Kinetics of the acid catalyzed hydrolysis of hydroxamic acids

Oxidation–reduction reactions of simple hydroxamic acids and plutonium(IV) ions in nitric acid

“…3) was, therefore, determined for both FHA and AHA where rate constants at 25.0 • C are 0.016 ± 0.001 dm 3 mol −1 min −1 for FHA and 0.00205 dm 3 mol −1 min −1 for AHA and activation energies were found to be 77.3 ± 1.6 kJ mol −1 (FHA) and 79.9 ± 2.9 kJ mol −1 (AHA) [19]. 1 The value for AHA is close to that reported by Mane and Jagdale in HCl [24] (82.4 kJ mol −1 ). Note that this equation is only valid up to 3 M HNO 3 as it is well known that at higher acidities a maximum rate is reached.…”

“…More accurately, the order with respect to acidity in the AHA case was actually 0.9. This is consistent with apparent orders with respect to [H + ] calculated from the data of Mane and Jagdale between 0-3.0 M acid concentrations for: hexanohydroxamic acid[23] in HCl and H 2 SO 4 , isobutyrohydroxamic acid in HCl and H 2 SO 4[14] and aceto-, isobutyl-and hexyl-hydroxamic acids in H 2 SO 4[24].…”

“…The hydrolysis kinetics for FHA and AHA were measured using a colorimetric method [13,14]. HNO 3 and XHA solutions were equilibrated at specific temperatures in a water bath prior to mixing.…”

“…This appears to be consistent with previous studies that showed a positive ionic strength effect. See, for instance, the data of Mane and Jagdale [23,24] where AHA and hexanohydroxamic acid hydrolysis rates at constant acidity show a chloride dependency of ca. 0.1-0.2.…”