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Rate coefficients were measured for the base-catalysed hydrolysis of a series of substituted 3-(phenoxy- or 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. © 1998 John Wiley & Sons, Ltd.

The infrared and 13C NMR spectra and the kinetics of alkaline hydrolysis of chromium, tricarbonyl[3-[(η6-aryl)methylene]-Z-1(3H)-isobenzofuranones] have been studied in comparison with those of 3-arylmethylene-Z-1(3H)-isobenzofuranones. The 13C NMR spectroscopy has been found to be the most suitable tool for recognition of the site of complexation in the 3-arylmethylene-Z-1(3H)-isobenzofuranone system. A statistically significant correlation has been found between the arithmetic means of the wave numbers of symmetric and asymmetric stretching vibrations of Cr(CO)3 group and σp constants of the substituents. The large slope of this linear dependence suggests an important role of the mesomeric mechanism in the transmission of electronic effects to the Cr(CO)3 moiety. The strong electron-withdrawing effect of the Cr(CO)3 group causes a significant decrease of the polarity of the phthalide CO bond. The reaction rates of the alkaline hydrolytic ring-opening reaction dramatically increase due to the effect of Cr(CO)3 group. The absorption bands of the carbonyl stretching vibrations are markedly split due to Fermi resonance effect. After mathematical correction for Fermi resonance the wave numbers of the unperturbed fundamental CO stretching vibration and the log k values of alkaline hydrolysis exhibit significant linear correlations mutually, as well as with Hammett σ substituent constants. Charton's transmissive factors γ(PhCr(CO)3) have been determined for tricarbonylchromiumphenyl system using the parameters of the linear correlations. The efficiency of the substituent effect transmission is high in CCl4, because a back-donation effect of the carbonyl ligands and decreases in CHCl3 due to the hydrogen bonding between carbonyl groups and solvent molecules. The preparation of some novel chromium, tricarbonyl[3-[(η6-aryl)methylene]-Z-1(3H)- isobenzofuranones] is described.