THERMODYNAMIC STUDY OF ASSOCIATED SOLUTIONS OF ALCOHOLS IN AROMATICS BY GAS-LIQUID-CHROMATOGRAPHY

The infinite dilution activity coefficients gamma(i), partial molar excess enthalpies H(i)EBAR and entropies S(i)EBAR of C1-C4 alcohols in inert solvents diphenyl-methane, dibenzyl and diphenylacetylene along with active solvents benzophenone and diphenylsulfoxide have been measured. The values of gamma(i) in inert solvent decrease in the order: methanol > ethanol > n-propanol > n-butanol; n-propanol > isopropanol; n-butanol approximately isobutanol > tert-butanol > sec-butanol. but no regular order has been found in active solvent. The activity coefficients have been treated by Kretschmer-Wiebe association model combining with a Hildebrand-Scatchar d term. The self association constants K(A) of alcohols in inert solvent decrease in the order: methanol > ethanol > n-propanol > n-butanol; n-propanol > isopropanol; n-butanol > tert-butanol > isobutanol approximately sec-butanol. At the same temperature, the values of K(A) of each alcohol in the studied inert solvents are nearly equal. It can be safely assumed that each alcohol in the solvents which have two benzene rings are all having a common value K(A). In addition, using the average K(A) in studied inert solvents, the cross association constant K(AB) of alcohol with active solvent has been evaluated. The values of K(AB) decrease in the order: methanol > ethanol > n-propanol > n-butanol; n-propanol > isopropanol; n-butanol > isobutanol > sec-butanol > tert-butanol. It has been found that the associated ability of alcohol with diphenylsulfoxide is greater than with benzophenone. On condition that the factor K(AB) is comparable with K(A), the value of gamma(i) would be close to unity. And the irregular phenomenon of gamma(i) in active solvent can be given a satisfactory explanation.