Computational study of epoxy-amine reactions

Density functional theory calculations were carried out for the title reactions. Ethylene oxide and methylamine were adopted as reactants. Amine clusters (dimer, trimer, tetramer, and pentamer) were considered, because the combination of one oxide and one amine molecule gave a large activation energy. An amine tetramer was found to react favorably with the oxide via various zwitterionic intermediates. A back-side S(N)2 nucleophilic attack of one amine and the subsequent proton relay up to the front side provide a stabilized reaction field. The amine-alcohol mixed reactant may react readily with the oxide, because the alcoholic O-H group is in contact with the oxide oxygen with the strong hydrogen-bond stabilization.