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Pyrolysis and photolysis of cis and trans-3, 5-dimethyl-3-acetyl-delta1-pyrazoline and cis and trans-3,5-dimethyl-3-carbomethoxy-delta1-pyrazoline. Chiu, Norman Wing Kwai 1964

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PYROLYSIS AND PHOTOLYSIS OP o i s AND trans-3,5-DIMETHYL-3-ACETYL-A 1 -PYRAZOLINE AND o i s AND trans-3,5-DIMETHYL-3-CARBOMETHOXY-A 1-PYRAZOLINE by NORMAN WING KWAI CHIU B.Sc., Dalhousie U n i v e r s i t y , 1962 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department o f CHEMISTRY We aopept t h i s t h e s i s as ponforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA J u l y , 1964 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 requirements f o r an advanced degree at the U n i v e r s i t y of • B r i t i s h Columbia,, I agree that 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 reference and study * .I f u r t h e r agree that per m i s s i o n f o r extensive copying of 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 granted by the. Head of 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 understood th a t ; c o p y i n g or 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 allowed without my w r i t t e n permission,. Department of CHEMISTRY 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 - i i - ABSTRACT The thermal and p h o t o l y t i c decomposition of c i s and tra_ns_ - 3 , 5-dimethyl - 3-acetyl -A" 1"-pyrazoline have been found to g i v e s i x p r o d u c t s . They have been separated and i d e n t i f i e d as 2 , 3 , 5-trimethyl-/£-dihydrofuran, c i s and t r a n s - 1 , 2 - d i m e t h y l - l - a c e t y l e y c l o p r o p a n e , c i s and trans - 3-methyl - 3-hexen - 2-one and 3-methyl -4-hexen -2-one. The f o r m a t i o n of eyclopropanes by p h o t o l y s i s showed some degree of s - t e r e o s p e c i f I c i t y . Both p y r o l y s i s and p h o t o l y s i s y i e l d e d o l e f i n s w i t h h i g h degree of 2 s t e r e o s p e c i f i c i t y . 2,3,5-TrImethyl-££"-dihydrofuran was a major product from the decomposition of c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - A - p y r a z o l i n e o n l y . P y r o l y s i s gave a h i g h e r r a t i o o f o l e f i n s t o eyclopropanes than p h o t o l y s i s . These decomposition r e a c t i o n s gave r e s u l t s analogous to those of c i s and t r a n s - 3 , 5 - d i m e t h y l - 3-earbomethoxy-^-pyrazoline. The product compositions from both the p y r o l y s i s and p h o t o l y s i s of c i s and trans_ - 3 , 5-dimethyl - 3-carbomethoxy-^"- p y r a z o l i n e have been found to show a s m a l l and r e g u l a r i n f l u  ence of the s o l v e n t and t h i s has been r e l a t e d t o the d i e l e c t r i c c onstant of the s o l v e n t . P y r o l y s i s and p h o t o l y s i s gave an o l e f i n to cyclopropane r a t i o of 57*43 and 21*79* r e s p e c t i v e l y , i n formamide, and 7*93 and 5*95, r e s p e c t i v e l y , i n cyclohexane. A s m a l l k i n e t i c s o l v e n t e f f e c t has been observed f o r the p y r o l y s i s of 3 , 5-dimethyl - 3-carboraethoxy-/^-pyrazoline. The r a t e of p y r o l y s i s a s . f o l l o w e d by the r a t e of n i t r o g e n evo-- I l i - l u t i o n has been found to decrease f o r the f o l l o w i n g s e r i e s of solvents« d l - n - b u t y l e t h e r , t e t r a l i n , nitrobenzene and form- amide. These r a t e s were a l l w i t h i n a f a c t o r of t h r e e . The absence of r a t e enhancement i n a s o l v e n t of h i g h d i e l e c t r i c constant has been used as an argument a g a i n s t an i o n i c I n t e r  mediate i n these r e a c t i o n s . L i q u i d phase p h o t o l y s i s of t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o - methoxy~£^-pyrazolIne at v a r i o u s temperatures ra n g i n g from o _.o -55 to 58 d i d not show a p p r e c i a b l e change i n the product compositions a t t r i b u t a b l e to the i n f l u e n c e of temperature. The s o l v e n t temperature t h e r e f o r e does not e f f e c t the amount of quenching of any "hot" i n t e r m e d i a t e . P h o t o l y s i s and p y r o l y s i s of c i s and trans - 3 , 5-dimethy 1 - 3-carbomethoxy-A - p y r a z o l i n e under i d e n t i c a l c o n d i t i o n s d i d not g i v e the same product composition. T h i s suggested the two r e a c t i o n s do not have a common Intermediate. No i s o m e r i z a t i o n between the c i s and t r a n s - 3 , 5 - d i m e t h y l - 3-carbomethoxy - A L-pyrazolines;has been observed as shown by the p a r t i a l p y r o l y s i s and p h o t o l y s i s of the t r a n s - p y r a z o l i n e . These r e s u l t s are d i s c u s s e d In view of c u r r e n t mecha- *1 n i s t l c p r o p o s a l s f o r the p y r o l y s i s and p h o t o l y s i s of & - p y r a z o l i n e s . - v i l i ACKNOWLEDGEMENT The author wishes to express h i s s i n c e r e a p p r e c i a t i o n to Dr, D. E. MeGreer who^ suggested t h i s r e s e a r c h p r o j e c t and under whose guidance and encouragement t h i s r e s e a r c h was performed. The author Is indebted to Mrs. E. B r i o n and Mr. P. Horn f o r the n u c l e a r magnetic resonance s p e c t r a , to Dr. A. Bernhardt, Mrs. A. A l d r i d g e and Mrs. C. Jenkins f o r the mic r o a n a l y s e s . F i n a n c i a l a s s i s t a n c e from the N a t i o n a l Research C o u n c i l of Canada f o r t h i s r e s e a r c h p r o j e c t i s deeply a p p r e c i a t e d . _ i v - TABLE OF CONTENTS Page I . I n t r o d u c t i o n 1 I I , S y n t h e s i s and I d e n t i f i c a t i o n of 3,3 ,,5-Trisubstituted /5^-Pyrazolines 1 1. 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 - p y r a z o l i n e 7 2. 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 - A 1 - p y r a z o l i n e .. 9 I I I . S e p a r a t i o n and I d e n t i f i c a t i o n of Products from the De composition of 3,5-DImethyl-3-aeetyl - A 1~pyrazolines ... 13 IV. Decomposition of 3 , 3 , 5 - T r i s u b s t i t u t e d Z^-Pyrazolines .. 21 V. D i s c u s s i o n 30 V I . Experimental 1. General statement 4 l 2. N - N i t r o s o - N - e t h y l urea 41 3. Diazoethane 42 4. Methyl Isopropenyl ketone 43 5. S ^ - D i m e t h y l - S - a c e t y l - ^ - p y r a z o l i n e 43 6. S e p a r a t i o n of e i s and tr_ans_-3,5-dimethyl-3- a c e t y l - ^ - p y r a z o l i n e 44 7. S e p a r a t i o n of c i s and trans-3,5-dimethyl-3- c a r b o m e t h o x y - ^ - p y r a z o l l n e 44 8. trans-3,5-Dimethyl-3-carbomethoxy-A^-pyrazollne hydrobromide 45 9. Thermal p y r o l y s i s of 3,5-dimethyl-3-acetyl- AJ"-pyrazoline 46 9a. 2,4-Dinltrophenyl hydrazones 59 - V - Page 10. Thermal 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 - A 1 - p y r a z o l i n e 50 11. Vapor phase p y r o l y s i s o f c i s and t r a n s - 3 , 5 - d i m e t h y l - 3-acet.yl-^"-pyrazoline 50 12. L i q u i d phase p y r o l y s i s o f 3 , 5-dimethyl - 3 - 1 a c e t y l - A - p y r a z o l i n e 51 13. L i q u i d phase 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 e e t y l - ^ " - p y r a z o l i n e 52 14. P h o t o l y s i s o f 3 , 5-dimethyl - 3-acetyl-£J['-pyrazoline •••• 52 15. P h o t 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 - ^ " - p y r a z o l i n e 53 16. Vapor phase p y r o l y s i s of c i s and tra_ns - 3 , 5-di- methyl - 3-earbomethoxy-Z^-pyrazoline 53 17. L i q u i d phase p y r o l y s i s of c i s and t r a n s - 3 , 5 - d i methyl - 3-carbomethoxy-^"-pyrazoline i n v a r i o u s s o l v e n t s 53 18. P h o t o l y s i s o f trans - 3 * 5-dimethyl - 3-carbomethoxy- ^ " - p y r a z o l i n e at v a r i o u s temperatures 5^ 19. P h o t 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 - c a r b o - methoxy-^"-pyrazoline i n Formamide at 23° 56 20. P a r t i a l p y r o l y s i s of 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 - ^ - p y r a z o l i n e 56 21. P a r t i a l l i q u i d phase p y r o l y s i s of t r a n s - 3 , 5 - d i - methyl-3-carbomethoxy-/£"-pyrazoline 57 22. K i n e t i c s t u d i e s of the p y r o l y s i s of 3 , 5-dimethyl - 3 - carbomethoxy-/^-pyrazoline i n v a r i o u s s o l v e n t s ....... 57 BIBLIOGRAPHY 60 - v i - LIST OF FIGURES F i g u r e Page I . Mechanism of ^ - p y r a z o l i n e f o r m a t i o n 1 I I . I o n i c mechanism f o r the p y r o l y s i s of 3 ,4-dimethyl- 3-carbomethoxy-A - p y r a z o l i n e s , 3 I I I . Products from the p h o t o l y s i s of 3*4~dimethyl - 3 - earbomethoxy-^s-pyrazolines 5 IV. N.m.r. a b s o r p t i o n showing.,the s e p a r a t i o n of 3*5- dimet.hyl - 3-carbomethoxy-^-pyrazoline i n t o i t s c i s and tr a n s isomers 8 V. N.m.r. sp e c t r a of trans-3,5-dlmethyl-3-earbomethoxy- &t-pyrazoline showing s p l i t t i n g s of C^-hydrogens .... 12 V I . Products from the decomposition of 3 , 5-dimethyl - 3 - earbomethoxy-Zr-pyrazolInes 13 VIIA. P r e p a r a t i v e vapor chromatogram showing the separa t i o n of products from the decomposition of 3 * 5-di- m e t h y l - ^ - p y r a z o l i n e s lh VIIB. A n a l y t i c a l vapor phase chromatogram showing the s e p a r a t i o n of 3-methyl-4-hexen-2-one and t r a n s - 1 , 2-dimethyl-l-aeety.lcyclopropane 14 V I I I . Products from the decomposition of 3 , 5-dimethyl- 3-acetyl-£r-pyrazolines 15 2 IX. N.m.r. spectrum o f 2 , 3 , 5 - t r i m e t h y l - & - d i h y d r o f u r a n .. 17 X. S t e r e o c h e m i s t r y o f the form a t i o n of o l e f i n s from ^ • - p y r a z o l i n e 38 XI. Apparatus f o r p h o t o l y s i s at low temperature 55 X I I . F i r s t o r d e r p l o t of l o g ^/(V^-V^.) verse s time f o r the p y r o l y s i s of 3 , 5-dimethyl - 3-carbomethoxy-^s L- p y r a z o l i n e i n v a r i o u s s o l v e n t s 58 ~ v i i - LIST OP TABLES Table Page I . N.m.r. data of c i s and trans_-3,5-»diraethyl -3-acetyl- A ^ ~ p y r a z o l i n e and c i s and t r a n s - 3 3 5 - d i m e t h y l - 3 - carbomethoxy-£i"~pyrazoline 11 I I . Product compositions f o r the decomposition of 3 , 5 - d i m e t h y l - 3 - a c e t y l - / ^ - p y r a z o l i n e s ' 22 I I I . Product compositions f o r the decomposition of 3<>5- d i m e t h y l - S - c a r b o m e t h o x y - ^ - p y r a z o l l n e s 23 IV. Product compositions f o r the sealed-tube p y r o l y s i s of c i s and trans_ - 3 , 5-dimethyl - 3-carbomethoxy-£^- o , p y r a z o l i n e i n v a r i o u s s o l v e n t s at 125 2o V. Product compositions of p h o t o l y s i s of c i s and trans - 3 , 5-dimethyl - 3-carbomethoxy-ft''-pyrazoline 27 - 1 - I . INTRODUCTION The a d d i t i o n of diazoalkanes to o(,/3-unsaturated c a r b o n y l compounds to form A ^ - p y r a z o l i n e s (1-5) and the p y r o l y s i s of these A ^ - p y r a z o l i n e s to form cyclopropanes (6,7) have been known f o r many y e a r s . Both the a d d i t i o n and p y r o l y s i s mecha nisms have been the s u b j e c t of d i s c u s s i o n . In p a r t i c u l a r , the meehanism f o r the p y r o l y s i s of A ^ - p y r a z o l i n e s i s s t i l l not s e t t l e d at p r e s e n t . The a d d i t i o n mechanism has been proven r e c e n t l y , by Huisgen and coworkers (8-10) 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 , s i m i l a r to the 1,3-dlpolar a d d i t i o n r e a c t i o n , r a t h e r than the two-step i o n i c mechanism (6,11) p r e v i o u s l y proposed. These routes to p y r a z o l i n e s are shown i n F i g u r e I . I t has a l s o R 1 R \ s C=C R J Y RCHN^ ,one-step two-step R — —H , —CH3 Y —-.COCH3, -COOCH3 R 1 • R 2 CT l^Y H ! 