A Kinetic Study of the Solvent Effect of Aquo-Dipolar Protic Solvent Systems on the Catalysed Solvolysis of Higher Hexanoates

The Kinetics of alkali catalysed hydrolysis of propyl hexanoate (a higher hexanotes) in aquo-propan-2-ol media was studies with a view to highlight the effect of a dipolar protic solvent (propan-2-ol) on the medicinal efficiency of the hydrolytic product of the ester (hexanote acid or caproic acid). The initial sharp decrease followed by slow and smooth depletion in the rate with gradual addition of the organic co solvent in the reaction media and with increasing temperature of the reaction has been explained in the light of solvation or desolvation of initial and transition state to the different extent. The increase and decrease respectively in the value of iso-composition and iso-dielectric activation energies of the reaction respectively have been observed and explained on the basis of solvation and desolvation to different extent of initial and transition states by the added solvent. Enhancement in the values of free energy activation ΔG* with simultaneous increase in enthalpy of activation ΔH* and entropy of activation ΔS* reveals that the specific solvation is taking place in the reaction media and propnal-2-ol acts like entropy controller and enthalpy stimulator solvent