Synthesis mechanism of dimethylhexane-1,6-dicarbamate from 1,6-hexamethylenediamine, urea and methanol: A molecular scale study based on density functional theory

Abstract

This work provides a molecular scale insight into non-phosgene synthesis based on the reaction of dimethylhexane-1,6-dicarbamate from 1,6-hexamethylenediamine, urea and methanol with computational electronic method. By exploring almost all possible reaction modes and comparing the effective barrier of each channel, this work analyzes the optimal reaction mechanism for both non-catalytic and self-catalytic systems. The mechanism without catalysis has a high effective free energy barrier (FEB) of 47.0 kcal mol−1. As for self-catalytic system, after sorting out the reaction pathway network, an effective FEB of 24.6 kcal mol−1 is confirmed which corresponds to dissociation of urea.