Studies of osmotic coefficients and volumetric behaviour on aqueous solutions of β-cyclodextrin at 298.15 K

2073-2080The osmotic coefficient, solute activity coefficients and apparent molar volume are determined for β-cyclodextrin (β -CD ) using the techniques of vapor pressure osmometry and digital densitometer in aqueous solutions (0.00164 to 0.01308 mol kg-1) at 298.15 K. The thermodynamic data of activities and partial molar volumes for solvent and solute are computed using appropriate methodology and equations. Theories of dilute solutions such as McMillan-Mayer and Flory-Huggins are applied to estimate the second virial coefficient (B*2) for β-CD, the number of binding sites and χ12 interaction parameter. Using the partial molar volume data at infinite dilution and B*2 value, the contribution due to solute-solvent and solute-solute interactions in terms of attractive and repulsive components are estimated. The values of B*2 and the components are compared with the values reported for mono-saccharides, disaccharides and other non-electrolytes. The results are discussed in terms of hydrophobic hydration and hydrophobic interaction

<span style="font-size:22.5pt;mso-bidi-font-size:15.5pt; line-height:115%;font-family:"Times New Roman","serif";mso-fareast-font-family: "Times New Roman";mso-fareast-theme-font:minor-fareast;mso-ansi-language:EN-US; mso-fareast-language:EN-US;mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">Study of dipole moment of 18-crown-6 in CCI₄<span style="font-size: 17.5pt;mso-bidi-font-size:10.5pt;line-height:115%;font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman";mso-fareast-theme-font:minor-fareast; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA; mso-bidi-font-weight:bold"> <span style="font-size:22.5pt;mso-bidi-font-size: 15.5pt;line-height:115%;font-family:"Times New Roman","serif";mso-fareast-font-family: "Times New Roman";mso-fareast-theme-font:minor-fareast;mso-ansi-language:EN-US; mso-fareast-language:EN-US;mso-bidi-language:AR-SA;mso-bidi-font-weight:bold">solutions at 298.15 K</span></span></span>

46-51<span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">Dielectric constant <span style="font-size:14.0pt;mso-bidi-font-size:7.0pt; font-family:" times="" new="" roman","serif""="">(Ɛ), <span style="font-size:15.0pt; mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">density (d) <span style="font-size:15.0pt;mso-bidi-font-size:8.0pt;font-family: " times="" new="" roman","serif""="">and refractive index (<i style="mso-bidi-font-style: normal">n) measurements at 298.15 K for solutions or 18-crown-6 in CCI4(0.5 to 25 ×10-3 weight fraction of solute) have been reported. The data, along with partial molar volume data for solute are subjected to analysis using various equations to obtain solute polarization and dipole moment values at finite and infinitely dilute concentrations. The dipole moment value of 3.5 D has been compared with gas-phase value and the values in solutions of benzene and cyclohexane, reported earlier. The unexpected large value of dipole moment obtained has been discussed in terms or conformation adopted by the cyclic polyether in a solvent environment. <span style="font-size:15.5pt;mso-bidi-font-size:8.5pt; font-family:" arial","sans-serif""="">It <span style="font-size:15.0pt; mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">is further explained that, in solution phase if 18C6 molecules exist in Ci symmetry conformation (this cannot have dipole moment), the atomic polarization via -CH2- chains must be making large contribution to account for the observed solute polarization. </span