Question

Why is `CO_2` a lewis acid?

Answer 1

Is it not an electron pair acceptor....?

Explanation:

Still the best way of making a `C-C` bond is to pour a Grignard reagent onto dry ice as shown...

`R-MgX + CO_2(s) stackrel("dry ether")rarr RCO_2^(-) + MgX_2(s)darr`

The carboxylate ion can be reprotonated by water work-up to give `RCO_2H`... And here carbon dioxide has accepted the formal pair of electrons conceived to be localized on the Grignard reagent...