Studies on Decomposition and Stabilization of Drugs in Solution. IV. Effect of Dielectric Constant on the Stabilization of Barbiturate in Alcohol-Water Mixtures

概要

論文の詳細を見る
The alkaline degradation of methylhexabital J. P. (hexobarbital I. P.) in ethanol-water and methanol-water mixtures was carried out and the following results and conclusions were obtained. 1) The change of reaction rate was tested by simplified Scatchard's equation (1). In both mixtures, relationship between logarithm of reaction rate at zero ionic strength and reciprocal of dielectric constant was negatively linear down to a dielectric constant of 55 to 50. The values of γ, distance of approach sufficient for the reaction, were 1.2 Å and 0.90 Å in ethanol-water and methanol-water mixtures, respectively. The order of the magnitude of these values is not out of theoretical requirements. 2) Activation energies of the reaction in ethanol-water mixtures were found to be 16,900 and 17,100 cal./mole at the dielectric constant of 65 and 60,respectively. In methanol-water mixtures, they were 20,600 and 24,500 cal./mole at the dielectric constant of 65 and 55,respectively. It was found that activation energy increases as the dielectric constant decreases, in both mixtures. 3) From these observations, it may be concluded that the stabilization of a barbiturate in solution by addition of ethanol or methanol is attributable to the decrease of dielectric constant of the medium.
公益社団法人日本薬学会の論文
1960-06-25