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Some reactions of chlorodimethylarsine and dimethylarsine Dawson, David S. 1964

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SOME REACTIONS: OF CHLORODIME THYLARSINE AND DIMETHYLARSINE by David S. Dawson A THESIS. SUBMITTED IN, PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE. DEGREE OF MASTER. OF SCIENCE i n the Department of Chemistry We. accept t h i s thesis as conforming to the required standard THE, UNIVERSITY. OF BRITISH COLUMBIA. September 1964 In presenting this thesis-in p a r t i a l fulfilment of the requirements for an advanced degree at the University of : B r i t i s h Columbia, I agree that the Library shall make i t freely available for reference and study, I further agree that per- . mission for extensive copying of this thesis for scholarly . purposes may be granted by the Head of my Department or by his representatives. I t i s understood that,copying or publi-cation of this thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission* Department of The University of B r i t i s h Columbia, Vancouver 8, Canada Date i ABSTRACT. Chiorodimethylarsine i s found to add across the t r i p l e bond of hexafluorobut-2-yne, forming 2- chloro-3-dimethy 1-arsinohexafluorobut^-2-ene. Arsenic t r i c h l o r i d e , dichloro-methylarsine and chlorodiphenylarsine do not react,, while chloromethylphenylarsine reacts with great d i f f i c u l t y . . Sim-i l a r l y , bls(trifluoromethyl)arsine and methylphenylarsine form adduets with the butyne. These reactions are discussed and related to electron a v a i l a b i l i t y . The hydrolysis, bromination and chlorination of the adduct (CR 3) 2AsCCCF 3)=CClCF 3 are des-cribed. The reaction of dimethylarsine with dichloromethylara-ine i s discussed, and a reaction path suggested. Dimethyl-arsine i s found to react with t r i f l u o r o a c e t i c acid, i t s anhy-dride, and acyl chloride, but the products were not a l l ident-i f i e d . s Perfluorocyclobutene reacts with dimethylarsinomagneslum bromide to give dimethylperfluorocyclobut-l-enylarsine. The cyclobutene does not react with chlorodimethylarsine. i v ACKNOWLEDGEMENT I wish to. express, my sincere thanks and appreciation to Dr. W..R. Cullen f o r h i s constant guidance throughout the experimental work, and f o r constructive c r i t i c i s m of the manuacript. i i TABLE OF CONTENTS: ABSTRACT i ACKNOWI^LGEMENT i v EXPERIMENTAL. 1 Section I: Reactions Involving Hexafluorobut-2-yne 2 (A) With Chioroarsines . 2 1.. Chior odime thy la r s i n e 2 Synthesis of Chlorodimethylarsine 2 Reaction.of the Arsine with Hexaf luorobut-2r-yne 2 (a) Irradiation-. 2 (b) Heat. 3 2., Other Ghloroarsines 5 Synthesis of Dichloromethy la r s i n e 5 Synthesis, of Chloromethylphenylarsine 6 Reaction-of Chloromethylphenylarsine with Hexa- _ fluorobut-2-yne . . . . 6 (B) With Secondary Arsines 7 I„ Bis(trifluoromethyl)arsine 7 Synthesis of Bis(trifluoromethyl)arsine 7 Reaction.of. the.Arsine with Hexafluorobut-2i-yne 7 2. Methylphenylarsine ' . . 9 Synthesis of the Arsine 9. Reaction of the Arsine with Hexafluorobut-2-yne 9 Section I I ; Reactions Involving 2-Chloro^-dimethyl-arsinohexafluorobut-2-ene . . i i (A) Thermal.Stability 11 (B) With Aqueous. Sodium Hydroxide. 11 (0) With Bromine 12: 1.. One Mole Bromine 12 2. Two Moles Bromine 13 (D) With Chlorine 14 (E) Bromination of 2,3-Bis(dimethylarslno)hexa- . fluorobut-2-ene .' 1 5 Section I I I : Reactions Involving Dimethylarsine 16 Synthesis of Dimethylarsine . . . 16 (A) With Dichlorome thy l a r sine 17 (B) With Trifluoroacetyl Chloride 17 (C) With Trifluoroacetic Acid 20 (D) With Trifluoroacetic Anhydride 21 (E.) With Methylmagnesium Bromide 21 Section IV: Reactions. Involving; Perfluorocyclobutene 21 (A) With Dime thy l a r s inomagne s ium Bromide 21 Synthesis of Dimethylarsinomagnesium Bromide 21 Reaction,of the Bromide>with the Butene 22 (B) With Chlorodimethylarsine. 22 I., I r r a d i a t i o n 22. 2. Heat . . 23 i i i RESULTS AND DISCUSSION. Reactions Involving Hexaf luorobut-2-yne. Reactions Involving 2-Chl orc^ 3-d ime thy l a r s ino-hexafluorobut-2-ene Reactions) Involving Dime thy l a r s ine Reactions Involving Ferfluorocyclobutene B3BLI0GKAPHX INTRODUCTION I t has long been known (1) that arsenic t r i c h l o r i d e w i l l add across the t r i p l e bond of acetylene, y i e l d i n g / ^ -chloro-vinyldichloroarsine (Lewisite). The reaction i s catalyzed by Lewis acids such as aluminum and mercuric chlorides, and pro-duces mainly the trans isomer. Dichlorophenylarsine w i l l also react with acetylene i n the presence of aluminum chloride to give several products;, including bisp^-chlorovinyl )phenylars-ine (2). Cullen and Brierley (3) found that 3,,3,3-trif luoropropyne reacts with chlorodimethylarsine',, under u l t r a v i o l e t i r r a d -iation,; to y i e l d lr^imethyIaraino--2,,3, 13j3-tetrafluoroprop~2-ene, rather than the expected (CH3)2A.sCH=CClCT3. .Hexaf luorobut-2-yne has been found to react with the Aa-As bonds of arsenic metal (4) and tetramethyldiarsine (cacodyl) (5), giving compounds containingAsC(CFg) =C(CFg)As u n i t s , e.g. (CH 3)2As-As(CH 3) 2 + CFgCiOQFg » .(CH3)2AsC(CFg)=C(CFg)Aa(CHg)2 This reaction occurs smoothly at. 20°t y i e l d i n g roughly a 1:1 r a t i o of c i s and trans isomers. The butyne does not react with perfluorocacodyl at 150° (5). I t has been found (6), however, that the reaction (OF 3) 2AarAsCCF 3) 2 + CFgC=CCF3 > (CF 3) 2AsC(CF 3)=C(CF 3)As(CF 3) 2 does occur with u l t r a v i o l e t irradiation,, y i e l d i n g mainly the trans form. . Dimethylarsine and hexaf luorobut-2-yne react at 20° to, form the adduct (CH )g^se.(CEFg)=GHCE3 (mainly trans) (?). Under the same conditions the arsine combines) with 3,3,3-trif luoro-v i propyne to generate both XCHg)2&sC(CEg)=CH-g. and CF3CH=CHAs(CH3)2 ( c i s and trans) (3). In view of these r e s u l t s , i t was of interest to conduct further work involving the reactions of hexaf luorobut-2-yne with arsenic compounds. The present investigation was directed primarily, at the reactions of the butyne with As-Cl and As-H bonds. 1. S. J.. GREEN and T. S. PRICE. J . Chem. Soc. 448 (1921). 2. C. K. BANKS,. F. H. KAHLER and C. S, HAMILTON. J . Am. Chem. Soc. 69_, 933 (1947). 3. W. R. CULLEN and P. BRIERLEY. Unpublished observations. 4. C. G..KRESPAN. J . Am. Chem. Soc. 83, 3432; ( I 9 6 I ) . ' 5. W. R. .CULLEN and N. KV HOTA. Can. J . Chem. 42, 1123 (1964). 6 . W. R. CULLEN, D. S. DAWSON and G . E. STYAN. J . Organometal. Chem. In press. 7. W..R.^. CUL1£N. Unpublished observations. 1 EXPERIMENTAL Since many of the reactants and products encountered i n t h i s work were v o l a t i l e and often unstable to a i r or water, conventional high vacuum techniques were employed In t h e i r man-ipulations. Unless; otherwise stated, reactions were done i n Caxlus tubes. Products exhibiting a reasonable v o l a t i l i t y were sep-arated i n the vacuum system by trap-to-trap d i s t i l l a t i o n using suitable low temperature baths. Low-volatility products were examined by d i s t i l l a t i o n at reduced pressure, usually i n an atmosphere of nitrogen. Product separation was also achieved by means of vapour phase chromatography, using an Aerograph gas chromatograph equipped with a dinonyl phthalate column. Molecular weight determinations of v o l a t i l e substances were made by Regnault's method. Microanalyses were carried out by Dr. Alfred Bernhardt,; Max Planck I n s t i t u t e , Mulheim, Germany. Infra red spectroscopy was used extensively throughout t h i s investigation f o r determining purity, i d e n t i f y i n g known compounds, and ascertaining the structure of new compounds. Most of the spectra were run on a Perkin-Elmer Model 137 (Infracord) double-beam instrument f i t t e d with sodium chloride optics. When greater d e t a i l was required, the Perkin-Elmer Model 2 1 was used. Vapours were contained i n a gas c e l l equipped with sodium chloride windows, l i q u i d s were run as fi l m s between sodium chloride d i s c s , while solids were incorp-orated into Nujol mulls or potassium bromide p e l l e t s . 2 Yarlan H.R.-60 (at 56.4 Mc/s) and A-60 spectrometers were used to obtain the * 9F and "^H nuclear magnetic resonance spectra. Unless otherwise stated, the l a t t e r were run r e l a t i v e to internal tetramethylsilane. Section I : Reactions- Involving Hexafluorobut-2-yne (A) With Chloroarsines 1. Chlorodimethylarsine  Synthesis of Chlorodimethylarsine^" Sodium, hyp©phosphite (88 g.) and concentrated hydrochloric acid (300 c c . ) yielded a solution of hypophosphorous acid. C275 e.c)» which was used to reduce dimethylarslnic acid (112: g.) i n concentrated hydrochloric acid (.200 c c ) . The crude chloro-dimethylarsine (108 g.) was d i s t i l l e d at atmospheric pressure i n a stream, of nitrogen. The f r a c t i o n b o i l i n g a t 104-110° was collected ( l i t . value 107°) 2. Reaction of the Arsine with Hexafluorobut-2-yne (a) I r r a d i a t i o n : chlorodimethylarsine (5.0 g.) and hexa-fluorobut-2-yne (9*5 g.) were irradiated with u l t r a v i o l e t light„ with constant ag i t a t i o n , f o r two: days, after which time the two colourless phases had become one amber coloured phase. The materials were taken into the vacuum system and a separ-ation was attained using a -78° bath. This yielded unreacted hexafluorobut-2-yne (5.6 g.) and a compound (8.7 g.) which d i s t i l l e d at 79-80° (50 mm.), 131-132;° (83 mm.) and was ident-i f i e d as 2-chloro-3-dimethylarainohexafIuorobut-2-ene. Found: C, 23.98; H, 1.90;; As, 24.63;: C l , 11.94; F, 37.50 %; M, 280. Calc. f o r CgHgAsClFg: C, 23.4; H, 1.99; As,, 24.8; C l , 11.7; 3 F„ 37.8 %; M, 303. I n f r a red spectrum ( l i q u i d f i l m ) : 2910 vw> 1584 W j ; 1420 vw» 1263 m, 1227 vs, 1187 a, 1156 vs, 1130 sh, 982 w, 896 w, 875 w,; 850 w, 780 w cm"*"1". The proton, magnetic reson-ance spectrum showed two peaks i n the high f i e l d region, the smaller at f - 8.44 and the larger as a distorted quartet cen-tred at T=8.69 (J £ 1.5 c.p.s.). The r a t i o of the areas was approximately 8.3:1. In the downfield region was a very small peak at r =2.54. The magnetic resonance spectrum showed two main bands at +118 and +285 c.p.s., r e l a t i v e to inter n a l benzotrifluoride. These are s p l i t into a quartet (high f i e l d ) and a multiplet (9 peaks),. J f o r both being 1.4. c.p.s;. Outside these l i e two much smaller quartets ( J = 15 c.p.s.), centred at +42 and +372 c.p .a. (b) Heat: chlorodimethylarsine (1.8 g.), aluminum chlor-ide (.15 g.) and hexafluorobut-2-yne (7.6 g.) were heated to 140° f o r 16 hours. Trap-to-trap d i s t i l l a t i o n of the v o l a t i l e materials yielded hexafluorobut-2-yne (4.0 g.) and a f r a c t i o n stopping i n a -46° bath. This f r a c t i o n was d i s t i l l e d at atmo-spheric pressure, y i e l d i n g three cuts: 147-148°, 148-154°, 154-158°. The f i r s t (very small) yielded an i n f r a red spect-rum ( l i q u i d f ilm) Identical with that of (CH 3) 2AsC(CF 3) : sGClCF 3.. Fractions two (the. large majority of the d i s t i l l a t e ) and three were i d e n t i c a l , as follows (liquid, f i l m ) : . 