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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >An ab initio study on thermal rearrangement reactions of 1-silylprop-2-en-1-ol H3SiCH(OH)CH=CH2
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An ab initio study on thermal rearrangement reactions of 1-silylprop-2-en-1-ol H3SiCH(OH)CH=CH2

机译：从头开始研究1-甲硅烷基丙-2-烯-1-醇H3SiCH（OH）CH = CH2的热重排反应

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The thermal rearrangement reactions of 1-silylprop-2-en-1-ol H3SiCH(OH)CH=CH2 were studied by ab initio calculations at the G2(MP2) and G3 levels. The reaction mechanisms were revealed through ab initio molecular orbital theory. On the basis of the MP2(full)/6-31 G(d) optimized geometries, harmonic vibrational frequencies of various stationary points were calculated. The reaction paths were investigated and confirmed by intrinsic reaction coordinate (IRC) calculations. The results show that the thermal rearrangements of H3SiCH(OH)CH= CH, happen in two ways. One is via the Brook rearrangement reactions (reaction A), and the silyl group migrates from carbon atom to oxygen atom passing through a double three-membered ring transition state, forming allyloxysilane CH2=CHCH2OSiH3. In the other, the reactant undergoes a dyotropic rearrangement; the hydroxyl group migrates from carbon atom to silicon atorn coupled with a simultaneous migration of a hydrogen atom from silicon atom to carbon atom, forming allylsilanol CH2=CHCH2SiH2OH (reaction B). The barriers for reactions A and B were computed to be 343.5 and 203.7 kJ/mol, respectively, at the G3 level. The changes of the thermodynamic functions, entropy (Delta S), entropy (Delta S-double dagger) for the transition state, enthalpy (Delta H), and free energy (Delta G) were calculated by using the MP2(full)/6-31G(d) optimized geometries, and harmonic vibrational frequencies of reactants, transition states, and products with statistical mechanical methods, and equilibrium constant K(T) and reaction rate constant k(T) in canonical variational transition-state theory (CVT) with centrifugal-dominant small-curvature tunneling approximation (SCT) were calculated over a temperature range 400-1300 K. The conventional transition-state theory (TST) rate constants were also calculated for the purposes of comparison. The influences of the vinyl group attached to the center carbon of the alpha-silyl alcohols on reactions were discussed.
机译：通过从头算在G2（MP2）和G3水平上研究了1-甲硅烷基丙-2-烯-1-醇H3SiCH（OH）CH = CH2的热重排反应。通过从头算分子轨道理论揭示了反应机理。根据MP2（full）/ 6-31 G（d）优化的几何形状，计算出各个固定点的谐波振动频率。研究了反应路径，并通过内在反应坐标（IRC）计算确定了反应路径。结果表明，H3SiCH（OH）CH = CH的热重排以两种方式发生。一种是通过布鲁克重排反应（反应A），甲硅烷基通过双三元环过渡态从碳原子迁移到氧原子，形成烯丙氧基硅烷CH2 = CHCH2OSiH3。另一方面，反应物经历了重排。羟基从碳原子迁移到硅原子上，同时氢原子同时从硅原子迁移到碳原子，形成烯丙基硅烷醇CH2 = CHCH2SiH2OH（反应B）。在G3水平上，反应A和B的势垒分别计算为343.5和203.7 kJ / mol。通过使用MP2（full）/ 6计算热力学函数，熵（Delta S），熵（跃迁S-双匕首），焓（Delta H）和自由能（Delta G）的变化。 -31G（d）优化了几何形状，采用了统计力学方法优化了反应物，过渡态和产物的谐波振动频率，并且在规范变分过渡态理论（CVT）中达到了平衡常数K（T）和反应速率常数k（T）在400-1300 K的温度范围内，以离心为主导的小曲率隧穿近似（SCT）进行了计算。为了比较，还计算了传统的过渡态理论（TST）速率常数。讨论了附着在α-甲硅烷基醇中心碳上的乙烯基对反应的影响。

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