量子化学计算阐明两可亲核试剂氰化钠和氰化银与溴乙烷亲核取代反应的不同反应性能  

Elucidating the Different Reactivity of Nucleophilic Substitution Reactions Between Ambiguous Nucleophiles MCN (M=Na, Ag) and C2H5Br Through Quantum Chemical Calculations

作　　者：张强 张冬菊[1] ZHANG Qiang;ZHANG Dong-Ju(School of Chemistry and Chemical Engineering,Shandong University,Jinan 250100,China)

机构地区：[1]山东大学化学与化工学院,山东济南250100

出　　处：《化学教育（中英文）》2024年第2期111-115,共5页Chinese Journal of Chemical Education

基　　金：国家自然科学基金(22273051);山东省高等教育本科教学改革研究项目(Z2022169);山东大学教育教学改革研究项目(2022Y072)。

摘　　要：两可亲核试剂参与的亲核取代反应是亲核取代反应的一种特殊类型,当两可亲核试剂与同一底物发生亲核取代反应时,由于进攻位点的不同,所得产物通常为混合物。以两可亲核试剂MCN(M=Na,Ag)与溴乙烷(C_(2)H_(5)Br)的亲核取代反应为例,通过量子化学计算研究了氰根离子中C和N分别作为亲核位点的反应性能,获得了与实验一致的结果。计算表明,对于NaCN,C原子亲核进攻形成乙腈比N原子亲核进攻形成异腈的能垒更低,反应的主要产物为乙腈;而对于AgCN,则情况相反,有利于形成产物异腈。通过分析轨道相互作用、Fukui函数和HOMO轨道成分阐明了2个两可亲核试剂不同反应性的微观本质,合理解释了实验与计算结果。Nucleophilic substitution reactions involving ambident nucleophiles are a unique type of reaction that typically results in mixed products due to different attack sites.This study investigates the reactivity of C and N in the cyanide ion as nucleophilic sites through quantum chemical calculations of the nucleophilic substitution reaction between ambiguous nucleophiles MCN(M=Na,Ag)and ethyl bromide(C_(2)H_(5)Br).The results are consistent with experimental data,and the calculations show that,for NaCN,the attack of the C atom as a nucleophile results in a lower energy barrier to form nitriles compared to the attack of the N atom to form isonitriles,leading to the formation of nitriles as the primary product.Conversely,for AgCN,the opposite is true,favoring the formation of isonitriles as the main product.The different reactivity of the two ambident nucleophiles is explained through analyses of the orbital interactions,Fukui functions,and HOMO orbital compositions,which reasonably elucidate the experimental and calculated results.

关 键 词：两可亲核试剂 亲核取代 反应机理 密度泛函理论计算 

分 类 号：O641.121[理学—物理化学] O621.255[理学—化学]