1 X J R R 1 R 2 R ^ f — W ^ N " ^ Y I I R* R ^ X N ^ I I I R< FIGURE I - Mechanisms of A 1*-pyrazoline formation, been shown (6,7) t h a t the carbon o^to the n i t r o g e n In the diazo- alkane adds to the double bond at the carbon 0 to the c a r b o n y l - 2 - group i n the o l e f i n . C I s - a d d i t i o n (6,7) i s i n d i c a t e d by the r e  a c t i o n of diazomethane w i t h methyl t i g l a t e (IV) and methyl a n g e l a t e (V) to g i v e c i s and trans - 3,4-dimethyl - 3-carbomethoxy- £^-pyrazoline (VI and VII) r e s p e c t i v e l y (12). The thermal decomposition of A ^ - p y r a z o l i n e s has been r e  p o r t e d t o y i e l d a product mixture c o n s i s t i n g of cyclopropane and o l e f i n s (6,7,13-19) i n some i n s t a n c e s , w h i l e i n others the mixture a l s o c o ntained the corresponding A 2 - p y r a z o l i n e (20) or no o l e f i n s (3,2l) at a l l . Few s t u d i e s have been made to d e t e r  mine the mechanism of the p y r o l y s i s r e a c t i o n s . From l i m i t e d I n  f o r m a t i o n both i o n i c (6,11,12) and d i r a d i c a l (20,22-24) mecha nisms f o r the thermal decomposition of ^ - - p y r a z o l i n e s have been proposed to e x p l a i n these p r o d u c t s . These p r o p o s a l s were made on the assumption that eyclopropanes are formed w i t h r e t e n t i o n of the geometry present In the o r i g i n a l p y r a z o l i n e s . Recent o b s e r v a t i o n s of p a r t i a l and complete l o s s of the above mention ed geometry have been r e p o r t e d (12,21,25). For example, van Auken and Rinehart r e p o r t e d (12) t h a t the p y r o l y s i s of t r a n s - 3 ,4-dimethyl - 3-earbomethoxy-A 1-pyrazoline (VII) g i v e s c i s - 1 , 2 - dimethyl-l-carbomethoxycyclopropane (X), t r a n s - 1 , 2 - d i m e t h y l - l - carbomethoxycyclopropane ( X I ) , methyl 2 , 3-dimethyl - 2-butenoate (XII) and methyl 2 , 3-dimethyl - 3-butenoate (XIII) In the r a t i o 1.00.1.22*1.16:©.155 and s i m i l a r l y , 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 - ^ - p y r a z o l i n e (VI) g i v e s X, XI, XII,and X I I I i n the r a t i o 1 .00X0 .70*3.73*0.24. These authors have suggested the f o l l o w i n g m o d i f i e d i o n i c mechanism (F i g u r e I I ) , which postu-- 3 - H H 3 0 - 6 COOCH, COOCH, .N GH 3 VI (methyls c i s ) or V I I (methyls t r a n s ) V I I I -N, H H - ^ C ^ OOCH, C H , +CH, IX C O O C H , H H 3 C * . ~ C O O C H 3 XI H-.C CH-, 3 \ / 3 c = c H - C * ' NC00CH o 3 3 XII E 2 \ / H 3 C — C H H „ C / C O O C H , X I I I FIGURE I I - I o n i c mechanism f o r the p y r o l y s i s of 3 ,4- dimethyl - 3-carbomethoxy - £ i-pyrazolines. l a t e s t h a t r o t a t i o n occurs i n the diazonium b e t a i n e i n t e r m e d i  ate ( V I I I ) , and thus r a c e m i z a t i o n at the anion c e n t e r can take p l a c e . The 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 , t h a t I s , 1 . 2 2 * 1 . 0 0 i n f a v o r of the trans-eyelopropane XI from the t r a n s - p y r a z o l i n e V I I and 1 . 0 0 * 0 . 7 0 i n f a v o r of the c i s - e y e l o p r o p a ne X from the c i s - p y r a z o l i n e V I , was e x p l a i n e d by the sug g e s t i o n t h a t the l o s s of n i t r o g e n i n going from V I I I t o IX i s s l i g h t l y f a s t e r than the r o t a t i o n i n V I I I due to the f a c t t h a t the l a t  t e r Involves c o n s e c u t i v e e c l i p s e d i n t e r a c t i o n o f methyl-carbo-- 4 - methoxy and methylenediazonium-methyl which p r o v i d e s some bar  r i e r to r o t a t i o n . I n s p i t e of the proposed common- in t e r m e d i a t e f o r the p y r o l y s i s of p y r a z o l i n e s VI and V I I , the r a t i o of e y c l o  propanes t o o l e f i n s are d i f f e r e n t , t h a t i s , .1.70 2 3.97 f o r the c i s - p y r a z o l i n e VI and 2.22°-1.31 f o r the t r a n s - p y r a z o l i n e V I I . Although t h i s mechanism would p r e d i c t the c o n v e r s i o n of the i n t e r m e d i a t e V I I I to p y r a z o l i n e s VI or V I I f a s t e r than n i t r o g e n l o s s from V I I I , 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~dimethyl -3-carbomethoxy"-£ L-pyrazoline. (VI) g i v e s no r e  arrangement In the recovered p y r a z o l i n e sample (12). T h e r e f o r e the v a l i d i t y of t h i s I o n i c mechanism f o r the thermal decom p o s i t i o n o f ^ - p y r a z o l i n e s needs f u r t h e r examination. P h o t o l y s i s of c i s -and trans_ - 3 , 4-dimethyl - 3-carbomethoxy- ^ - p y r a z o l i n e (VI and VII) has been r e p o r t e d (.12) to g i v e s t e r e o s p e c i f i c a l l y c i s and t r a n s - l , 2 - d i m e t h y l - l - c a r b o m e t h o x y - cyclopropane (X and XI) r e s p e c t i v e l y , and methyl t i g l a t e (IV) and methyl angelate (V) r e s p e c t i v e l y (Figure I I I ) . Rinehart and van Auken (12) have proposed a molecular mechanism to ex p l a i n these o b s e r v a t i o n s of p h o t o l y s i s of ^ " - p y r a z o l i n e s . The t r a n s i t i o n s t a t e i n v o l v e d would be XIV i n which the breakage of bonds N n - C r - and N o - 0 o and the f o r m a t i o n of bonds C 0 - C j - and 1 5 2 3 3 5 N 1-N 2 are simultaneous, hence the eyclopropanes formed r e t a i n the geometry which i s present i n the p y r a z o l i n e s . S i m i l a r l y , the s t e r e o s p e c i f i e r e g e n e r a t i o n of methyl t i g l a t e (IV) and methyl angelate (V) c o u l d then be e x p l a i n e d through a s i m i l a r t r a n s i t i o n s t a t e XV. T h e r e f o r e on the b a s i s of these p h o t o l y s i s _ 5 - r e s u l t s , the p h o t o l y s i s o f A ^ - p y r a z o l i n e s has been assumed to he s t e r e o s p e c i f i c i n g e n e r a l . H H3C- £OOCH, VI X .COOCH, H COOCHQ \ / J / = \ H.3C CH 0 5 3 IV _CH, VII XI H 0C .C00CH o 3 \ / 3 N C H 3 V FIGURE I I I - Products from the p h o t o l y s i s of 3 , 4 - d i - methyl-3-carbomethoxy-,&?--pyrazolInes. COOCH 3 3 \/ A V XIV H H 30- I xv OOCH, H, In t h i s l a b o r a t o r y however, a p r e l i m i n a r y i n v e s t i g a t i o n (26) has shown t h a t the p h o t o l y s i s r e a c t i o n s of c i 3 and t r a n s - 3,5-dimethyl-3-earbomethoxy-£ L-pyrazoline (XVI and XVII) g i v e mixtures o f cyclopropanes, w i t h some l o s s of s t e r e o s p e c i f i c i t y , and o l e f i n p r o d u c t s . GOOCH, J C O 0 C I L N H H. 3 XVI H 3 C 1 - fS)H 3 XVII 6 With the f i n d i n g t h a t c i s and t r a n s - S ^ - d i a l k y l - A 1 - p y r a z o l i n e s c o u l d he separated by f r a c t i o n a l d i s t i l l a t i o n , a new system f o r s t u d y i n g the s t e r e o c h e m i s t r y has become a v a i l  a b l e . Thus, the purpose of the present i n v e s t i g a t i o n i s to examine the thermal and p h o t o l y t i c decompositions of c i s and t r a n s - 3 , 5 - d i m e t h y 1 - 3 - c a r b o m e t h o x y - p y r a z o 1 i n e (XVI and XVII) and t h e i r analogs, e 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 - A 1 - p y r a z o l i n e (XVIII and XIX) i n an attempt t o f i n d out more i n f o r m a t i o n about these r e a c t i o n s . ,COCH ,COCH 3 XVIII XIX _ 7 - I I . SYNTHESIS AND IDENTIFICATION OF 3 ,3 ,5- TRISUBSTITUTED A 1-PYRAZOLINES I I - l . c i s and trans - 3 , 5-dimethyl - 3-carbomethoxy-£r-pyrazoline (XVI and XVII) 3 , 5-Dimethyl - 3-carbomethoxy-/S L-pyrazoline (XX) prepared by the a d d i t i o n of methyl methacrylate (XXI) to diazoethane i n e t h e r (17) has been shown by n.m.r. a n a l y s i s to be a 40^60 mixture of the two p o s s i b l e geometric isomers. S e p a r a t i o n of H C00CH o COOCH„ t h i s mixture (Figure IV) by f r a c t i o n a l d i s t i l l a t i o n u s i n g a Nester and Faust 1 8-inch by 6-mm. s p i n n i n g band s t i l l gave a lower b o i l i n g f r a c t i o n up to 93$ pure and a h i g h e r b o i l i n g f r a c t i o n o f 99+$ p u r i t y . N.m.r. analyses of these two f r a c t i o n s and the o r i g i n a l mixture p y r a z o l i n e showed t h a t the lower b o i l i n g isomer was the 40$ component and the h i g h e r b o i l i n g isomer was the 60$ component. P h o t o l y s i s r e a c t i o n s have been c a r r i e d out on both the lower and the h i g h e r b o i l i n g f r a c t i o n s , and i t was found (complete r e s u l t s w i l l be d i s c u s s e d l a t e r ) t h a t the former g i v e s mainly cis - 1 , 2-dimethyl-l-carbomethoxycyclopropane (X) and the l a t t e r g i v e s mainly trans - 1 , 2-dimethyl-l-carbomethoxy- 3 3 H XXI XX „ 8 - [A) Lower b o i l i n g f r a c t i o n 'B) P y r a z o l i n e mixture XX (C) Higher b o i l i n g f r a c t i o n (C) XVII (99*$) XVI si" (B) XVII (60$) (A) X V I (4b$) XVII (7$), 6.3 { XVI (93$) 6:3 r FIGURE IV - N.m.r. a b s o r p t i o n s showing the s e p a r a t i o n of 3 ,5- dimethyl - 3-carbomethoxy-^ - p y r a z o l i n e (XX) i n t o i t s c i s (XVI) and t r a n s (XVII) isomers. - 9 - cyclopropane ( X I ) . On the b a s i s of the f a c t t h a t the photo- 1 l y s i s of A. - p y r a z o l i n s g i v e s cyclopropane s t e r e o s p e c i f I c a l l y (12), the lower b o i l i n g isomer was assig n e d the s t r u c t u r e c i s - . 3 , 5"dimethyl - 3-carbomethoxy-A* 1'-pyrazoline (XVI) and the h i g h e r b o i l i n g isomer was assig n e d the s t r u c t u r e t r a n s - 3 , 5 - d i m e t h y l - 3~carbomethoxy-£^~pyrazoline (XVII). F u r t h e r proof of s t r u c  t u r a l assignments i s based on the h i g h e r y i e l d of the t r a n s - p y r a z o l i n e XVII than the c i s - p y r a z o l i n e XVI on p r e p a r a t i o n . S t e r i c hindrance due to the and methyl groups c i s to each other- i n XVI would slow down I t s fo r m a t i o n when compared to XVII. I n order to o b t a i n more evidence, the hydrobromide s a l t (XXII) of 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 - ^ - p y r a z o l i n e (XVII) has been prepared and i s p r e s e n t l y b e i ng analyzed by the s i n g l e c r y s t a l X-ray method. XXII i s white c r y s t a l l i n e s o l i d w i t h m e l t i n g p o i n t at 152-153°. I I - 2 . c i s and trans - 3 , 5-dimethy 1 - 3-acetyl-A 1"-pyrazoline (XVIII and XIX) 3 , 5 - D i m e t h y l - 3 - a c e t y l - A 1 - p y r a z o l i n e (XXIII) was prepared by the a d d i t i o n of methyl i s o p r o p e n y l ketone to an e t h e r - methanol s o l u t i o n of diazoethane. I t i s a c o l o r l e s s l i q u i d COCH, H COGH- r |C 5 V / 3 . PCEL fe=C' -|- CH 3CHN 2 e t h e r - ^ . ^ ""3 E/ N C H 3 "* methanof E^(f " N 5 " XXIII which b o i l s at 56-57°/!.2 mm. and turns y e l l o w i s h on prolonged - 10 - exposure t o atmosphere. The n.m.r. spectrum of XXIII showed i t to be a 40°-60 mixture of the two p o s s i b l e geometric Isomers and t h e r e was no a b s o r p t i o n of proton a t t a c h e d to a n i t r o g e n atom. F r a c t i o n a l d i s t i l l a t i o n of XXIII by s p i n n i n g band s t i l l at reduced p r e s s u r e gave a lower and a h i g h e r b o i l i n g f r a c t i o n of 81$ and 97$ p u r i t y r e s p e c t i v e l y , and they were found t o be the 40$ and 60$ components of XXIII r e s p e c t i v e l y . The r e s u l t s of the p h o t o l y s i s r e a c t i o n s of the lower b o i l i n g and the h i g h e r b o i l i n g isomers showed t h a t the former g i v e s mainly c i 3 - l , 2 - d i m e t h y l ~ l - a c e t y l c y c l o p r d p a n e (XXIV) and the l a t t e r g i v e s mainly t r a j o s - 1 , 2-dime thy 1-1 -a c e t y l c y c lopropa ne (XXV). T h e r e f o r e on the b a s i s of s t e r i e hindrance d u r i n g the for m a t i o n of 3 , 5-dimethyl - 3-acetyl~£ L-pyrazoline (XXIII) and the r e s u l t s o f the p h o t o l y s i s r e a c t i o n s , the lower b o i l i n g isomer was as s i g n e d t o be c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - ^ - p y r a z o l i n e (XVIIl) and the h i g h e r b o i l i n g isomer was as s i g n e d to be t r a n s - 3 , 5 - d i m e t h y l - 3 - a e e t y l - ^ - p y r a z o l i n e (XIX) . T h i s i s analogous t o the assignment t o the c i s and trans_ - 3 , 5-dlmethyl- 3-earbomethoxy-£ L-pyrazoline (XVI and XVII). The n.m.r. data o f 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 - ^ - p y r a z o l i n e (XVI and XVII) and c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - a e e t y l - ^ " - p y r a z o l i n e (XVIII and XIX) a i t t a b u l a t e d i n Table I . TABLE N.m.r. data o f 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 - ^ - p y r a z o l i n e (XVIII and XIX) and c i s and trans - 3 , 5-dimethyl - 3-carbomethoxy-i£-pyrazollne (XVI and XVII) Sample A c e t y l methyl hydrogens E s t e r methyl hydrogen C^-methyl hydrogen C^-methyl hydrogens -hydro gens C4-hydros ;ens XVI 6.33 8.38 8.51 5.42 7.68 9.14 s i n g l e t s i n g l e t doublet s e x t e t 2. .doublets 2 doublets J* 7 . 