Kinetic Studies On The Thermal Cis-To-Trans Isomerization Of 1-Phenyltriazenes Derived From Cyclic Amines

Rate constants for thermal cis-to-trans isomerization of N-(phenylazo)-substituted nitrogen ring heterocyles were determined as a function of phenyl ring substitution, cyclic amine ring size, and organic solvents. Observed first-order rate constants are found to increase with increasing electron-withdrawing character of the para substituent, with larger amine rings, and with increasing solvent polarity. Overall, trends observed are consistent with geometrical isomerization taking place through rotation around the nitrogen-nitrogen double bond via a polarized transition state.