Reactivity comparison of five- and six-membered cyclic carbonates with amines: Basic evaluation for synthesis of poly(hydroxyurethane)

The reaction of six- and five-membered cyclic carbonates, 5-(2-propenyl)-1, 3-dioxan-2-one (1) and 4-(3-butenyl)-1,3-dioxolan-2-one (2) with hexylamine and benzylamine was carried out in N,N-dimethylacetamide at 30, 50, and 70 degreesC. The six-membered cyclic carbonate 1 proceeded quantitatively wit h hexylamine at 30 degreesC for 24 h, while the five-membered cyclic carbon ate 2 converted in 34%. The reaction rate constants at 50 degreesC are eval uated as follows; 1.42 L/mol.h (1 with hexylamine) > 0.29 L/mol.h (1 with b enzylamine) > 0.04 L/mol.h (2 with hexylamine) > 0.01 L/mol.h (2 with benzy lamine). The activation energies in the reactions of 1 and 2 with hexylamin e were estimated to be 10.1 and 24.6 kJ/mol, respectively. The ring-strain energy was calculated by the semi-empirical method using the PM3 Hamiltonia n. The ring-strain energy of the six-membered cyclic carbonate was 2.86 kca l/mol larger than that of five-membered one. (C) 2000 John Wiley & Sons, In c.