 5 ) . 3 2 . D . E . M c G r e e r , N . W . K . C h i u , a n d M . G . V i n j e , C a n . J . C h e m . , 4 3 , 1 3 9 8 ( 1 9 6 5 ) . 3 3 . N . W . K . C h i u , M . S c . T h e s i s , U n i v . of B r i t i s h C o l u m b i a , 1 9 6 4 . 160 -3 4 . R . J . C r a w f o r d a n d D . M . C a m e r o n , C a n . J . C h e m . , 4 5 , 691 ( 1 9 6 7 ) . 3 5 . R . J . C r a w f o r d a n d A . M i s h r a , J . A m . C h e m . S o c . , 8 8 , 3 9 6 3 • ( 1 9 6 6 ) . 3 6 . A . M i s h r a , P h . D . T h e s i s , U n i v . o f A l b e r t a , 19 6 5 . 3 7 . R . J . C r a w f o r d a n d D„ M . C a m e r o n , J . A m . C h e m . S o c . , 8 8 , 2 5 8 9 ( 1 9 6 6 ) . . ~ 3 8 . R . J . C r a w f o r d a n d L . H . A l i , i b i d . , 8 9 , 3 9 0 8 ( 1 9 6 7 ) . 3 9 . R . J . C r a w f o r d a n d G . L , E r i c k s o n , i b i d . , 8 9 , 3 9 0 7 ( 1 9 6 7 ) . 4 0 . S . S e l t z e r , i b i d . , 8 5 , 14 ( 1 9 6 3 ) . 4 1 . R . H o f f m a n n , A b s t r a c t s of t h e 1 5 1 s t N a t i o n a l M e e t i n g o f T h e A m e r i c a n C h e m i c a l S o c i e t y , P i t t s b u r g h , P a . , M a r c h 1 9 6 6 , P a p e r 1 0 9 K . 4 2 . R . H o f f m a n n , J . A m . C h e m . S o c , _90, 1 4 7 5 ( 1 9 6 8 ) . 4 3 . D . E . M c G r e e r a n d W . - S . W u , C a n . J . C h e m . , _ 4 5 , 461 ( 1 9 6 7 ) . 4 4 . W . - S . W u , M . S c T h e s i s , U n i v . o f B r i t i s h C o l u m b i a , 1 9 6 6 . 4 5 . W . R . R o t h a n d M „ M a r t i n , A n n . , 7 0 2 , 1 ( 1 9 6 7 ) . 4 6 . E . L . A l l r e d a n d j l . L . S m i t h , J . A m . C h e m . S o c , _89, 7 1 3 3 ( 1 9 6 7 ) . 4 7 . P . S c h e i n e r , J . A m . C h e m . S o c . , _90, 9 8 8 ( 1 9 6 8 ) . 4 8 . K . B . W i b e r g , C h e m . R e v . , _55, 713 ( 1 9 5 5 ) . 4 9 . E . H . H a l e v i , P r o g r e s s . P h y s . O r g . 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R e a c t i o n s , _14, 2 7 0 ( 1 9 6 5 ) . 5 9 . H . O . H o u s e a n d G . H . R a s m u s s o n , J . O r g . C h e m . , _26, 4 2 7 8 ( 1 9 6 1 ) . 6 0 . M . P o m e r a n t z , J . A m . C h e m . S o c . , _89, 6 9 4 ( 1 9 6 7 ) . 6 1 . C . M a n n i c h a n d K . R i t s e r t , B e r . , 5 7 , 1 1 1 6 ( 1 9 2 4 ) . 6 2 . P . K o u r i m a n d V . V a c e k , T e t r a h e d r o n L e t t e r s , 1 0 5 1 ( 1 9 6 2 ) . 6 3 . S . G . C o h e n , S . J . G r o s z a s a n d D . B , S p a r r o w , J . A m . C h e m . S o c . , J_2, 3 9 4 7 ( 1 9 5 0 ) . 6 4 . M . J . G o l d s t e i n a n d G . L . T h a y e r , J r . , J . A m . C h e m . S o c , 8 7, 1 9 2 5 ( 1 9 6 5 ) . 6 5 . J . H i n e " P h y s i c a l O r g a n i c C h e m i s t r y " , 2 n d e d . , M c G r a w - H i l l , N e w Y o r k , N . Y . , 1 9 6 2 , C h a p t e r 4 . 6 6 . S . S e l t z e r , J . A m . C h e m . S o c . , 83, 2 6 2 5 ( 1 9 6 1 ) . 