Organic Phototransformations in Nonhomogeneous Media - American

18 Photoassisted Sonosynthesis of l,2,3,4-Tetrakis(methylthio)hexafIuorobutane MADELINE S. TOY and ROGER S. STRINGHAM

Downloaded by FUDAN UNIV on March 28, 2017 | http://pubs.acs.org Publication Date: May 14, 1985 | doi: 10.1021/bk-1985-0278.ch018

Science Applications International Corporation, Sunnyvale, C A 94089

The synthesis of isomeric 1,2,3,4-tetrakis(methylthio)hexafluoro-n-butane was finally achieved by photoassisted sonication, after the numerous attempts through the various methods had failed. A successful method described here consists of reacting trans-1,4-bis(methylthio)hexafluoro-2-butene in an excess of methyl disulfide with an added appropriate gas (hexafluoropropane) to increase and control the pressure in the reaction vessel. The heterogeneous mixture was then subjected to the combined photolysis and sonication at 50°C. The FNMR and mass spectral data of the product and the by-product 1,2,4-tris(methylthio)-3-H-hexafluoro-n-butane were presented. 91

T h i s work s t u d i e s t h e s y n t h e s i s o f p o l y m e t h y l t h i o adducts o f hexaf1uorobutadi ene. The p o l y m e t h y l t h i o p e r f 1 u o r o a l k a n e s wi11 then be e x p l o r e d f o r t h e i r o x i d a t i o n p r o d u c t s , perfluoroalkanepolysulfonic acids. The i n t e r e s t i n the m u l t i f u n c t i o n a l s u l f o n i c a c i d s i s based on t h e oxygen r e d u c t i o n k i n e t i c s o f t r i f l u o r o methane s u l f o n i c a c i d on p l a t i n u m b e i n g s i g n i f i c a n t l y h i g h e r than i n phosphoric acid ( 1 , 2 ) . The improved performance i s p o s s i b l e due t o t h e h i g h e r oxygen s o l u b i l i t y and t h e lower a d s o r p t i o n o f CF S0r* a n i o n s on P t ( 3 - 5 ) . The CF S(LH i s a l s o thermally e x t r e m e l y s t a b l e t o a t I g a s t 350 C ( 6 ) , t>ut has t h e drawback o f a low b o i l i n g p o i n t a t 162 C (7). Due~To t h e o p e r a t i o n temperature o f t h e p r e s e n t p h o s p h o r i c a c i d f u e l c e l l a t 150 t o 200 C , t h e p o s s i b l e p o t e n t i a l o f t h e h i g h e r m o l e c u l a r weight p e r f l u o r o a l k a n e p o l y s u l f o n i c a c i d s becomes a p p a r e n t . The l a t t e r would not o n l y reduce t h e vapor pressure o f t h e monobasic acid, but a l s o i n c r e a s e i t s f u n c t i o n a l groups (>2) f o r t h e f u e l c e l l e l e c t r o l y t e applications. 3

been

The known s y n t h e s i s o f p e r f l u o r o a l k a n e p o l y s u l f o n i c a c i d s has l i m i t e d t o t h e g e n e r a l f o r m u l a H 0 S ( C F ) S 0 H by Ward (8) 3

2

3

0097-6156/85/0278-0287506.00/0 © 1985 American Chemical Society

Fox; Organic Phototransformations in Nonhomogeneous Media ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

ORGANIC PHOTOTRANSFORMATIONS IN NONHOMOGENEOUS MEDIA

288

through the h y d r o l y s i s and t h e o x i d a t i o n perfluoroalkanes (Eq. 1):

o f « , - b i s (methyl t h i o ) ω

600 p s i


1/2 n C F , = C F

+ CrUSSCH.

9

350° C

> CH-S(CF ) SCH, d u o 9

n

(1)

When we r e a c t e d h e x a f l u o r o - 2 - b u t y n e and methyl d i s u l f i d e , t h e r e a c t i o n proceeded r e a d i l y i n good y i e l d t o form t h e i s o m e r i c 1:1 adducts [i.e., c i s - and t r a n s - 2 , 3 - b i s ( m e t h y l t h i o ) h e x a f l u o r o - 2 butene i n equal mole r a t i o ] , b u t t h e f o r m a t i o n o f t h e m e t h y l t h i ο adducts w i t h h e x a f l u o r o b u t a d i e n e was d i f f i c u l t ( 9 ) . T h i s agrees w i t h t h e p r e v i o u s a l k y l d i s u l f i d e and t h e t e r m i n a l o l e f i n i c bond r e a c t i o n ( E q . 2, where k _ / k [RSSR] i s r e l a t i v e l y large) p r o c e e d i n g t o a v e r y poor y i e i d o f the adduct ( 1 0 ) : 1

