Reaction of CF₃ radicals with methylchlorosilanes

Abstract

Arrhenius parameters have been measured for H abstraction from the alkylchlorosilanes CH3SiCl3, (CH3)2SiCl2, and (CH3)3SiCl, and also for (CH3)4Si[Formula: see text]where k is in ml mole−1 s−1. Halogen abstraction does not occur with these compounds nor with SiCl4. CF2CH2 is formed from the hot molecule produced when the silylmethyl radical combines with CF3[Formula: see text]

Reaction of CF3 radicals with group IV tetramethyls

“…Our values for the rate constants k , , [7]. We have also shown a very marked dependence of the activation energy and the rate constant, with chemical shift, for the H abstraction reactions of CF, radicals with the methylfluorosilanes [ 11.…”

“…Recent observations on H abstraction from organosilicon compounds [l, 7,113 yield A factors in the range 1011.5-1012.4. The present results fit into this normal range, but differ from those of Chaudrhy and Gowenlock [2], who report A factors differing by two orders of magnitude in the reaction of methyl radicals with group IV methyls.…”

“…The results are tabulated in Table 111. Much smaller quantities of CH, products were obtained in the systems CF, + Ge(Me), and CF, + Si(Me), , the additional complication due to reactions (7) and (8) is thus expected to be less than in the CF, + Sn(Me), system. We have previously shown the pressure dependence of the silicon system [I, 71 (Included in Table 111 are results for CF, + Ge(Me), .…”

“…We propose that this allows a radical exchange reaction involving a 5-coordinate intermediate, thus : I n order to apply this relationship, we require to estimate the CF,CH, produced from the various sources. From the data of Giles and Whittle [6] on CF,CH,/CF,CH, ratios resulting from reactions (7) and (8), we have selected a value of 2.2 for this ratio under conditions approximating those of the present work. Thus, from a knowledge of the total CF,CH, formed we can calculate the amount of CF,CH, resulting from reaction (8) and from reactions (12) Considering the experimental difficulties, good agreement is obtained.…”

An evaluation of the kinetic data for hydrogen abstraction from silanes in the gas phase

“…A similar trend has been observed by Bell and Zucker in the reactions of CFa with methylchlorosilanes. 77 Polar effects relating to the above systems are discussed in Section C.…”