6 7 . S . S e l t z e r a n d F . T . . D u n n e , J 8 A m . 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S o c , 8 6 , 5 6 4 ( 1 9 6 4 ) . 7 6 . J . C . W r i g h t , S o u t h w e s t R e g i o n a l M e e t i n g o f t h e A m e r i c a n C h e m i c a l S o c i e t y , L i t t l e R o c k , A r k . , D e c e m b e r , 1 9 6 7 , r e p o r t e d i n C h e m . a n d E n g . N e w s , J a n . 1, 2 8 ( 1 9 6 8 ) . 7 7 . S . S e l t z e r a n d E . J . H a m i l t o n , J r . , J . A m . C h e m . S o c . , 8 8 , 3 7 7 5 ( 1 9 6 6 ) . 7 8 . S . W i n s t e i n a n d J . T a k a h a s h i , T e t r a h e d r o n , 2 , 3 1 6 ( 1 9 5 8 ) . 7 9 . H . S i m o n a n d D . P a l m , A n g e w . C h e m . , I n t e r n a t . E d n . , _5, 9 2 0 ( 1 9 6 6 ) . 8 0 . F . A r n d t i n A . H . B l a t t e d . , O r g . S y n . , C o l l . V o l . I I , 461 ( 1 9 5 5 ) . 8 1 . R . H e i l m a n n a n d J . - M . B o n n i e r , C o m p t . r e n d . , 2 4 8 , 3 4 4 2 ( 1 9 5 9 ) . 8 2 . A . S . D r e i d i n g a n d R . J . P r a t t , J . A m . C h e m . S o c . , _76, 1 9 0 2 ( 1 9 5 4 ) . 8 3 . R . 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M „ J a c k m a n , " A p p l i c a t i o n s o f N u c l e a r M a g n e t i c R e s o n a n c e S p e c t r o s c o p y i n O r g a n i c C h e m i s t r y " , P e r g a m o n , N e w Y o r k , 1959^ C h a p . 7 . • 9 1 . A . I„ V o g e l , " P r a c t i c a l O r g a n i c C h e m i s t r y " , 3 r d . e d . , L o n g m a n s , L o n d o n , 1 9 & 1 , p . 4 8 5 . • 9 2 . N . W e i n e r i n A . H . B l a t t e d . , O r g . S y n . , C o l l . V o l . I I , 2 79 ( 1 9 5 5 ) . 9 3 . G . T . M o r g a n a n d E . W a l t o n , J . C h e m . S o c , 1 0 6 4 ( 1 9 3 3 ) . 9 4 . R . C . P e t e r s o n , J . H . M a r k g r a f a n d S„ D . R o s s , J . A m . C h e m . S o c . , _83, 3 8 1 9 ( 1 9 6 1 ) . 9 5 . T h e M e r c k I n d e x , 7 t h . e d . , M e r c k a n d C o . , I n c . , R a h w a y , N . J . , 1 9 6 0 . 9 6 . " H a n d b o o k o f P h y s i c s a n d C h e m i s t r y " , 3 6 t h . e d . , C h e m i c a l R u b b e r -P u b l i s h i n g C o . , C l e v e l a n d , O h i o , 1 9 5 4 . 9 7 . S . S e l t z e r a n d S . G . M y l o n a k i s , J , A m . C h e m . S o c , 8 9 , 6 5 8 4 ( 1 9 6 7 ) . 9 8 . M . L . H a l b e r s t a d t a n d J . P . C h e s i c k , J . A m . C h e m . S o c , 8 4 , 2 6 8 8 ( 1 9 6 2 ) . 9 9 . E . V o g e l , A n g e w . C h e m . , _72, 4 ( 1 9 6 0 ) . 1 0 0 . J . H a m e l i n , C . R . A c a d . S c . , P a r i s , 2 6 1 , 4 7 7 6 ( 1 9 6 5 ) . 1 0 1 . J . H a m e l i n a n d R . C a r r i e , C . R . A c a d . S c . , P a r i s , 2 6 1 , 5 5 4 5 ( 1 9 6 5 ) . 

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