The kinetics of the carbonylation of methanol to methyl formate in the presence of sodium methoxide is reported in this paper. It is found that the presence of an inert nonpolar solvent has a significant effect on the rate of the reaction. The composition of the solvent is found to have a significant effect on the forward and reverse rate constants. This is also accompanied by a decrease in the activation energy of the reaction. These effects are consistent with the Scatchard equation which relates the rate constant to the dielectric constant of the reaction medium.