3.35 vw, 6.25 m, 7.05 w, 8.05 vs, 8.4 s, 8.6 vs.,, 8.8 s, 10.05 w, 11.1 w, 11.4 m, 11.6 w, 12.4 w, 14.2 m.yu . This material analyzed to be 2-di-methylarsinoheptafluorobut-2-ene.. Found: C,, 24.97j H, 2.04; As„ 25.97; F, 46.57 %; M, 26g. Calc. f o r - C ^ k s F 7 : C, 25.2; 4 K, 2.10; As, 26.2;; F, 46.5 %; M, 286. The experiment was repeated (20 hrs. at 140°), using 20.3 g. chlorodimethylarsine and 39.4 g. hexaf luorobut-2-yne, i n three sealed tubes (no aluminum chloride). The v o l a t i l e materials were combined i n the vacuum system while the small amount remaining was d i s t i l l e d at .67 mm. Unfortunately the temperature rose steadily and essentially uniformly throughout — n o i clear cut b o i l i n g ranges could be seen. The two f r a c t i o n s taken had ranges 84-106° and 106-170°. The material remaining i n the d i s t i l l i n g pot came over at 125-156° (10~ 3 mm.). Trap-to-trap d i s t i l l a t i o n of the .volatile materials yielded hexafluorobutr-2-yne (14.8 g.) and a large portion stopping i n a -78° bath. This material was d i s t i l l e d at a t -mospheric pressure-—four fractions were taken: 101-105°, 110-117° (large), 119-130°, 132-142° (very l a r g e ) . The sec-ond boiled mainly at 115-117°, the fourth at 142°. These two were examined by vapour phase chromatography (column at 132°) and found to contain the same compounds (three major peaks) In. the following approximate r a t i o s : f r a c t i o n #2, 3.3:3.6:lj f r a c t i o n #4, 1:8:4. Samples of each of the three major comp-onents were collected, analyzed and subjected to i n f r a red examination. The analysis r e s u l t s : Component S C % H % As, % C l % F/ * 1 . . .26 47.48 ** - 31.71 2 20.10 2.99 30.67 14.53 3 23.81 2.08 24.65 11,97 37.99 The t h i r d component analyzes to be 2r-chloro-3-dimethylarsino-hexafluorobut-2-ene. Calc. f o r C~H~AsClF R; C, 23.8; H, 2.00; * Lack of material prevented further determinationa. ** Obtained by subtracting the sum of the others from 100 %. 5 As, 24.75; C l , 11.73; F, 37.7 %. The i n f r a red spectra of the three are as follows ( l i q u i d f i l m s ) : #1; 3.35 w„ 3.45 w, 6.0 m, 7.0 wr, 7.1 w, 7.2 m, 7.25 s,; 7.6 m, 7.65 s, 7.75 vs, 7.9 vs, broad 8.2: - 9.1 vs., 9.25 w, 9.75 w, 10.3 m, 10.5 w, 10.95 w, 14.55 w ^ i #2: 2990 w, 2895 w, 1737 w, 1584 m, 1423 m, 1273 s, 1232: vs (broad), 1187 vs (broad), 1151 vs (very broad), 983 m, 895 m, 875 w, 852: m, 829 w, 781 m, 731 vw, 651 s cmT1; #3: 2995 vw (broad), 2905 vw, 1744 vw (broad), 1585 m, 1420 w, 1273 a, 1236 vs (broad), broad 1214 - 1123 vs, 986 m, 896 w, 872 w, 854 m, 782 m, 735 vw, 700 w, 654 s cmT1 2. Other Chloroarsines The results of these experiments are summarized i n the table below. Quantitative recovery of the butyne was obtained from a l l the experiments except the one indicated. Wt. of CFgCECCFg (g.) Reaetant Conditions 28.4 AsClg (10.7 g.) UV i r r a d i a t i o n , 2 days 11.2 AsClg. (9.4 g.) Heat (135°), 2 days* 17.9 CHgAaClg (4.8 g.) . UV i r r a d i a t i o n , 1 day 12.3 CHgAsCIg (4.7 g.) Heat (105°), 2 days* 10.2 (CgH^gAsCl (4.5 g.) UV i r r a d i a t i o n , 2 days 11.3 C 6H 5(CH 3)AsCl (10.0 g.) UV i r r a d i a t i o n , 3 days** Synthesis of Dichlormethylarsine Arsenic t r i o x i d e (37 g » ) , sodium hydroxide (65 g.) and 80% ethanol (750 c c . ) were combined;; two l i q u i d phases were formed. Methyl iodide (117 g.) was added and the mixture a l -lowed to stand f o r 20 hours, whereupon the ethanol and unreacted methyl Iodide were d i s t i l l e d o f f . Excess concentrated hydro-chloric: acid and a l i t t l e water were added, a f t e r which the * AlClg added. ** 8.0 g. butyne recovered 6 mixture was saturated with sulfur dioxide f o r one hour. The s o l i d product was heated with concentrated hydrochloric acid (i h r , ) , then d i s t i l l e d at 16 mm. The middle f r a c t i o n (121-132°) (31.1 g.) was refluxed with s i l v e r chloride (50.g.) u n t i l dark colour gone, leaving the colourless dichloromethyl-arsine and bright yellow s i l v e r iodide. The arsine was d i s t i l -l e d at atmospheric pressure, b.p. 130-133° ( l i t . value 133°)^. The y i e l d was 4.8 g. .4 Synthesis of Chloromethylphenylarsine , Dichlorophenylarsine (181 g.) was synthesized from phenylarsonic acid (168 g.) and concentrated hydrochloric acid (400 c.e.), saturated with sulfur dioxide ( i hour)", i n the pres-ence of a trace of potassium iodide. The dichlorophenylarsine was converted by aqueous sodium hydroxide and dimethyl sulfate to methylphenylarsonic acid, which was reduced to the chloromethylphenylarsine by sulfur dioxide, i n the presence of excess concentrated hydro-ch l o r i c acid and a trace of potassium Iodide. The arsine was shaken up with anhydrous calcium chloride and d i s t i l l e d (17 mm.) over s i l v e r chloride (b.p. 123-125°) ( l i t . value 127° at 23 mm.)4. Reaction of Chloromethylphenylarsine with Hexafluorobut-2-yne The recovery of the butyne was not quantitative, ind-ic a t i n g that some reaction had occurred. The non-volatile product yielded the following i n f r a red spectrum ( l i q u i d film):. 2.9 w, 3.5 m (broad), 6.3 vw, 6.75 vw, 7.0 m, 7.15 w, 7.7 vw, 8.15 va, 8.65. vs, 8.75 vs, 9.15 w, 9.3 m, 9.75 vw, 10.0 w, 10.65; vw, 11.0 w, 11.75 m„ 12 .1 vw, 13.2 s, 13.5 vs, 14.4 vsw, 7 (B) With Secondary Arsines 1. Bis(trifluoromethyl) arsine Synthesis of Bis(trifluoromethy1)arsine (a) Synthesis of te t r a k i s ( t r i f luorome thy D d i a r s i n e (per-fluorocacodyl): arsenic t r i c h l o r i d e (24.6 g.) and t r i s ( t r i -fluoromethyl)arsine (16.8 g.) were heated at 220° (3 days)* Concurrent with t h i s , 24.7 g* AsClg were heated with 16.6 g. (CFg)gAs. The two l i q u i d s were immiscible. After two days, there was l i t t l e difference i n volumes of the two phases;, quite a b i t of me t a l l i c arsenic had deposited on the sides of the tubes. After another day of heating, the only v i s i b l e difference was an increase i n the arsenic deposit. The contents of the vessels were mixed and d i s t i l l e d at. atmospheric pressure, using a dry-ice condenser.. The f i r s t f r a c t i o n , (CTgJgAs, (27.6 g.) d i s t i l l e d at 33-35°; the second, (CF 3) 2AsCl, (2.1 g.) at 35-65°; the t h i r d , CTgAsClg, (65-100°) was small. The second f r a c t i o n was shaken, up with mercury (60 g.) f o r two days and the v o l a t i l e products, (CF^gAsrA-sXCFg)^ (1.7 g.) taken o f f . (b.) Synthesis of the arsine: anhydrous hydrogen chloride (4.5g.), mercury (118 g.) and perfluorocacodyl (3.0 g.) were reacted on the shaker (1 week). The presence of a white powder (presumably, mercurous chloride.) i n the tube, was evidence that reaction had occurred. Trap-to-trap d i s t i l l a t i o n of the vola-t i l e materials yielded unreacted hydrogen chloride (4.0 g.), perfluorocacodyl (.1 g.), and bis(trifluoromethyl)arsine (2.9 g.), of known i n f r a red spectrum. Reaction of the Arsine with Hexaf luorbbut-2-yne Bis ( t r i f luoromethyl) arsine (2.9 g.) and hexaf luorobut-2-yne 8 (II .0 g.) were combined andallowed to stand at room temperature. After thawing, the mixture formed one phase, a colourless l i q u i d . No apparent change occurred thereafter. After two days the material was ( a l l ) taken into the vacuum system;; i n f r a red examination showed that l i t t l e i f any reaction had occurred. The compounds were then heated at 130° (24 hrs.). Examination of the products showed that p a r t i a l reaction had occurred, but absorption s t i l l occurred at the As-H stretching frequency. The material was then heated, f o r a further three days, but because of a malfunction of the thermostat, the temperature rose: to 210° f o r part or a l l of that time. Some yellow-brown s o l i d was produced, but except f o r t h i s a l l material went into the vacuum system. Trap-to-trap d i s t i l l a t i o n afforded hexa-fluorobut-2-yne (8.2; g.),, containing a l i t t l e s i l i c o n t e t r a -f l u o r i d e andfluoroform; a small f r a c t i o n stopping i n a -23° bath;; and a f r a c t i o n stopping i n a -46° bath. The -23° f r a c -t i o n yielded the following i n f r a red spectrum ( l i q u i d f i l m ) : 5.85 vw, 6.15 vw, 6.25 w, 7.45 m, 7.6 s, broad 7.8. - 9.2 vs, 9.25 vs, 9.4 m, 9.7 vw, 10.05 w, 10.2 vw, 10.65 vw, 10.8 vw, 11.4 w, 11.65 vw, 13.1 w, 13.35 w, 13.6 m, 13.7 w, 13.8 w, 14.1 vw, 14.55 w^ . The -46° f r a c t i o n (5.0 g.) was d i s t i l l e d at atmospheric pressure, y i e l d i n g two f r a c t i o n s : 98-99° and 100-101°. Yapour phase chromatography showed each f r a c t i o n to be v i r t u a l l y the same; after p u r i f i c a t i o n by t h i s technique, the compound analyzed to be 2-bis(trifluoromethyDarsino-1,1,1,4,4,4-hexafluorobut-2-ene. Found* C, 19.31; H, .27; As, 19.87; F, 60.47 %. Gale, f o r C 6HAsF 1 2: G,, 19.2; H, .27; As, 19.9; F, 60.6 %. Infra red spectrum (second fraction) 9 (vapour, 29 mm.): 3100 vw, 2302 vw, 1793 vw, broad 1728 -1693 vw, 1649 vw,, 1385 m, 1360 m„ 1331 vs., 1265 vs*, 1215 s*, 1173 va*, 1131 a*, 1099 a*, 1067 m, 1029 m, 1003 w, 949 vw, 887 m, 858 m, 820 vw, 735 a, Tig a cm?1 The proton magnetic spectrum (sample not purified) showed a quartet ( J = 7.5 c.p.s.) centred at T = 3.07, and a peak at r = 2:.67. Each peak of the quartet was s p l i t into a further approximate quartet ( J # 1.5 c.p.s.). 