ARRHENIUS PARAMETERS FOR H-N)SIHN, N = 1-3((CH3)(4)

Rate constants for the reactions of H atoms with the methylsilanes, (C H3)(4-n)SiHn, n = 1-3, have been measured over the temperature range 2 98-580 K in hash photolysis experiments in which H atoms were produced by the mercury-sensitized photolysis of H, and monitored by Lyman-alp ha absorption. The values obtained, for n = 1-3, respectively, are giv en by, k(1)/cm(3) s(-1) = (3.29 +/- 0.26) x 10(-11) exp[(-1407 +/- 34) /T] k(2)/cm(3) s(-1) = (7.87 +/- 0.58) x 10(-11) exp[(-1582 +/- 31)/T] k(3)/cm(3) s(-1) = (8.59 +/- 0.45) x 10(-11) exp[(-1585 +/- 20)/T] Th e results show that methyl substitution increases the reactivity of th e Si-H bond towards H atom attack. Comparison is made with previously published data, and with attack by other atoms and free radicals.