气相中BrO-与CH3Cl反应机理的理论研究

摘要

采用二阶微扰(MP2)计算方法,在aug-cc-pVDZ基组下对反应中各驻点进行了全几何结构参数优化,并在相同基组下进一步用CCSD(T)方法进行了单点能计算.结果表明,BrO与CH3Cl的反应先通过一个传统的SN2反应,生成富能中间体IM2(BrOCH3…Cl),接着中间体IM2解离为SN2机理的产物P1(BrOCH3+Cl);而且还能继续发生氧、碳间的消除反应和氧上的取代反应,前者生成P2(CH2O+Br-+HCl),后者生成P3(CH3OCl+Br-).其中,传统的SN2为主反应通道,SN2诱导消除反应和取代反应为竞争的次反应通道,计算结果与实验相吻合.%The reaction mechanism of BrO- with CH3Cl has been investigated using the MP2 level of theory with aug-cc-pVDZ basis set. The single-point energies have also been refined at the CCSD(T)/augcc-pVDZ level to get more accurate energies. Computational results indicate that BrO- +CH3Cl initially proceed a traditional SN2 mechanism, generating an energy-enriched intermediate IM2 (BrOCH3 … Cl),then followed by decomposition of IM2 produce P1 (BrOCH3+Cl) in SN2 mechanism. IM2 can also occur an elimination reaction between carbon and oxygen atoms. Further substitution reaction takes place on oxygen atom. The former primary generates P2 (CH2O+ HCl+Br- ), the latter primary produces P3 (CH3OCl+Br-). The channel of traditional SN2 reaction is the main reaction channel, while the minor channels of SN2-induction elimination reactions and substitution reactions are the competitive reaction channels. It is very reasonable and considerably consistent with the experimental.