0 J*7 .5 Jgem"-^ • 9 J g e n T ^ .8 J v i c ~ ^ * 5 J v i c ^ 8 . o XVII 6.27 s i n g l e t 8.63 s i n g l e t 8.55 doublet J=7.0 5.43 s e x t e t J«7.5 8.28 2 doublets ^gem~ 1 2 ,8 J v i c ~ 8 ' 0 8.43 „ d o u b l e t " 8.56 2 doublets J g e r r T 1 2 ' 6 J v i o " " 8 ' 0 8.45 „ d o u b l e t ^ XVIII 7.78 s i n g l e t 8.40 s i n g l e t 8.52 doublet J* 7 . 0 5.66 s e x t e t J^7.4 7.57 9.30 2 doublets 2 doublets Jgem^-'-S.O Jg e m—12.8 J v i e ~ 8 * 7 J v l c - 7 . 7 XIX 7.65 8.63 8.48 5.67 8.53 s i n g l e t s i n g l e t doublet s e x t e t m u l t i p l e t J*6.0 J*7.4 1) A V l l l and AIA were done on • 205& s o l u t i o n i n 0014, AVI and A V I I were done on 30^ . s o l u t i o n i n CCI4, and the values i n parentheses were observed i n 1 0 $ s o l u t i o n . 2) Chemical s h i f t i n t' u n i t and c o u p l i n g constant i n c.p.s. #) Due to the small chemical s h i f t s e p a r a t i o n the outer d o u b l e t s o f the AB system . were not observed (see F i g u r e V ) . - 12 w £ O O C H 3 XVII 81.56? ; 8 . 2 8 * v l c « 8 . 0 " J v i c * 3 " 8 ' 0 " 30$ v/v i n CCli| ! . 8 .45^ 8.43 r J=*8.0^ J«8 .OfM 10% v/v i n C C l ^ FIGURE V - N.m.r. sp e c t r a of t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o - methoxy-A 1-pyrazoline (XVII) showing s p l i t t i n g s of C 4-hydrogens. - 13 3* I I I . SEPARATION AND IDENTIFICATION OF PRODUCTS FROM THE DECOMPOSITION OF 3,5~DIMETHYL-3-ACETYL-A*-PYRAZOLINES P r e l i m i n a r y s t u d i e s (17,26) on the decomposition of 3 , 5 - dimethyl - 3-carbomethoxy-A*-pyrazoline (XX), i t s e l s (XVI) and tr a n s (XVII) isomers have shown f i v e products to he formed as shown i n F i g u r e VI ( f o r p h o t o l y s i s , an a d d i t i o n a l product XXI was obtained) H. GOOCH. £OOCH, H , XVI .COOCH. H^C W XVII GOOCH, H CH 0 \ S 3 CH - C C ^COOCH, 3 2 : XXVI XI CH-jCH- >0HO %=c' g N^OOCH, XXVII ° \ 3 _ / = S * 3 H - C - C ^ H . C O O C H 3 H 2 C C x C 0 0 C H : CH^ XXVIII XXI FIGURE VI - Products from the decomposition o f 3 , 5 - d i - m e t h y l - S - c a r b o m e t h o x y - ^ - p y r a z o l i n e s . In the present study, the decomposition of 3 , 5-dimethyl- 3 - a c e t y l - A - p y r a z o l i n e ( X X I I I ) , i t s c i s (XVIII) and t r a n s (XIX) - 14 - XXXII LI XXV XXIV XXV+XXXII I  XIV XXIX "XXX R e t e n t i o n time d i f  f e r e n c e &0.12 min, B 17.7 15.7 12.2 10.5 6.2 * R e t e n t i o n time i n minutes 1 A FIGURE V I I '- A. P r e p a r a t i v e vapor chromatogram showing the s e p a r a t i o n of products from the decomposition of 3 , 5 - d I m e t h y l - l - a c e t y l - Z r - p y r a z o l i n e s . B. A n a l y t i c a l vapor phase chromatogram showing the s e p a r a t i o n of 3-methyl-4-hexen-2-one (XXXII) and t r a n s - l , 2 - d i m e t h y l - l - a c e t y l c y c l o p r o p a n e (XXV) - 15 - isomers a f f o r d e d a mixture of s i x products as shown by ana l y t i c a l vapor phase chromatography (Figure VII) w i t h b o i l i n g p o i n t s ranging from 119° to 152°. These products are shown i n Figure V I I I and have been i d e n t i f i e d as described below. Pre- HO COCH, XXIII £OCH, J P w XVIII f^CH, •N H 3C XIX ^OCH- ,COCH, TJOCH, XXV / H H3C N0' CH 3 XXIX V CH CH CH 3 \2 / 3 c = c H OCH C=C / \ CH 3CH 2 COCH3 XXX ? H3 CH3CH = CH-CH-COCH3 XXXI XXXII FIGURE V I I I - Products from the decomposition of 3,5- dimethyl-S-acetyl-A^-pyrazolines. p a r a t i v e vapor phase chromatographic separation gave f i v e f r a c t i o n s i n which the second f r a c t i o n was found to be a mixture (Figure VII) of 1 -acetyl-tra_ns-l,2-dimethylcyelopro- pane (XXV) and 3-methyl-4-hexen-2-one (XXXII) i n the r a t i o of approximately 85 s15 depending on the c o n d i t i o n of decom p o s i t i o n . The separ a t i o n of t h i s mixture of XXV and XXXII w i l l be discussed l a t e r . The p y r o l y s i s products have been charac-- 16 - t e r i z e d on the b a s i s of t h e i r n.m.r. and I n f r a r e d s p e c t r a l data and elemental m i c r o a n a l y s i s and t h i s i s d e s c r i b e d below. 2 , 3 * 5-Trimethyl-£ - d i h y d r o f u r a n (XXIX) has been r e p o r t e d (27) to b o i l at 118.5° at 746 mm. which agreed w i t h the v a l u e , o 120 , of t h i s work. I t s i n f r a r e d spectrum i n d i c a t e d the presence of carbon-carbon double-bond a b s o r p t i o n at 5.87M and v i n y l e t h e r a b s o r p t i o n at 8.21M and 9.63 JX (28). There was no i n d i c a t i o n o f a b s o r p t i o n i n the I n f r a r e d or n.m.r. (Fi g u r e IX) sp e c t r a a t t r i b u t a b l e to the a c e t y l methyl protons. N.m.r. ab s o r p t i o n of an u n r e s o l v a b l e m u l t l p l e t centered at 8.43 *t was a t t r i b u t a b l e t o the methyl groups a t t a c h e d t o C 2 and C^.' There were t h r e e groups of m u l t l p l e t centered a t 7.98 T , 7.40't and 5.59 Y which can be assign e d to the hydrogens on (two hydro gens) and C (one hydrogen). These t h r e e protons c o n s t i t u t e d a 5 t y p i c a l ABX system (29) w i t h J A B«*tl4 .5 c.p.s., J A Xe> 8 . 0 c.p.s., J B X — 9.5 c.p.s., A^ - ^ 3 5 . 5 c.p.s., A . A X ^ l 4 4 . 5 c.p.s. and A g X ^ 1Q9 c.p.s. In order t o e s t a b l i s h the c y c l i c s t r u c t u r e of t h i s 2 , 3 j 5 - t r i m e t h y l - A - d i h y d r o f u r a n (XXIX), the n.m.r. spectrum of a s i m i l a r c y c l i c compound, the 2-methyl-A?-dihydrofuran (XXX- I I I ) (30) was obtained f o r comparison. The n.m.r. spectrum of XXXIII showed a b s o r p t i o n at 8.30 f ( m u l t i p l e t ) , 5.55 X ( m u l t l  p l e t ) , 7.47 TT* ( m u l t l p l e t ) and 5.78 ( t r i p l e t w i t h Jc=t9.3 c.p. s.) a t t r i b u t a b l e t o C 2 methyl hydrogens, v i n y l hydrogen, G^ and G^ hydrogens r e s p e c t i v e l y . A comparison of the n.m.r. sp e c t r a of XXIX and XXXIII showed good c o r r e l a t i o n between s i m i l a r l y s i t u a t e d protons, conforming the s t r u c t u r a l a s s i g n -- 17 - FIGURE IX - N.m.r. spectrum of 2 , 3 , 5 - t r i m e t h y l - f c - d i h y d r o - f u r a n (XXIX) - 18 - ment of - 2 , 3 , 5-trimethyl-& - d i h y d r o f u r a n (XXIX) . cis - 3-Methyl - 3-hexen - 2-one (XXX) and t r a n s - 3 - m e t h y l - 3 - hexen-2~one (XXXI) have been found to have b o i l i n g p o i n t s at 145-145 .5° and 156.5-158° r e s p e c t i v e l y . Rohrmann and Shoule (31) r e p o r t e d the s y n t h e s i s of 3-tnethyl-3~hexen-2-one and gave i t s b o i l i n g p o i n t v a l u e , 151°• I t i s p o s s i b l e t h a t t h e i r o^fi- u n s a t u r a t e d ketone was a mixture of the two p o s s i b l e geometric Isomers XXX and XXXI. The presence of carbon-carbon double- bond and o^fi-unsaturated c a r b o n y l f u n c t i o n were i n d i c a t e d by i n f r a r e d bands at 6.-18 M and 5 .91 Jd r e s p e c t i v e l y , f o r the c i s - 3-methyl-3-hexen-2-one. (XXX) and at 6.07 M and 5.96 JX r e  s p e c t i v e l y , f o r the trans - 3-methyl - 3-hexen - 2-one (XXXI). The n.m.r. s p e c t r a of XXX and XXXI showed a b s o r p t i o n at 7.86 "t ( s i n g l e t ) and 7.81 H ( s i n g l e t ) due to a c e t y l methyl hydrogens, at 8.12 X ( m u l t i p l e t ) and 8.39 Y ( m u l t i p l e t ) due to v i n y l methyl hydrogens and at 4.44 'i ( m u l t i p l e t ) and 3.52 •f ( m u l t i - p l e t ) due to v i n y l hydrogens, r e s p e c t i v e l y . The assignment of geometry to c i s and trans - 3-methyl - 3-hexen - 2«one (XXX and XXXI) were based on the lower f i e l d v i n y l p roton a b s o r p t i o n of the l a t t e r at 3 . 5 2 f than the former at 4.44 1\ In XXXI the v i n y l hydrogen i s c i s to the a c e t y l group, whereas i n XXX, the v i n y l hydrogen Is t r a n s to the a c e t y l group. I n other words, the v i n y l hydrogen i n XXXI Is c l o s e r to the a c e t y l group than i n XXX, t h e r e f o r e the diamagnetic a n i s o t r o p y of the carbon-oxygen double-bond i n a c e t y l group would d e s h i e l d the v i n y l proton i n XXXI to a g r e a t e r extent t o g i v e a lower f i e l d a b s o r p t i o n - 19 - (32). T h i s s h i f t i n the v i n y l hydrogen r e g i o n has been observed i n many other c i s and t r a n s p a i r s of o l e f i n s (38). 1-Acetyl-c is - 1 , 2-dimet.hylcyclopropane (XXIV) and 1- a c e t y l - t r a n s - l , 2 - d i m e t h y l c y c l o p r o p a n e (XXV) showed no i n f r a  red a b s o r p t i o n bands a t t r i b u t a b l e t o carbon-carbon double-bond * but c a r b o n y l conjugated t o the cyclopropane r i n g (33) at 5.90>* f o r XXIV and 5.96 A f o r XXV > and i n a d d i t i o n , t h e r e was a band at 9.76 M f o r XXV due to a b s o r p t i o n of cyclopropane r i n g (3^0 . T h e i r n.m.r. s p e c t r a showed no s i g n a l due to proton attached to the carbon-carbon double-bond but h i g h f i e l d a b s o r p t i o n c h a r a c t e r i s t i c of cyclopropane r i n g p r o t o n s . These r i n g p r o  ton a b s o r p t i o n s appeared as two groups of s i g n a l s ; . c e n t e r e d at 8.68 f (two hydrogens) and 9.7^ 1* (one hydrogen) i n the case of l - a o e t y l - c i s - l , 2 - d i m e t h y l c y c l o p r o p a n e (XXIV) and i n the r e g i o n of 8.75 '£ to 9.06 TT7 i n the ease o f 1-acetyl-trans_- 1 , 2-dimethylcyclopropane (XXV). These m u l t i p l e t s were p a r t l y obscured by a b s o r p t i o n of methyl groups. The s t e r e o c h e m i s t r y of XXIV and XXV were made by comparison of t h e i r n.m.r. sp e c t r a to those of the analogous carbomethoxy-cyclopropanes, namely l-carbomethoxy-cls_-l , 2-dimethylcyclopropane (X) and 1- carbomethoxy-trans-l , 2-dlmethylcyclopropane (XI) whose s t e r e o  chemistry has a l r e a d y been determined by van Auken and Rinehart (12) on the b a s i s of c o m p e t i t i v e s a p o n i f i c a t i o n s i n which the l e s s h i n d e r e d carbomethoxy group of X was consumed more r a p i d l y than t h a t of XI. - 20 - 3-Methyl-4-hexen-2-one (XXXII) was e l u t e d at the same time as 1 - a c e t y l - t r a n s - 1 , 2 - d i m e t h y l c y c l o p r o p a n e (XXV) from the p r e p a r a t i v e vapor phase chromatography column. Attempts to separate t h i s ^ ^ - u n s a t u r a t e d ketone XXXII by u s i n g columns packed w i t h v a r i o u s substances were not s u c c e s s f u l . Bromina- t i o n o f the mixture c o n s i s t i n g 3-methyl-4~hexen-2-one (XXXII) and 1- a c e t y l - t r a j i s - 1 , 2 - d i m e t h y l c y e l o p r o p a n e (XXV) i n carbon t e t r a c h l o r i d e gave XXV and trans-3-methyl-3-hexen-2-one (XXXI) i n s t e a d of the dibromide of XXXII as i n d i c a t e d i n the pr e p a r a  t i v e vapor phase chromatogram. Since 3-methyl-4-hexen-2-one (XXXII) was s t a b l e at the temperature of the column, the con v e r s i o n of XXXII or i t s dibromide to XXXI must have o c c u r r e d b e f o r e i t was i n j e c t e d i n t o the column. Although 3-methyl-4- hexen-2-one (XXXII) was not I s o l a t e d pure, I t s presence was i n d i c a t e d i n the n.m.r. spectrum of the mixture w i t h 1 - a c e t y l - t r a n s - l , 2 - d i m e t h y l c y c l o p r o p a n e (XXV). Those a b s o r p t i o n s a t t r i b  u t a b l e t o XXXII are shown below. I t was not p o s s i b l e to d i s - 4.57 i ( m u l t i p l e t ) ^6.94 *f ( m u l t i p l e t ) CH 3CH^H-CH-COCH 3 ^  7.97 Y ( s i n g l e t ) 8.32 r 3""*"—-—8.92 Y (doublet, Jc^7.0 c.p.s.) (doublet, J ~ 4 . 