The Alkaline and Acid Hydrolysis of n-Butylacetate in Methanol-Water Mixtures

Chemistry Department, Faculty of Science, Moharram Bey, Alexandria, Egypt Manuscript received 2 December 1980, revised 9 February 1982, accepted 8 July 1982 Alkaline and acid hydrolysis of \(n\)-butylacetate ins carried tut is aqueous methanol at 10-25° for the alkaline and at 25-50° for the acid hydrolysis. In alkaline hydro­lysis. the reaction was irreversible and the bimolecular rate constants decreased steadily with progressive increase of the organic solvent in the reaction medium. In the acid hydrolysis, the reaction attained an equilibrium which depended upon the solvent composition With progressive additions of methanol to the acidic ester solution, the overall and reverse reaction rates increased gradually while the forward reaction rate decreased. The characteristic kinetic behaviours are discussed in the light of the Back-Strain" effect and solvation phenomena. The effect of dielectric constant on reaction rate is interpretted by the treatment of Amis, based on simple electrostatic consideration of ion-dipole interactions. The isocomposition, isodielectric energy and logarithm of the Arrhenius frequency factor are also calculated and interpretted in terms of solvation effects. Mechanisms for alkaline and acidic hydro­lyses are proposed which account for the role and the effects of the solvent on the reaction rate. The thermodynamic parameters ΔG*, Δ H*, ΔS* are calculated as a support to the proposed mechanisms.