Kinetics of carbon dioxide (CO2) with ethylenediamine, 3-amino-1-propanol in methanol and ethanol, and with 1-dimethylamino-2-propanol and 3-dimethylamino-1-propanol in water using stopped-flow technique

Abstract

Pseudo first order rate constants of homogeneous reactions of carbon dioxide (CO2) with primary amines, ethylenediamine (EDA) and 3-amino-1-propanol (3AP), in methanol and ethanol in the concentration range of 20–120 mol m−3; and with tertiary amines, 3-dimethyl-amino-1-propanol (3DMA1P) and 1-dimethylamino-2-propanol (1DMA2P), in water in the concentration range of 20–120 mol m−3 were measured using a stopped-flow apparatus in a temperature range of 293–313 K. Dissociation constants for aqueous 3DMA1P and 1DMA2P systems at different temperatures were also measured. Both tertiary amines were found to react faster with CO2 than N-methyldiethanolamine (MDEA). The orders of the reaction were determined and the constants were regressed using the mechanism that fitted best the experimental data for each system. Second order reaction rate constants of ethylenediamine (EDA) in methanol and ethanol were higher than those of 2-((2-aminoethyl)amino) ethanol (AEEA), a fast reacting amine, whereas the rates of reaction of 3AP were found to be less than those of monoethanolamine (MEA) in methanol and ethanol. As expected, for both EDA and 3AP, the second order reaction rate constants were found to be lower in non-aqueous media than in water.