BASE-CATALYZED-HYDROLYSIS OF GAMMA-LACTONES - REACTIVITY-STRUCTURE CORRELATIONS FOR 3-(SUBSTITUTED PHENOXYMETHYLENE)-(Z)-1(3H)-ISOBENZOFURANONES AND THIOPHENOXYMETHYLENE)-(Z)-1(3H)-ISOBENZOFURANONES

Rate coefficients were measured for the base-catalysed hydrolysis of a series of substituted 3-(phenoxy-or thiophenoxymethylene)-(Z)-1(3H)-i sobenzfuranones (3-phenoxy- or thiophenoxymethylenephthalides) in 70% (V/V) aqueous dioxane at 30.0 degrees C, in addition to the carbonyl s tretching frequencies in chloroform and tetrachloromethane following d econvolution and band separation, when required. The Hammett reaction constants for the alkaline hydrolysis of the 3-/4-substituted phenoxy and thiophenoxy series are ca 0.75 and 1.10, respectively. These resul ts are related to electrostatic field and resonance effects. Successfu l correlations between the carbonyl stretching frequencies and substit uent constants and the rates of alkaline hydrolysis were found. Comput ational studies using the semi-empirical AM1 method correctly model bo th the details of the mechanistic pathway and the substituent effects. (C) 1998 John Wiley gr Sons, Ltd.