On the mechanism of isomerization of α-hydroxypropionaldehyde to hydroxyacetone

Dimeric lactaldehyde and lactaldehyde-2-d in anhydrous or aqueous pyridine isomerize to hydroxyacetone. The isomerization is catalyzed by protic species that includes self-catalysis by the starting material and product, and catalysis by water and other Brönsted acids. The deuterium isotope effect which has values between 4 and 7, the isotopic exchange data, and the proton nmr assignment of the open dimer are consonant with the enediol mechanism with a rate-determining step involving the enolization of the open dimer.