Thermodynamic and volumetric properties of hydroxamic acids in dimethylsulfoxide at T = (298.15 to 313.15) K

Physical properties, such as density, (ρ) and refractive index, (n) of three hydroxamic acids (N-phenylbenzo-, N-phenyl-4-methyl-3-nitrobenzo-, and N-phenyl-4-nitrobenzo-) were measured in dimethyl sulfoxide (DMSO) as a function of concentrations at T = (298.15, 303.15, 308.15, and 313.15) K . The apparent molar volumes ($V_{\varphi }^0$), limiting apparent molar volumes ($V_{\varphi }^0$) at infinite dilution, slope ($S_V^{*}$) and Hepler's constant (${\partial }^2{V}_{\varphi }^0\partial T^2$) are calculated from the experimental values of densities (ρ) by applying the Masson's equation. The apparent molar expansibilities at infinite dilution (${{\varphi }^0}_E$), molar volumes (V), thermal expansion coefficient (α₂) and the excess molar volumes (V^E) are also computed. The precise refractive indices (n) data have been used to evaluate the steric parameters viz. molar refractions (R_M), polarizability (α) and excess molar refraction ($R_M^E$) of these molecules. It is inferred from these results that the above mentioned drugs act as structure-making compound due to hydrophobic hydration of the molecules in the drug.