Base-catalyzed dehydrohalogenation with potassium t-butoxide in t-butyl alcohol of the acetals obtained from homologues of α-bromoacetaldehyde and ethylene glycol [2-(α- bromoalkyl)-1, 3-dioxo-lanes] or 1, 3-propanediol [2-(α-bromoalkyl)-1, 3-dioxane] provides the corresponding ketene acetal, in some cases exclusively and in others as the major product along with a smaller proportion of the α, β-unsaturated acetal. In contrast, similar ...