Kinetics of the condensation of acetaldehyde with formaldehyde in aqueous alkaline solutions at 5–20°
Abstract
The kinetics of the early stages of the condensation of acetaldehyde with formaldehyde to form β-hydroxypropionaldehyde and bishydroxymethylacetaldehyde (precursors to pentaerythritol) have been investigated in aqueous alkaline solutions at 5–20°. The rate of monohydroxymethylation of acetaldehyde is expressed as v=k1k2[CH3CHO][CH2O]·[base]/(k–1+k2[CH2O]). β-Hydroxypropionaldehyde, the product of monohydroxymethylation of acetaldehyde, is prepared in good yield from acetaldehyde and formaldehyde. The rate of hydroxymethylation of β-hydroxypropionaldehyde fits the rate equation analogous to that for the monohydroxymethylation of acetaldehyde. The results show that the rate of hydroxymethylation for one hydrogen atom of β-hydroxypropionaldehyde is four times that of monohydroxymethylation of acetaldehyde. The apparent energy and entropy of activation are 22·1 kcal. mole–1 and 14 e.u. for hydroxymethylation of acetaldehyde and 22·9 kcal. mole–1 and 17 e.u. for hydroxymethylation of β-hydroxypropionaldehyde. A probable mechanism involving an attack of conjugate base of acetaldehyde on free formaldehyde is suggested and discussed.