KINETIC STUDIES OF THE SOLVENT EFFECT OF AQUO-DMSO SOLVENT SYSTEMS ON THE EXTENSIVE THERMODYNAMIC PROPERTIES OF ACID CATALYSED SOLVOLYSIS OF HIGHER METHANOATES

With a view to study the solvent effect on the estensive thermodynamic properties of Acid catalysed solvolysis of higher methanoate, the kinetics of the section was studied in water-DMSO media of varying composition consisting of 20% to 80% (v/v) of DMSO 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 DMSO in the reaction media. It was found that from 0.267 to 1.642 molecules of water are associated with the activated complex and from this, it is concluded that in the presence of DMSO in the reaction media, the mechanistic pathways of the reaction is changed from bimolecular to unimolecular. The depletion observed in the values of iso-composition activation energy of the reaction shows that the transition state is solvated and initial stage is desolvated with addition of DMSO in reaction media. The unity value of slope of the plots of log k values against log [H+ ] values shows that the reaction follows AAC 2 mechanism. From the values of iso-kinetic temperature i.e. 290, it may be concluded that in water-DMSO reaction media, there is weak but considerable solventsolute interaction.