DISTRIBUTION OF DISPERSE DYES BETWEEN <i>n</i>-HEPTANE AND CHLORINATED <i>n</i>-HEPTANE

Abstract

Isotherms were measured for distributions of model disperse dyes (benzene, azobenzene, p-amino-azobenzene, p-nitroazobenzene, 4-amino-4′-nitroazobenzene, 4-N-methylamino-4′-nitroazobenzene, and 4-N, N-dimethylamino-4′-nitroazobenzene) between water and n-heptane and between water and 3.5% chlorinated n-heptane at various temperatures. From the results the thermodynamic parameters were calculated for the process which consists of the transfer of one mole of the dye molecule from n-heptane to 3.5% chlorinated n-heptane.Dye in n-heptane (mole fraction) → Dye in 3.5% chlorinated n-heptane (mole fraction)The unitary free energy changes accompanied by the process were all negative. This indicates that the dye molecules were more stable in chlorinated n-heptane than in n-heptane. From the thermodynamic parameters obtained in this work the interaction between the dye molecule and chlorinated n-heptane molecule was discussed. It was concluded that the ability of the chlorine atom of chlorinated n-heptane to form hydrogen-bonds with proton-donating groups of the dye molecule might be a main source of the stability of the dye molecule in chlorinated n-heptane.The fact that an introduction of an amino group into the dye molecule caused a marked increase in enthalpy change supported this conclusion.