Question

Why does halogen substitution on a carbonyl, deactivate the carbonyl?

Answer 1

It does.......? Perhaps not..

Explanation:

The standard representation of the ipso carbon in an acid halide is as................

`R-stackrel(delta+)C(=stackrel(delta-)O)X`, sometimes, to illustrate this polarity we MIGHT write:

`R-stackrel(+)C(-stackrel(-)O)X`

And this is thus liable to react with a nucleophile, (with a formal negative charge),

`RC(=O)X + Nu^(-) rarr RC(=O)Nu + X^-`,

or with 2 equiv of nucleophile:

`RC(=O)X + 2Nu^(-) rarr RC(-O)^(-)Nu_2 + X^-`.