2

k [RSSR] > RSCr^CrHR' )SR + RS- (2) 9

RS* + C H ^ C H R ' ^ U - R S C H ^ H R ' k

- l

k' R S . + HC=CR' = = b RSCH=CR' K

k' —

[RSSR] j> RSCH=C(R')SR + RS ·

(3)

-1

In c o n t r a s t , Heiba and Dessan (10) a l s o observed and e x p l a i n e d t h a t the a d d i t i o n o f R S r a d i c a ' P ' t o t h e a c e t y l e n i c bond ( E q . 3 , where k' . / k ' ^ R S S R ] i s v e r y s m a l l ) was much l e s s r e v e r s i b l e than i t s a d d i t i o n n o the o l e f i n ( E q . 2 ) . Our r e s u l t s o f CrUSSChL r e a c t i n g w i t h h e x a f l u o r o - 2 - b u t y n e and n o t w i t h h e x a f l u o r o b u t a d i e n e a r e i n agreement w i t h Heiba and D e s s a n . One i n t e r p r e t a t i o n f o l l o w i n g t h e same t r e n d s u g g e s t s , t h a t the s o n i c i r r a d i a t i o n i n E q . 4 may have f u n c t i o n e d i n d e c r e a s i n g the r e v e r s i b i l i t y o f CH SSCH addition to CF =CFCF=CF during photoexcitation (resembling E q . 2, e x c e p t where k f « / ^ [ C r U S S C h L ] is greatly reduced t o f a v o r t h e adduct formation)". Our s e v e r a l attempted a d d i t i o n s o f C H S S C H t o CFp=CFCF=CF reactions by p h o t o l y s i s alone with prior emulsiTication, solution photolysis, sonolysis singly, and t h e r m o l y s i s up t o 230 C f o r 24 hours were u n s u c c e s s f u l ; b u t t h e combined p h o t o l y s i s and u l t r a s o u n d p r o v i d e d a c o n v e n i e n t path t o s y n t h e s i z e t h e trans-1,4-bi s(methylthio)hexaf1uoro-2-butene (I, the trans-1, 4 - a d d u c t ) as t h e major p r o d u c t i n the p r e s e n c e o f t r a c e amount o f t h e o t h e r 1:1 adducts and minor q u a n t i t y o f o l i g o m e r s ( E q . 4) (11): #

3

3

2

2

3

3


2

18.

1,2,3,4-Tetrakis(methylthio)hexafluorobutane

TOY AND STRINGHAM

289

UY CF =CFCF=CF 2

2

+ XS.CH SSCH 3

CH SCF C=CCF $CH

3

3

2

trans-I

2

(major

product)

CH S(C F ) SCH 3

4

6

oligomers

CH SCF C=CCF SCH


3

cis-I

2

2

(trace)

3

n

3

+

(minor)

+ CH SCF CF CF=CFSCH 3

2

+

3

2

c i s - and t r a n s - I I

3

(4)

(trace)

The f o u r 1:1 adduct p r o d u c t s were the two commonly e x p e c t e d c i s and t r a n s - I and t h e o t h e r two were v e r y unusual a d d u c t s , which were l a t e r i d e n t i f i e d as c i s - and t r a n s - l , 4 - b i s ( m e t h y l t h i o ) h e x a fluoro-l-butene (II). S u b s e q u e n t l y , we s u b j e c t e d t r a n s - I and CH SSCH t o v e r y h i g h p r e s s u r e a t 16,000 atm and 200 C f o r 24 hours. There was c e r t a i n d i s a p p o i n t m e n t i n the p r o d u c t s , which were c i s - and t r a n s - I I i n s t e a d of the d e s i r e d s a t u r a t e d a d d u c t . A p o s s i b l e e x p l a n a t i o n f o r the h i g h p r e s s u r e e x p e r i m e n t was t h a t the t r a n s - I i s o m e n zed w i t h complete bond m i g r a t i o n from t h e internal to the terminal olefinic bond (12). This result s u g g e s t s t h a t the t r a c e amount o f c i s - and t r a n s - I I i n E q . 4 may be formed by a s o n i c a t i o n e f f e c t , which c r e a t e s l o c a l i z e d v e r y h i g h p r e s s u r e and t e m p e r a t u r e . These l o c a l i z e d s i t e s are f o r m e d , because the v e r y h i g h i n t e n s i t y waves p a s s i n g t h r o u g h a l i q u i d cause l o c a l vaporization of the l i q u i d in a process called acoustic cavitation. This phenomenon i n v o l v e s the rapid f o r m a t i o n growth and i m p l o s i v e c o l l a p s e o f gas v a c u o l e s w i t h i n t h e l i q u i d , which g e n e r a t e s l o c a l i z e d h o t s p o t s , l a s t i n g o n l y a few nanoseconds. D u r i n g t h e s e s h o r t p e r i o d s , some p h o t o e x c i t a t i o n may have i n i t i a t e d c e r t a i n uncommon a c t i v a t e d species. The r e s u l t s were the f o r m a t i o n o f new p r o d u c t s d i s t i n c t from photochemical and thermal p r o c e s s e s . 3

