A kinetic study of the high temperature rearrangement of 4-ethyl-3,5-diphenyl-4H-1,2,4-triazole

Citation
Or. Gautun et Phj. Carlsen, A kinetic study of the high temperature rearrangement of 4-ethyl-3,5-diphenyl-4H-1,2,4-triazole, J HETERO CH, 38(4), 2001, pp. 955-959
Citations number
11
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF HETEROCYCLIC CHEMISTRY
ISSN journal
0022152X → ACNP
Volume
38
Issue
4
Year of publication
2001
Pages
955 - 959
Database
ISI
SICI code
0022-152X(200107/08)38:4<955:AKSOTH>2.0.ZU;2-C
Abstract
The kinetics of the thermal rearrangement 4-ethyl-3,5-diphenyl-4H-1,2,4-tia zoles, 1, to the corresponding 1-ethyl-3,5-diphenyl-1-alkyl-1H-1,2,4-triazo les, 2, was studied in 15-Crown-5 and octadecane at 330 degreesC. The react ion was very slow in octadecane but proceed well in 15-Crown-5. The reactio n order for the reaction was not constant but changed from an initial secon d order rate law towards a first order rate law as the reaction progressed. This was confirmed by the concentration dependent reaction order, n(c), wh ich was larger than the time dependent rate law, n(t). The rationale for th e observation was, that at high substrate concentrations the reaction order was second order while at lower concentrations a competing solvent assiste d reaction plays an increasing important role. The data were in agreement w ith a mechanism in which the neutral 4-alkyl-triazoles in an intermolecular nucleophilic displacement reaction form a triazolium triazolate, which in a subsequent nucleophilic reaction gives the observed product.