Studies on the Solvent Effect of Aquo-DMSO Solvent Systems on the [H+] Ion Catalysed Hydrolysis of Butyl Formate

The solvent effect of Aquo-dipolar aprotic organic solvent systems was highlighted by studying the kinetics of the acid catalysed solvolysis of an aliphatic formate (Butyl formate) in water-DMSO media (aquo-dipolar aprotic organic solvent systems) of various composition having 20 to 80% of DMSO at five different temperatures ranging from 20 to 40°C. In the beginning, fast decrease followed by slow depletion in the rate with gradual addition of the organic co-solvent in the reaction media and also with increasing temperature of the reaction has been explained in the light of solvation of initial and transition states to different extents. The changes in the values of iso-composition and iso-dielectric activation energies of the reaction have also been explained in the light of solvation and desolvation of initial and transition states to different extent. Increase in the numerical values of free energy of activation (ΔG*) with simultaneous enhancement in the values of enthalpy of activation (ΔH*) and entropy of activation (ΔS*) of the reaction, reveals that DMSO acts as enthalpy accelerator and entropy controller solvent. Effects of ionic strength and [H+ ] ion on the rate of reaction have also been studied and it is concluded that the acid catalysed hydrolysis of Butyl formate is ion-dipolar reaction and it follows AAC 2 mechanistic pathways in water-DMSO reaction media.