Solvent effect on the allylic oxidation of cyclohexene catalyzed by nitrogen doped carbon nanotubes

• Solvents affect the oxidation of cyclohexene catalyzed by N-doped CNTs.
• The higher polarity is beneficial for the activity in aliphatic solvents.
• Aromatic solvents are less reactive due to the competitive adsorption.
• A modest solvent basicity is required for high reactivity.
• 2-cyclohexen-1-one selectivity slightly increases with solvent polarity.

A wide spectrum of, up to 22, organic solvents, including aprotic/protic aliphatics/aromatics, was studied to achieve a comprehensive understanding to the solvent effect on the cyclohexene oxidation. It was found that the catalytic activity was significantly influenced by the viscosity, polarity and basicity of solvents in this reaction. Among these solvents, the polar aprotic aliphatic solvents displayed higher catalytic reactivities than other types of solvents. A volcano curve was found describing the dependence of activity on solvent basicity because of the suitable stability of intermediates. Among the solvents investigated, acetonitrile afforded the highest activity and selectivity of 2-cyclohexen-1-one, because of a good compromise between strong polarity and moderate basicity.

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