3

Boudjouk and c o - w o r k e r s r e p o r t e d the r a t e enhancements by s o n o l y s i s on a number o f heterogeneous r e a c t i o n s such as Wurtz type c o u p l i n g of organic halides (13) and organometal1ic c h l o r i d e s (14) i n the p r e s e n c e o f l i t h i u m w i r e , c y c l o a d d i t i o n o f a c t i v a t e d o l e f i n s i n the p r e s e n c e o f z i n c powder (15) and the Reformatsky r e a c t i o n (16) r e q u i r i n g n e i t h e r f r e s h l y p r e p a r e d z i n c powder (17) nor acTî catalysis (18). Significant rate a c c e l e r a t i o n s o f the B a r b i e r r e a c t i o n Γ Τ 9 ) , the s y n t h e s i s o f the t h i o amides (20), the l i t h i u m aluminum T ï y d r i d e r e d u c t i o n o f a r y l h a l i d e s ( 2 1 ) , and the s i l i c o n - s i l i c o n double bond f o r m a t i o n from d i m e s i t y l a T c h l o r o s i l a n e and l i t h i u m w i r e (22) a l s o p o i n t t o the considerable synthetic potential of sonolysis. Suslick and co-workers reported the chemical uses of sonication in the homogeneous systems on metal c a r b o n y l s t o i n i t i a t e c a t a l y s i s and to form unusual p r o d u c t s , which were not analogous t o e i t h e r photochemical or thermal reactions, such as the ligand a s s o c i a t i o n product F e ^ ( C 0 ) from F e i C O i ^ and f i n e l y divided 1 ?


290


iron (23-25). U l t r a s o u n d - p r o m o t e d r e a c t i o n s were a l s o a p p l i e d t o the s y n t h e s e s and r a t e enhancements o f f l u o r i n a t e d compounds such as p e r f l u o r o a l k y l i o d i d e s i n t h e presence o f z i n c and carbon dioxide to give p e r f l u o r o a l k a n o i c a c i d s (26,27).


