NMR studies of hindered rotation and thermal decomposition of novel 1‐aryl‐3,3‐dialkyltriazenes

Abstract

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 ¹H 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.