Polarographic reduction of aldehydes and ketones. Part XIII. Effect of hydration and carbanion–enolate formation on the electrolysis of glycolaldehyde
Glycolaldehyde is reduced at the dropping mercury electrode in two two-electron steps: In the first the C–OH bond is reductively cleaved and acetaldehyde is formed, this being then reduced in the consecutive second step. The reduction current which corresponds to cleavage of the C–OH bond is governed by the rate of the base-catalysed dehydration of hydrated glycolaldehyde. Reduction of acetaldehyde is limited both by the rate of conversion of the carbanion-enolate formed in the first two-electron uptake, and by the rate of establishment of the hydration of acetaldehyde. Polarographic results indicate that less than 10% of glycolaldehyde is present in dilute aqueous solutions in the non-hydrated form.