DIAZENES .I. DECARBOXYLATION OF PHENYLDIAZENECARBOXYLIC ACID

The synthesis of several aryldiazenecarboxylic acid4 esters and their conversion to the corresponding salts, XArN=NCOO-M+, are described. The rate constant for hydrolysis of C6H6N=NCOOCH3 (1) at 4° is ~2.0 X 102 1. mole-1 sec-1, 104 faster than that of the homomorphic ester, C6H5CH=CHCOOCH3. The rate constant for the reaction of 1 with sodium methoxide in anhydrous methanol is ~3 X 10-31. mole-1 sec-1 at 25°, and the pKa of phenyldiazene (3), C6H5N=NH, is estimated as no more than 27 from a comparison of the rate constants for reaction with hydroxide ion and methoxide ion. Spectroscopic data (ultraviolet-visible, infrared, and nuclear magnetic resonance) are reported for many of the diazene derivatives. A technique for following the decarboxylation of phenyldiazenecarboxylate anion, C6H5N=NCOO- (2), in the absence of oxygen has been developed. The rate of decarboxylation varies linearly with hydrogen ion concentration over the pH range 10.4-11.9. Arguments in favor of a mechanism proceeding via carbon dioxide loss from the zwitterion C6H5N=NH+COO- are presented. © 1968, American Chemical Society. All rights reserved.