The hydration and polymerisation of succinaldehyde, glutaraldehyde, and adipaldehyde

Abstract

The ¹H n.m.r. spectra of solutions of succinaldehyde, glutaraldehyde, and adipaldehyde in deuterium oxide have been studied. At room temperature, the major component of solutions of succinaldehyde and glutaraldehyde is a cyclic monohydrate which is accompanied by the free aldehyde OCH·CH₂·[CH₂]_n·CH₂CHO, the acyclic monohydrate (DO)₂CH·CH₂·[CH₂]_n·CH₂·CHO, and the dihydrate (DO)₂CH·CH₂·[CH₂]_n·CH₂·CH(OD)₂; at higher temperatures the free aldehyde content increases, mainly at the expense of the cyclic monohydrate. Adipaldehyde, by contrast, forms only the acyclic dihydrate. Although the undiluted aldehydes polymerise readily, their neutral aqueous solutions are stable for Iong periods; acidification induces rapid polymerisation. A common mechanism is suggested for hydration and polymerisation.