TRANSITION-STATES IN THE CRYSTALLINE PHASE - THERMAL REARRANGEMENTS OF SOLID 4H-1,2,4-TRIAZOLES

In the crystalline state the 4-methyl and 4-ethyl substituted 4H-1,2,4 -triazoles were found to undergo thermal rearrangement to the correspo nding l-alkyl substituted triazoles. The same reaction took place in t he melts. Reaction rates were measured in both phases, and the activat ion parameters determined. The methyl substituted triazole reacted fas ter than the ethyl compound (methyl: E(a) 104 kJ mol(-1) vs. ethyl E(a ) 173 kJ mol(-1)). The results were in agreement with a nucleophilic-t ype group transfer mechanism. The activation parameters for reactions in the solid state could be correlated with the interatomic distances between the I-N atoms of the triazole rings and the alpha-atom of the 4-alkyl groups in a neighboring molecule.