2:. Methylphenylarsine 4 Synthesis of the Arsine Zinc amalgam was prepared by s t i r r i n g (l£ hrs.) zinc dust (137 g.) i n a solution of mercuric chloride (27.5 g.) i n water (750 c c ) , followed by f i l t e r i n g and washing. Chloro-methylphenylarsine (50.5 g.) was reduced, i n a nitrogen atmo-sphere, by the amalgam i n methanol (250 c c ) , and concentrated hydrochloric acid (120 c c ) . The acid was added dropwise (1-| h r s . ) , followed by s t i r r i n g f o r another hour. The mixture was d i s t i l l e d with the exclusion of a i r into a separatory fun-n e l , whence i t was transferred into a suitable vessel, into which anhydrous calcium chloride had been placed. The d i s t i l -l a t i o n was aided considerably near the end by the addition of water to the reaction vessel, apparently because of azeotrope formation. The y i e l d was 37.3 g. methylphenylarsine (unpur-i f i e d ) . The product would not go into the vacuum system. Reaction of the Arsine with Hexaf luorobut-2-yne Methylphenylarsine (5.6 g.) and hexafluorobut-2-yne (13.3 g.) were reacted at room temperature (a dry-box was used 4£ mm. pressure 10 when putting the arsine into the Carius tube). At room temp-erature the mixture consisted.of two colourless l i q u i d phases, but within a few minutes the lower, phase became yellowish. I t became yellower and larger while the vessel became s l i g h t l y warm. Within half an hour after thawing, the mixture had be-come one phase, a yellow-orange l i q u i d . Within 18 hours amber-coloured crystals had appeared, but no further v i s i b l e change occurred. The vessel was opened to the vacuum system; the v o l a t i l e material was unreacted hexafluorobut-2-yne (7.4 g.). The non-v o l a t i l e material, which appeared to be a mixture of o i l and c r y s t a l , was extracted from the tube with a minimum of carbon —3 tetrachloride. The product was d i s t i l l e d at 10 mm., the . . . . , \ solvent having f i r s t been pumped off at room temperature. Two fractions were taken: 47-49.5° and 53-64°, the second f r a c t i o n having come over mainly at 54°. An u n d i s t i l l a b l e s o l i d residue, remained behind. Infra red examination indicated that the fractions were i d e n t i c a l while proton magnetic res -onance showed i n the second f r a c t i o n a very small amount of impurity at T = 8.5, the "*"H spectra being otherwise i d e n t i c a l : two high f i e l d peaks, at T = 9.07 (smaller) and the larger as a distorted quartet centred at T = 8.94, the area r a t i o being 11.1:1; two down f i e l d quartets centred at Y = 4.60 (smaller) and T = 3.64 ( l a r g e r ) , the area r a t i o s being roughly 11:1. The coupling constant f o r these was 8.5 c.p.s. Each peak of the larger quartet was s p l i t into a quartet, the coupling con-stant being 2 c.p.s. A complex system (aromatic protons) was. centred at T - 3.1. The reference was external tetramethylsilane. 11 This compound analyzed to be 2-methylphenylarsino-l ,1,1,4,4,4-hexafluorobut-2-ene. Found: C, 39.99, H, 2.89;; As, 22.63; F, 34.73 %, Calc. f o r G 1 ] LH gAsF 6: C, 40.0; H, 2.73;; As, 22.70; F, 34.55 %. Infra red spectrum ( f i r s t fraction) ( l i q u i d f i l m ) : 3070 w, 2930 vw, 2280 vw, 1641 w, 1582: w, 1485 w, 1438 m, 1363 w, 1330 s, 1283 m, 1255 vs ( s l i g h t l y broad), 1143 vs (broad), 1077 w, 1069 vw, 1023 w, 998 w, 870 w, 850 m, 844 m, 737 s, 721 vw, 693 s, 641 s cm?1 The compound was heated at 140° (3 days). Proton mag-netic resonance revealed that no isomerization had taken place. Section I I : Reactions Involving 2-Chloro-3-dimethylarsino- hexaf luorofout-2-ene (A) Thermal S t a b i l i t y A sample of the compound was heated to 220° (3 days)• A mass of very dark brown s o l i d was observed which appeared to be mostly carbon. Infra red. examination of the v o l a t i l e mat-e r i a l showed I t to be mainly s i l i c o n t e t r a f l u o r i d e . (B) With Aqueous Sodium Hydroxide The adduct (1.229 g.) was hydrolyzed by excess 10% aqueous sodium hydroxide at 105° ( 3 i hrs.). Trap-to-trap d i s t i l l a t i o n of the products passing through a -78° bath (.118 g.) yielded fluoroform and a trace of hexafIuorobut-2-yne, of known i n f r a red spectra, and a f r a c t i o n having the following spectrum (vapour, 35 mm.): 6.0 w, broad 6.2 - 6.5 vw, 7.15 vw, 7.35 m, 7.6 vs, 7.9 vs, unresolved 8.3 - 8.9 va, 10.4 s, 11.1 m, 11.6 a, broad 13.2 - 14.3 w^ <. The molecular weight of the material passing through the -78° bath was determined twice. The values were 130 and 133. Chloride ion wars found i n the aqueous r e -12 malnder, but only traces of f l u o r i d e ion could be detected. (C) With Bromine 1. One Mole Bromine Bromine (.5 g.) and 2-chloro-3-dimethylarsinohexafluoro-but- 2-ene (1.0 g.) In carbon tetrachloride (5 c c . ) were reac-ted at room temperature. The bromine was taken up immediately; after three days some flocculent needle-like crystals were observed. The solvent was pumped o f f , leaving a mass of cream coloured c r y s t a l s . After a month i t was observed that these crystals had l i q u i f i e d ; ; a second preparation l i q u i f i e d a f t e r four days In warm weather. The s o l i d i s permanently l i q u i f i e d at 100°. These crystals gave the-following i n f r a red spectrum (KBr p e l l e t ) : 3040 vw, 2930 vw, 2920 vw, 2330 w,, 1692 vw, 1606 m, 1555 vw, 1538 vw, 1516 vw, 1505 vw, broad 1418 - 1395 w, 1244 vs, 1199 s, 1172 vs., 1140 va, 1000 w, 917 m, 885 w, 875 w, 810 vw, 796 vw, 705 m, 688 vw, 673 m,, 667 w cmT1 The l i q u i d decomposition product analyzed to be 2"-chloro-3-bromome thy larsinohexaf luorobut- 2-ene. Found.: C, 16.38; H,,0.87; As, 20.35.;: Br, 21.64; C l , 9.84;; F, 30.91 %. C a l c f o r CgHgAsBrClFg? C, 1.6.3; E, 0.8;; As, 20.2; Br, 21.8;. C l , 9.66; F, 31.0 %, Infra red spectrum ( l i q u i d f i l m ) : 3.4 vw, 6.25 m, 7.1 vw, 8.1 vs, 8.35 s, 8.6 vs, 10.0 w, 11.35 m, 11.6 w, 12.3 vw, 12.4 vw, 14.2 ny*. Vapour phase chromatography showed that the l i q u i d was one substance; i t d i s t i l l e d at 106-115° (70 mm.). The proton magnetic resonance spectrum showed a d i s t -orted quartet centred at f = 7.95, J ~ 1.5 c.p.s. Two small peaks occurred at T = 7.54 and 2.47. 13 l g The F magnetic resonance spectrum consisted of two quartets ( J = 15 c.p.s.) centred at -954 and -1400 c.p.s. r e l -ative to external t r i f l u o r o a c e t i c acid. Between these lay two much weaker absorptions, the high f i e l d one being a quartet ( J = 15 c.p.s.) and. the other a distorted quartet. Between and close to these lay two even weaker absorptions,, which under high resolution were observed to be a quartet (.J# 1.4 c.p.s.) and a broad multiplet (low f i e l d ) . Each of these three p a i r s consis ted.of. approximately equal absorptions. The solid. (.3808 g.,, .824 mmole.) was. heated ( l i hrs.) i n a sealed tube at 100°, after which the material was taken into the vacuum system. The f r a c t i o n passing through a -78° bath was shown by i n f r a red examination to be methyl bromide (.082 g.,, .863 mmole.). This was confirmed by the molecular weight. Found: 93j, CH^Br requires 95. 2. Two Moles Bromine Bromine (1.5 g.) was reacted with 2-chloro-3-dimethyl-arsinohexafluorobut—2-ene (1.4 g.) i n carbon tetrachloride (5 c c . ) . A l i g h t coloured s o l i d was produced immediately but the bromine was not completely taken up. Within four days the s o l i d disappeared, leaving a reddish amber solution, which became very pale yellow i n two more days. Most of the mater-i a l went into the vacuum system; trap-to-trap d i s t i l l a t i o n yielded methyl bromide (.64 g., 73 % ) , carbon tetrachloride, and a f r a c t i o n (-23° bath) having the following i n f r a red spectrum ( l i q u i d f i l m ) : 3.4 vw, 4.25 vw, 6.3 a, 7.15 w, 7.4 vw,, 8.1 vs,, 8.6 vs, 9.3 m, 10.05 m, 10.3 vw, 11.2 vw, 11.4 m, 11.7 w, 12.0 w/, 12.3 m, 13.0 vw, 13.2-m, 14.2 s, 14.35 m, 14 14.55 w, 14.7 w/^» Bromine (.5 g,) and 2-chloro-3-bramomethylarsinohexafluoro-but—2-ene (1.2: g.) i n carbon tetrachloride (5 c c . ) produced a dark red-brown solution at room temperature; after 18 hours the colour had lightened considerably. When the solution be-came colourless, the material was taken into the vacuum system. Trap-to-trap d i s t i l l a t i o n again yielded methyl bromide (.24 g.» 80 % ) . The f r a c t i o n stopping i n a —23° bath was combined with the same f r a c t i o n from the previous bromination and. d i s t i l l e d at 39 mm., y i e l d i n g two f r a c t i o n s : 92-93° and 98-103°. (D) With Chlorine. Chlorine: ( . 