Patent ID: 7368612

Claim:
A method of producing high-purity hydroxypivalaldehyde and/or dimer thereof, comprising: reacting isobutyl aldehyde with formaldehyde in a presence of a basic catalyst; distilling off a low boiling point component including unreacted isobutyl aldehyde to obtain an aqueous solution; adding a diluent to the aqueous solution; cooling the aqueous solution to crystallize at least one of the hydroxypivalaldehyde and the dimer thereof; and subjecting the aqueous solution to a solid-liquid separation, followed by washing with an organic solvent and/or water to obtain at least one of the high-purity hydroxypivalaldehyde and the dimer thereof, wherein the aqueous solution containing at least one of the hydroxypivalaldehyde and the dimer thereof obtained by distilling the low boiling point component off is diluted by adding the diluent and a basic compound, so that the concentration of at least one of the hydroxypivalaldehyde and the dimer thereof becomes 5 to 23% by mass, the concentration of formaldehyde becomes 0.2 to 2.5% by mass, and the pH value becomes 5.0 or more, then the solution is crystallized at a temperature of 20 to 45° C., consequently the crystal of at least one of the hydroxypivalaldehyde and the dimer thereof is subjected to the solid-liquid separation and washed.