Theoretical kinetic studies are performed on the multichannel thermal decomposition of acetaldehyde. The geometries of the stationary points on the potential energy surface of the reaction are optimized at the MP2(full)/6-311++G(2d,2p) level of theory. More accurate energies are obtained by single point energy calculations at the CCSD(T,full)/augh-cc-pVTZ+2df, CBS-Q and G4 levels of theory. Here, by application of steady-state approximation to the thermally activated species CH₃CHO* and CH₂CHOH* and performance of statistical mechanical manipulations, expressions for the rate constants for different product channels are derived. Special attempts are made to compute accurate energy-specific rate coefficients for different channels by using semiclassical transition state theory. It is found that the isomerization of CH₃CHO to the enol-form CH₂CHOH plays a significant role in the unimolecular reaction of CH₃CHO. The possible products of the reaction are formed via unimolecular decomposition of CH₃CHO and CH₂CHOH. The computed rate coefficients reveal that the dominant channel at low temperatures and high pressures is the formation of CH₂CHOH due to the low barrier height for CH₃CHO → CH₂CHOH isomerization process. However, at high temperatures, the product channel CH₃ + CHO becomes dominant.

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乙醛多通道气相单分子分解动力学的理论研究

对乙醛的多通道热分解进行了理论动力学研究。在理论上的MP2（full）/ 6-311 ++ G（2d，2p）水平上优化了反应势能表面上固定点的几何形状。通过在CCSD（T，full）/ augh-cc-pVTZ + 2df，CBS-Q和G4理论水平上进行单点能量计算可获得更准确的能量。在此，通过对热活化物质CH ₃ CHO *和CH ₂进行稳态近似导出CHOH *和统计机械操作的性能，以及不同产品渠道的速率常数表达式。通过使用半经典过渡状态理论，进行了特殊的尝试来为不同的通道计算准确的特定于能量的速率系数。发现CH ₃ CHO的异构化为烯醇形式的CH ₂ CHOH在CH ₃ CHO的单分子反应中起重要作用。反应的可能产物是通过CH ₃ CHO和CH ₂ CHOH的单分子分解形成的。计算出的速率系数表明，低温和高压下的主要通道是CH ₂的形成。CHOH是由于CH ₃ CHO→CH ₂ CHOH异构化过程的势垒高度低而引起的。然而，在高温下，产物通道CH ₃ + CHO占主导地位。