Ab initio and DFT calculations on the gas phase elimination kinetics of 2, 2-diethoxy-ethylamine and 2, 2-diethoxy-N, N-diethyl-ethylamine

The mechanisms for the gas phase molecular elimination kinetics of 2, 2-diethoxy-ethylamine and 2, 2-diethoxy-N, N-diethyl-ethylamine were examined at MP2/6-31G, B3LYP/6-31G, B3LYP/6-31G (d, p), MPW91PW91/6-31G. MPW91PW91/6-31G (d, p), PBEPBE/6-31G, and PBEPBE/6-31G (d, p) levels of theory. These elimination processes involve two parallel reactions. The first parallel reaction gives ethanol and the corresponding 2-ethoxyethenamine. The latter compound further decomposes to ethylene, CO, and the corresponding amine. The second parallel reaction produces ethane and the corresponding ethyl ester of an a-amino acid. Calculated thermodynamic and kinetic parameters from PBEPBE calculations were found to be in good agreement with the experimental values. The transition states of the parallel reactions are best described as four-membered cyclic structures. The intermediate 2-ethoxy-ethenamine undergoes a consecutive elimination through a six-membered cyclic transition state mechanism. Bond indexes and synchronicity (Sy) parameters are in agreement with concerted semi-polar transition state structures.