Stability of pyridine-2-aldoxime methiodide II. Kinetics of deterioration in dilute aqueous solutions

Authors

  • Robert I. Ellin,

    1. Physiology Division, Directorate of Medical Research, U. S. Army Chemical Research and Development Laboratories, Army Chemical Center, Md.
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  • James S. Carlese,

    1. Physiology Division, Directorate of Medical Research, U. S. Army Chemical Research and Development Laboratories, Army Chemical Center, Md.
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  • Albert A. Kondritzer

    1. Physiology Division, Directorate of Medical Research, U. S. Army Chemical Research and Development Laboratories, Army Chemical Center, Md.
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Abstract

The decomposition of 2-PAM was studied at pH values 0.5 to 13 and at temperatures ranging from 37 to 87°. At constant pH and temperature, the observed rate of deterioration of 2-PAM was first order with respect to drug concentration. Below pH approximately 4, hydrogen ion catalysis of the acid form of oxime occurs; above pH 4, the reaction is either an hydroxyl ion catalysis of the acid form of oxime or is noncatalytic in which there is a direct attack on the oximate species. Two mechanisms have been postulated for the breakdown of 2-PAM. Specific velocity constants, energies of activation, and frequency factors have been determined for both mechanisms. The pH of maximum stability has been determined from initial rate constants over the entire pH range. General equations relating the half-life of 2-PAM solutions to temperature and pH have been derived.

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