Kinetics of Hydrolysis of 1-Acetoxy-, 1-Acetoxy-8-hydroxy-, and 1,8-Diacetoxynaphthalenes; Intramolecular Participation by a Hydroxy Group

Article abstract of DOI:10.1039/P29880000571

Consecutive hydrolysis of the acetoxy groups in 1,8-diacetoxynaphthalene in aqueous alkaline solution can be studied kinetically because hydrolysis occurs more rapidly for the diacetate than for 1-acetoxy-8-hydroxynaphthalene which is mostly present in the ionised form.The dependence of the rate coefficient (k₂) for hydrolysis of 1-acetoxy-8-hydroxynaphthalene on the concentration of hydroxide ion is complex because of the equilibrium between the ionised and un-ionised forms and their different reactivities.The equilibrium between the ionised and un-ionised forms has been measured separately and the data are combined with the kinetic results to show that the linear dependence of k₂ on -> at high concentrations is due to reaction of the ionised form with OH^-.At low concentrations, the curved dependence of k₂ on -> can be explained by reaction of ionised 1-acetoxy-8-hydroxynaphthalene with solvent.The value of the rate coefficient (k₄) for this reaction, in comparison with the value for the reaction of 1-acetoxynaphthalene with water, shows that the hydroxy group assists the attack of water by intramolecular general base catalysis.A kinetic solvent isotope effect K₄(H2O)/k₄(D2O) 2.2 +/- 0.5 is observed.

Full text of DOI:10.1039/P29880000571

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