Study of Ion-Solvent Interaction during Acidic Dissociation of Glycine in 10, 20 And 30% Dioxane in Dioxane-Water System At 318.15K by Potentiometric Method

Abstract

Ion solvent interaction was studied by free energy transfer during acidic dissociation of Glycine in 10,20 and 30% dioxane in dioxane-water system at 318.15K and free energy was given by the thermodynamic relation </p> <p>ΔG<sub>t</sub> = 2.303RTΔpK<sub>1</sub></p> <p>where ΔG<sub>t</sub> = free energy transfer when solvent change from water to dioxane-water.</p> <p>ΔpK<sub>1</sub> = pK<sub>s1</sub>-pK<sub>w1</sub></p> <p>where pK<sub>w1</sub> = -log K<sub>w1</sub> negative logarithmic of dissociation constant of glycine in water.</p> <p>pK<sub>s1</sub> = -log K<sub>s1</sub>negative logarithmic of acid dissociation constant of glycine in dioxane-water.</p> <p>For this purpose acidic dissociatio constant of glycine was determined potentiometrically by setting up the cell:</p> <p>H<sub>2</sub>(Pt) | Glycine, HCl, X% Dioxane, Hg<sub>2</sub>Cl<sub>2 </sub>| Hg …(C-1)</p> <p>m<sub>1 </sub>m<sub>2</sub> (100-x)% water</p> <p>and e.m.f. of the cell was given by the formula:</p> <p>E = E<sup>0</sup>- 2.303RT/F (log m<sub>H</sub><sup>+</sup> m<sub>cl</sub><sup>-</sup> + log Ɣ<sub>H</sub><sup>+</sup> Ɣ<sub>Cl</sub><sup>_</sup>) …(1)</p> <p>In the equation (1) activity coefficient of the solution has been taken into consideration to understand ion solvent interaction and activity coefficient is given by the relation:</p> <p>log Ɣ<sub>H</sub><sup>+</sup> Ɣ<sub>Cl</sub><sup>_</sup> = -2A¢√μ/(1+ √μ) +ꞵ<sub>1</sub>μ …(2)</p> <p>Equation (2) is modified Davies equation given by B. Prasad and hence acidic dissociation constant of glycine can be calculated by calculating m<sub>H</sub><sup>+</sup> as: log m<sub>H</sub><sup>+ </sup>= (E<sup>0 </sup>- E)/K - log m<sub>Cl</sub><sup>_</sup> + (2A¢√μ/(1+ √μ)) - ꞵ<sub>1</sub>μ …(3)