Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reactions:    
Benzaldehyde, p-Tolualdehyde, p-Nitrobenzaldehyde, Acetophenone.

The +I effect is more in ketone than in aldehyde. Hence, acetphenone is the least reactive in nucleophilic addition reaction. Among aldehyde, the +l effects is the highest in p-tolualdehyde because of the presence of the electron donating –CH₃ group and the lowest in p-nitro bezaldehyde because of the presence of the electron withdrawing –NO₂ group. Hence, the increasing order of the reactivates of the given as;