REACTION-KINETICS OF COS WITH PRIMARY AND SECONDARY-AMINES IN ALCOHOLIC SOLUTIONS

The reaction kinetics of carbonyl sulphide (COS) with primary (monoethanolamine, diglycolamine and 2-amino-2-methyl- 1 -propanol) and secondary (diethanolamine, 2-(methylamino)ethanol, di-isopropanolamine and morpholine) amines in alcoholic solutions were studied using a conductimetric stopped flow technique at 278-298 K. Solvents investigated included methanol, isopropanol, ethylene glycol and propylene glycol. Experimental data obtained at various amine concentrations (0.1-1.5 kmol M-3) gave apparent orders in amine between 1 and 2, which confirms that thiocarbamate formation is not a single-step process but involves a zwitterion intermediate. Quantitative rate data show that the reaction rates of COS in alcoholic solutions (particularly in glycols) are higher than those in water. This indicates that the COS selectivity of industrial processes employing alcoholic solvents such as AMISOL is due not only to the increased physical solubilities but also to the increased reaction rates.