A thick colorless or pale-yellow liquid, it is a versatile and valuable intermediate with diverse impacts.

Acetaldehyde dimerizes upon treatment with aqueous sodium hydroxide:[2] This is the prototypical aldol reaction.

Distillation of 3-hydroxybutanal is sufficiently forcing to effect this conversion:[2] Hydrogenation of 3-hydroxybutanal gives 1,3-butanediol: This diol is a precursor to 1,3-butadiene, precursor to diverse polymers.

Polymerization of 3-hydroxybutanal is also spontaneous, but can be stopped with the addition of water.

Aldol has been used in making perfumes and in ore flotation.