Does alkyl substitution affect the silicon-hydrogen bond strength in silane? Kinetic studies of the reactions of atomic chlorine and bromine with trimethylsilane and an ab initio investigation

Abstract

Abstract:The kinetics of the elementary reactions of C1 and Br with HSi(CH3), (1 and 2) have been measured by flashphotolysis/time-resolved atomic resonance spectroscopy over the approximate temperature range 300-460 K. The results are3 kJ mol-I/RT) cm3 s-l, with confidence limits of about *20%. The activation energy of 2, combined with an estimated activation energy for the reverse reaction, yields a bond dissociation enthalpy of D298(H-Si(CH3)3) = 398 * 6 kJ mol-', which is about 14 kJ mol-l larger than D298(H-SiH3). This difference is supported by ab initio calculations. Implications for AH&Si(CH3),) and the Si-Si bond strength in disilanes are discussed in the text. exp(l.3 & 0.8 kJ mol-I/RT) cm3 s-l and k2 = (7.6 3.3) X

Theoretical study and rate constants calculation for the reactions of SiH3radical with SiH3CH3and SiH2(CH3)2

“…For comparison, the calculated reaction enthalpy of reaction SiH(CH 3 ) 3 with SiH 3 at the MC‐QCISD//MP2/6‐31+G(d,p) level as well as the available experimental reaction enthalpy is also listed in Table 3. The theoretical Δ H value 3.1 kcal/mol, for the reaction SiH(CH 3 ) 3 + SiH 3 is in good agreement with the corresponding experimental value 3.3 ± 1.7 kcal/mol, which was derived from the standard heats of formation [SiH(CH 3 ) 3 , −39.00 ± 0.96 kcal/mol28; SiH 4 , 8.21 kcal/mol29; SiH 3 , 47.97 ± 0.60 kcal/mol30; Si(CH 3 ) 3 , 4.07 ± 1.67 kcal/mol31]. In view of this good agreement obtained above, it is expected that the enthalpy of the title reactions calculated at the same level is reliable.…”

Effect of Doped Transition Metal on Reversible Hydrogen Release/Uptake from NaAlH4

“…[68][69][70] As shown in Scheme 1: the first step involves the breaking of an Al À H bond from the TMAl 3 H 12 complex and the formation of a four-membered intermediate (TM-Al 2 -H 7 -H 8 ). This step is followed by the formation of the dihydrogen coordinated with the TM by breaking the Al 2 ÀH 7 bond.…”

Enthalpies of Formation and Reaction for Primary Reactions of Methyl‐ and Methylmethoxysilanes from Density Functional Theory

“…Total energies and zero‐point energies in Hartree are given in Table 1 along with the total atomization energy, Σ D 0 , thermal corrections to the enthalpy and standard enthalpies of formation at 0 K, and 298 K in kcal/mol. Experimental enthalpies of formation at 298 K where available in the literature14,24–31, along with the corresponding deviations of the theoretical values, which are also given in Table 1. The average absolute deviation is 3.89 kcal/mol which compares well with the 3.11 kcal/mol reported for species in the expanded G2 test set 14.…”