Acetals and ethers-xiii Reaction products of 2-butenal with ethylene glycol

The unsaturated cyclic acetal, 2-(1-propenyl)-1,3-dioxolane (2), has been found as an intermediate product in the p-toluenesulfonic acid catalysed reaction of 2-butenal with an excess of ethylene glycol. The final product consisted of 2-2-(2-hydroxyethoxy)-propyl]-1,3-dioxolane (3), and a small amount of geometric isomers of cis- and trans-5-(2-hydroxyethoxy)-7-methyl-1,4-dioxepane (4a and 4b, respectively).