8 c.p.s.) XXXII t i n g u i s h whether the v i n y l hydrogens i n the molecule are c i s or t r a n s t o each o t h e r . Elemental m i c r o a n a l y s i s of the mixture c o n t a i n i n g 3-methyl-4-hexen-2-one (XXXII) and 1-acetyl-trans_- 1,2-dimethylcyclopropane (XXV) was i n good agreement to the em p i r i c a l formula C H 0, which i s common to both XXV and XXXII. - 21 - IV. DECOMPOSITION OF 3,3,5-TRISUBSTITUTED A 1-PYRAZOLINES P r e l i m i n a r y i n v e s t i g a t i o n s have -keen, shown t h a t the p y r o l y s i s of c i s and trans - 3 , 5-dimethyl - 3-carbomethoxy - A 1 - p y r a z o l i n e (XVI and XVII) a f f o r d s f i v e products ( F i g u r e V I, p. 13 )> namely, c i s and trans - 1 , 2-dlmethyl-l-carbomethoxy- cyclopropane (X and X I ) , methyl c i s and t r a n s - 2 - m e t h y l - 2 - pentenoate (XXVI and XXVII) and methyl 2-methyl - 3-pentenoate (XXVIII)I on p h o t o l y s i s , an a d d i t i o n a l peak, methyl methacry- l a t e (XXI), was found. S i m i l a r p y r o l y s i s r e a c t i o n s , as r e p o r t  ed i n t h i s work, were c a r r i e d out on 3 , 5 - d i m e t h y l - 3 - a c e t y l - A 1 - p y r a z o l i n e ( X X I I I ) , i t s c i s (XVIII) and t r a n s (XIX) isomers and found to g i v e s i x products ( F i g u r e V I I I , p. 15)° 1 - a c e t y l - c i s and t r a n s - 1 , 2 - d i m e t h y l c y c l o p r o p a n e (XXIV and XXV), 2 ,3 ,5- t r i m e t h y l - A 2 - d l h y d r o f u r a n (XXIX), c i s and t r a n s - 3 - m e t h y l - 3 - hexen-2-one (XXX and XXXI) and 3-methyl-4-hexen-2-one (XXXII). P h o t o l y s i s of these a c e t y l - p y r a z o l i n e s (XXIII, XVIII and XIX) gave no a d d i t i o n a l p r o d u c t . These r e s u l t s are t a b u l a t e d i n Tables I I and I I I . I t can be seen that the decomposition r e a c t i o n s of 3 ,5- d i m e t h y l - 3 - a c e t y l - A ^ " - p y r a z o l i n e (XXIII), i t s c i s (XVIII) and t r a n s (XIX) isomers g i v e r e s u l t s t h a t resemble those of 3 ,5- d i m e t h y l - 3 - c a r b o m e t h o x y - A 1 - p y r a z o l i n e (XX), i t s c i s (XVI) and t r a n s (XVII) isomers r e s p e c t i v e l y . P y r o l y s i s gave h i g h e r r a t i o of o l e f i n s t o eyclopropanes than d i d p h o t o l y s i s . In the TABLE I I Product compositions f o r the decomposition of 3 > 5-dimethyl - 3-acetyl - A - p y r a z o l i n e s Sample Reaction c o n d i t i o n s Cyclopropane Unsaturated ketone Dihydro- c i s t r a n s cis-«k/S t r a n s - o ^ f uran XXIV XXV XXX XXXI XXXII XXIX XVIII ( c i s ) Vapor phase p y r o l y s i s at 125° 27 48 : 7 3 2 13 XIX (trans) Vapor phase p y r o l y s i s at 125° 67 19 2 7 2 3 XXIII (mixt.) L i q u i d phase p y r o l y s i s , 100° 36 18 15 18 4 9 XVIII ( c i s ) L i q u i d phase p y r o l y s i s , 100° 22 25 27 2 10 14 XIX (trans) L i q u i d phase p y r o l y s i s , 100° 62 17 1 17 3 0 XXIII (mixt.) Thermal p y r o l y s i s at 250° 48 32 5 , 3 3 9 XVIII ( c i s ) Thermal p y r o l y s i s at 250° 28 41 12 1 2 16 XIX (trans) Thermal p y r o l y s i s at 250° 60 27 1 6 3 .3 XXIII (mixt.) P h o t o l y s i s i n ether at 35° 39 4 2 4 6 3 6 XVIII ( c i s ) P h o t o l y s i s i n ether at 35° 59 28 .1 0 6 6 XIX (tr a n s ) P h o t o l y s i s i n ether at 35° 21 70 2 1 4 2 TABLE I I I Product compositions f o r the decomposition of 3 , 5-dimethyl - 3-carbomethoxy-& L-pyrazolines Reaction c o n d i t i o n s Cyclopropane Unsaturated e s t e r Methyl methacry- l a t e Sample c i s t r a n s cis -0^2 . trans- <*$ p»i X XI XXVI XXVII XXVIII XXI XX (mixt.) Vapor phase p y r o l y s i s (17) 53 42 3 2 1 0 XVI ( c i s ) Vapor phase p y r o l y s i s (17) 23 65 • 5 2 5 0 XVII (trans) Vapor phase p y r o l y s i s (17). 76 15 1 3 5 0 XX (mixt.) L i q u i d phase p y r o l y s i s (17) 45 27 10 15 3 0 XVI ( c i s ) L i q u i d phase p y r o l y s i s (17) 18 48 32 0 2 0 XVII (trans) L i q u i d phase p y r o l y s i s (17) 60 15 0 22 3 0 XVI ( c i s ) P h o t o l y s i s i n ether at 35° 6 l 23 6 2 2 6 XVII (trans) P h o t o l y s i s i n ether at 35° 22 65 0 5 2 6 _ 24 - o l e f i n f r a c t i o n of the products, c i s - 3 , 5 - d i m e t h y l - A - p y r a z o l i n e s gave predominantly the oG^-c i s - o l e f i n s and tra_ns_-3,5-dimethyl- ^ - p y r a z o l i n e s gave predominantly the o ( , ^ - t r a n s - o l e f i n s . In the cyclopropane f r a c t i o n of the products, c i s and t r a n s - 3 , 5 - d i - methyl-A^-pyrazolines gave more t r a n s and c i s - l , 2 - d i m e t h y l - cyclopropane r e s p e c t i v e l y , whereas on p h o t o l y s i s , they were i n r e v e r s e d abundance. The o n l y s i g n i f i c a n t d i f f e r e n c e between the keto and e s t e r p y r a z o l i n e s was the d i h y d r o f u r a n product XXIX which was formed from the decomposition r e a c t i o n s of the keto pyrazo l i n e s . I t i s noteworthy t h a t t h i s product was formed from o n l y one of the keto p y r a z o l i n e s , c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y . l - A 1 - p y r a z o l i n e ( X V I I I ) , i n s i g n i f i c a n t amount. On the b a s i s of the p o s t u l a t e d p o l a r Intermediate In the p y r o l y s i s r e a c t i o n i t Is a n t i c i p a t e d t h a t the p o l a r i t y of the s o l v e n t might i n f l u e n c e the product r a t i o and the r a t e of r e  a c t i o n , hence p y r o l y s i s i n a number of s o l v e n t s w i t h d i e l e c t r i c c o n stants v a r y i n g from 2D f o r cyclohexane to 109D f o r form- amide have been c a r r i e d out on the c i s and trans_ - 3 , 5-dimethyl- 3-carbomethoxy-A^-pyrazoline (XVI and X V I I ) . Samples of 0.2 ml. of the e s t e r p y r a z o l i n e i n 20 ml. of s o l v e n t i n a s e a l e d tube were heated f o r 90 minutes at . 1 2 5 ° . For low b o i l i n g s o l v e n t s , the s o l v e n t was removed by d i s t i l l a t i o n through a s p i n n i n g band Column under r e f l u x c o n d i t i o n , and the c o n c e n t r a t e d s o l u t i o n was analysed by a n a l y t i c a l vapor phase chromatography. For - 25 - formamide, the products were recovered from the s o l v e n t on a vacutam l i n e by pumping f o r two hours. These r e s u l t s (Table IV) showed a s m a l l and r e g u l a r i n f l u e n c e of the d i e l e c t r i c constant of the s o l v e n t on the product composition. In form- amide, up to 57$ of the product was o l e f i n s , whereas i n cyclohexane, on l y 7$ of the product was o l e f i n s . P h o t o l y s i s of c i s and trans - 3 j > 5~dlmethyl - 3-carbomethoxy- lt-pyrazoline (XVI and XVII) i n s o l v e n t s of v a r y i n g d i e l e c t r i c c onstants showed a s i m i l a r s o l v e n t e f f e c t on the product com p o s i t i o n as i n the p y r o l y s i s r e a c t i o n s but In l e s s e r degree" f o r example, i n formamide, up to 21$ of the product was o l e  f i n s whereas i n cyclohexane, i t was 5$. The ^.kinetic s o l v e n t e f f e c t has been examined f o r the p y r o l y s i s of 3 , 5-dImethyl - 3-carbomethoxy-fif'-pyrazoline (XX) i n v a r i o u s s o l v e n t s and i t was found t h a t the r a t e of p y r o l y s i s decreased i n the order of d i - n - b u t y l e t h e r , t e t r a l i n , n i t r o  benzene and formamide. The r a t e s i n these s o l v e n t s were a l l w i t h i n a f a c t o r of t h r e e ( F i g u r e s X I I -and—3EEB). L i q u i d phase p h o t o l y s i s of 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 - A 1 - p y r a z o l i n e (XVII) has been c a r r i e d out i n s o l v e n t s such as 2 , 3-dimethylbutane and d i e t h y l e t h e r at v a r i o u s tem pe r a t u r e s r a n g i n g from -55° t o 58° i n an attempt t o determine the temperature e f f e c t on p h o t o l y s i s of ^ - p y r a z o l i n e s . Pro duct a n a l y s i s by a n a l y t i c a l vapor phase chromatography showed no a p p r e c i a b l e change a t t r i b u t a b l e to the i n f l u e n c e of tern-TABLE IV Product compositions f o r the sealed-tube 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 - c a r b o m e t h o x y - ^ - p y r a z o l i n e i n v a r i o u s s o l v e n t s at 1 2 5 ° 1 = Solvent Cyclopropane Unsaturated e s t e r Sample c i s t r a n s c i s - f l ^ t r a n s - s ^ » fr& # Cyclohexane X XI XXVI XXVII XXVIII XVI ( c i s ) 2 . 0 7 D 2 5 6 2 1 2 0 1 XVI ( c i s ) Cyelohexane 2 . 0 7 D 3 0 5 5 1 1 3 1 XVI ( c i s ) E t h y l ether 4 . 3 4 D 2 5 5 6 1 6 2 1 XVI ( c i s ) Methanol 3 3 . 6 D 2 1 3 9 3 4 4 2 XVI ( c i s ) A c e t o n i t r i l e 3 7 . 5 D 2 1 42 3 1 4 2 XVI ( c i s ) Formamide 1 0 9 D 1 9 3 3 4 4 2 2 " XVII (trans) # Cyclohexane 7 7^ 2 . 0 7 : D 7 0 2 3 1 5 1 XVII (trans) Cyclohexane 2 . 0 7 D 7 2 2 0 0 6 2 XVII (trans) E t h y l ether 4 . 3 4 D 6 6 1 8 0 1 3 3 XVII (trans) Methanol 3 3 . 6 D 48 6 0 4 4 2 XVII (trans) A c e t o n i t r i l e 3 7 . 5 D 6 7 6 0 2 5 2 XVII (trans) Formamide 1 0 9 D 3 1 1 2 0 5 2 5 # at 81°, not i n sealed-tube. TABLE V Product compositions of p h o t o l y s i s of c i s and t r a n s - 3 , 5 - d i - methyl - 3-carbomethoxy-^"-pyrazoline Cyclopropane Unsaturated ester Methyl methacry- l a t e Sample Solvent and temperature c i s t r a n s els-^p trans-atyS ^ X XI XXVI XXVII XXVIII XXI XVII ( tr a n s ) 2 , 3-Dimethyl butane 58° 28 ' 63 3 4 2 0 XVII ( t r a n s ) E t h y l ether (26) 35° 22 65 0 5 2 6 XVII ( tr a n s ) E t h y l ether 0° 27 56 1 7 3 6 XVII ( tr a n s ) E t h y l ether -20° 25 55 1 8 3 8 XVII ( t r a n s ) E t h y l ether -55° 25 53 1 10 4 7 XVI ( c i s ) Cyclohexane^ 81° 43 45 7 0 1 4 XVII ( t r a n s ) Cyclohexane^ 81° 46 45 0 4 1 4 XVI ( c i s ) Formamide 23° 54 21 9 5 1 .10 XVII ( t r a n s ) Formamide 23° 15 58 2 16 3 6 # a t 81, py r o l y s i s a l s o occurred at a r a t e t h r e e times slower than -pyrolyoirj-. - 28 - p e r a t u r e . These r e s u l t s are shown i n Table V. P h o t o l y s i s and p y r o l y s i s gave the same pro d u c t s , t h e r e  f o r e they- might w e l l i n v o l v e the same i n t e r m e d i a t e . In order to determine whether the product composition was dependent on temperature or on the nature of the r e a c t i o n , p h o t o l y s i s and p y r o l y s i s of c i s and t r a n s - S ^ - d i m e t h y l - S - c a r b o m e t h o x y - A 1 - p y r a z o l i n e (XVI and XVII) were c a r r i e d out at the same tem p e r a t u r e , 8l°, wi t h cyclohexane as s o l v e n t . I t was found the e v o l u t i o n of n i t r o g e n to be th r e e to f o u r times f a s t e r by p h o t o l y s i s than by p y r o l y s i s . The product compositions from these two r e a c t i o n s were not the same d e s p i t e the f a c t t h a t they were run under i d e n t i c a l c o n d i t i o n s . The r e s u l t s under these c o n d i t i o n s i n d i c a t e as i n other systems t h a t p h o t o l y s i s \ g r e a t e r - y i e l d e d eyclopropanes w i t h h i g h degree of r e t e n t i o n of geome t r y of the s t a r t i n g p y r a z o l i n e