9 g., 1.2.7 mmole.) was reacted with 2-chloro-3-dime thy larsinohexaf luorobut- 2-ene (4.0 g., 13.2 mmole.) i n carbon tetrachloride (3 c c ) . At room temperature the mixture was a very pale yellow l i q u i d . I t was allowed to stand f o r one week. The v o l a t i l e materials were taken into the vacuum system, leaving a c r y s t a l l i n e white s o l i d . Only a negligible amount passed through a -78° bath; the carbon tetrachloride was d i s -carded. The tube was f i l l e d with nitrogen and the s o l i d then heated at 50° (1 n r . ) , which l i q u i f i e d a l l but a few c r y s t a l s . The tube was again, heated at 5Q° (22£ hra.),, which l i q u i f i e d the remaining c r y s t a l s . The v o l a t i l e products contained no appreciable amount of methyl chloride. A separation was a t -tained with a -96° bath, the majority passing through and having the following i n f r a red spectrum (vapour, 72 mm.): 3.3 m, 7.35 w, 7.75 w, 7.9 m, 8.4 s, 8.6 a, broad 9.6 - 10.2 vw, 12.55 m*,; 13.45 s, 13.6 m, 14.0 sjm. The spectrum of the -96° * Probably due to CC1 A. 15 fraction, (vapour, 13 mm.):: 5.55 w, 7.05 w, broad 7.2 - 7.5 w, 7.65 m, 7.9 m,, 8.2 m, 8.6 s, 8.9 m, g.8m,, 12.55 a*^. The non-volatile f r a c t i o n ( l i q u i d f Urn): 3.3 vw, 6.15 m, 7.1 w, 8.0 vs, 8.25 s, 8.55. vs., 9.9 nt, 10.7 m, 11.2 m, 12.25 vw,, 14.0 m, 14.75 w^j. The non-volatile product was heated i n vacuo i n a sealed tube at 140° (3 days), and the v o l a t i l e materials admitted to. the vacuum system, leaving only a very small amount of dark coloured s o l i d . Trap-to-trap d i s t i l l a t i o n yielded three f r a c -tions. The first, stopping i n a —136° bath,, showed a molecular weight of 63 and had the following i n f r a red spectrum (vapour, 74 mm.): 3020 m, 2400 vw, 1610 vw, 1590 w, broad 1490 - 143Q w, 1405 w, 1365 m, 1330 w, 1280 v s D , 1190 va D, 1155 w, broad 1065 -985 w, 925 w, 900 mb,. broad 865 - 825 w, 745 a, 735 m, 715 a cm!1 The second, passing through the -136° bath, showed a molecular weight of 91, and had the following spectrum (vapour,.67 mm.): 3020 m, 2510 vw, 2380 w, 2150 vw, 2100 vw, 1975 vw, broad 1860 -1740 vw, 1610 m, 1580 w, 1400 m, 1360 m, 1285 v s b c , 1195 v s D C , 1150 m, 1110. w, lOOOw, 925 s„ 900 sb„ 840 m, 795 w, 745 m, 730 a, 69O m cmT1 The t h i r d f r a c t i o n stopped i n a -78° bath and gave t h i s spectrum (vapour, 13 mm.): 3000w, 1680 vw, 1650 vw, 1600 m, 1345 vw, 1250 vs, 1190 vs, 1025 m, 920 a„ 840.m, 795 w, 725 s, 69Q; m cm?1 (E) Bromination of 2:.3-Bls(dimeth.ylarsino)hexafluorobut-2-ene Bromine (7.15 g., 44.8 mmole.), carbon tetrachloride a Probably due to CC1 4. D Probably due to CTgCsCCFg. c 4 mm. pressure. 16 (20 c c . ) and 2,3-bis(dimethylars:mo)hexaf luorobut-2-ene (8.3 g., 22.3 mmole.) were mixed; upon thawing the mixture reacted im-mediately with the: production of some yellowish-white s o l i d . A l l the bromine waa taken up immediately. The vessel was a i r lowed to stand (5 days);; no further change was seen. The products were admitted to the vacuum system, but. a l i t t l e of the l i q u i d remained i n the tube along with the s o l i d . The l i q u i d material was yellow (that i n the vessel darkened after exposure to the a i r f o r a day). The s o l i d was pale y e l -low. Trap-to-trap d i s t i l l a t i o n revealed hexafluorobut-2-yne and a l i t t l e s i l i c o n tetrafluoride among the v o l a t i l e products, of known i n f r a red spectra. The molecular weight of the f r a c -t i o n stopping i n a -136° bath, containing most of the butyne, was determined to be 114.. The low v o l a t i l i t y f r a c t i o n yielded the following i n f r a red spectrum ( l i q u i d film.).;. 3.4 w, 3*5 w, 4*25 vw, 4*85 vw, 5.55 vw, 6.35 m, 7.1 w, 7.2 m, 8.1 vs, 8.6 vs, 10.35 w, 11.1 w, 11.8 w, 12.05 m, 12.6 w, 13.65 vw, 14.6 ny^ . This f r a c t i o n was d i s t i l l e d at 35 mm., giving, four f r a c t i o n s : 54-62°, 73-83°, 86-90°, 103-109°. The l a s t two had to be com-bined. The f i r s t and part of the second, were bromodimethyl-arsine, of known i n f r a red spectrum. The l i q u i d which did not go into the vacuum system gave the following i n f r a red spectrum ( l i q u i d f i l m ) : 3.4 v, 3.5 w, 4.25 w, 6.15 w, 6.35 m, 7.2 w, 8.1 vs, 8.6 vs, 10.3 w, 10.85 w, 11.8 w, 12.65 w, 13.1 w, 14.6 m^. Section I I I : Reactions Involving Dimethylarsine  Synthesis of Dimetfrylarslne • •:_ Chlorodimethylarsine (35 c c ) was reduced by zinc and 17 hydrochloric acid, i n the presence of ethanolic mercuric chloride, i n a nitrogen atmosphere, to dimethylarsine (16.4 g.). (A) With Dichloromethylarsine Dimethylarsine (5.5 g.,, 51.9 mmole.). and dichloromethyl-arsine (3.9 g.» 24.2 mmole.) were placed i n a Carius tube with a double constriction. Upon warming to room temperature, the reaction produced considerable amounts of an orange-rust s o l i d , and an intense blue-violet mirror on one small part of the tube. A considerable quantity of mobile l i q u i d remained. After one hour, the s o l i d was chocolate-rust c o l o u r e d j a f t e r four days, a d e f i n i t e chocolate colour. The v o l a t i l e products were admitted to the vacuum system. A large amount of uncondensable material was present which showed a molecular weight of 2*2, indicating hydrogen. The s o l i d (1.9 g.) was reacted with bromine (7.1 g.) i n s l i g h t ex-cess i n order to convert i t to arsenic tribromide and methyl bromide. The arsenic tribromide weighed 6.9 g.; the excess bromine, 0*2 g.;; the recovered methyl bromide, 1.9 g. The methyl bromide and excess bromine were separated by a -96° bath. Chlorodimethylarsine, of known i n f r a red spectrum, was detected i n the v o l a t i l e products of the o r i g i n a l reaction; dimethylarsine i t s e l f was absent. (B) With Trifluoroacetvl Chloride Dimethylarsine (.801 g.) and t r i f l u o r o a c e t y l chloride (1.143 g.) were sealed i n a Carius tube. When the mixture reached room temperature, i t consisted of one phase, a yellow l i q u i d , indicating that reaction had occurred. The materials 18 were a l l taken into the vacuum system. Trap-to—trap d i s t i l -l a t i o n yielded hydrogen chloride (.15 g., 55 % ) , i d e n t i f i e d by the molecular weight (found: 37.7; HC1 requires 36.5); un-reacted t r i f l u o r o a c e t y l chloride (.25 g.), of known i n f r a red spectrum; and a f r a c t i o n y i e l d i n g the following spectrum (vap-our, 35 mm.): 2.85 w, 3.25 w, 3.4 m, 3.5 m, 5.55 s, 5.8 s, 7.1 m, 7.4 w, 7.5 m, 7.9 vs, 8.1 vs, 8.4 vs, 8.7 va, 9.0 vs,, 9.75 vw, 10.05 vw, 10.5 w, 11.0 vs, 11.7 m, 11.9 nyu. When th i s material was exposed to the atmosphere an instantaneous, r e a c t i o n occurred, forming a brown s o l i d and colourless l i q u i d . This l i q u i d yielded the following i n f r a red spectrum (vapour, 22: mm.): 3060 w, 2990 w, 1810 s, 1420 w, 1360 m, 1340 m, 1270 s, 1240 s, 1190 vs, 1140 vs, 1110 vs, 995 w, 950 vw, 905 m, 830 sh, 825 m, 7g5 m, 770 vw, 725 ah, 720 m, 715 sh, 705 sh, 670 w cm"1 This reaction had been performed with a small excess of t r i f l u o r o a c e t y l chloride. I t was repeated, on a larger scale, w i t h a small excess of the arsine, using 4.362: g. t r i f l u o r o -acetyl chloride and 3.845 g. dimethylarsine. Upon thawing, the mixture again formed one phase, a yellow l i q u i d ; some e f f e r -vescence was noted. As i t approached room temperature, the l i q u i d became hazy and dark amber coloured, A few needle-shaped crystals could be seen. Afte r 24 hours the l i q u i d was rust coloured, mobile and opaque. The products were admitted to the vacuum system. Un-condensable material was present, the molecular weight of which was found to be 31.3, suggesting carbon monoxide. This material was discarded through a -lg6° bath and the rest of 19 the v o l a t i l e products were condensed into the vacuum system. Only a very small amount of material (solid) remained, i n the tube. Trap-to-trap d i s t i l l a t i o n yielded, along with traces of fluoroform, s i l i c o n , t e t r a f l u o r i d e and carbon dioxide, hy-drogen chloride (.66 g., 55 % ) , t r i f l u o r o a c e t y l chloride (.25 g.), and two unidentified f r a c t i o n s , one stopping i n a -23° bath (1.32 g.), the other i n a -46° bath (5.64 g.). The l a t t e r yielded the following i n f r a red spectrum (vapour,, 23 mm.): 3.3w, 3.4 w., 3.5 vw, 5.55 s, 5.8 m, 7.05 w, 7.35 w, 7.5 m, 7.9 vs, 8.05 s, 8.4 vs, 8.6 vs., 8.85 va, g.O s, 10.05 w, 11.0 s, 11.55 w, 11.9 w, 12.0 w, 12.9 vw, 13.7 w, broad 14.0 - 14.3 vw, 14.9 w^y. This f r a c t i o n was a clear yellow l i q u i d which upon exposure to a i r became colourless with a brown, pr e c i p i t a t e . The yellow li q u i d , was p u r i f i e d on the gas chromatograph, y i e l d i n g three f r a c t i o n s . The f i r s t was very small and was t r i f l u o r o a c e t y l -dimethylarsine, of known i n f r a red spectrum.. The t h i r d f r a c -t i o n was much larger and was i d e n t i f i e d from i t s spectrum as: being chlorodlmethylarsine. The middle f r a c t i o n was the l a r -gest. Infra red spectrum, (vapour): broad 3.3 - 3.6 w, 5.55 vs, 5.7 w, 7.1 w, 7.35 m, 7.5. s, 7.9 s, 8.1 vs, 8.4 vs, 8.85 vs, g.05 s, 10.05 w, 11.1 m,, 11.5 w, 11.9 w„ 13.0 m, 14.8 m^. The colourless l i q u i d formed by exposure to a i r was d i s t i l l e d at atmospheric pressure. Three fractions, were taken: 104— 114°, 115-118°, 122-126°. The f r a c t i o n stopping i n a -23° bath (1.32 g.) (m.p. 13-14°) „ suspected of being cacodyl, was reacted with bromine (I.00 g.) (1:1 mole r a t i o ) i n a sealed tube with carbon t e t r a -chloride (2 c . c ) . The brWihe~was taken up immediately. " The 20 products, were not a l l identified,, but the presence of flu o r i n e and oxygen was observed i n the i n f r a red spectra. Methyl brom-ide (.27 g.) was also obtained, (C)With Trifluoroacetic Acid Dimethylarsine (.783 g., 7.39 mmole.), and t r i f l u o r o a c e t i c " acid (.847 g., 7.44 mmole.) were heated at 130° (29 hrs.). Some uncondensable gas was produced;; the remaining material was only very s l i g h t l y v o l a t i l e and yielded the following i n -f r a red spectrum (vapour, 3 mm.): broad 2.9 - 3.35 m, 3.4 m, 3.5 m, 4.3 w, 5.7 s, 6.0 s, 7.1 s, broad 7.8 - 8.1 s, broad 8.2 - 9.1 vs, 9.2 s, 9.4 s, 10.9 m, 11.1 m, 11.9 *m, 12.5 m, 13.85 m, 14.2 ny< • Some of t h i s material (1.40 g.) was heated again at 130° f o r a further 40 hours. Examination of the prod-ucts revealed some decomposition (to fluorof orm). The mixture (1.33 g.) was then heated at 160° (67 hrs . ) , which resulted in. the formation of two l i q u i d phases: the upper was clear and very pale yellow while the lower was colourless but s l i g h t l y hazy. Neither was very v o l a t i l e . No s i g n i f i c a n t further reac-t i o n had occurred, other than the formation of more fluoroform, and carbon dioxdde. Two fractions were obtained by trap-to-trap d i s t i l l a t i o n . Their spectra are as follows: stopping i n a -23° bath ( l i q u i d f i l m ) : broad 2.8, - 4.0 m, 3.5 w, 4.35 vw, 6.0 s, 7.05 m, 7.85 m, broad 8.3 - 8.55. vs, 8.75 vs, 9.4 m, broad 10.75 - 11.4 w, 12.0 m, 12.5 m, 13.85 ny*; stopping i n a -46° bath ( l i q u i d f i l m ) : broad 2.8 - 4.0 s, 6.0 m, 6.15 m, 7.15 w, 7.85 s, 8.5 vs, 8.75 vs, 9.05 s, 9.4 s, 11.95 m, 14.0 HLJA . I t i s believed that these l i q u i d f i l m s picked up water from the atmosphere. 