STABILITY OF WATER-SOLUBLE CARBODIIMIDES IN AQUEOUS-SOLUTION

A dimethylbarbituric acid reagent has been used to follow the kinetics of loss of two water-soluble carbodiimides, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and the structurally related 1-ethyl-3-(4-azonia-4,4-dimethylpentyl) carbodiimide (EAC), in aqueous solution as a function of pH and added chemical reagents. In 50 mm 2-(N-morpholino)ethanesulfonic acid at 25°C, EDC has t 1 2 values of 37, 20, and 3.9 h at pH 7.0, 6.0, and 5.0, respectively, while the corresponding values for EAC are 12, 2.9, and 0.32 h. Iodide, bromide, or chloride, at 0.1 m, has very little or no effect on carbodiimide stability. However, 0.1 m glycine methyl ester or 0.1 m ethylenediamine causes a significant increase in the rate of loss of EAC and EDC, while the presence of 0.1 m phosphate, 0.1 m hydroxylamine, or 0.01 m ATP decreases the half-lives to ≤0.4 h at all pH values. © 1990.