than those from p y r o l y s i s . I t was a l s o found t h a t the r a t i o of o l e f i n s to eyclopropanes from these r e a c t i o n s was lower f o r the p h o t o l y s i s than the p y r o l y s i s . A f u r t h e r t e s t of the e a r l i e r proposed mechanism was based on the f a c t t h a t t h e r e should be r o t a t i o n of the C^-Cjj bond i n the diazonium hfttaine i n t e r m e d i a t e XXXIV and t h a t i t would form 3 , 5-dimethyl - 3-carbomethoxy-A^-pyrazoline (XX) by c y c l i z a t i o n f a s t e r than l o s s of n i t r o g e n . L i q u i d phase p y r o l y s i s of trans - 3 , 5-dimethyl - 3-carbomethoxy-.A t 1-pyrazoline (XVII) at 90° was c a r r i e d to 50$ completion, and the recovered unreacted p y r a z o l i n e was analysed by n.m.r.' I t was found t h a t - 29 - COOCH- COOCH f c „ , • r < 3 / 3 ~ \ Q H _ J J • eyclopropanes N 3 **"* / \ 3 —***• H 3 C * N N ^ H 3C and o l e f i n s XX XXXIV not more than 1% i s o m e r i z a t i o n of XVII to c i s - 3 , 5 - d i m e t h y l - 3 - A" carbomethoxy-A- L-pyrazoline (XVI) had o c c u r r e d , (^similar r e s u l t was observed when tr£ns_ - 3 , 5-dimethyl - 3-carbomethoxy-A 1- p y r a z o l i n e (XVII) i n d i e t h y l e ther was p a r t i a l l y p h o t o l y s e d at 35°. - 30 - V. DISCUSSION The thermal p y r o l y s i s of c i s and trans_ - 3 , 4-dimethyl - 3 - carbomethoxy-A 1-pyrazollne (VI and VII) has been r e p o r t e d by Rinehart and van Auken (12) to proceed w i t h r a c e m i z a t i o n at C^ to g i v e cyclopropane products i n which the methyls are c i s and t r a n s w i t h that cyclopropane which r e t a i n s the geometry present i n the p y r a z o l i n e b e i ng s l i g h t l y predominant. For example, the c i s - p y r a z o l i n e VI g i v e s c i s - l , 2 - d i m e t h y l - l - c a r - bomethoxycyclopropane (X) and tr a n s - 1 , 2 - d i m e t h y l - 1 - c a r b o - methoxycyclopropane (XI) i n the r a t i o of 1.00*0.70 whereas the trans-pyrazo 1ine V I I g i v e s X and XI i n the r a t i o of 1.00*1.22. Rinehart and van Auken suggested t h a t r o t a t i o n COOCH, 3 VI A. „ C 0 0 C H o Ho0. £ 0 0 C H o H 3Q ^OOCH^ H 3 C _ \/ ^ 3 * \ / N"IL ~r*0H X XI : V I I about the O^-C^ bond i n the dlazonium bsfcaine i n t e r m e d i a t e V I I I accounts f o r the l o s s of geometric i n t e g r i t y and th a t H 3C £ 0 0 C H < ^ H 3 Ng V I I I - 31 the l o s s of n i t r o g e n Is o n l y s l i g h t l y slower than r o t a t i o n to g i v e a h i g h e r y i e l d of the cyclopropane which r e t a i n s the ge ometry present In the p y r a z o l i n e . In the present work, i t was found t h a t the thermal p y r o l y s i s of c i s and trans - 3 , 5-dlmethyl - 3 - c a r b o m e t h o 3 c y-A 1- p y r a z o l i n e (XVI and X V I I ) , c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - acetyl-A - p y r a z o l i n e (XVIII and XIX) a l s o proceeds w i t h r a c e m i z a t i o n at to g i v e cyclopropane products i n which the methyls are c i s and t r a n s but the cyclopropane w i t h i n v e r  s i o n of the geometry present i n the p y r a z o l i n e was found p r e  dominant. For example, the r a t i o of c i s and t r a n s - l , 2 - d i - m e t h y l - l - a c e t y l c y c l o p r o p a n e (XXIV and XXV) from the thermal p y r o l y s i s of XVIII and XIX were 22*25 and 62*17 r e s p e c t i v e l y . ^ £ O C H 3 n/V XIX A second important f e a t u r e of the present work i s t h a t the f o r m a t i o n of o l e f i n s from the p y r o l y s i s of 3 * 5-dimethyl- A 1 - p y r a z o l i n e s - i s h i g h l y s t e r e o s p e c i f i c . The r a t i o of c i s and trans - 3-methyl - 3-hexen - 2-one (XXX and XXXI) from the p y r o l y s i s 32 - 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 - / ^ - p y r a z o l i n e (XVIII and XIX) were 27»2 and 1*17 r e s p e c t i v e l y . T h i s s t e r e o s p e c i - f i c i t y has not b e e n observed p r e v i o u s l y s i n c e a n a p p r o p r i a t e C O C H , H. XVIII £OGrL H CH ^ / 3 c=c CH CH NCOCH 3 2 3 XXX (27fo) CH CH CH 3 \2 / 3 A .c=cf CH 3CH 2 ^ H 3 c=c H / XCOCH, XXXI (2%) H C CH 3CH 2 \ COCH, XIX XXXI (17$) XXX (Ifo) model has not been a v a i l a b l e . The form a t i o n of o l e f i n s has p r e v i o u s l y been thought t o be formed through the i n t e r m e d i a t e H 3C COGCH, C H , 2 XXXIV H CH-, CH0CH_. \ / 3 3 \2 C=C / \ CH 3CH 2 COGCH 3 H CH 0 / 3 \ COOCH, XXVI XXVII XXXIV or XXXV i n which r o t a t i o n around the s i n g l e bonds would g i v e a mixture of c i s and t r a n s o l e f i n s . For the dlazonium' bjafcalne XXXIV to g i v e such s t e r i c c o n t r o l i t would r e q u i r e t h a t the anion c e n t e r must r e t a i n i t s asymmetry. T h i s Is not a n t i c i p a t e d on the b a s i s of s t u d i e s by Cram and coworkers (39). In the p y r o l y s i s and p h o t o l y s i s of 3 J , 5-dimethyl -3 -- 33 - a c e t y l - A 1 - p y r a z o l i n e ( X X I I I ) , i t s c i s (XVIII) and t r a n s (XIX) isomers, an a d d i t i o n a l product 2 , 3 , 5 ~ t r i m e t h y l - A 2 - d i h y d r o f u r a n (XXIX) was o b t a i n e d . T h i s can be formed through the diazonium b c t a i n e i n t e r m e d i a t e (XXXV) which has a. resonance form of XXXVI. Again f r e e r o t a t i o n around C^-C^ bond p r e d i c t s t h a t ,COCH XXXV XXXVI XXIX c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l ~ A - p y r a z o l i n e (XVIII and XIX) would g i v e the same i n t e r m e d i a t e XXXVI on p y r o l y s i s , and hence they should g i v e the same amount of d i h y d r o f u r a n XXIX. Experimental r e s u l t s , however, showed the amount of XXIX ob t a i n e d from the i s o m e r i c p y r a z o l i n e s were s i g n i f i c a n t l y d i f  f e r e n t . F o r example, thermal p y r o l y s i s of c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - A 1 " - p y r a z o l i n e (XVIII and XIX) at the i n  j e c t o r of the vapor phase chromatography instrument gave 16$ and 3$, r e s p e c t i v e l y , of 2 , 3 , 5 - t r i m e t h y l - A - d i h y d r o f u r a n (XXIX), and p y r o l y s i s of neat l i q u i d samples gave 14$ and 0% r e s p e c t i v e l y . These r e s u l t s seem to i n d i c a t e t h a t the forma t i o n of the d i h y d r o f u r a n was predetermined by the molecular s t r u c t u r e of the p y r a z o l i n e s . In f a c t , the s t e r i c i n t e r a c t i o n of and methyl groups i n c i s - S ^ - d i m e t h y l - S - a c e t y l - A 1 - p y r a z o l i n e (XVIII) might be expected to f o r c e the a c e t y l group i n t o a f a v o r a b l e p o s i t i o n f o r d i h y d r o f u r a n f o r m a t i o n . - 34 - I t i s a n t i c i p a t e d t h a t the f o r m a t i o n of an i o n i c dlazonium b a t a i n e i n t e r m e d i a t e l i k e I I from A ^ - p y r a z o l i n e s ( I I I ) would cause the k i n e t i c s of the r e a c t i o n to show a h i g h  er r a t e i n more p o l a r s o l v e n t s , s i n c e the process i n v o l v e s the 3> -N R2 Y Y= -COCH3, -COOCHo 2 I I f o r m a t i o n of i o n i c charges from a n e u t r a l s p e c i e s (37). In o t h e r woYds, the r a t e of p y r o l y s i s of A ^ - p y r a z o l i n e s should be f a s t e r i n a s o l v e n t of h i g h p o l a r i t y than a s o l v e n t of low p o l a r i t y . The r e s u l t s of the present work showed the r a t e of p y r o l y s i s of A ^ - p y r a z o l i n e s , as i n d i c a t e d by the r a t e of n i t r o  gen e v o l u t i o n , to be f a s t e r i n non-polar s o l v e n t s , such as d i  n - b u t y l e t h e r or t e t r a l i n than i n p o l a r s o l v e n t s , such as nitrobenzene or formamide by the s m a l l f a c t o r of t h r e e . T h i s o p p o s i t e k i n e t i c e f f e c t i n d i c a t e s t h a t the i n t e r m e d i a t e i n p y r o l y s i s has l e s s I o n i c c h a r a c t e r than the s t a r t i n g m a t e r i a l , the A 1 - P y r a z o l i n e . T h e r e f o r e , i t i s not l i k e l y t h a t the therm a l p y r o l y s i s of A ^ - p y r a z o l i n e s proceeds through an i o n i c mecha nism w i t h the dlazonium b u t a i n e I I as the t r a n s i t i o n s t a t e . The s m a l l d i f f e r e n c e i n r a t e of p y r o l y s i s i n p o l a r and non- p o l a r s o l v e n t s suggests the mechanism of the p y r o l y s i s of A 1 - p y r a z o l l n e s to be e i t h e r f r e e r a d i c a l or molecular s i n c e these do not Involve l a r g e i o n i c c h a r a c t e r . - 35 - One f u r t h e r argument can be made a g a i n s t the proposed i o n i c mechanisms f o r thermal p y r o l y s i s . T h i s mechanism would p r e d i c t t hat the diazonium b e t a i n e i n t e r m e d i a t e , f o r example XXXIV, would form p y r a z o l i n e by r i n g c l o s u r e f a s t e r than the l o s s of n i t r o g e n . Since the product a n a l y s i s p r e d i c t s r o t a t i o n ' C O O C H - N?H3 H3C N 2 XXXIV about Cg-G^ bond, one would a n t i c i p a t e t h a t when t r a n s - 3 , 5 - dimethyl - 3-carbomethoxy-^"-pyrazoline (XVII) i s p a r t i a l l y p y r o l y s e d , the recovered sample should show both XVII and I t s c i s isomer XVI. T h i s has not been found to occur i n t h i s work o r i n the work of van Auken and RInehart (12). P a r t i a l photo l y s i s of XVII a l s o gave a s i m i l a r r e s u l t . The p o s s i b i l i t y of the diazonium b n t a i n e I I as the i n t e r m e d i a t e f o r the p y r o l y s i s of ^ - p y r a z o l i n e s i s t h e r e f o r e e l i m i n a t e d . R1. ^ R 2 y R H " " N 2 I I Y = - C O C H 3 , - C O O C H o Recent work In t h i s l a b o r a t o r y (4o) has d i s c o v e r e d a CMT€- p y r a z o l i n e system which g i v e s k i n e t i c s t h a t i s - s e n s i t i v e to - 36 - s o l v e n t p o l a r i t y as expected f o r an i o n i c Intermediate. The O C O O C H , K /—* C00CH o other minor | | N C N W 3 4 . \ ^ N — 7 C N p r o d u c t s . XXXVII XXXVIII A 1 - p y r a z o l i n e XXXVII In t h i s case has two e l e c t r o n withdrawing groups which can s t a b i l i z e d a dlazonium b ^ t a i n e i n t e r m e d i a t e to a g r e a t e r degree. I t i s apparent that p y r o l y s i s of ^ " - p y r a z o l i n e s might f i t a spectrum of c o n d i t i o n s i r i which symmetric s u b s t i t u t i o n around the azo group leads to b r e a k i n g of both bonds 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 s t a t e . In h i g h l y unsymmetrical / ^ - p y r a z o l i n e s l i k e XXXVII one bond breaks b e f o r e the o t h e r . Such a s i t u a t i o n has been shown to be the case f o r l i n e a r azo compounds ( 4 l ) where compounds XXXIX, XL,and,XLI (0=--C^B.^) H Q C C H - H o C , C H o H C 3 \ / 3 3 v / 3 3 \ C H - N = N - C H C H - N = N - C H J ! H - N = N - C H , 0 0 0 C H 3 0 XXXIX XL XLI show equal b r e a k i n g of both bonds, unequal b r e a k i n g of both bonds and i n i t i a l b r e a k i n g of one bond. These r e s u l t s were obtained by secondary deuterium e f f e c t s on the k i n e t i c s . I t i s apparent t h a t i n the p y r o l y s i s of c i s and t r a n s - 3,5-dimethyl-3-carbomethoxy-A 1-pyi ,azolIne (XVI and XVII) we have an Intermediate s i t u a t i o n where the C - N bonds are break-- 37 - i n g i n the t r a n s i t i o n s t a t e p o s s i b l y to d i f f e r e n t degrees and s u f f i c i e n t p o l a r i t y developes i n the molecule a f t e r the t r a n  s i t i o n s t a t e to make the products s e n s i t i v e to the s o l v e n t used. Such a model c o r r e c t l y p r e d i c t s the o l e f i n r e a i f i o ' n 1 ^ ^ P h o t o l y s i s o f c i s and trans - 3 , . 