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

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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.