Objectives: To study the effect of molecular interactions present in ternary system on refractive index with respect to different concentration. To evaluate the optical parameters by examine the change in refractive index. Methods: The compound under study was synthesized and purified by recrystallization. DMSO used for preparation of different series of concentration was purchased as analytical reagent grade (AR) of minimum assay of 99.9%. Different concentration was prepared from stock solutions. For density measurement we have adopted used calibrated pycknometer. To measure refractive index we have used Abbes Refractometer (AR-56, COSLAB). For maintaining required desired temperature we have continuously circulated water through refractometer. Findings: In this article, we are reporting the measurement of density, refractive index, molar refraction and polarizability constant as function of temperature at different concentration. We found that density has inverse relationship with temperature which can be well explained with respect to molar volume effect. Moreover, refractive index also declines with rise in temperature due to weakening of solute-solvent and solute-solute interactions. Due to this optical property related to refractive index are found to change. Novelty: Work reported in this article is not studied earlier. Our work with study of refractive index in ternary mixture system helps to understand the electronic component of radiation with the molecules. Keywords: 6-(4-chlorophenyl)-1, 2, 3, 4-tetrahydro-4-oxo-2-thioxopyrimidine- 5-carbonitrile, Refractive index, Molar refraction, Molar polarizability, Molecular interactions

Solute-solute and solute-solvent interactions of 4-oxo-2-thioxo pyrimidine carbonitriles have been analysed by densitometric and viscometric study in 60% aqueous dimethyl sulphoxide (DMSO) at 303.15 K. From the experimental data the related parameters such as apparent molar volume, limiting apparent molar volume, semiempirical parameter, Falkenhagen coefficient and Jones Dole coefficient were evaluated. Such parameter gives identification of molecular interactions.

Introduction: In this reported work, we have used 80 % aqueous dimethyl sulphoxide (DMSO) for density and viscosity measurement of pyrimidine-5-carbonitrile at 298.15 K. The obtained experimental results show that as concentration increases density and viscosity increases. From the results of density and viscosity, we have found apparent molar volume, limiting apparent molar volume, semi-empirical parameters, Falkenhagen coefficients and Jones Dole coefficients. Method: The apparent molar volume and limiting apparent molar volume having negative values indicated electostrictive solvation of ions and weak or absence of ion solvent interactions respectively. Result & Discussion : Falkenhagen coefficients are independent of concentration and possess positive values that shows strong solute-solute interactions. Jones-Dole coefficient with negative value shows weak solute-solvent interactions. The strong solute-solute interactions were present in A-1 as compared to A-2 compound because of the high electronegativity of oxygen atom. These parameters provides information about the type of the molecular interactions such as solute-solute, solute-solvent and solvent-solvent. Conclusion: We have reported density and viscosity study of 4-amino-2-hydroxy-6- phenylpyrimidine-5-carbonitrile and 4-amino-2-mercapto-6-phenylpyrimidine-5-carbonitrile in 80 % aqueous DMSO solution at 298.15 K. A stronger molecular association is observed in A-2 than A-1 shown by negative values of Øv.

In present work, the concentration and temperature dependence of the thermodynamic properties of 3-substituted Schiff base of 4-piperidyl N-(4-chlorophenyl)maleimide compound in 80% DMSO was estimated. Concentration (0.002-0.01 M) and temperature (298-313 K) dependent densitometric and viscometric measurement were employed to evaluate limiting molar volume (φv 0), semi-empirical parameter (Sv), Falkenhagen (A) and Jones-Dole (B) viscosity coefficient. The obtained results suggest the presence of weaker solute-solvent interactions and stronger solute-solute interactions. It was observed that these interactions strongly depend on the temperature of the system. Furthermore, the Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of the system were also evaluated. The negative values of ΔG and ΔH and positive values of ΔS indicating reaction was spontaneous and exothermic in nature.

Viscometric studies for ternary mixture of 6-(4-chlorophenyl)-1,2,3,4-tetrahydro-4-oxo-2thioxopyrimidine-5-carbonitrile in 60% dimethyl sulphoxide was carried out at different temperatures ranging between 298 and 313 K over different concentration. From viscometric data Delta G, Delta S and Delta H were evaluated. The result shows that the magnitude of Delta G and Delta H are negative while Delta S is positive showing spontaneity of reaction according to thermodynamics pointing structure breaking takes place between solute and solvent. As Delta H is negative and Delta S positive, the reaction is spontaneous at low temperatures (decreasing the magnitude of the entropy term). The thermodynamic study reveals that as concentration increases spontaneity of reaction decreases.