Effets de complexation de l'ester lors de la catalyse par l'eau ou les sels de l'hydrolyse alcaline des esters maloniques: etude cinetique,spectroscop

When water or salts are added, catalytic effects on alkaline hydrolysis of malonic esters in methanol are observed; they are definitely greater than those observed with monoesters. Kinetic data in the presence of salts suggest that ester-M⁺ complexation phenomena is predominant and prevails over HO^-, M⁺ ionic association. Infrared and Raman spectra of esters in water-alcohol mixtures, with or without added salts, indicate the formation of 1:1 and 1:2 complexes with each carbonyl of the diester and one proton donor molecule as well as with Li⁺.Ab initio calculations of these diesters and of their complexes allow the estimation of the positive charge density at the carbonyl group carbon as well as the LUMO energy levels; they lead to an interpretation of these entities reactivities according to perturbation theory. Only orbital control of alkaline hydrolysis of esters gives an account of the relative reactivities of mono- and diesters with or without added salts. The only consideration of charges at the carbonyl carbon is, on the other hand, inadequate for justifying all the observed phenomena.