4-dlmethyl - 3-earbomethoxy- ^ - p y r a z o l i n e (VI and VII) have been r e p o r t e d by van Auken and Rineh a r t ( 12 ) to gi v e s t e r e o s p e c i f I c a l l y c i s and t r a n s _ - l , 2 - d i - methyl-l-carbomethoxycyclopropane (X and XI) r e s p e c t i v e l y , the major s i d e products are methyl t i g l a t e (IV) and methyl an g e l a t e (V) r e s p e c t i v e l y . /COOCH^ ... - H COOCH ^ \ fC * k X O O C H o \ / KJ1 K3<fX/^m3 HoC \ ^ v xi 3^ CH3 V I X ( 3 , 4 ) IV ( 1 . 0 ) H3C ^ C O O C H ^ H y _ M C H 3 H 3 ^ = r / O O C H 3 c VCH, V I I 3 XI ( 2 1 . 3 ) V ( 1 . 0 ) P h o t o l y s i s of c i s and t r a n s - 3 , 5 - d l m e t h y l - 3 - c a r b o m e t h o x y - A 1 - p y r a z o l i n e (XVI and XV I I ) , 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 - ^ " - p y r a z o l i n e (XVIII and XIX) resemble v e r y c l o s e l y to the p y r o l y s i s of the same. The major d i f f e r e n c e observed i s t h a t , the p h o t o l y s i s gave a h i g h e r y i e l d of cyclopropane w i t h r e t e n t i o n of the geometry present i n the p y r a z o l i n e , and the p y r o l y s i s gave a. lower y i e l d of cyclopropane w i t h r e t e n t i o n of - 38 - XVI, Y=COOCR"3 XVIII, Y = COCH 3 CH H CH, c i s - o l e f i n product XVII, Y=COOCH 3 XIX, Y=COCH 3 H CHo / t r a n s - o l e f i n product The p r e f e r r e d conformation of the p y r a z o l i n e isomers p l a c e s the pseudo e q u a t o r i a l hydrogen on C^ i n a b e t t e r p o s i t i o n f o r m i g r a t i o n t o C,_ concerte d w i t h n i t r o g e n e l i m i n a t i o n than the pseudo a x i a l hydrogen. FIGURE X - Ste r e o c h e m i s t r y of the fo r m a t i o n of o l e f i n s from b. - p y r a z o l i n e s . - 39 - the geometry present In the p y r a z o l i n e . For example, the r a t i o s of c i s and t r a n s - 1 , 2 - d i m e t h y l - l - a c e t y l c y c l o p r o p a n e (XXIV and XXV) were 59*28 and 21:70 f o r the p h o t o l y s i s of XVIII and XIX r e s p e c t i v e l y . A s i m i l a r s o l v e n t e f f e c t on the £ O C H 3 K H O I ^ A ^ C O C H 3 H 3 C ^ y \ > w ^ 3 C ^ " ^"01 JC0GH, 3 XVIII xxiv (59$) XXV (28$) xP0CH3 H 3 C ^ ' N ^ N ^ H 3 . H 3 ^ ^ H 3 XIX XXV (70) XXIV (21$) product composition as observed i n the p y r o l y s i s was a l s o ob served i n the p h o t o l y s i s . The two r e a c t i o n s t h e r e f o r e are c l o s e l y r e l a t e d but not I d e n t i c a l as shown by p h o t o l y s i s and p y r o l y s i s at same temperature and s o l v e n t In which d i f f e r e n t product compositions r e s u l t e d . ' I t i s p o s s i b l e the p h o t o l y s i s i n v o l v e s a d i f f e r e n t con- . f o r m a t i o n of the same Intermediate as the p y r o l y s i s w i t h v a r i a t i o n e i t h e r due to a d i f f e r e n t amount of a v a i l a b l e energy or due to induced s t r u c t u r a l f e a t u r e s from the p r i o r e l e c  t r o n i c a l l y e x c i t e d I ntermediate. The n u c l e a r magnetic r e s o  nance s p e c t r a (Table I) of the A ^ - p y r a z o l i n e s showed l a r g e d i f f e r e n c e s i n the chemical s h i f t p o s i t i o n s of the hydrogens on C / | , e s p e c i a l l y i n c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - A * ' - p y r a z o l i n e _ 40 - (XVIII), and cis - 3 , 5-dlmethyl - 3-earbomethoxy-A - p y r a z o l i n e ' (XVI) . For example, hydrogens i n XVIII absorbed at 7.57 tf and 9.30-f, those of XVI absorbed at 7.68 • tf' and 9.14 com pared to 8.28 'i and 8.56 tf f o r the t r a n s - e s t e r - p y r a z o l i n e (XVII) and 8.53 tf1 f o r the t r a n s - k e t o - p y r a z o l i n e (XIX). These d i f f e r e n c e s i n chemical s h i f t s c o u l d w e l l be r e l a t e d to d i f  f e r e n c e s i n conformation i n these s p e e i e s . I f t h i s i s so then i t Is obvious t h a t the molecules i n some cases are e n t e r i n g r e a c t i o n w i t h c o n s i d e r a b l e d i f f e r e n c e s i n t h e i r geometry. -.41 - V I . EXPERIMENTAL V I - 1 . General statement M e l t i n g p o i n t s and b o i l i n g p o i n t s are u n c o r r e c t e d . M e l t  i n g p o i n t s were determined by a mi c r o s c o p i c m e l t i n g p o i n t ap paratus ( R e i c h a r t , A u s t r i a ) and most b o i l i n g p o i n t s were de termined by the micro 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 were measured wi t h a Perkin-Elmer Model 137 spectrophotometer f i t t e d w i t h sodium c h l o r i d e o p t i c s . N u c l e a r magnetic resonance s p e c t r a were recorded on a V a r i a n A s s o c i a t e s Model A-60 spectrophotometer by Mrs. E. B r i o n and Mr. P. Horn. T e t r a m e t h y l s i l a n e was used as I n t e r n a l standard. The vapor phase chromatography u n i t s used were an Aero graph Model A-90-P ( p r e p a r a t i v e s c a l e ) and a Perkin-Elmer Model 226 ( a n a l y t i c a l s c a l e ) . The elemental microanalyses were performed by Dr. A. Bern hardt of Germany and by Mrs. A. A l d r i d g e and Mrs. C. J e n k i n s . V I - 2 . N - N i t r o s o - N - e t h y l urea The method f o r the p r e p a r a t i o n of N-nitroso-N-methyl urea (35) was adapted w i t h some m o d i f i c a t i o n . Three hundred grams (5 moles) of urea was d i s s o l v e d i n a s o l u t i o n of 123 g. (1.5 moles) of ethylamine h y d r o c h l o r i d e , 300 ml. of water and a few drops of - 42 - c o n c e n t r a t e d h y d r o c h l o r i c a c i d . The mixture was b o i l e d g e n t l y under r e f l u x f o r t h r e e hours a n d , v i g o r o u s l y f o r a q u a r t e r hour. A f t e r c o o l i n g to room temperature, 110 g. (1.5 moles) of 98 per cent sodium n i t r i t e was added and the mixture was d i v i d e d i n t o s i x equal p o r t i o n s . Each p o r t i o n was c h i l l e d w i t h i c e and added to an i c e - c o l d s o l u t i o n of 17 g. (0.17 mole) of concentrated s u l f u r i c a c i d i n 110 g. of i c e w i t h s t i r r i n g at such a r a t e t h a t the temperature remained below 5 ° . The N- n i t r o s o - N - e t h y l urea, which rose to the s u r f a c e as pale yellow c r y s t a l s , was c o l l e c t e d on a f i l t e r and washed wi t h l e e - c o l d water and d r i e d by s u c t i o n t i l l constant weight (approximately t h r e e h o u r s ) . The y i e l d was 87 g. (0.75 mole) or 50 per cent of the t h e o r e t i c a l y i e l d . V I - 3 . Diazoethane F i f t y grams (O.285 mole) of N - n i t r o s o - N - e t h y l urea was added to v i g o r o u s l y s t i r r e d i c e - c o l d s o l u t i o n of 300 ml. of anhydrous ether-methanol ( 5 : l ) and 125 ml. of 40$ potassium hydroxide a t such a r a t e t h a t the r e a c t i o n was under c o n t r o l and the r e a c t i o n temperature remained below 5°» The orange c o l o r e d diazoethane-ether-methanol s o l u t i o n was decanted from the aqueous l a y e r , washed w i t h 100 ml. of i c e - c o l d water and d r i e d w i t h anhydrous potassium hydroxide p e l l e t s f o r two hours. The y i e l d was approximately 35-40 per cent as estimated by the r e a c t i o n s w i t h methyl i s o p r o p e n y l ketone and methyl met h a c r y l a t e . - 43 - VI-4. Methyl i s o p r o p e n y l ketone A commercial sample (K and K Laboratory, P l a i n s v i l l e , N.Y.) was p u r i f i e d by mixing w i t h an equal volume of anhydrous e t h y l e t h e r w i t h s t i r r i n g . A polymer r e s i d u e p r e c i p i t a t e d i n s t a n t l y and was f i l t e r e d w i t h f l u t t e d f i l t e r paper. The f i l  t r a t e was d i s t i l l e d at atmospheric pressure and the f r a c t i o n w i t h a b o i l i n g p o i n t of 9 5 ± 2 ° was c o l l e c t e d and used immedi a t e l y . V I - 5 . S ^ - D i m e t h y l - S - a c e t y l - A 1 - p y r a z o l i n e (XXIII) To an i c e - c o l d diazoethane-ether-methanol s o l u t i o n was added the f r e s h l y d i s t i l l e d methyl i s o p r o p e n y l ketone s l o w l y w i t h s t i r r i n g u n t i l the orange c o l o r d i s a ppeared. The s o l v e n t mixture was removed by a f l a s h evaporator at water a s p i r a t o r p ressure and the r e s i d u e d i s t i l l e d to g i v e a c o l o r l e s s l i q u i d , b.p. 56-57°/1.2 mm. (50 per cent based on the q u a n t i t y of methyl Isopropenyl ketone used). A n a l . C a l c d . f o r C 7 H 1 2 N 2 ° 5 °> 59.97" H, 8.63; N, 19.99- Found: C, 59.60° H, 8.22* N, 20 .27 . The n.m.r. spectrum (20$ v/v i n CCl^) showed i t to be a mixture of 40$ c i s and 60$ t r a n s isomers (see below) as e s t i  mated by the i n t e g r a l s o f the a c e t y l methyl hydrogens of the two isomers. - 44 - V I - 6 . S e p a r a t i o n of c i s and t r a n s - 3 , 5 - d l m e t h y l - 3 - a c e t y l - A - p y r a z o l i n e (XVIII and XIX) The 3 > 5-dimethyl - 3-acetyl-A 1-pyrazoline (XXIII) was f r a c t i o n a l l y d i s t i l l e d u s i n g a Nester and Faust 1 8-inch by 6-mm. spinning-band s t i l l at 0.2 to 0.3 mm. w i t h the s t i l l pot immersed i n o i l bath maintained between 65-70°. During the en t i r e d i s t i l l a t i o n , the vapor came over at 32-35°/0.2-0.3 mm. The n.m.r. analyses of the lower and h i g h e r b o i l i n g f r a c t i o n s showed they c o n t a i n e d 8 l $ c i s - p y r a z o l i n e XVIII and 87$ t r a n s - p y r a z o l i n e XIX r e s p e c t i v e l y . These analyses were based on the i n t e g r a l s o f the a c e t y l methyl hydrogens a b s o r p t i o n s at 'J.fQ't f o r the e l s Isomer and at 7.65 <i f o r the t r a n s isomer. The c i s and t r a n s geometric assignments were based on the comparison of n.m.r. s p e c t r a l data w i t h those of c i s and t r a n s - 3 , 5 - d i - methyl - 3-carbomethoxy-& L-pyrazoline (XVI and XVII) (Table I) and the s t e r e o s p e c i f I c f o r m a t i o n of c i s and t r j n s - 1 , 2 - d i m e t h y l - 1-acetylcyclopropane (XXIV and XXV) from XVIII and XIX r e  s p e c t i v e l y by p h o t o l y s i s . The n.m.r. s p e c t r a l data o f 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 - ^ - p y r a z o l i n e (XVIII and XIX) are t a b u l a t e d i n Table I . V I - 7 . S e p a r a t i o n of c i s and trans - 3 , 5-dlmethyl - 3-carbomethoxy- ^ - - p y r a z o l i n e (XVI and XVII) 3 , 5-Dimethyl - 3-carbomethoxy - ^ J "-pyrazoline (XX) prepared (17) from dlazoethane and methyl methacrylate was f r a c t i o n a l l y - 45 - d i s t i l l e d 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-dimethyl-3-acetyl - A 1-pyrazoline (XVIII and XIX) t o g i v e c i s and trans-3,5-dimethyl-3-carbomethoxy-^'-pyrazoline (XVI and XVII) of 93$ and 994-$ pure r e s p e c t i v e l y , at temperature between 48-53°/0.1-0.3 mm. XVI and XVII showed d i f f e r e n t chemical s h i f t s f o r the e s t e r methyl hydrogens at 6.33 if and 6.27 T r e s p e c t i v e l y , and t h i s is" the b a s i s f o r d i s t i n g u i s h i n g the two isomers. Geometric assignments were based on the p h o t o l y s i s r e s u l t s In which the cis-3,5-dimethyl-3-carbo- methoxy-A. - p y r a z o l i n e (XVI). gave c i s - l , 2 - d i m e t h y l - l - c a r b o - methoxycyclopropane (X) and the trans_-3,5~dimethyl~3-carbo- m e t h y l - A ^ - p y r a z o l i n e (XVII) gave trans-1,2-dimethyl-l-oarbo- methoxycyclopropane (XI) as main product, and the lower y i e l d of the c i s - p y r a z o l i n e XVI (40$) due to s t e r i c hindrance of the methyl groups at and C,-. The n.m.r. s p e c t r a l data of c i s and trans_-3,5-dimethyl- 3-carbomethoxy-^? --pyrazoline (XVI and XVII) are t a b u l a t e d i n Table I . VI-8. trans-3,5-DImethyl-3-carbomethoxy-£J'-pyrazoline hydro- bromide. (XXII) To a mixture of 0.4 