The kinetics and mechanism of the hydrolysis of esters of cis- and trans-2-hydroxycyclopentanecarboxylic acid and 3-hydroxybutyric acid

Abstract

The hydrolysis of ethyl cis-2-hydroxycyclopentanecarboxylate is 1·8 to 11 times faster than that of ethyl cyclopentanecarboxylate in 0·1 M-sodium hydroxide in aqueous dioxan (mole fraction of dioxan 0 to 0·329). This is probably not the result of intramolecular hydrogen bonding since ethyl trans-2-hydroxycyclopentanecarboxylate for which such bonding is not possible reacts as fast or faster than the cis-ester. It is tentatively suggested that the smaller dependence of the rates of hydrolysis of the hydroxy-esters on dioxan concentration compared to the unsubstituted ester is the result of solvent sorting. Similar behaviour is found for the hydrolysis of the 2-naphthyl esters and for the ethyl and 2-naphthyl esters of 3-hydroxybutyric acid.

The rates of hydrolysis of the hydroxy-esters are enhanced in borate buffers possibly as a result of borate-ester formation followed by intramolecular nucleophilic catalysis.

I.r. spectroscopic studies show that the esters of cis-2-hydroxycyclopentanecarboxylic acid are strongly intramolecularly bonded in carbon tetrachloride solution and that those of 3-hydroxybutyric acid are weakly intramolecularly hydrogen bonded. The esters of trans-2-hydroxycyclopentanecarboxylic acid are not intramolecularly hydrogen bonded.