Analysis of hydroxamic acids and hydrazides; preparation and properties of dinitrophenyl derivatives of hydroxamic acids, oximes, hydrazides, and hydrazones.

The cleavage of gelatin to smaller molecular units by aqueous hydroxylamine or hydrazine under relatively mild conditions of temperature and pH has suggested the existence of “ester-like” or imide linkages in this protein (1). The amide bonds of gelatin were cleaved only to a minor extent and could not account for the large change in molecular weight. It is known, however, that prolonged treatment of proteins with hydroxylamine or hydrazine under more drastic conditions results in cleavage of amides (2) and certain peptide bonds (3, 4), and concomitant formation of hydroxamates or hydrazides. Esttrification of free carboxyl groups of proteins followed by their conversion to hydroxamatcs or hydrazides presents useful analytical possibilities. Proteins modified in this manner may then be analyzed for hydroxamate or hydrazide by one of the methods to be described below, and allowed to react with fluorodinitrobenzene to form dinitrophcnyl drrivatives. Thr dinitrophenylhydroxamate derivatives may be made to undergo a Lossen rearrangement as described for model compounds and gelatin in another paper. The present communication outlines methods for quantitative estimation of hydroxamate and hydrazide groups of model compounds, and describes a procedure for dinitrophenylation of hydroxamates, hydrazides, oximes, and amidoximes. Some properties of the dinitrophenyl derivatives are also described.