ABINITIO CALCULATIONS ON SILICON ANALOGS OF THE ALLYL RADICAL

被引:22
作者
COOLIDGE, MB [1 ]
HROVAT, DA [1 ]
BORDEN, WT [1 ]
机构
[1] UNIV WASHINGTON, DEPT CHEM, SEATTLE, WA 98195 USA
关键词
D O I
10.1021/ja00033a009
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Calculations at the CI-SD/6-31G* level of theory have been performed in order to determine the effect on the A-H bond dissociation energy (BDE) in X-AH3 (A = C and A = Si) of replacing X = H3C- by X = H2C = CH- and H2Si = CH- and of replacing X = H3Si- by X = H2C = SiH- and H2Si = SiH-. The conjugative stabilization energies (CSEs) of the resulting allylic radicals have been obtained from the energies calculated to be required to twist a terminal AH2. group out of conjugation. Except for X = H2C = CH- and H2Si = CH- in X-CH2., these two definitions of allylic resonance energy give nearly identical values. The reason for the calculated difference between -DELTA-BDE and CSE in H2C = CH-CH2. and in H2Si = CH-CH2. is discussed. It is also found that, with the exception of H2Si = CH-SiH2., the calculated allylic resonance energies are generally those expected from the pi-BDEs in H2C = CH2, H2C = SiH2, and H2Si = SiH2. It is shown that pyramidalization at silicon lowers the resonance energy of H2Si = CH-SiH2. from that expected, based on the strength of the C-Si pi-bond in H2C = SiH2.
引用
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页码:2354 / 2359
页数:6
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