Evidence for intramolecular electrostatic catalysis as a possible mechanism in the hydrolysis of vinyl ethers in aqueous solution
作者:Torbjoern Halvarsson、Nils Aake Bergman
DOI:10.1021/jo00001a047
日期:1991.1
The hydrolysis of the vinyl ether functional group in 2-methoxybicyclo[2.2.2]oct-2-ene-1-carboxylic acid (2) has been found to be catalyzed by intramolecular electrostatic catalysis by the carboxylate ion of the substrate.1 The rate constant ratios of the charged and the neutral form of the substrate are 32.3 and 31.2 for catalysis by hydronium ion and acetic acid, respectively. This is in contrast to ratios that have been found for vinyl ethers hydrolyzed by intramolecular general-acid catalysis, where large rate ratios for catalysis by hydronium ion but small rate ratios, normally a factor 2, when catalyzed by acetic acid are observed. The solvent isotope effect, 3.4 +/- 0.5, is close to what has been predicted for electrostatic catalysis in the hydrolysis of prostacyclin (1).