A study for kinetics and oxidation reaction of substituted benzyl alcohols using 2,4′-Bipyridinium dichromate

초록

2,4′-Bipyridinium dichromate [(C <inf>10</inf>H <inf>8</inf>N <inf>2</inf>H) <inf>2</inf>Cr <inf>2</inf>O <inf>7</inf>] was synthesized by the reaction of 2,4′-bipyridinie with chromium trioxide in H <inf>2</inf>O. The structure was characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4′-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase in the order of the dielectric constant (ε), in the order: cyclohexene < chloroform < acetone < N,N′-dimethylformamide. In the presence of hydrochloric acid, 2,4′-bipyridinium dichromate effectively oxidized benzyl alcohol and its derivatives (p-CH <inf>3</inf>, H, m-Br, m-NO <inf>2</inf>) in N,N′-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant (ρ) was -0.65 at 303 K. The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

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