Kinetic study of abiotic amino acid formation by UV-irradiation

Abstract

Glycine was produced in a solution of 2-aminoethanol, methylamine, ethylamine, or acetonitrile by UV-irradiation. The concentrations of the reactants and glycine were analyzed under six different conditions. Each reaction was assumed to be a first-order reaction. Then, the rate constant of the degradation of the reactants, and also those of the formation and degradation of glycine were calculated. Each rate constant of the glycine degradation was at least 10 times larger than that of the glycine formation. Glycine did not accumulate but instead disappeared on prolonged UV-irradiation when the reactants were supplied to the environment only once at initiation of the irradiation. Furthermore, the concentrations of glycine under six different conditions were calculated using the determined rate constants when the reactants were supplied continuously to the model environment. Glycine concentrations did not continue to increase with an increase in the duration of irradiation. The maximum concentration of glycine was determined by the rate constant of the degradation of the reactant, and also by the rate constants of the formation and degradation of glycine. Therefore, determination of the rate constants was shown to be important for considering the prolonged phenomenon of chemical evolution.