Thermophysical and excess properties of hydroxamic acids in DMSO

In this work, densities (ρ) and refractive indices (n) of N-o-tolyl-2-nitrobenzo- and N-o-tolyl-4-nitrobenzo-, hydroxamic acids have been determined for dimethyl sulfoxide (DMSO) as a function of their concentrations at T = (298.15, 303.15, 308.15, 313.15, and 318.15) K. These measurements were carried out to evaluate some important parameters, viz, molar volume (V), apparent molar volume (Vϕ  ), limiting apparent molar volume (Vϕ0), slope (SV∗), molar refraction (RM) and polarizability (α  ). The related parameters determined are limiting apparent molar expansivity (ϕE0), thermal expansion coefficient (α2) and the Hepler constant (∂2Vϕ0/∂T2). Excess properties such as excess molar volume (VE), deviations from the additivity rule of refractive index (nE), excess molar refraction (RME) have also been evaluated. The excess properties were fitted to the Redlich–Kister equations to estimate their coefficients and standard deviations were determined. The variations of these excess parameters with composition were discussed from the viewpoint of intermolecular interactions in these solutions. The excess properties are found to be either positive or negative depending on the molecular interactions and the nature of solutions. Further, these parameters have been interpreted in terms of solute–solute, solute–solvent interaction and structure making ability of solute in DMSO.

Excess molar volumes (VE) vs mole fraction (x2) of (A) N-o-tolyl-2-nitrobenzo- and (B) N-o-tolyl-4-nitrobenzo-hydroxamic acids in DMSO at different temperatures: ■, 298.15 K; , 303.15 K; , 308.15 K; , 313.15 K; and , 318.15 K.Figure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideHighlights
► ρ, n of the system hydroxamic acids in DMSO are reported.
► Apparent molar volume indicates superior solute–solvent interactions.
► Limiting apparent molar expansibility and coefficient of thermal expansion.
► Behaviour of this parameter suggest to hydroxamic acids act as structure maker.
► The excess properties have interpreted in terms of molecular interactions.