The solvent effect of t-butanol on the alkali catalysed solvolysis of Methyl caprate was studied by carrying out the hydrolysis of the ester in water-t-butanol media of varying composition consisting of 30 to 80% 1-butanol (v/v) at different temperatures ranging from 20 to 40°C. The specific rate constant values of the reaction were found to decrease with increasing concentration of t-butanol in the reaction media. The iso-composition and iso-dielectric activation energies (Ec and Ed) of the reaction were found to increase and decrease respectively with increasing concentration of the solvent (t-butanol) in the reaction media and with increasing the dielectric constant values of the reaction media. From these findings, it is inferred that the transition and initial states of the reaction are desolvated and solvated respectively with the addition of t-butanol in the reaction media. It was found that number of water molecules associated with the activated complex decreases from 1.506 to 0.424 with increasing temperature from 20°C to 40°C and this tells us that with addition of t-butanol in the reaction media, the mechanistic path followed by the reaction is changed from unimolecular to bimolecular. Form simultaneous enhancement in values of all the three thermodynamie activation parameters ie in ΔG* ΔH* and ΔS*, it has been concluded that in presence of t-butanol the reaction is enthalpy dominating and entropy controlled and specific solvation is taking place in the water-t-butanol media. From the values of iso-kinetic temperature, i.e. 331.42, it may be concluded that the reaction in water-t-butanol media obeys Barclay-Butler rule and there is strong solvent-solute interaction in the reaction media.
Dr. Kumari Priyanka (2025) studied this question.