What is the action of dil NaOH on ethanal (acetaldehyde) ? Name the reaction

Explanation

Acetaldehydes undergo self condensation in presence of NaOH to from `beta` - hydroxy aldehydes.
`CH_(3)overset(O)overset("||")(C )H+H-CH_(2)CHO overset(H overset(..)(O)^(-))rarr underset(("acetaldol"))underset("3 - hydroxy butanal")(CH_(3)-overset(" OH")overset("|")("C")H-CH_(2)-CHO)`
Name of the reaction is aldol condensation.