ROBERT -1. BEKKESER.SD [CONTRIBUTIOS FROM
THE
RICHARD HICKNER
Yol. hO
CHEMICAL LABORATORIES O F PURDUE UNIVERSITY]
The Stereochemistry of the Addition of Silicochloroform to Acetylenes B Y ROBERTA. HESKESEK
.LKD
RICIIARD ;i. HICKNER
RECEIVED MARCHlY, I958 The stereochemistry of the addition of silicocliloroforrn to three aliphatic 1-alkynes and plien!-lacetyleiie wa5 investigated. The reactions were catalyzed either b y benzoyl peroxide or platinized charcoal. Comparison of the infrared spectra of thc adducts with those of authentic compounds showed that the peroxide-catalyzed reaction involves a stereospecific trans addition of the elements of H and SiCll to produce cis-olefins, while platinized charcoal gives a stereospecific cis addition t o produce trans-olefins. The stability of the products under the reaction conditions was demonstrated.
The addition of silicochloroforrn (HSiC13) to acetylenes and olefins is a well-known reaction1 and the subject of several patents.2 The experiniental conditions for the addition of S S i H type compounds to unsaturated linkages have been varied. For example, peroxidesla and platinized charcoal?d have been used and even acid3f4 and base.5 It seems likely that under certain of the aforementioned conditions ( e . g., peroxide-catalyzed) a free radical chain mechanism is operative.6
+ peroxide --+ ,SiCI, + >C-C< --+ HSiCIB
.Sic],
; I
I 1
G-CSiCI,
,
,
,
t
,SiCl3
I
Since the stereochemistry of free radical addition reactions is of current interestj7-'* it seemed appropriate to examine the stereochemistry involved in the addition of silicochloroform to acetylenes, particularly since some of these reactions are of considerable industrial interest. The acetylenes chosen for study were 1 -pentyne, 1-hexyne, I-heptyne and phenylacetylene. If, indeed, the addition proceeds by the free radical chain shown above, the intermediate radical would have a rigid structure (see I below) in the case of acetylenes, and stereochemical trends should be detected easily. (1) ( a ) E . \T. Pietruiza, L. H. Xoinnier and F. C . Whitmure, 'L'iixs 482 (1948); ( h ) 4 J. B a r r y , I,, DePree. J. \V,(;ilkey .in11 D. 1.: l i o o k , ihici, 69, 2 Y l i i ( I s t i ) ; rc) C. A . Burkhard a n d K . >I Krieble. ibir/., 69, 2687 (1017); (d) C. I.. Agre a n d SV. Hilling, ibid ,
74, 3883 (1952); ( e ) D. G . White a n d E. G . Kochow, tbi,l., 76, 3807 I.. Speier, K . Zimmerman and J. n'ebster. i b i d . , 1 8 , g ) J. I,. Sljeier, J. A Wehster and G. 11. Barnes, ihi'l., (:I)
4.5J;
H C . .\liilcr :iud I< J . B a r r y , I). l i
S,Schreiiier, li. S . l'dtcnt 2,:
