Why in Nucleophilic addition-elimination reactions,does the #C=O# bond break when the nucleophile is added and not the#C-CL# bond ?

Question

Ellie Adams · Accepted Answer

I take it you refer to nucleophilic attack on an #"acyl halide"#?

#"Reaction: " Nu^(-) + Cl(O=)CRrarr(Nu)(""^(-)O)(Cl)CRrarr Nu(O=)CR +Cl^-# The carbonyl is presumed to stabilize the negative charge of the nucleophile, presumably by resonance. The ipso carbon is thus 4-coordinate, and we could trap such an intermediate by quenching with, say, #Me_3SiCl# to give #(Nu)(Me_3SiO)(Cl)CR#. Does that answer your question?

Isaac Aronson · Answer

undefined In nucleophilic addition-elimination reactions, the C=O bond breaks because oxygen is more electronegative than carbon, making the carbonyl carbon partially positive. This partial positive charge makes it susceptible to attack by the nucleophile. Additionally, breaking the C=O bond allows the oxygen to accommodate the new bonds formed during the reaction.