Experimental M a t e r i a l s and A p p a r a t u s . Hexafluorobutadiene, hexafluoropropane, and 1,2-dichloro-1,1-di f1uoroethane were purchased from PCR, methyl disulfide and c h l o r o f o r m from A l d r i c h , and d e u t e r a t e d c h l o r o f o r m from S t o h l e r . These r e a g e n t s were checked by i n f r a r e d spectroscopy and u s e d as r e c e i v e d , e x c e p t f o r t h e m e t h y l d i s u l f i d e , which was r e d i s t i l l e d . A s o n i c a t o r (Model W-370) was purchased from Heat SystemsU l t r a s o n i c w i t h a cup horn a t t a c h m e n t . The horn was the r e s o n a n t body, which v i b r a t e d a t 20 kHz (20,000 c y c l e s p e r second) and s e r v e d as a second stage o f a c o u s t i c a m p l i f i c a t i o n . The s t a n d a r d tapped t i t a n i u m d i s r u p t e r horn was immersed i n c i r c u l a t i n g water a t 50 C d u r i n g s o n i c a t i o n . S t a n d a r d vacuum m a n i p u l a t i o n s were a p p l i e d . P r e s s u r e s were measured w i t h a H e i s e gauge (0-100 cm Hg a b s o l u t e w i t h 500 i n c r e m e n t s ) t o a c c u r a c y o f 1 mm Hg. The amount o f v o l a t i l e r e a c t a n t was determined by P-Y-T measurements, assuming i d e a l gas behavior. A sealed quartz r e a c t i o n vessel c o n t a i n i n g the r e a c t a n t s was v e r t i c a l l y suspended i n t h e water i n t h e horn c u p . A 200-watt high pressure mercury a r c lamp was t h e o u t s i d e i r r a d i a t i o n s o u r c e , which was f o c u s e d w i t h a q u a r t z c o n d e n s i n g lens. T h i s l e n s g a t h e r e d about 40% o f t h e e m i t t e d u n f i l t e r e d l i g h t p a s s i n g through t h e water l e v e l i n the horn cup and i n t o the r e a c t a n t s ; w h i l e t h e r e a c t a n t s i n t h e 1 mm w a l l t h i c k q u a r t z s e a l e d tube were under s o n i c a t i o n . With t h e i d e n t i c a l c o n d i t i o n s but s u b s t i t u t i n g Pyrex f o r q u a r t z , no r e a c t i o n p r o d u c t s were found. The U V - a b s o r p t i o n c h a r a c t e r i s t i c s o f t h e r e a g e n t s d e s c r i b e d below a r e a t t h e ground s t a t e . The CH SSCHo absorbs U Y - l i g h t below 300 my and i s a s t r o n g a b s o r b e r ( e . g . , t n e molar e x t i n c t i o n c o e f f i c i e n t s o f 250 1/mole-cm a t 240 my and o f 1500 1/mole-cm a t 210 my) ( 2 8 , 2 9 ) . H e x a f l u o r o b u t a d i e n e absorbs UY below 260my w i t h the molar e x t i n c t i o n c o e f f i c i e n t such as 130 1/mole-cm a t 240πιμ ( 3 0 ) ; whereas t h e U V - a b s o r p t i o n o f t r a n s - I i s below 220 my and i s a v e r y weak a b s o r b e r w i t h the molar e x t i n c t i o n c o e f f i c i e n t o f 0.044 1/mole-cm a t 200 my. C H S S C H i s a p p a r e n t l y t h e dominant UY-absorber and i t may have g r e a t l y reduced o r t o t a l l y s c r e e n e d o f f the a v a i l a b l e U Y - i r r a d i a t i o n f o r t r a n s - I . However, t h e s e e x t i n c t i o n c o e f f i c i e n t s a r e f o r ground s t a t e s p e c i e s . When they are photoexcited within the l o c a l i z e d high p r e s s u r e and temperature s i t e s due t o s o n i c a t i o n , t h e i r v a l u e s a r e l i k e l y t o be d i f f e r e n t . 3

3

3

The HNMR and FNMR were r e c o r d e d on a N i c o l e t s p e c t r o m e t e r o p e r a t i n g a t 282 MHz and 35°C. The F chemical s h i f t s o f the p r o d u c t s a r e c o n v e r t e d t o 6 - v a l u e s u p f i e l d from fluorotrichloromethane by u s i n g t h e v a l u e o f 6 1 . 9 ppm f o r 1,2-dichloro-l,1-difluoroethane. The l a t t e r compound CH C1CF C1 was added as an internal standard. The FNMR data o f t h e p r o d u c t s show AB 19

1 9

2

?


1

18. TOY AND STRINGHAM

2,3,4-Tetrakis(methylthio)hexafluorobutane

t

291

patterns indicating restrictive r o t a t i o n , as the geminal F-F c o u p l i n g c o n s t a n t was p r e v i o u s l y r e p o r t e d a t J ( 4 A , 4 B ) (2) m (jo = 230.0 Hz f o r ( C F . ) C F C F H C F S C H , where chemical s h i f t s o f F and 9

(3)

J

0

1

q

L

6

F were 88.6 and 203.8 ppm from C F C 1


r e s p e c t i v e l y (31,32). The mass s p e c t r a were determined on a LKB 90UU Model GC/MS instrument. The elemental a n a l y s i s was o b t a i n e d by a YG-model ZAB double f o c u s i n g h i g h r e s o l u t i o n mass s p e c t r o m e t e r . The i n f r a r e d s p e c t r a were measured on a P e r k i n - E l m e r 567 spectrophotometer and w i t h a chromatographic i n f r a r e d a n a l y z e r (CIRA 101). The u l t r a v i o l e t s p e c t r a were determined by a U V - v i s i b l e s p e c t r o p h o t o m e t e r ( H i t a c h i P e r k i n Elmer Model 139). 3

