NMR-STUDIES OF HINDERED ROTATION AND THERMAL-DECOMPOSITION OF NOVEL 1-ARYL-3,3-DIALKYLTRIAZENES

1-Aryl-3,3-dialkyltriazenes have been synthesized by coupling the corresponding diazonium salts of substituted aniline derivatives with dialkylamines. The thermostability of these compounds was investigated by differential scanning calorimetry; activation energies of 240-280 kJ mol-1 were determined for the thermal decomposition. The hindered rotation of the dialkylamino group was studied by H-1 NMR exchange measurements. Both experiments are interpreted in terms of an involvement of a 1,3-dipolar structure of the -N=N-N- functional group. The influence of substituents, both on the aromatic ring and at the amino group, on the kinetic and activation parameters is investigated; results are analysed on the basis of mesomeric and steric effects on the dipolar charge distribution in the molecule.