Synthesis of Ring-Substituted Phenyl Hydrazinecarboxylates and Study of Their Protonation in Dimethyl Sulfoxide Solutions

The p K a values of nineteen phenyl hydrazinecarboxylate hydrochlorides R-C 6 H 4 OCONHNH 2 ·HCl (R = H, 3- and 4-Cl, 3- and 4-O 2 N, 4-Me) and their 1-methyl or 2-methyl derivatives were determined by potentiometric titration with tetrabutylammonium hydroxide in DMSO. IR spectra of the hydrazinecarboxylates and their hydrochlorides revealed that the hydrazinecarboxylate protonation occurs at N 2 . The methods of synthesis of phenyl hydrazinecarboxylate and their N -methyl derivatives were optimized.