Kinetic Stability Study of Selected Hydroxamic Acids Using HPLC/UV

The kinetics of the acid and base hydrolysis of salicylhydroxamic acid (SHAM) and O acetyl-salicylhydroxamic acid (OAc-SHAM) were studied using High Performance Liquid Chromatography with UV-Detection (HPLC-UV). The effect of temperature and pH values on the hydrolysis was investigated. It was found that both SHAM and OAc-SHAM were more stable in basic media (high pH values) and at lower temperatures; whereas all reactions were found to follow pseudo-first order kinetics. Reaction rate constants (k) were calculated at different temperatures and pH values. The general trend was that as pH values of the solution increase (basic media), the rate constant decreases indicating a slow hydrolysis rate for both acids. Also, low hydrolysis rates were observed with decreasing the temperature in all cases. The oxidation was also investigated with a solution of 1.0 % hydrogen peroxide (H2O2) as the oxidizing agent. OAc-SHAM was found to be insoluble in the H2O2 solution. While SHAM was almost hydrolyzed in two hours at room temperature