The Acid-Catalysed Solvolysis of Alkoxymethyl Esters. Part V. Hydrolysis of beta-Chloroethoxymethyl Esters.

Mechanisms of Acylal Hydrolysis in Sulfuric Acid Solutions

“…In the case of strongly stabilized carbonium ions, the unimolecular process can predominate even in dilute acids and no bimolecular hvdrolysis is observed, as for example with tertbutyl acetate (13). In this sense then, an acylal like methoxymethyl acetate can be seen to fit this latter category, the methoxymethyl carbonium ion is stabilized sufficiently that only the unimolecular hydrolysis is observed (5,6). With the aryloxymethyl acetates however, the intermediate oxycarbonium ion should be considerably less stabilized due to the competition for the oxygen electron pairs between the phenyl ring and the cationic center.…”

“…A mixture of A-l(b) and A,,-2 reactions has been suggested with formic acid acylals (5, 6) (more efficient bimolecular attack) and with 2-chloroethoxy acylals (8) (destabilized oxycarbonium ion). Methylene diacetate and ethylidene diacetate follow only the bimolecular route (9), presumably in order to avoid the formation of an acyloxycarbonium ion.…”

Preparation and Structure of Novel Macrocyclic Oligoesters from 6,8-Dioxabicyclo[3.2.1]octan-7-one

“…The acetal esters of the type RCOOC^OR' are, in general, hydrolyzed in the presence of an acid catalyst by the normal unimolecular alkyl-oxygen fission designated by AalI,25,26 but in some cases unimolecular and bimolecular reactions occur simultaneously. 27 In the acid-catalyzed hydrolysis of 1,3-dioxolan-4-ones (five-membered cyclic acetal esters), two mechanisms have been proposed on the basis of kinetic data:28 Unsubstituted l,3-dioxolan-4-one undergoes acid-catalyzed hydrolysis by bimolecular acyl-oxygen fission (Aac2, mechanism), while an introduction of one or two methyl groups at the carbon 2 changes the mechanism to AAiT-like mechanism.…”