MNDO ANALYSIS OF REGIOSPECIFICITY IN REACTIONS OF 1,5-SUBSTITUTED AND 2,5-SUBSTITUTED TETRAZOLES

MNDO calculations have provided useful insights for analysis of both the metalation and alkylation steps of the reactions of 1,5- and 2,5-substituted tetrazoles with tert-butyllithium and iodomethane, Although the results suggest that equilibrium thermodynamics will favor the formation of the 1,5- and 2,5-diethyl compounds, the relative height of the calculated energy barriers indicates that kinetics will favor production of the 5-(2-propyl) product in both cases. Factors affecting the ultimate balance in favor of the thermodynamic product in the case of 2-methyl-5-ethyltetrazole and the kinetic product in the case of 1-methyl-5-ethyltetrazole are revealed in the details of the calculations. Since the models employed are appropriate only for a medium of unit dielectric constant, solvent effects on the rates of reaction have been examined by means of Laidler-Eyring theory, which is useful in systems where many of the molecules exhibit large dipole moments.