Thermodynamic properties of ethanol solution of chiral camphors and its derivatives

Enthalpies of mixing and the densities of ethanol solution of R- and S-enantiomers of camphor, 10-camphorsulfonamide, 10-camphorsulfonic acid, camphorquinone, and 10-camphorsulfonyl chloride have been measured for a wide range of mole fractions of heterochiral components at 298.15 K. Enthalpies of mixing were exothermic for all concentrations and heterochiral solutions were more stable than each of the homochiral solutions. Enthalpic stabilization of mixing of heterochiral solutions was increased with a decreasing concentration of all the camphor derivatives measured. The sequence of enthalpic stabilization on mixing was 10-camphorsulfonyl chloride, 10-camphorsulfonic acid, 10-camphorsulfonamide, camphor, and camphorquinone. Apparent molar volumes were determined and excess volumes of mixing of heterochiral solutions were small and negative. Enthalpic stabilizations were found to be dependent on dipole–dipole interaction between solutes and solvents.