Base-catalysed hydrolysis of γ-lactones: reactivity–structure correlations for 3-(substituted phenoxy- and thiophenoxymethylene)-(Z )-1(3H )-isobenzofuranones

✍ Scribed by Keith Bowden; Richard J. Ranson; Alexander Perjéssy; Margita Lácová; Oĺga Hritzová; Walter M. F. Fabian

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 152 KB
• Volume: 11
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199807)11:7<467::aid-poc15>3.0.co;2-0

✦ Synopsis

Rate coefficients were measured for the base-catalysed hydrolysis of a series of substituted 3-(phenoxyor thiophenoxymethylene)-(Z)-1(3H)-isobenzfuranones (3-phenoxy-or thiophenoxymethylenephthalides) in 70% (v/v) aqueous dioxane at 30.0 °C, in addition to the carbonyl stretching frequencies in chloroform and tetrachloromethane following deconvolution 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 results are related to electrostatic field and resonance effects. Successful correlations between the carbonyl stretching frequencies and substituent constants and the rates of alkaline hydrolysis were found. Computational studies using the semi-empirical AM1 method correctly model both the details of the mechanistic pathway and the substituent effects.