Kinetics and mechanism of izomerization of N-alkoxycarbonyl-5-aroxytetrazoles

Article abstract of DOI:10.1023/A:1013947228772

The kinetics and mechanism of the N²-N¹-isomerization of 2-methoxycarbonyl-5-(p-X-phenoxy)-tetrazoles (X = H, CH₃, NHCOCH₃, Cl, Br, NO₂) were studied by ¹H NMR spectroscopy in a DMSO-d₆-CDCl₃ mixture (25: 75). The rate of isomerization of the N²-isomer into N¹-isomer fit the first-order equation (after three half-conversion periods). The isomerization is accompanied by hydrolysis and decarboxylation. The Hammett plot of In(k_Xlk_H) for the isomerization showed a good correlation with σ^- values (p^- = 1.33, r = 0.965). A poor correlation with σ values was obtained. The kinetic data, the effect of solvent polarity, the substituent effects, and the results of AM1 quantum-chemical calculations suggest an ionic mechanism of the isomerization in polar solvents and a concerted mechanism in nonpolar solvents.