(1) Isobutyraldehye + formaldehyde + NaOH/H2O → II (C5H10O2)

what is the structure?

2 answers

(CH3)2CHCHO will react with formadehyde under basic conditions to give

(CH3)2C(CH2OH)(CHO)

Normally during this reaction the alcohol would be expected to dehydrate but there is no second proton adjacent to the CHO group

For mechanism see
http://en.wikipedia.org/wiki/Aldol_reaction
its difficult recognizing what rxn to use