21 (D) With Trifluoroacetic Anhyoride Dimethylarsine (1.831 g., 17.3 mmole.) and t r i f l u o r o -acetic anhydride (.4.158 g., 19.8 mmole.), aft e r being mixed at. - I 9 6 0 , reacted instantly upon thawing, producing a clear yellow l i q u i d . The reaction was noticeably exothermic. The v o l a t i l e products were taken into the vacuum system (a s l i g h t amount of uncondensable material was observed); a considerable amount, however, remained i n the tube. This i n v o l a t i l e mater-i a l had the following i n f r a red spectrum ( l i q u i d f i l m ) : 2 .9 w, broad 3*25 - 3.5 w, 4.2 w, 4.6 vw, 5.0 vw, 5.7 m, 6.1 m, 7.1 w, 7.85 w, broad 8.0 - 9.1 s, 10.8 vw, 11.15 w, broad: 12.1 - 12.8 12.5 w, 13.8 w, 14.2; Wy«. Since trap-to-trap d i s t i l l a t i o n did not effect a separation of the v o l a t i l e products, they were d i s t i l l e d at atmospheric pressure. This procedure proved only p a r t i a l l y satisfactory, since the temperature of the material d i s t i l l i n g over rose steadily and at an essentially unchanging rate throughout. The upper l i m i t s of the b o i l i n g ranges of the three fractions taken were 100°, 115°, 160°. (E.) With Methylmagnesium Bromide This reaction, and the addition, to the product of per-fluorocyclobutene, i s discussed under the section dealing with the l a t t e r substance. Section IV: Reactions Involving. Perfluorocyclobutene (A) With Dimethylarsinomagnesium. Bromide Synthesis of Dimethylarsinomagnesium Bromide , Dimethylarsine (4.3 g.) and methyl magnesium bromide solution* (13 c c ) , diluted with ethyl ether (10 c c ) , were * One mole solute i n 316 c c solution (solvent: ethyl ether). 22 put Into a large Carius tube v i a a side constriction which had been f i t t e d onto the side of the tube. This vessel had also been equipped with a double constriction at the top, the outer one of which had been previously sealed o f f . As the mixture thawed, effervescence was observed. The tube was allowed to stand f o r three days, after which time a yellow-gray precip-itate had formed. Reaction of the Bromide with the Butene The tube was opened to the vacuum system and the uncon— densable material was pumped off without removing the vessel from the l i q u i d nitrogen. Perfluorocyclobutene (11.7 g.) was then added and the tube sealed o f f . When the mixture had thawed, two l i q u i d phases were noted, the ether being the upper layer. After standing (20min.), the s o l i d became brown coloured and the tube became s l i g h t l y warm to the touch. A f t e r a further ten minutes the lower phase had become an extremely viscous paste, whereupon the vessel was placed on the shaker (17 h r s . ) . Trap-to-trap d i s t i l l a t i o n yielded a l o w - v o l a t i l i t y product (3.8 g.) plus a very v o l a t i l e f r a c t i o n (23.9 g.) containing the ether and excess perfluorocyclobutene. The product, d i -me thy lperfluorocyclobut-l-enylarsine, boiled at 127-129° at atmospheric pressure, and yielded the following i n f r a red spectrum ( l i q u i d f i l m ) : 3.3 vw, 3*35 w, 3.45 vw, broad 4.1 -4.8 vw, 6.0 a, 7.05 m, 7.2 s, 7.9 vs, 8.3 s,. 9.0 vs, 9.95 vw, 10.55 vs, 11.05m, 11.55 m, 12.25 s, 14.65 vw/*. (B) With.Chlorodimethylarsine 1 . I r r a d i a t i o n Perfluorocyclobutene (10.0 g.) was combined, with chloro-23 dimethylarsine (4.0 g.) y i e l d i n g one l i q u i d phase and a l i t t l e f l occulent snow-white pre c i p i t a t e . U l t r a v i o l e t I r r a d i a t i o n on the shaker (2 days) resulted i n an amber l i q u i d and dark brown pre c i p i t a t e . Trap-to-trap d i s t i l l a t i o n yielded perfluoro-cyclobutene (7.7 g.) and a f r a c t i o n (4.4 g.) stopping i n a -78° bath. The i n f r a red spectrum of t h i s f r a c t i o n was that of un-changed chlorodimethylarsine—no trace of the very strongly absorbing C-F stretching could be detected. 2. Heat Perfluorocyclobutene (7.7 g.) and chlorodimethylarsine (4.4 g.) were heated at 105° (5 days) i n the presence of a l i t t l e aluminum chloride (sublimed into the vessel). After two. days, some c r y s t a l l i n e , waxy, caramel-coloured s o l i d could be seen;; after the f i v e days, a considerable amount of amor-phous brown-black s o l i d had formed. Trap-to-trap d i s t i l l a t i o n afforded perfluorocyclobutene (7.6 g.) and a f r a c t i o n (3.2 g.) whose i n f r a red spectrum indicated that no s i g n i f i c a n t reaction had taken place.. 24 RESULTS. AND DISCUSSION Section I ; Reactions Involving Hexafluorobut-2-yne (A) With Chloroaraines 1 1 Chloroarsines undergo addition reactions with acetylenes, \ • • • 5 the best known of which Is the formation, of Lewisite : A l C l o <W * A s C 1 3 or H g C l ^ CHCl=CHAsCl2 (1) 1. Chlorodime thy l a r s i n e In the present investigation hexaf luorobut-2-yne was reacted with chlorodimethylarsine under u l t r a v i o l e t i r r a d -i a t i o n , and also at 140° i n the dark. These w i l l be discussed separately. (a) I r r a d i a t i o n y i e l d s 2-chloro-3-dimethylarsinohexa-fluorobut-2-ene: (CHgJgAsCl + C F 3 C S C C E 3 (CHg)2AsC(CF3)=CClCF3 (2) The isomeric d i s t r i b u t i o n of t h i s adduct was studied using nuclear magnetic resonance. The l 9 F spectrum shows two main bands between two considerably smaller ($5% of t o t a l area) quartets ( J = 15 c.p.s.). The main bands s p l i t under high resolution into a quartet (high f i e l d ) and a m u l t i p l e t (nine peaks), J being 1.4 c.p.s. i n both cases. The coupling constant of 15 c.p.s. i s assigned to the c i s isomer; that of 1.4 c.p.s., to the trans . Both c i s and trans CFg-CFg coupling should y i e l d quartets; the greater m u l t i p l i c i t y observed i n the low f i e l d band of the trans isomer i s believed due to coupling through space of the CF 3 group gem to the methyl groups, with the methyl hydrogens. This same effect should occur i n the 25 case of the c i s form, and i n f a c t the peaks of the low f i e l d c i s quartet are broadened, with each peak being s p l i t into an approximate sextet. The "^H spectrum shows the methyl peak as a distorted quartet. Since compounds of the type (CHgJgAsRf normally 7 - ' show an unsplit methyl peak , the s p l i t t i n g i n t h i s instance i s believed due to CHQ-CFQ through space coupling. The tvro smaller peaks i n t h i s spectrum are ascribed to impurity. (b) I t i s known thataluminum chloride catalyzes the formation of ^ -cnlorovlnyldichloroarsine (Lewisite) from arsenic t r i c h l o r i d e and acetylene, as do some other Friedel-Craft s a l t s such as mercuric chloride^ and i t was thought that aluminum chloride would catalyze reaction between chlorodimethylarsine and hexaf luorobut-2-yne: A „ _ + (CHgJgAsCl + AlClg A1C1 4 + (GHgigAs (3) CF3C=CCF3 + (CHgJgAs* — > GFg-Cs ^ C-CFg — > CFg-C^C-CFg (4) CH^CH, ^ C H 3 ) 2 A S + A l C l " + CF3-C=C-CF3 (CH 3) 2AsC(CF 3)=GClCF 3 + AlClg (5) ( C H g ^ s + S t e r i c considerations would appear to favour the trans con-f i g u r a t i o n . The expected product, 2-chloro-3-dimethylar&inohexa-fluorobut-2-ene, i s indeed formed, but i t i s accompanied by the formation of 3-dimethylarsinoheptafluorobut-2-ene. A third product i s observed i n the least v o l a t i l e portion of the reaction mixture; t h i s compound gives an i n f r a red spect-rum very si m i l a r to that of 2-chloro-3-dimethylarsinohexa-26 fluorobut-2-ene, the differences occurring i n the C = C and C - C l stretching regions. The s h i f t of the C = C frequency to higher energy may Indicate an increase i n the electronegativ-i t y of ethylenic substituents. A suggested structure i s (CKg) gA.sC(CFg) =CFCF2C1. I t i s believed that the carbonium ion arrived at In the previous mechanism may experience a 1,2—shift before abstracting a chloride ion: (CH 3) 2AsC(CF 3)=CCF 3 > (0EQ)2ks0(CFQ)^CFCJ2 (6) (CHg)2 As C(CT 3) = CFCF2 + A l C l ^ > (CHQ) gAsC (.GFg.) =CFCT2C1 + AlClg In conjunction with the above investigation, chlorodimeth-ylarsine and hexafluorobut-2-yne were heated (on a much larger scale) i n the absence of aluminum chloride. The reaction pro-ceeds smoothly and again the product i s (CHgigAsCCCFg^CClCFg predominantly. The f a i l u r e of 3-dimethylarsinoheptafluorobut-2-ene to form i n appreciable quantity suggests that i t s ; form-ation depends upon the aluminum chloride, perhaps involving AlCIgF. Aluminum chloride i s known to bring about the follow-8 ing f l u o r i n e replacement reaction : ASCI 3 * CT2=CT2 A 1 G l s > cy-or^g CM The same very low v o l a t i l i t y product formed i n the pres-ence of aluminum chloride i s observed i n the absence of the s a l t . This substance i s believed to be l-chloro-3-dimethyl-arsinohexaf luorobut-2-ene. The v o l a t i l e products on examination by vapour phase chromatography showed three major components. The f i r s t was a fluorocarbon, containing hydrogen and a double, bond. The second and t h i r d yielded nearly i d e n t i c a l i n f r a red spectra 27 and were thought to be the two^  geometrical isomers of 2-chloro— 3-dimethylarsinohexaf luorobut—2-ene, but analysis shows only that the t h i r d f r a c t i o n i s t h i s adduct. The analysis of the middle fraction, i s exceedingly d i f f i c u l t to interpret;, a l l attempts to correlate the figures to a molecule of reasonable structure have f a i l e d . I t i s of interest that chlorodimethylarsine and hexa-fluorobut-2-yne do react smoothly on heating without the aid of a Frledel-Craft catalyst. I t i s believed that the reaction i s i n i t i a t e d by the auto'-ionization of the arsine: 2 (GH 3) 2&sCl : " (CHgJ^sClg + (CHg)-^* (g) The reaction then proceeds as indicated i n the previous mech-anism, with the (CHgJgA-sClg ion functioning i n the same way as A l C l ^ . The ease of reaction in. the absence of aluminum chloride suggests that the auto-ionization i s quite pronounced. 