The rate constants of the thermal dissociation of carbaminic acid esters in fatty acids were determined. In the case of phenylcarbaminic acid alkylestees, the rates showed the following order. tert-Bu>>isoPr≥MeThe relative rates may be considered to denote the ability of —OR groups as proton acceptors and the results of the experiment can be explained by the inductive effect of the substituted alkyl-groups.In the case of alkylcarbaminic acid phenyl-esters, the rates showed the following order. Acetyl>>isoPr>MeThe relative rates may be considered to denote the ability of (Remark: Graphics omitted.) groups as proton donors. In acetylcarbaminic acid phenylester, because of the resonance effect of the (Remark: Graphics omitted.) and COOR groups, the intervening nitrogen aquires a positive potential. The phenomenon will make the hydrogen attached to nitrogen have more tendency to transfer, hence the reaction. That isopropylcarbaminic acid phenylester dissociates faster than methyl-carbaminic acid phenylester will be explained by the steric effect of alkyl-groups.The rates of the thermal dissociation of esters depend on the nature of the solvent acids.
脂肪酸中
氨基甲酸酯热分解的速率常数被确定。对于
苯基氨基甲酸烷基酯,速率显示以下顺序:叔丁基>>异丙基≥甲基。相对速率可以被视为表示—OR基团作为质子受体的能力,实验结果可以通过取代烷基的诱导效应来解释。对于烷基
氨基甲酸苯酯,速率显示以下顺序:乙酰基>>异丙基>甲基。相对速率可以被视为表示(注:图形省略)基团作为质子供体的能力。在乙酰基
氨基甲酸苯酯中,由于(注:图形省略)和COOR基团的共振效应,中间的氮原子获得正电位。这一现象将使得与氮原子相连的氢原子更倾向于转移,从而发生反应。异丙基
氨基甲酸苯酯比
甲基氨基甲酸苯酯更快分解的现象将通过烷基的空间效应来解释。酯的热解速率取决于溶剂酸的性质。