Kinetics Study of Solid-State Oxidation and Reduction

Abstract

Solvent waste is a leading factor in the financial and environmental costs of synthetic chemistry. Solid state reactions are of interest to the greater scientific community because they have the potential to significantly minimize solvent waste. Synthetic Organic chemistry involves a wide range of applications including pharmaceuticals, food additives, paints and coatings, and new technologies. Oxidation of an alcohol is a fundamental process within organic chemistry to synthesize an aldehyde or a ketone, both of which are abundant in biological and industrial applications. In this research we explore the kinetics of the oxidation of diphenylmethanol to benzophenone in the solid state, monitored via IR spectroscopy. The oxidation of diphenylmethanol to benzophenone using potassium permanganate was successful as evidenced by IR subtraction spectra. Preliminary results indicate that this reaction follows a rate law of kt1/4, associated with a nucleation mechanism. While the product observed from this reaction is identical to that observed under traditional solvent based conditions, the mechanism appears to be quite different. However, a water byproduct is formed over the course of the solid state oxidation reaction when potassium permanganate is used as an oxidant, rendering it not truly solvent free. The water produced may also behave as a base, facilitating the completion of the oxidation reaction. Currently a series of solid state oxidants and bases are being evaluated for effectiveness at oxidation under truly solid state conditions. Additionally, the reverse reaction (reduction of benzophenone to diphenylmethanol) is also being investigated with the use of the hydride transfer reagent sodium borohydride. Preliminary results suggest that this reaction is also possible in the solid state. Future work will include quantifying the effects of temperature on reaction rates in the solid state as well as determination of activation energies and rate laws.