2. Other Chloroarsines Hexafluorobut-2-yne does not react with arsenic t r i c h l o r -ide, dlchloromethylarsine, chlorodiphenylarsine, or chloro-methylphenylarsine*, under the conditions of heating and/or Irra d i a t i o n selected. In view of the ready reaction of the butyne with chlorodimethylarsine, on both heating and i r r a d -i a t i o n , i t Is clear that the addition of As-Cl across the t r i p l e bond i s very dependent upon the electronegativity of the sub-stituents on the arsenic atom. Although s t e r i c hindrance may play a part in, the case of the aromatic arsines, i t certainly i s not a factor with the other two. The butyne, whether i n * P a r t i a l , reaction with t h i s arsine, see experimental. 28 the ground or excited state, w i l l show only l i m i t e d a v a i l a -b i l i t y of the acetylenic electrons, because of the t r i f l u o r o -methyl groups. As mentioned e a r l i e r , arsenic t r i c h l o r i d e does., react with acetylene i t s e l f . . , Thus t h i s addition reaction is; dependent, upon electron a v a i l a b i l i t y * both acetylenic and ars-enic lone p a i r electrons being pertinent. On going from dlehloromethylarsine to chlorodiphenyl-arsine, the lone p a i r a v a i l a b i l i t y should be appreciably increased. However i n t h i s molecule, s t e r i c hindrance could be quite pronounced. Another f a c t o r may be d e l o c a l i z a t i o n of the lone p a i r into the aromatic systems: "As < > etc. (10) C l C l I t i s believed that t h i s effect i s small, because of the known reluctance of the arsenic atom to form a double bond. * Substitution of a phenyl group by a methyl both increases. the lone p a i r a v a i l a b i l i t y and decreases the s t e r i c hindrance and any lone p a i r d e l o c a l i z a t i o n . These effects are i n f a c t s u f f i c i e n t to allow the molecule to react very slowly with the butyne. This same very slow reaction shows that substitution of a methyl group i n chlorodimethylarsine by a phenyl greatly i n h i b i t s reaction. (B) With Secondary Arsines 1. B i s C t r i f luoramethyl)arsine Hexafluorobut-2-yne and bis(trifluoromethyl)arsine on , heating react with d i f f i c u l t y as follows: (CFgJ^sH + CF3C=CCF3, -^-» (CjTg)2AsC-(GF3)=CHCF-g (II) 29 At room temperature the reaction (CHgigAsH + GTgCsCCEg — ( G H g i g A s C t C T g ^ C H C F g (12) proceeds instantaneously, producing mainly the trans isomer0'. The much smaller tendency of the perfluoro analogue to react with the butyne suggests that the reaction me. chanism involves the arsenic lone pair,, these electrons being less available when electronegative substituents are placed on the arsenic atom. The proton magnetic resonance spectrum, reveals the pres-ence of only one isomer ( i . e . only one quartet) and that t h i s isomer i s trans (each peak i s s p l i t into a further quartet)• However since the reaction mixture reached 210° i t cannot be stated that the c i s isomer does not form at 130°. The peak at T= 2*67 i s believed due to impurity.. I t i s suggested that the addition of secondary arsines to hexafluorobut-2-yne proceeds v i a attack of the arsenic lone p a i r on an acetylenic carbon atom, r e s u l t i n g i n the f o l -lowing zwitterion intermediate: 3 ^ « 3 *2 I f the proton then s h i f t s to the negative carbon atom, the product i s c i s . I f , however, t h i s intermediate abstracts a proton from another arsine molecule, the product would be predominantly i f not completely trans. 2. Methylphenylarsine Under ordinary conditions the reaction 30 CH3(CgH5)AsH + CFgCECCFg > CH3(CgH5)AsC(CF3)=CHCF3 (13) proceeds; smoothly, but slowly ( i hour), which i s convincing evidence that the addition of the arsenic hydrides, as w e l l as the chlorides, to the t r i p l e bond depends upon the a v a i l -a b i l i t y of the arsenic lone p a i r . The substitution of one of the electron-donating methyl groups of dimethylarsine by a phenyl should cause an appreciable decrease i n the a v a i l a b i l -i t y of the lone o p a i r . From electronegativity considerations alone, t h i s effect should be small compared with the substitu-t i o n of both methyl groups by trifluoromethyIs. The observed results are indeed consistent with these statements. Again, the r e a c t i v i t y of the methylphenyl-arsine may be lowered by s t e r l c hindrance and resonance d e r e a l i z a t i o n of the lone p a i r . The *H spectra of the product reveal the presence of both isomers: an 11:1 r a t i o of trans to c i s . Thus i f the proposed mechanism, i n t h i s case involving the intermediate C F 3 - C ^ - C T 3 ^3: i s correct, t h i s reaction involves mainly intermolecular proton transfer rather than intramolecular, since the l a t t e r process would y i e l d the c i s isomer. The same argument may be submitted i n the ease of dimethylarsine. In f a c t , since dimethylarsine and hexafluorobut^2-yne do not react i n the gas phase0 , , i t would appear that the intermediate i s short l i v e d and dissociates; very quickly i n the absence of an im-31 mediate c o l l i s i o n with a proton source, such as could be provided i n the l i q u i d phase. From t h i s i t would follow that the intramolecular proton transfer,, i n t h i s case at l e a s t , offers no* contribution. Therefore i t i s suggested that the roughly 9% cis-2-methylphenylarsino-l,l,l,4,4,4-hexaflucre*-but-2-ene which was obtained resulted not from intramolecular proton transfer but rather from attack from the s t e r i c a l l y hindered c i s d i r e c t i o n . Section IIg Reactions Involving 2-Chloro-3-dimeth.ylaraino- hexafluorobut—2-ene > (A) Thermal S t a b i l i t y The compound Is completely decomposed a f t e r three days at 220°. The very dark brown s o l i d which i s produced appears to be mainly carbon, the v o l a t i l e s being primarily s i l i c o n t e t r a f l u o r i d e • (B) With Aqueous Sodium Hydroxide I t was expected that hydrolysis of (CHgJgAaCCCFgXJClCFg would cleave the arsenic-fluorocarbon bond, and that the v o l -a t i l e product would be 2-chloro-l,l,l,4, t4,4-hexafluprobut^2-ene. The i n f r a red spectrum of the v o l a t i l e material i s highly suggestive of the expected chloro-olef i n , i n p a r t i c u l a r a presumed G=G stretching absorption ( 6 . 0 ^ ) , a n a three peaks at 10.4, 11.15 and 11.65^. The l a t t e r peak also occurs i n the spectrum of the unbydrolyzed adduct and i s believed due to C-Cl stretch-. The production of hexafluorobut-2-yne i s not unexpected, since the chloro-olefin could be expected to lose a molecule 32 of hydrogen chloride i n the highly basic environment. The butyne being present In only trace amounts i s understandable, since i t has been found by separate experiment that the comp-ound I t s e l f undergoes hydrolysis to fluoroform under these conditions.. The low y i e l d of v o l a t i l e material (100% chloro-o l e f i n = .806 g.) i s probably due to continued hydrolysis, leading to carbonate and trifluoroacetate ions, i n addition to chloride. Carbonate formation would e n t a i l production of fluoroform, which i s i n f a c t observed. CO With Bromine 1. One Mole Bromine The adduct readily reacts with one mole of bromine. Infra red examination of the s o l i d product revealed the cont-inued presence of a double bond, indicating that the arsenic atom had been oxidized to the pentavalent state: (CH 3)^sC(CF 3)<rciCFg + B r 2 — > ^(CHg) 2AsBr'^C(CF 3)=CClCF 3 (14) This i s not surprising i n view of the three electronegative groups attached to the two ethylenic carbons. The ff electrons l i n k i n g these two atoms should be considerably l e s s available f o r the formation of new bonds, than those i n a normal double bond. I t seems l i k e l y also that there would be an appreciable s t e r i c barrier to bromination of the double bond. This s o l i d product slowly l i q u i f i e s on standing at 20°, y i e l d i n g methyl bromide and the bromomethylarsino compound: ^(CH 3) 2AsBr^C(CF 3)=CClCF 3 — » (.CHgAsBr)C(CF3)=CClCFg + CHgBr 05) The same reaction occurs much fa s t e r at 100°. The 1 9 F spectrum of (CHqAsBr)CL(CF3)=CClCF3 shows two large 33 quartets ( J = 15 c.p.s.) J a much, weaker quartet ( J =15 c.p.s.) and distorted quartet (low f i e l d ) between thesej and a quartet (J £ 1.4 c.p.s.) and broad multiplet (low f i e l d ) between and close to these, the l a t t e r p a i r being considerably weaker s t i l l . Since a s p l i t t i n g of 15 c.p.s. i s associated with the c i s form , i t i s seen that t h i s isomer i s predominant. The i n t e r -mediate absorptions are believed due to impurity, probably cIs-2-chloro-3-dibromoarsinohexafluorobut-2-ene. The weak bands represent the trans bromomethylarsino compound, which i s present to the extent of less, than 5%. As would be expected from consideration of the spectrum of the . dimethylarsino adduct, the large low f i e l d quartet i s broadened, as i n f a c t are a l l the low f i e l d bands. Again, t h i s down f i e l d broadening i s ascribed to CFg-GHg coupling. I t i s seen that bromination of the predominantly trans dimethylarsino adduct y i e l d s mainly the c i s bromomethylarsino compound. This isomerization i s not yet understood; i t appears., however, that the same phenomenon occurs upon bromination of 2-dimethylarsino-l,l,l,4,4,4-hexafluorobut-2-ene 1 0. The H spectrum shows the methyl peak as a distorted t r i p l e t . As i n the case of the dimethylarsino compound, t h i s s p l i t t i n g i s believed due to CHg-CEg coupling through space. Two smaller peaks also appear i n t h i s spectrum, but again they are l i k e l y due to impurity. 