ml. of trans-3,5-dimethyl-3-carbo- methoxy-A^-pyrazoline (XVII) i n 3 ml. of anhydrous e t h y l e t h e r was added s l o w l y w i t h constant s t i r r i n g a s o l u t i o n of anhydrous e t h y l e t h e r s a t u r a t e d w i t h anhydrous hydrogen bromide gas. The p a l e yellow p r e c i p i t a t e was r e c r y s t a l l i z e d from e t h a n o l - e t h e r to g i v e 0.75 g. of white c r y s t a l s , m.p. 152-153°. Larger - 46 - c r y s t a l s were obtained by slow r e c r y s t a l l l s a t i o n from e t h a n o l . A n a l . C a l c d . f o r C^H^NgOgBr* C, 35.46; H, 5.53? N, 11.82. Founds C, 35.47° H, 5.32) N, 12.16. V I - 9 . Thermal p y r o l y s i s of 3 , 5 - d i m e t h y l - 3 - a e e t y l - A ] * ~ p y r a z o l i n e (XXIII) The I n j e c t o r port of the vapor phase chromatography u n i t (Aerograph Model A-90-P) was used as the apparatus f o r thermal p y r o l y s i s . A sample of the p y r a z o l i n e XXIII was i n j e c t e d i n t o the i n j e c t o r p o r t by means of a hypodermic s y r i n g e , the pyro l y s i s products were e l u t e d through the column where s e p a r a t i o n o c c u r r e d and c o l l e c t e d at the c o l l e c t o r s e p a r a t e l y . F i v e f r a c t i o n s were obtained and i t was found t h a t the second f r a c t i o n was a mixture of two components. A l l these s i x com ponents have been i d e n t i f i e d as i n d i c a t e d below, where b o i l i n g p o i n t , r e f r a c t i v e index, r e t e n t i o n time i n the vapor phase ehromatogram u s i n g a 1 0-ft. d i d e c y l p h t h a l a t e column of one q u a r t e r i n c h diameter at 140°, i n j e c t o r at 255° w i t h helium flow pressure at 48 p . s . I . , product composition i n per cent of t o t a l products are given.(se F i g u r e V I I , P. 14). 2 , 3 , 5-Trimethy.l-A 2-dihydrofuran (XXIX) : b.p. 119-120°, 24 o P4 n£ 1.4305 ( l i t . (27) b.p. I I8 .3-II8 .6 /746 mm., ng 1.4390), 6.2 minutes and 9$. I n f r a r e d bands (5$ v/v i n CCl^) at 5 . 8 7 ^ (s) due to carbon-carbon double-bond s t r e t c h i n g , 8.21 M (s) and 9.63 JX (s) due to v i n y l e ther s t r e t c h i n g (28). The n.m.r. spectrum (30$ v/v i n CCl,,) showed s i g n a l s of v i n y l methyl - 47 - hydrogens at 8.43 IT* ( m u l t i p l e t ) , C,_ methyl hydrogens at 8 . 7 9 ^ (doublet w i t h J-«6.1 c . p . s . ) , C^ hydrogens at 7.40 tf (two doublets) and 7.98 tf (two doublets) and C,_ hydrogen at 5 . 5 9 ^ (Sextet w i t h f u r t h e r s p l i t t i n g ) . The hydrogens at and C^ c o n s t i t u t e d a t y p i c a l ABX system (29) w i t h ^ A X ™ 1 ^ * 5 C « P - S « * A A B ~ 3 5 . 5 c.p.s., AgxCs-109 c.p.s., J A B ^ l 4 . 5 c.p.s., J A X ^ 8 . 0 c.p.s. and c.p.s. (F i g u r e I X ) . These chemical s h i f t s 2 are at expected p o s i t i o n s as compared to 2-methyl-k, -d i h y d r o  f u r a n (XXXIII) (30) whose chemical s h i f t s are at 8.30 tf ( m u l t i  p l e t ) , 5.55 tf ( m u l t i p l e t ) , 7.47 tf ( m u l t i p l e t ) and 5,78 tf ( t r i  p l e t w i t h J 2 9 . 3 c.p.s.) due to C 2 methyl hydrogens, C^ v i n y l hydrogen, and hydrogens r e s p e c t i v e l y . A n a l . C a l c d . f o r C 7H 1 20« C, 74.95" H, 10.78. Found: C, 74.951 H, 10 . 9 0 . cis - 3-Methyl - 3-hexen - 2-one (XXX): b.p. 145 - 1 4 5 . 5 ° , n 2 ^ 1 .4370, 12 .2 minutes and 6$. I n f r a r e d (5$ v/v In CCl^) bands at 5.91><- (s) and 6.l8yU (w) a t t r i b u t a b l e to the o(,/£-unsaturated earbonyl and carbon-carbon 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. spectrum (10$ v/v i n CCl^) showed peaks of a c e t y l methyl hydrogens at 7.86 tf ( s i n g l e t ) , v i n y l methyl hydrogens at 8.12 tf ( m u l t i p l e t ) , methylene hydrogens at 7.73 tf ( m u l t i p l e t ) , a l k y l methyl hydrogens at 9.02'tf ( t r i p l e t w i t h J ^7.3 c.p.s.) and v i n y l hydrogen at 4.44 tf ( m u l t i p l e t ) . Geometric assignment 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 ^ H ^ O : C, 74.95° H, 10.78. Founds C, 75.021 H, 10 .77 . - 48 - trans-3-Methyl-3-hexen-2-one; (XXXI): b.p. 156.5-158°, n 2' 3 1.4481, 17.7 minutes and 7$. I n f r a r e d spectrum (5$ v/v i n CCl^) showed a b s o r p t i o n s at 5.96 A (s) and 6.07 (w) due to ^ ^ - u n  s a t u r a t e d c a r b o n y l and carbon-carbon 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. spectrum (10$ v/v i n CCl^) showed peaks of a c e t y l methyl hydrogens at 7.81 1* ( s i n g l e t ) , a l k y l methyl hydrogens at 8.93 ^ ( t r i p l e t w i t h J<*7.5 c . p . s . ) , v i n y l methyl hydrogens at 8.39 'c ( m u l t l p l e t ) , methylene hydrogens at 7.76't ( m u l t i p l e t ) and v i n y l hydrogen at 3.52 ^ ( m u l t l p l e t ) . The geometric assignments f o r the c i s and trans-3-methyl- 3-hexen-2-one (XXX and XXXI) were based on the lower chemical s h i f t of the v i n y l proton i n XXXI. Since i n XXXI, the v i n y l proton Is c i s to the c a r b o n y l and hence c l o s e r t o the diamagnet- i c a n i s o t r o p y of the carbon-oxygen double-bond which d e s h i e l d s the v i n y l proton t o a g r e a t e r extent t o g i v e a low <f-value (32). A n a l . C a l c d . f o r C H 0* C, 74.95* H, 10.78. Found: C, 75.03J H, 10.81. c i s - l , 2 - D i m e t h y l - l - a c e t y l c y c l o p r o p a n e (XXIV): b.p. 151.5- 152.5°, n 2 i | 1.4376, 15.7 minutes and 44$. I n f r a r e d (5$ v/v i n CCljj) spectrum showed bands a t 5.96//. (s) and 9.76/U. (tn) due to s t r e t c h i n g of c a r b o n y l conjugated to cyclopropane r i n g and c y c l o propane r e s p e c t i v e l y . The n.m.r. spectrum (20$ v/v i n CCl^) showed the f o l l w i n g peaks, a c e t y l methyl hydrogens at 8.00 *t ( s i n g l e t ) , G 1 methyl hydrogens at 8.72 i. ( m u l t i p l e t ) , C 2 methyl hydrogens at 8.82 t! ( m u l t i p l e t w i t h main peak at 8.84 t ! ) , other r i n g hydrogens at 8.68 't (two hydrogens, m u l t l p l e t under C-^  - 4 9 - methyl hydrogens s i g n a l ) and 9.74 tf (one hydrogen, m u l t i p l e t ) - . Assignment of geometry w i l l be d i s c u s s e d below. Repeated e l e  mental m i c r o a n a l y s i s gave low value of carbon composition. t r a n s - l , 2 - D i m e t h y l - l - a c e t y l c y c l o p r o p a n e (XXV) and 3-meth- yl - 4~hexen - 2-one (XXXII)t these two components e l u t e d t o g e t h e r w i t h r e t e n t i o n time of 10.5 minutes, they c o n s t i t u t e d 34$ of the t o t a l p r o d u c t s . A n a l y t i c a l vapor phase chromatographic a n a l y s i s showed the mixture t o c o n s i s t of 85$ of XXV and 15$ of XXXII. Bromination of the mixture u s i n g 5$ bromine i n carbon t e t r a  c h l o r i d e gave t r a n s - 1 , 2 - d i m e t h y l - l - a a e t y l c y c l o p r o p a n e (XXV) and trans - 3-methyl - 3-hexen - 2-one (XXXI) as i n d i c a t e d by p r e p a r a t i v e vapor phase chromatography s e p a r a t i o n . The n.m.r. spectrum of the o r i g i n a l mixture i n d i c a t e d the presence of XXV and XXXII and w i l l be d i s c u s s e d s e p a r a t e l y below. A n a l . C a l c d . f o r C^H^O: C, 74.95" H, 10.78. Found* C, 74.87° H, 10.91. t r a n s - l , 2 - D i m e t h y l - l - a c e t y l o y c l o p r o p a n e (XXV) *• b.p. 136.5- 137°, 1.4275. I n f r a r e d (5$ v/v i n CCl^) band at 5 - 9 0 ^ due to c a r b o n y l conjugated to cyclopropane r i n g . The n.m.r. spectrum (20$ v/v i n CCl^) showed the a b s o r p t i o n of a c e t y l methyl hydro gens at 7.86 tf ( s i n g l e t ) , C 1 methyl hydrogens at 8.62 tf ( s i n  g l e t ) , C^ methyl hydrogens at 9.O3 tf ( m u l t i p l e t ) , and C^ hydrogens at two s e t s of m u l t i p l e t i n the r e g i o n between 8.75 tf and 9.60 rC. The assignment o f geometry t o c i s and t r a j i s _ - l , 2 - d i  methyl-.1-a c e t y l c y c lopropane (XXIV and XXV) was based on the com p a r i s o n of t h e i r n.m.r. s p e c t r a to those of the analogous e y c l o  propanes, the c i s and tr a n s - 1 , 2 - d i m e t h y l - l - c a r b o m e t h o x y c y c l o p r o -- 50 - pane (X and. XI) whose geometry have been determined (12) . 3-Methyl-4-hexen~2-one (XXXII) '* t h i s compound had not been i s o l a t e d to g i v e s u f f i c i e n t sample f o r complete i d e n t i f i  c a t i o n . The presence of XXXII was i n d i c a t e d by the n.m.r. spectrum-of the mixture of XXXII and trjans - 1 , 2-dimethyl - 1 - a c e t y l c y c l o p r o p a n e (XXV). Some s i g n a l s of XXXII were ob- seured by those of XXV, the f o l l o w i n g were r e a d i l y observed and a s s i g n e d as f o l l o w s , a c e t y l methyl hydrogens at 7.97 't ( s i n g l e t ) , methyl hydrogens at 8.92 *t (doublet w i t h J<*7 c . p . s . ) , v i n y l hydrogens at 4.57 f ( m u l t i p l e t ) and v i n y l methyl hydrogens at 8.32 *£ (doublet w i t h J ^ 4 . 8 c . p . s . ) . The n.m.r. spectrum i n d i  c a t e d the sample to be a -unsaturated ketone because of the h i g h a c e t y l methyl hydrogens a b s o r p t i o n at 7 . 9 7 ^ and the o l e f i n p r oton a b s o r p t i o n at 4.57'if. VI - 1 0 . Thermal 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 - ^ - p y r a z o l i n e (XVIII and XIX) The same procedure as f o r the thermal 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 - / ^ " - p y r a z o l i n e (XXIII) was used ..for the thermal 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 b y l - 3 - a c e t y l - ^ " - p y r a z o l i n e (XVIII and XIX). These r e a c t i o n s gave the same products as the thermal p y r o l y s i s of XXIII but i n d i f f e r e n t r a t i o . These r e s u l t s are r e c o r d e d i n Table I I . VI - 1 1 . Vapor phase p y r o l y s i s of c i s and trans_ - 3 , 5-dimethyl - 3 - 1 " a c e t y l - A - p y r a z o l i n e (XVIII and XIX) - 51 - The apparatus f o r the vapor phase p y r o l y s i s was a one-, l i t e r round f l a s k equiped w i t h a ground stopcock and a f i n g e r (45-mm. x 10-mm.) oppo s i t e the stopcock. Three m i c r o l i t e r sample of XVIII or XIX i n a c a p i l l a r y tube was pl a c e d i n the f i n g e r and c o o l e d w i t h l i q u i d n i t r o g e n , and the f l a s k was then evacuated below 0.3 mm. The r e a c t i o n f l a s k was heated i n an oven preheated to 125° f o r t h i r t y minutes. I t was then connect ed t o a vacumn l i n e and the products were c o l l e c t e d i n a U-tube coo l e d w i t h l i q u i d n i t r o g e n . F i f t y m i c r o l i t e r s of anhydrous ether -w«rs added, and the mixture was analysed by a n a l y t i c a l vapor phase chromatography u s i n g a 150-ft. x 0 . 0 1-in. P e r k i n - Elmer column "R" at 100° w i t h n i t r o g e n flow pressure of 12 p.s. i . The analyses showed t h a t the vapor phase p y r o l y s i s r e a c t i o n s of c i s and trans_-3,5-dimethyl -3-acetyl-£?"