Reactivity towards NAR is directly proportional to positive charge on SP2-C [Carbonyl compound >C=O]

Reactivity towards NAR  ∝  +ve charge on SP²C

Reactivity order towards NAR 

CCl₃—HC^{+ δ}=O^{- δ}  >  H₂C^+δ=O^{- δ}   >  CH₃—HC^{+ δ}=O^{- δ}  >  CH₃CH₂—HC^+δ=O^{- δ}

Reason:-
-->More +ve charge on carbon atom

-->More recative towards NAR