Reactions of azolium cations. I. Kinetics and mechanism of alkylation of 5-phenyltetrazole with isopropyl alcohol in aqueous sulfuric acid media

✍ Scribed by A. O. Koren; P. N. Gaponik; V. A. Ostrovskii

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 460 KB
• Volume: 25
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550251209

✦ Synopsis

Alkylation of 5-phenyltetrazole with isopropyl alcohol in 84-99% sulfuric acid medium occurs regioselectively a t N2 position of the heterocycle to produce 2-isopropyl-5-phenyltetrazole. The regioselectivity is conditioned by lH, 4H-5-phenyltetrazolium cation being the alkylation substratum. The reaction mechanism is proved to be two-stage one. Its first and rate-limiting stage is an interaction between the azolium cation and isopropyl cation generated from protonated isopropyl alcohol. The reaction rate constant was estimated as 0.47 L mol-' s-l at 25°C. Water activity scale was used for quantitative description of equilibrium of isopropyl cation formation from the protonated alcohol, and the equilibrium constant ~K R + = -5.3 was evaluated from the data of the alkylation kinetics.