2. Two Moles Bromine On reaction of the adduct with two moles of bromine, one mole i s taken up quickly, but the second reacts much more slowly. Two possible routes are: 34 JBr«AsCCGP«)=CClGFo + 2 CH^Br (16) CCHo)JlsC-((JPo)=CClC5Po + 2 Br,.—/1 ^ . , d 0 5 d d ^ d d CHgAsBr C l CFg^C-i-CFg + CHgBr (17) Br Br Infra red examination of theproducts, and the y i e l d of methyl bromide, indicate that (16) occurs. Thus the double bond i n t h i s adduct Is inert to bromine under ordinary conditions. The reaction which does, occur probably goes through the f o l -lowing stages: (CH Q) 2AsC(CT 3)=CClCF 3 * B r g ^GH3)^aBr^C(C5F3)«CClCSF^J (18) ^OT 3) 2AsBr 2^C(CIF 3)=CClCF^ s l o w > (CHgAsBr)C(CF3)=CC1CF3 + CHgBr Q9) (CHgAsBr)C(CF3)=CClCF3 + B r 2 S l o w > Br^sC(CFg)=CClCF 3 + CHgBr (20) Further evidence i s offered by the following reaction: 2-chloro—3-bromQmetbylarsinohexafluorobut-2-ene plus one mole bromine generate methyl bromide and probably 2-chloro-3-dibromo-arsinohexafluorobut-2-ene, the l a t t e r being also produced by the reaction of the dimethylarsino adduct d i r e c t l y with two moles of bromine: CCHJLsBrOC(GFQ)=CClGF« + B r 0 d d . . V^Br9AsCCGF„)=CClGFo + (2) CHqBr (21) (CH 3) 2AsC(CF 3)=CClCF 3 +. 2Br 2 • Unexpectedly the bromine i s not taken up immediately but rather very slowly. Thus the pentavalent species. (CHgAsEr^Cp^^JGlCEg i s not readily achieved, i f at a l l (arsenic tribromide w i l l ,not take up bromine). Another p o s s i b i l i t y i s that the bromine cleaves off the methyl group to give methyl bromide and the dibromoarsino compound. The C-H. stretching absorption i n the d i s t i l l a t e of the low v o l a t i l i t y material* i s believed due to •Obtained by combining the low v o l a t i l i t y products from the bromination of the bromomethylarsino compound, and the bromin-ation (2 moles) of the dimethylarsino adduct. 35 dibromamethylarsine, which would, mean that the arsenic-olefin bond i s cleaved by the bromine to a certain extent, (D) With Chlorine The dimethylarsino adduct and chlorine react to produce a white s o l i d , which was thought to be jjCH 3)^sCl^C(CF 3)=CClCF 3, and which might have been expected to decompose on heating i n the following manner: jjCH 3)2As(lQc.(CF 3)=CClCF 3 (CHgAsCl)C(CF 3) =CC1CF3 + CHgCl (22) However, although heating produces a l i q u i d (non-volatile) that does not s o l i d i f y , i t does not r e s u l t i n any s i g n i f i c a n t amount of methyl chloride. This l i q u i d on heating to 140° again gives no methyl chloride. The resul t i n g l i q u i d , however, does go into the vacuum system. Infra red examination, of the two l i q u i d s shows that they are s i m i l a r but not i d e n t i c a l , and are both olef i n i c (E) Br ominat ion of 2,3-Bis (dime thy l a r s ino) hexaf luorobut-2-ene In conjunction with the halogenation of {CH^AsCCCFg^CClCFg, i t was of interest to react the bls(dimethylarsino) compound with two moles of bromine, i n p a r t i c u l a r to determine whether the double bond would again r e s i s t bromination and whether the products would be methyl bromide and 2,3-bis(bromomethylarsino)-hexafluorobut-2-ene. The i n f r a red spectrum of the very low v o l a t i l i t y material shows an absorption at 6.35^, assigned to the double bond of the bis(bromomethylarsino) species, and a weaker absorption at 6.15^ , believed due to. the bis(dibromo-arsino) compound. The very v o l a t i l e material consisted of methyl bromide, hexafluorobut-2-yne and—traces of s i l i c o n 36 te t r a f l u o r i d e . Brcmodimethylarsine i s also a product. The most s t a r t l i n g r e s u l t of t h i s reaction i s the form-ation of hexafluorobut-2-yne. The immediate uptake of the bromine indicates that the i n i t i a l product i s the wholly penta-valent arsenical, which i s expected, but the production of hexafluorobut-2-yne and brcmiodimethylarsine means that the arsenic-olefin bond breaks upon decomposition of the i n t e r -mediate, as well as arsenic-methyl bonds. I t i s s i g n i f i c a n t that the decomposition y i e l d s the butyne rather than 2,3-dibromo-hexafluorobut-2-ene or 2-bromo-3-bromomethylarsinohexafluorobut-2-ene. I f the decomposition of the pentavalent compound occurs v i a a r a d i c a l mechanism, then i t i s quite l i k e l y that the un-paired electron at the o l e f i n i c carbon atom becomes delocalized into the double bond, thereby causing elimination of the arsenic atom (with unpaired electron) from the other unsaturated carbon. This would give a t r i p l e bond. This scheme e n t a i l s the release of bromine, which would then immediately be taken up i n either of two ways: B r 2 + (CHgJgAsBr —» QcHgJgAsBrg — > CHgAsBr2 + CHgBr (23) 2 B r 2 + (CHgAsBr)C(Ci,g)=C(CF3) (CHgAsBr) > jjt CHgAsBrg) C( CFg) =C (CFg) (CHgAsBrg)j > Br2AsC(CFg)=C(CFg)AsBr2+ 2CHgBr or CEgC^CCFg + 2CHgAsBr^ + Br 2 (24) No attempt was made to separate the hexafluorobut-2-yne and methyl bromide f o r weighing purposes, since th e i r b o i l i n g points d i f f e r by only 25°. The value of 114 found f o r the apparent molecular weight of the mixture indicates a very nearly 1:2 mole r a t i o respectively, the calculated value f o r 37 t h i s r a t i o being 117. Section I I I ; Reactions Involving Dimethylarsine (A) With Dichloromethylarsine Dimethylarsine i s known to react with chlorodimethyl-. 1 1 arsine : (CHgJgAsGl .+ RAs;(CH3)2 > (CHgi^a-AstCHg^ + HC1 (25) I t was predicted that dimethylarsine would react with dichloro-methylarsine, and i t was of p a r t i c u l a r interest to determine whether the t r i a r s i n e (IV) i s formed: HAs(CIJg)2 ^ H G 1 + C ^ g l a ^ e ^ ^ ^ a (26) GHgAsClg + RAs(CHg) 2~~^~R^l~T7cH^^ (III) Reaction occurs at 20° giving a chocolate brown s o l i d , plus chlorodimethylarsine and hydrogen chloride. Hydrogen i s also generated but the reason f o r t h i s i s not f u l l y understood. The appearance of the s o l i d i s s i m i l a r to that of the polymer (GHgAa)n (V). Reaction of the s o l i d with excess bromine was used as a. means of analysis and the calculated values tabulated below clearly indicate that i t i s the polymer (CHgAs)^: Reactant (1.9 g.) Wt. B r 2 Used (g.) Wt. Product (g.) CHgBr ASBTg I l l 5.3 2.0 5.2 TV 7.1 3.0 6.0 V 6.75 2.0 6.65 found 6.9 1.9 6.9 The path f o r the reaction n CHgAsCl 2 + n (CHg)2AsH ^(CHgAs) n •+ n (CHgJgAsCl + nHGL (27) may be represented schematically as follows: 38 -HOI, H G L-(CHgAa)n + HC1« (CHgJgAsH + CHgA-sClg^i^ (•C^)^As(CH3)Ca.^=±-(C!H3)^sGl + HAs(CHg)Cl C C H g J g A s H p ^ ^ 7 /(GHg)2AsH; - H C l ^ ^ j-HCl ( C H Q ) ^ s-AsCCTU-AsXCH.J„ (CH„)0As-As(CHQ)H d ^ d d ^ ^  (CHgJgAsCl; -HC1 6 Z • - 3 The f i r s t step i n the reaction of dimethylarsine with dichloro-nrethy l a r s ine i s probably the formation of chlorotrimethyldiarsine ( I I I ) . Since (25) i s an equilibrium r e a c t i o n 1 1 , i t follows that hydrogen chloride w i l l cleave the arsenic-arsenic bond i n (III),. even I f only to a small extent. Moreover, i n view of the high p o l a r i t y of the H-Cl bond, the s l i g h t p o l a r i t y of the As-As bond i n (III) (due to the chlorine atom) should result i n the cleavage products being mainly chlorodimethylarsine and chloro-methylarsine, rather than the sta r t i n g materials. The l a t t e r compound would react with i t s e l f to produce the polymer (V) and hydrogen chloride, or with dimethylarsine or chlorodimeth-y l a r s i n e . I f with chlorodimethylarsine, then (III) would result.; i f with dimethylarsine, the product would be trimethyldiarsine, which would react with chlorodimethylarsine to form the t r i -arsine (IV). Of course (III) should react to a greater extent with dimethylarsine than with hydrogen chloride, the products being hydrogen chloride and (TV), but again t h i s should be an e q u i l -ibrium reaction, thus leading eventually to complete conversion to chlorodimethylarsine, hydrogen chloride and (V). (B) With Trifluoroacetyl Chloride I t was predicted that dimethylarsine and t r i f l u o r o a c e t y l V 39 cMori.de would react, with elimination of hydrogen chloride: CFgCOCl + HAs(CRg) 2 > CFgCOAs(CRg) 2 + HCl (28) The reaction i s i n f a c t much more complex, y i e l d i n g chloro-dimethylarsine, hydrogen, chloride and two unidentified sub-stances. With s l i g h t excess acyl chloride, the i n f r a red spectrum of the medium v o l a t i l i t y material shows two absorp-tions i n the double bond region, one of which (5.8^) corres-ponds with that of t r i f luoroacetyldimethylarsine. With s l i g h t excess arsine, a very s i m i l a r spectrum i s obtained, one d i f -ference being that the, 5*55^ absorption i s stronger than at 5.8^ „ Instead of weaker. The l a t t e r l i q u i d contains i n f a c t very l i t t l e of the acetyl-arsine, consisting mainly of chloro-dimethylarsine