The Effect of the Substituents (Alkyl-groups) on the Thermal Dissociation of Carbaminic Acid Esters

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≥Me The 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>Me The 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 phenyleste...