Procedure. T r a n s - I was p r e p a r e d by an u l t r a s o n i c photolysis method and s e p a r a t e d by gas-chromatography from the product m i x t u r e as p r e v i o u s l y d e s c r i b e d ( E q . 4 ) ( 1 1 ) . I (10 mmole) was added to an e x c e s s of C H S S C H i n a q u a r t z tube w i t h a q u a r t e r i n c h ( o u t s i d e d i a m e t e r ) neck, which was a t t a c h e d t o the vacuum m a n i f o l d and evacuated a t -196 C u s i n g a l i q u i d n i t r o g e n b a t h . An a p p r o p r i a t e amount o f h e x a f l u o r o p r o p a n e was then condensed on top g f the f r o z e n m i x t u r e of I and C H S S C H i n the q u a r t z tube a t -196 C. At ambient temperature the p r e s s u r e i n s i d e the q u a r t z tube was checked t o be about 100 p s i . The q u a r t z tube was c o o l e d a g a i n t o -196 C, e v a c u a t e d and s e a l e d under vacuum. The vacuums e a l e d q u a r t z t u b e was warmed t o a m b i e n t t e m p e r a t u r e and suspended v e r t i c a l l y w i t h the l i q u i d - l i q u i d i n t e r p h a s e i n the q u a r t z bulb under the water l e v e l i n the cup horn of the sonicator. The i m m i s c i b l e c o l o r l e s s l i q u i d s e a s i l y homogenized under u l t r a s o u n d and were s i m u l t a n e o u s l y s u b j e c t e d t o u l t r a v i o l e t i r r a d i a t i o n for 6 hours. The temperature o f the c i r c u l a t i n g water i n the cup horn was m a i n t a i n e d a t 50 C. At the end o f the r e a c t i o n t i m e , the mercury lamp and the s o n i c a t o r were t u r n e d o f f and the s e a l e d q u a r t z tube was removed from the horn c u p . The homogeneous l i q u i d i n the tube was c o o l e d t o -196 C and the tube was opened. The l i q u i d c o n t e n t was vacuum d i s t i l l e d t o remove the e x c e s s methyl d i s u l f i d e . The c o n v e r s i o n o f I t o the main product l,2,3,4-tetrakis(methylthio)hexafluoro-n-butane ( I I I ) and by-product 1,2,4-tri s ( m e t h y l t h i o ) - 3 - H - h e x a f l u o r o - n - b u t a n e ( IV) was e l u c i d a t e d by GC-mass s p e c t r o s c o p y t o be about 50% y i e l d o f I I I and 40% of IV. The two i s o m e r i c r a t i o s o f I I I and IV v a r i e d with experynental c o n d i t i o n s . 3

3

3

3

The FNMR ( C F C U ) o f I I I shows two peaks f o r each i s o m e r . I s o m e r A: 684.0 [ c o a l e s c e d AB s y s t e m , relative peak area 4,4F,CF2(1)], 157.2 [broad s i n g l e t , r e l a t i v e peak area 2,2F, CF(2)]. Isomer B: 082.3 [ c e n t e r AB system, J(1A,1B)= 220 Hz, r e l a t i v e peak area 4, 4 F , C F ^ l ) ] , 152.7 [ b r o a d s i n g l e t , r e l a t i v e peak area 2,2F,CF(2)]. The""GC-mass s p e c t r a l data o f I I I show two s p e c i e s , which fîàve d i f f e r e n t e l u t i o n times but w i t h i d e n t i c a l + p a r e n t ions a t m/e v a l u e 350 (CgF5H]oS4 ) and a l s o w i t h the same mass fragments. These results indicate that there a r e two isomers i n I I I . Mass s p e c t r o s c o p i c weight o f the two isomers o f I I I : C a l c d .

f o r C8F6Hi S : 349.9726. 2

4

Found: 349.9726.



