Question

The general order of reactivity of carbonyl compounds for nucleophilic addition reactions is 

(a) H₂C = O > R₂C = O > Ar₂C = O > RCHO > ArCHO 

(b) H₂C = O > RCHO> R₂C = O > ArCHO > Ar₂C = 0 

(c) ArCHO > Ar₂C = O > RCHO > R₂C = O > H₂C = O 

(d) Ar₂C = O > R₂C = O > ArCHO > RCHO > H₂C = O

Answer 1

(b) H₂C = O > RCHO> R₂C = O > ArCHO > Ar₂C = 0 

An aryl group, due to -I effect is expected to speed up the reacton, however, due to resonance it stabilizes the reactant very much and thus causes net deactivation.