`C_(6)H_(5)-CHO` `CH_(3)CHO` `HCHO` All the equally reactive
Solution :AMONG Carbonyl Compounds, reactivity decrease with INCREASE in alkyl groups as alkyl groups `(+I` effect) decrease positive character on C-atom. Thus, the correct order of reactivity is, `HCHO gt CH_(3)CHO gt C_(6)H_(5)CHO`