A re-evaluation of hydroxylammonium acetate as a carbonyl reagent — the effect of dielectric constant change on titration end-points

Abstract

The determination of carbonyl groups with hydroxylammonium acetate in acetic acid has been re-examined. The reaction of hydroxylammonium acetate with acetic acid has been found to yield non-basic products, first acethydroxamic acid and eventually diacetylhydroxylamine, which do not interfere with the analyses. Calculations based on kinetics show that loss of the reagent is negligible in most cases, and in the extreme, involves only 0.9% of the amount originally present. Analyses in acetic acid media throughout are compared with those in which the titrations were conducted in benzene-acetic acid or carbon tetrachloride-acetic acid mixtures whose compositions were chosen to yield the most favorable titrations. The slopes of the titration curves were uniformly improved in the systems containing inert solvents, as predicted by consideration of the effect of dielectric constant change. Analytical precision was slightly improved except for aromatic aldehydes. Neither inert solvent system seemed superior to the other. The undesirable effect of small amounts of water is discussed.