Ethyl vinyl ether, EtO—CH=CH₂, hydrolyzes in weakly acidic water to acetaldehyde and ethanol. Under the same conditions, diethyl ether does not hydrolyze. Quantitative comparisons of the hydrolysis rates of the two ethers under comparable conditions show that ethyl vinyl ether hydrolyzes about 10¹³ times faster than diethyl ether. The rapid hydrolysis of ethyl vinyl ether suggests an unusual mechanism for this reaction. The acetaldehyde formed when the hydrolysis of ethyl vinyl ether is carried out in D₂O/D₃O⁺ contains one deuterium in its methyl group (that is, DCH₂—CH = O). Suggest a hydrolysis mechanism for ethyl vinyl ether consistent with these facts.