and an unidentified substance. The low v o l a t i l i t y product from the excess arsine exper-iment was believed to be cacodyl, because the products from the excess acyl chloride reaction react v i o l e n t l y with a i r . Cac-odyl andbromine i n 1:1 mole r a t i o simply y i e l d two moles bromo-dimetbylarsine; bromination of t h i s material however produces several products, Including methyl bromide andeither bromo- or chlorodimethylarsine. But since some of the product material contains f l u o r i n e , and the unbrominated material melts at 13-12 14°, the l a t t e r i s not cacodyl (f.p. -6°) I t i s clear that the reaction between dimethylarsine and t r i f l u o r o a c e t y l chloride i s f a i r l y complicated. Since the carbonyl carbon of the l a t t e r carries an appreciable pos-i t i v e charge, I t should, be vulnerable to nucleophilic attack such as could be produced by the highly available arsenic lone p a i r . Such attack could cause d i r e c t elimination of. chloride ion from the carbon atom, whereafter proton loss from the arsenic atom would y i e l d the acetyl-arsine. Another mani-fe s t a t i o n of s uch attack, might be the formation of the i n t e r -mediate Cl:. G E 3 - J " Z — * f ( G B 3 y 2 ( Y I ) 0" H followed by i n t r a - or intermolecular proton transfer to the oxygen atom. Since oxygen, i s considerably more electroneg-ative than chlorine, t h i s mechanism might compete favourably with chloride; elimination. The r e s u l t i n g alcohol should, however, react readily with the acyl chloride: C l Q 0 C l I H II I CF3-(J-0H + C1-C-CF3 — » CFg-C-Q-C-CF3 +. HCl (29) ka{CE2)2 A s ( C H o ) 0 ( V I I ) D * The large f r a c t i o n of unidentified product (medium v o l a t i l i t y ) gives a spectrum highly suggestive of the CFg -g-O-G^ group ( i n p a r t i c u l a r the peaks at 5.55, 7.35 and 7.5^ < ); i t seems, doubtful, however, that (VII) could pass through a -23° bath. The formation of carbon monoxide and fluorof orm may be due to decomposition of the alcohol, which probably would also y i e l d chlorodimethylarsine. The arsenic lone pair might also attack the oxygen atom, of t r i f l u o r o a c e t y l chloride. This atom should be somewhat electron deficient because of the C l and CF 3 groups. Moreover, since there is. e ssentially no p o l a r i t y i n the As-H bond, there should be no e l e c t r o s t a t i c d r i v i n g force f o r these two groups to add across the carbonyl i n a p a r t i c u l a r way. The r e s u l t i n g "ether"', CF 3-CHCl-0As(CH 3) 2, may be the low v o l a t i l i t y product. 41 T r i f l u o r o a c e t y l chloride might be expected to: cleave the G-As bond: C l 0 0 C l I % II .11 I CF 3-CH-0As(CH 3) 2 + CFg-C-Cl — » CFg-C-O-CH-CFg + (CHgJgAsCl (30) (YIII) The ester (YIII) could be expected to behave as did the large unidentified fraction.as regards v o l a t i l i t y and Infra red ab-sorption. Chlorodimethylarsine i s i n f a c t a major product, and i t s presence i s an explanation f o r the absence of dimeth-ylarsine and the presence of t r i f l u o r o a c e t y l chloride i n the products even though the former was i n excess, since these two arsines react to form cacodyl. Yet another p o s s i b i l i t y i s the reduction of the. acyl chloride by dimethylarsine to 2,2,2-.trifluoroethanol, followed by reaction, of t h i s alcohol with another mole of. the chloride: 0 ' 0 CFg-C-Cl * CFgCHgOH — » CFg-C-OCHgCFg + HCl (31) (IX) The ester (IX) also could, be expected to behave as did the large unidentified, f r a c t i o n ; i n f a c t , the intensity of the C-H absorption i n the i n f r a red spectrum makes (IX) more a t -tra c t i v e than ( Y I I I ) . (C) With Trifluoroacetic Acid I t was anticipated that dimethylarsine and t r i f l u o r o -acetic acid, would react i n t h i s way: CFgCOOH + HAs(CHg) 2 ——-> CFgC0QAs(CH3)2 + Hg, (32) (X) The actual reaction path i s exceedingly d i f f i c u l t to ascertain. The main reaction product (very low v o l a t i l i t y ) shows, a strong double bond absorption (presumably C=0) at 6.Cy/ • The "ester** CX) absorbs at 5.7^ . Addition of dimethylarsine across the carbonyl bond would, not r e s u l t i n a compound, with a double bond other than the aeetyl-arsine CTQGCAsCGHgig, which absorbs, at 5*8^ • This substance Is not produced.to any appreciable degree. Another p o s s i b i l i t y i s the formation of the onium compound 0 H CF 3-G-a" +As(GH 3) 2 (XX) H although t h i s seems unlikely because the material was l i q u i d . However, t r i f l u o r o a c e t i c acid i s a strong acid, and i t i s known that dimethylarsine i s considerably more basic than other . 13 ' arsines (D) With Trifluoroacetic Anhydride Bimethylarsine reacts readily with t r i f l u o r o a c e t i c an-hydride, but as was the case with t r i f l u o r o a c e t i c acid, the reaction is; not simple. I t appears that the f i r s t step i s as follows: "(CH^gAsH + (CF 3C0) 20 > CFgCQA&CCHg)2 + CFgCOOH (33) The remainder of the arsine reacts with the t r i f l u o r o a c e t i c acid as well as remaining anhydride. This scheme i s supported by the presence i n the products both of t r i f l u o r o a c e t i c acid and the same substance of very low v o l a t i l i t y produced by the dimethylarsine-trifluoroacetic acid, reaction. The presence of unreacted anhydride i s also observed, but the i n f r a red spectra do not definitely-confirm the presence of the acetyl-arsine. This may be due to the f a i l u r e to obtain a good sep-aration of the products. (E) With Methylmagnesium Bromide This reaction, and the addition, to the product of per-fluorocyclobutene, are discussed In the. section dealing..with the l a t t e r substance. Section IV; Reactions Involving Perfluorocyclobutene (A) With Bimethylarsinomagnesium Bromide Synthesis of Bimethvlarsinomagnesium Bromide This compound was-prepared from dimethylarsine and-meth-ylmagnesium bromide: (CHgJgAsH + CHgMgBr > (CHgJgAsMgBr + CH^ (34) Since i t was to be used in. a reaction, and had to be kept out of contact with the atmosphere,, the effervescence during i t s synthesis and the presence of uncondensable material i n the products (methane) was deemed s u f f i c i e n t evidence that dimeth-ylarsinomagnesium bromide had formed. Reaction of the Bromide with the Butene Bimethylarsinomagnesium bromide and perfluorocyclobutene react to form dime thy lperfluorocyclobut-1-enylarsine: (CHgigAsMgBr +. CF=CF-CF2-CF2 — > (CHg) gAsC^CF-CFg-GFg + MgBrF (35) The considerable v u l n e r a b i l i t y of perfluorocyclobutene to nu-d e o p h i l i c a t t a c k — i t i s attacked by amines and mer cap t a n s 1 4 — suggests that the reaction occurs v i a attack of the arsenic lone p a i r onto an o l e f i n i c carbon atom. This should r e s u l t i n immediate loss of flu o r i d e ion from t h i s atom, followed by elimination of MgBr* from the arsenic atom. OA (B) With CMorodimethylarsine 1. I r r a d i a t i o n Perfluorocyclobutene andchlorodimethylarsine do not react on i r r a d i a t i n g even though the mixture forma one l i q -uid, phase, while the arsine reacts smoothly with hexafluoro>-but-2-yne i n spite of the two being immiscible. This suggests that either the cyclobutene molecule i s not excited at a l l by the radiation, or that the l i f e t i m e of the excited state i s so s hort that the probability of i t c o l l i d i n g with another molecule i s very low. Since no trace of the strongly absor-bing C-F stretching bands i s observed i n the i n f r a red spec-trum, the former circumstance i s preferred, especially since the reactants are miscible. This complete lack of reaction would also appear to rule out f a i l u r e of the d i r a d i c a l to react f o r some other reason, such as s t e r i c hindrance. 2. Heat No s i g n i f i c a n t reaction occurs between chlorodimethyl-arsine and perfiuorocyclobutene, even i n the presence of alum-inum chloride, whereas hexaf luorobut-2-yne combines readily with the arsine. I t i s believed that the reactive species i s (CHgigAs*, the anions being AlCT^' or (CHgJgAsClg, or both. I f t h i s i s so, then i t remains to account f o r t h i s cation reacting with the butyne but not the cyclobutene, even though one l i q u i d , phase i s achieved (only) i n the l a t t e r instance. Steric hind-rance probably plays a small p a r t , i n that the cation cannot approach the unsaturated bond from a l l directions, as i s the case with the acetylene. The main factor however appears to 45 be the much decreased v u l n e r a b i l i t y of the butene to ele c t r o -p h i l i c attack, as compared with the butyne, owing to. the pres<-ence of a flu o r i n e atom on each of the unsaturated carbon atoms. This i s substantiated by the known great r e a c t i v i t y of perfluorocyclobutene toward nucleophiles, as previously men-tioned. 46 BIBLIOGRAPHY 1. G. W.. RAIZISS and J . L. GAYRON. Organic arsenical compounds. The Chemical Catalog Co., Inc., New York. 1923. p. 54. 2. I b i d . p.55. 3. I b i d . p.41. 4.. E. J . CRAGOE, Jr.,, R. J . ANDRES, R. F. COLES, B. ELPERN, •'• J . F. MORGAN and C. S. HMXLTGN. J . Am.. Chem. S o c 69, 925 (1947). 5. S. J . GREEN and T. S. PRICE. J . Chem. Soc. 448 (1921). 6. P.. M. TREICHEL, E. PITCHER and F.. G. A. STONE... Inorg. Chem. 1, 511 (.1962). 7. W. R. CULLEN., D. S. DAWSON and G. E. STYAN. J . Organometal. Chem. In press. 8. A. B. BRUKER, T. G. SPIRIDONOVA and L. Z.. SOBOROYSKII. J . Gen. Chem. (U.S.S.R.) 2Q, 347 (1958). 9. W. R. CULLEN. Unpublished observations. 10. W. R. CULLEN, D.. S, DAWSON and G... E.. STYAN. Unpublished observations. 11. W. R. CULLEN.. Can. J . Chem. 41, 322 (1963). 12. G... W. RAIZISS and J . L. GAYRON.. Op. c i t . p.63. 13. I b i d . p.46. 14. W. R. CULLEN and P. S. DHALTWAL. Unpublished observations. / 

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