Ketene divinylacetal (IV) has been prepared by a stepwise dehydrochlorination of chloroacetaldehyde di-(8-chloroethyl)-acetal (I). The first dehydrochlorinations occur at the j3-chloroethyl groups to yield the vinyl 8-chloroethyl-and divinylacetals of chloroacetaldehyde (11) and 111). While relatively stable to water and alcohols in the absence of acid, IV reacts vigorously with both in the presence of a trace of acid. IV is quite ...