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采用MP2/6-31++G~(**)//B3LYP/6-31++G~(**)方法研究了丙氨酸和甘氨酸在水分子作用下质子迁移的相对难易,探讨了甲基取代效应。得到2个主要结论:(1)甲基取代甘氨酸中的α-H后,削弱了迁移质子所在的化学键,有利于质子迁移;(2)通过比较甲基取代前后的质子迁移过程,发现甲基效应使反应能垒降低了3.076 kJ·mol~(-1),使反应吸热减少了5.221 kJ·mol~(-1)。
The MP2 / 6-31 ++ G ** (**) / B3LYP / 6-31 ++ G ~ (**) method was used to study the relative proton transfer of alanine and glycine under water molecules The methyl substitution effect. The main conclusions are as follows: (1) Methyl substituted glycine α-H, weakened the migration of protons in the chemical bond, is conducive to proton migration; (2) By comparing the proton transfer process before and after methyl substitution, methyl The effect reduces the reaction energy barrier by 3.076 kJ · mol ~ (-1) and reduces the endothermic reaction by 5.221 kJ · mol ~ (-1).