292

The ^FNMR ( C F C 1 J o f IV e x h i b i t s four peaks f o r each isomer. Isomer Α: δ 8 7 . 3 [ c e n t e r AB system, J(1A,1B)=228 H z , r e l a t i v e peak a r e a 2 ^ , 0 1 ^ ( 1 ) ] , 161.3 [ s e p t e t , J ( 2 , 5 ) = 1 8 Hz, r e l a t i v e peak a r e a 1, I F , C F ( 2 ) ] , 193.6 [ d o u b l e t o f q u a r t e t s , J ( 3 , 5 ) = 5 6 Hz, r e l a t i v e peak "area 1 , 1 F , C F ( 3 ) ] , 8 6 . 0 [ c e n t e r AB s y s t e m , J(1A,1B)=228 H z , r e l a t i v e peak area 2 , 2 F , C F p ( 4 ) ] . Isomer Β : ό 8 4 . 1 [ c o a l e s c e d AB s y s t e m , r e l a t i v e peak a r e a ^ ^ F j C F ^ l ) ] , 165.7 [complex s i n g l e t , r e l a t i v e peak area 1 , 1 F , C F ( 2 ) ] , 195.4 [ d o u b l e t o f s e x t e t , J ( 3 , 5 ) = 5 4 Hz, r e l a t i v e peak a r e a 1 , l F , C F ( 3 ) ] , 84.4 [ c e n t e r AB s y s t e m , J(1A,1B)=231 Hz, r e l a t i v e peak area 2,2F,CF£(4)]. The GC-mass s p e c t r a l data o f IV show two s p e c i e s , which Tiave d i f f e r e n t e l u t i o n times b u t w i t h i d e n t i c a l p a r e n t i o n s at 3 0 4 ( C F H . Q S ) and t h e same mass f r a g m e n t s . These r e s u l t s i n d i c a t e tnal: t n e r e a r e two isomers i n IV. Mass s p e c t r o s c o p i c w e i g h t o f t h e two isomers o f IV: C a l c d . f o r C F H S : 303.9849. Found: 3 0 3 . 9 8 5 1 .


7

7

6

3

6

1 Q

3

R e s u l t s and D i s c u s s i o n I t was o r i g i n a l l y thought t h a t the s o n i c a t i o n approach would promote m i s c i b i l i t y a t t h e i n t e r f a c e o f the heterogeneous system and a l s o would r a i s e the e l e c t r o n i c s t a t e s o f a small p o r t i o n o f the r e a c t a n t s above t h e i r ground s t a t e , which would h o p e f u l l y enhance t h e a d d i t i o n r e a c t i o n . We l a t e r f o u n d , t h a t o n l y t h e s i m u l t a n e o u s p h o t o e x c i t a t i o n and u l t r a s o n i c i r r a d i a t i o n p l u s t h e a d d i t i o n o f an a p p r o p r i a t e gas ( e . g . , h e x a f l u o r o p r o p a n e ) , which i n c r e a s e d the p r e s s u r e i n the r e a c t i o n v e s s e l , formed the f u l l y saturated products. The added p r e s s u r e above t h e l i q u i d phase i s a n o t h e r parameter r e q u i r e d t o form the d e s i r e d s a t u r a t e d p r o d u c t and s h o u l d have a f f e c t e d t h e temperature and p r e s s u r e a t t h e l o c a l i z e d ' h o t s p o t s ' c r e a t e d by s o n i c a t i o n . Under p h o t o a s s i s t e d s o n o s y n t h e s i s , the p r o c e s s o f i n i t i a t i o n may be c o n s i d e r e d t o i n v o l v e two s t e p s , t h e f i r s t b e i n g t h e h o m o l y t i c S — S b o n d - b r e a k i n g i n CH~SSCH~ t o y i e l d a p a i r o f m e t h y l t h i o f r e e r a d i c a l s CH S* 3

UV CH SSCH Q

)))

Q

(5)

> 2 CH^S'

and t h e second t h e i r r e v e r s i b l e d e c o m p o s i t i o n d i s p r o p o r t i o n a t i o n a t a much lower r a t e CH SSCH 3

3

)))

of

CH SSCH 3

» CH SH + CH =S 3

3

by

(6)

2

where t h e t h i o f o r m a l d e h y d e i s l i k e l y t o p o l y m e r i z e adduct i n t h e presence o f CH S- r a d i c a l s ,

o r t o form an

3

2CH S- + nCH =S 3

2

> CH S(CH S) SCH 3

2

n

(7)

3

where n=l o r g r e a t e r . Our u n p u b l i s h e d r e s u l t s have shown o l i g o m e r i c p r o d u c t s , which c o n t a i n no f l u o r i n e . The m e t h a n e t h i o l (Eq. 6) i s decomposed t o form hydrogen atom and CH S« r a d i c a l . ?


18.

293

l,2,3,4-Tetrakis(methylthio)hexafluorobutane

TOY AND STRINGHAM

UY CH-SH

J

M)

6

» CrLS* + Η·

(8)

Organic Phototransformations in Nonhomogeneous Media - American

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