Premium
Theoretical study of thermal rearrangements of α‐silylalcohols: Effects of substituents attached to the silicon atom on the reactions
Author(s) -
Yu Yongming,
Feng Shengyu
Publication year - 2006
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.21018
Subject(s) - chemistry , hydrogen atom , atom (system on chip) , ring (chemistry) , silicon , transition state , ab initio , hydrogen , carbon fibers , carbon atom , photochemistry , crystallography , catalysis , organic chemistry , group (periodic table) , materials science , composite number , computer science , composite material , embedded system
To investigate the effects of substituents attached to the silicon atom on the thermal rearrangement reactions of α‐silyl alcohols, the thermal rearrangement reactions of dimethylsilyl methanol (CH 3 ) 2 SiHCH 2 OH and vinylsilyl methanol CH 2 CHSiH 2 CH 2 OH were studied by ab initio calculations at the G3 level. Geometries of various stationary points were fully optimized at the MP2(full)/6‐31G( d ) and MP2(full)/6‐311G( d , p ) levels, and harmonic vibrational frequencies were calculated at the same levels. The reaction paths were investigated and confirmed by intrinsic reaction coordinate (IRC) calculations at the MP2(full)/6‐31G( d ) level. The results show that two dyotropic reactions could occur when (CH 3 ) 2 SiHCH 2 OH or CH 2 CHSiH 2 CH 2 OH is heated. One is Brook rearrangement reaction (reaction A), and the dimethylsilyl or vinylsilyl groups migrates from carbon atom to oxygen atom coupled with a simultaneous migration of a hydrogen atom from oxygen atom to carbon atom passing through a double three‐membered ring transition state, forming dimethylmethoxylsilane (CH 3 ) 2 SiHOCH 3 or methoxylvinylsilane CH 2 CHSiH 2 OCH 3 ; the other is a hydroxyl group migration (reaction B) from carbon atom to silicon atom, coupled with a simultaneous migration of a hydrogen atom from silicon atom to carbon atom, via a double three‐membered ring transition state, forming trimethylsilanol (CH 3 ) 3 SiOH or methylvinylsilanol CH 3 SiH(OH)CHCH 2 . The G3 barriers of the reactions A and B were computed to be 312.8 and 241.4 kJ/mol for (CH 3 ) 2 SiHCH 2 OH, and 317.6 and 233.7 kJ/mol for CH 2 CHSiH 2 CH 2 OH, respectively. On the basis of the MP2(full)/6‐31G( d ) optimized parameters, vibrational frequencies, and G3 energies, the reaction rate constants k ( T ) and equilibrium constants K( T ) were calculated using canonical variational transition state theory (CVT) with centrifugal‐dominant small‐curvature tunneling (SCT) approximation over a temperature range of 400–1800 K. The influences of methyl and vinyl groups attached to the silicon atom on reactions are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007