Rate constants for H+(CH3)4-nSiHn, n=1-4

Rate constants for the reactions of H atoms with SiH4 and the methylsilanes, (CH3)(4-n)SiHn, n = 1-4, have been measured at 298 K in pulsed photolysis experiments with H atoms produced by the mercury-sensitised photolysis of H-2 and monitored by Lyman-alpha absorption. The values obtained, for n = 1-4, respectively, are: k(1) = (2.70 +/- 0.20) x 10(-13), k(2) = (3.94 +/- 0.29) x 10(-13), k(3) = (3.88 +/- 0.21) x 10(-13), and k(4) = (3.38 +/- 0.16) x 10(-13) cm(3) s(-1). These results show that methyl substitution enhances;he reactivity of the Si-H bond towards H atom attack, and comparisons are made with the corresponding reactions of Cl, Br and O atoms. (C) 1998 Elsevier Science B.V.