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采用MP2/6-31++G**//B3LYP/6-31++G**方法研究了丝氨酸和甘氨酸水致质子迁移的相对难易,探讨了羟甲基取代效应。得到两个主要结论:1)羟甲基取代甘氨酸中的α-H后,其吸电子效应削弱了迁移质子所在的化学键,导致质子迁移所需的最少水分子数目由2个减少为1个;2)通过比较羟甲基取代前后的质子迁移过程,发现羟甲基效应使反应势垒降低了0.917 kJ/mol,使反应吸热减少了6.766 kJ/mol。
The MP2 / 6-31 ++ G ** // B3LYP / 6-31 ++ G ** method was used to study the relative proton transfer caused by serine and glycine in water, and the effect of hydroxymethyl substitution was discussed. Two main conclusions are obtained: 1) When the methylol substituted for α-H in glycine, its electron-withdrawing effect weakens the chemical bond where the proton migrates, resulting in the reduction of the minimum number of water molecules required for proton transfer from 2 to 1; 2) By comparing the proton transfer process before and after hydroxymethyl substitution, it was found that the methylol effect reduced the reaction barrier by 0.917 kJ / mol and the endothermic reaction decreased by 6.766 kJ / mol.