-pyrazoline (XVIII and XIX) gave the same products as the thermal p y r o l y s i s of the same compound but i n d i f f e r e n t r a t i o . These r e s u l t s are r e c o r d  ed i n Table I I . VI - 1 2 . L i q u i d phase p y r o l y s i s of 3 , 5-dimethyl - 3-acetyl-/^ L- p y r a z o l i n e (XXIII) Nine and a h a l f grams of XXIII i n a 25 ml. round f l a s k equiped w i t h a water c o o l e d condenser was heated i n an o i l bath, p y r o l y s i s s t a r t e d at 90° w i t h the e v o l u t i o n of n i t r o g e n gas and became vig o r o u s at 105°. The h e a t i n g was stopped when n i t r o g e n gas ceased to come o f f . The y i e l d was 7 g. or 93 per cent of the t h e o r e t i c a l amount. The mixture was separated by p r e p a r a t i v e vapor phase chromatography u s i n g a 1 0-ft. d i d e e y l p h t h a l a t e 52 - column of one q u a r t e r i n c h diameter at 140 w i t h helium flow pressure at 48 p . s . i . to g i v e the same products as the thermal p y r o l y s i s - o f the same compound but i n d i f f e r e n t r a t i o . The r e  s u l t i s recorded i n Table I I . vT-13* L i q u i d phase p y r o l y s i s of c i s and trans_ - 3 , 5-dimethyl - 3 - • a c e t y l - A 1 - p y r a z o l i n e (XVIII and XIX) One q u a r t e r m i l l i l i t e r of XVIII or XIX i n a 150-mm. x 8- mm. pyrex tube was heated i n an o i l bath at 100° u n t i l the evo l u t i o n of n i t r o g e n gas ceased. Product composition of the pro ducts was analysed by a n a l y t i c a l vapor phase chromatography as d e s c r i b e d above. The r e s u l t s are recorded i n Table I I . V I - 1 4 . P h o t o l y s i s of 3 * 5 - d i m e t h y l - 3 - a c e t y l - A - p y r a z o l i n e (XXIII) A mixture of 1 ml. of XXIII and 25 ml. of anhydrous ether i n a 50 ml. round f l a s k equiped w i t h a water c o o l e d condenser was i r r a d i a t e d with a 450-watt Hanovia mercury lamp f o r s i x hours under r e f l u x c o n d i t i o n . The completion of p h o t o l y s i s was determined by the absence of n i t r o g e n peak i n the chromatogram when a sample was I n j e c t e d i n t o the p r e p a r a t i v e vapor phase chromatography u n i t or a l t e r n a t e l y , by measuring the t h e o r e t i c a l amount of n i t r o g e n t h a t evolved (the top of the condenser was connected to a gas measuring b u r e t ) . Most of the s o l v e n t was d i s t i l l e d o f f at atmospheric p r e s s u r e and the c o n c e n t r a t e was analysed by e i t h e r p r e p a r a t i v e or a n a l y t i c a l vapor phase chroma tography as d e s c r i b e d above. The same products but at ' d i f f e r e n t - 53 compositions than the l i q u i d phase p y r o l y s i s of the same com pound r e s u l t e d . The r e s u l t i s recorded i n Table I I . VI -15. P h o t 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 - / J " - p y r a z o l i n e (XVIII and XIX) A mixture of 0 . 5 m l . of XVIII or XIX and 5 ml. of anhy drous ether In a 25 ml. round f l a s k equiped w i t h a water cooled condenser was p h o t o l y s i s as d e s c r i b e d above. The mixture a f t e r p h o t o l y s i s , without c o n c e n t r a t i n g the s o l v e n t , was analysed by a n a l y t i c a l vapor phase chromatography. The r e s u l t s are recorded i n Table I I . VI -16. Vapor phase p y r o l y s i s of c i s and trans_ - 3 , 5-dimethyl - 3 - carbomethoxy-A 1-pyrazoline (XVI and XVII) The same procedure as the vapor phase 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 - / ^ - p y r a z o l i n e (XVIII .and XIX) was used f o r the vapor phase p y r o l y s i s of XVI and XVII. Analy t i c a l vapor phase chromatogram showed the same products as the vapor phase p y r o l y s i s o f 3 j 5-dimethyl - 3-carbomethoxy-£^-pyrazo- l i n e (XX) but In d i f f e r e n t r a t i o (17) r e s u l t e d . These r e s u l t s are r ecorded i n Table I I I . VI - 1 7 . L i q u i d phase 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 - c a r b o m e t h o x y - A - p y r a z o l i n e (XVI and XVII) i n v a r i o u s s o l v e n t s - 54 - A mixture od 0.2 ml. of XVI or XVII and 20 ml. of s o l v e n t In a s e a l e d tube (30-cm. x 2.5-cm.) which had been p r e v i o u s l y evacuated t o below 0.1 mm. was heated In an oven at 125-130° f ° r one and a h a l f hours. For v o l a t i l e s o l v e n t s , the s o l v e n t was r e  moved by d i s t i l l a t i o n through a spinning-band column under r e f l u x c o n d i t i o n , the concentrated sample was analysed by a n a l y t i c a l vapor phase chromatography. For the s o l v e n t formamide, the pro ducts were removed from the s o l v e n t on a vacumn l i n e by pumping f o r two hours and s i m i l a r l y a n a l y s e d . S o l v e n t s ( d i e l e c t r i c con s t a n t s at 20° are giv e n i n parentheses (44)) used i n these p y r o l y s e s were cyclohexane (2.07 D), e t h y l e ther (4.34 D), methanol (33.6 D), a c e t o n i t r i l e (37.5 D) and formamide (109 D). These r e s u l t s are summarized i n Table IV. VI - 1 8 . P h o t o l y s i s of trans - 3 , 5-dlmethy l-3-carbomethoxy~£i"- p y r a z o l i n e (XVII) at v a r i o u s temperatures. The apparatus f o r these r e a c t i o n s i s shown i n F i g u r e X I. A mixture o f 0.2 ml of XVII and 5 ml. of anhydrous e t h e r was pl a c e d i n the r e a c t i o n v e s s e l A, the c e n t r i f u g a l pump F was turned on which pumped the mobile c o o l i n g s o l u t i o n e t h a n o l through F, I i n t o B and back t o E. A . s u i t a b l e c o o l i n g agent was pl a c e d In D and the temperature at E was taken as th a t o f the p h o t o l y s i s . As soon as the temperature at E came to consta n t , the mercury lamp G (Hanovia, 450-watt) was turned on and the temperature at D was lowered a few degrees i n order to keep the temperature at E c o n s t a n t . I r r a d i a t i o n was terminated when the t h e o r e t i c a l amount of n i t r o g e n gas had evolved. T h i s experiment - 55 - r A - R e a c t i o n v e s s e l , 13-mm. x 150-mm. B - C o o l i n g j a c k e t CL. - A i r j a c k e t E - Dewar f l a s k w i t h ethanol as mobile c o o l i n g s o l u t i o n D - Dewar f l a s k w i t h c o o l i n g agent P - C e n t r i f u g a l pump Q _ 450-watt Hanovia mercury lamp H - Gas measuring buret I - C o o l i n g c o i l FIGURE XI - Apparatus f o r p h o t o l y s i s at low temperature. - 56 - had been performed at t h r e e d i f f e r e n t temperatures, 0 , -20 o and -55 u s i n g i c e - s a l t , carbon t e t r a c h l o r i d e - D r y Ice and chloroform-Dry Ice r e s p e c t i v e l y , as c o o l i n g agents at D. A l l r e a c t i o n p r o d u c t s , without c o n c e n t r a t i n g the s o l v e n t , were analyzed by a n a l y t i c a l vapor phase chromatography and t h e i r r e  s u l t s are summarized i n Table V. VI - 1 9 . P h o t o l y s i s of c i s and trans - 3 , 5~dimethyl - 3-carbomethoxy- 1 o A . - p y r a z o l i n e (XVI and XVII) i n formamide at 23 The same procedure as d e s c r i b e d i n the preceeding para graph was used f o r these p h o t o l y s e s . The c o o l i n g agent at D was water at 22-23°. These r e s u l t s are recorded i n Table V. VI - 2 0 . P a r t i a l p h o t o l y s i s of trans - 3 , 5-dimethyl - 3-carbomethoxy- ^ - p y r a z o l l n e (XVII) A mixture of 1 g. of XVII (99+$) and 10 ml. of anhydrous et h e r i n a 25 ml. round f l a s k equiped w i t h a water c o o l e d con denser whose top end was connected to a gas measuring buret was i r r a d i a t e d w i t h a 450-watt Hanovla mercury lamp. The i r r a d i a t i o n was terminated when 75 ml. (50 per cent of the t h e o r e t i c a l amount) of n i t r o g e n gas had evolved, and the r e s u l t i n g s o l u t i o n was connected to a vacumn l i n e to removed the s o l v e n t and the products from p h o t o l y s i s . The recoved p y r a z o l i n e was analysed by n.m.r. which showed t h a t the n.m.r. s p e c t r a of the recovered p y r a z o l i n e and the s t a r t i n g p y r a z o l i n e w e c f c p r a c t i c a l l y i d e n t i c a l t o each o t h e r . - 5 7 - VI-21. P a r t i a l l i q u i d phase p y r o l y s i s of t r a n s - 3 , 5 - d l m e t h y l - 3 - carbomethoxy-fc, 1-pyrazoline (XVII) One gram of XVII (99+$) i n a 100-mm. x 13-mm. pyrex tube connected t o a gas measuring buret was heated to 95° at an' o i l bath. Heating was stopped when 75 n i l . (50 per cent o f the theo r e t i c a l amount) of n i t r o g e n gas had evolved. A f t e r removing the p y r o l y s i s products i n a vacumn l i n e , the recovered p y r a z o l i n e was analysed by n.m.r. which showed t h a t the n.m.r. s p e c t r a of the recovered p y r a z o l i n e and the s t a r t i n g p y r a z o l i n e wei^.practi c a l l y i d e n t i c a l to each o t h e r . VI - 2 2 . K i n e t i c S t u d i e s of the p y r o l y s i s of 3 , 5-dimethyl - 3-carbo- methoxy-A^-pyrazoline (XX) at v a r i o u s s o l v e n t s The apparatus c o n s i s t e d of a 150-mm. x 13-mm. pyrex tube 1 whose top end was connected t o a gas measuring b u r e t . S i x m i l l l - o l i t e r s of s o l v e n t i n the tube was heated i n an o i l bath to 1C0-1 , 0 .2 ml. of XX was added i n t o the s o l v e n t and p y r o l y s i s begun. The volume of n i t r o g e n evolved and the time were recorded at i n t e r v a l s . I t has been shown (45) t h a t the p y r o l y s i s of A 1 - p y r a z o l i n e s g i v e s good f i r s t o rder k i n e t i c s , and that the h a l f - l i f e , t | , of the p y r a z o l i n e i s equal t o ( l o g 2)/m, where m i s the slope of the s t r a i g h t l i n e o b t a i n e d by the f i r s t o rder p l o t of the q u a n t i t y l o g (V<»/%o-Vfc) verses time, t . T h i s p y r o l y s i s r e a c t i o n of XX had been done i n the f o l l o w i n g s e r i e s of s o l v e n t s , d i - n - b u t y l e t h e r , t e t r a l i n e , n itrobenzene and formamide, and the h a l f - l i v e of XX i n these s o l v e n t s had been found to be 26.2, 29.0, 43.6 and 83.1 minutes, r e s p e c t i v e l y ( F i g u r e X I I ) . 1.0 o 30 6o 90 120 150 TIME (Minutes) FIGURE XII - F i r s t order p l o t of l o g £2_— v s . time f o r the p y r o l y s i s o f 3 ,5- ~~ ~~ Yoo - V t dimethyl - 3-carbomethoxy-i^'-pyrazoline in. v a r i o u s s o l v e n t s . - 59 - VI - 9 a. 2 , 4 - D i n i t r o p h e n y l hydrazones To a mixture of f i f t y m i c r o l i t e r s of ketone and 3 n i l . of 2 , 4 - d l n i t r o p h e n y l hydrazirre-dlglyme s o l u t i o n (36) was added 2 drops of conc e n t r a t e d h y d r o c h l o r i c a c i d and the mixture was allowed to stand f o r at l e a s t 24 hours (otherwise o i l y r e s i d u e r e s u l t e d when water was added). Water was then added dropwise w i t h s t i r r i n g t i l l cloudy, p r e c i p i t a t i o n normally completed a f t e r two or thr e e hours. The p r e c i p i t a t e was c o l l e c t e d and r e c r y s t a l l i z e d from diglyme-water. The m e l t i n g p o i n t s of the 2,4-DNPH d e r i v a t i v e s of 2 , 3 , 5 ~ t r i m e t h y l - A 2 - d i h y d r o f u r a n (XXIX), c i s and t r a n s - l , 2 - d l m e t h y l - l - a c e t y l c y c l o p r o p a n e (XXIV and XXV) 0 0 and cis - 3-methyl - 3-hexen-2-one (XXX) were 295-8 , 118.5-119.5 • o , 0 307-9 and 156.5-157 r e s p e c t i v e l y , trans - 3-methyl - 3-hexen-2- one gave two 2,4-DNPH der i v a t i v e s . " one p r e c i p i t a t e d b e f o r e o water was added, m.p. 158.5-159 » and the other p r e c i p i t a t e d a f t e r water was added, m.p. 156-156.5°. These two 2,4-DNPH d e r i v a t i v e s of trans - 3-methyl - 3-hexen-2-one (XXXI) were not the same as i n d i c a t e d by t h e i r mixed m e l t i n g p o i n t , 154-157°, and by the f a c t t h at the second d e r i v a t i v e p r e c i p i t a t e d o n l y a f t e r water was added. I t has been shown (42 ,43) t h a t *(,^-un- z. s a t u r a t e d ketones g i v e two 2,4-DNPH d e r i v a t i v e s , A - p y r a z o l i n e and s y n - a l k y l 2,4-DNPH. Hence one^the two 2,4-DNPH d e r i v a t i v e s 2 of XXXI ob t a i n e d c o u l d be a A - p y r a z o l i n e , and the other a s y n - a l k y l 2,4-DNPH. BIBLIOGRAPHY 1. E. Buehner, M. F r i t s c h , A. Papendieck and H. W i t t e r , Ann., 273, 214 (1893),. 2. K. von Auwers and E. Cauer, I b i d . , 4?Q, 284 (1929). 3. K. von Auwers and F. Konig, i b i d . , 496, 27, 252 (1932). 4. K. von Auwers and 0 . Ungemach, Ber., 66, 1206 (1933). 5. R. J . Landborg, Ph.D. T h e s i s , S t a t e Univ. of Iowa, 1959. 6. B. 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