The given reaction is an example of a Grignard reaction:
When chlorobenzene (C₆H₅Cl) reacts with Mg in ether, an intermediate is formed (C₆H₅MgCl).
Said intermediate then reacts with CO₂ producing a benzoic acid salt (C₆H₅CO₂X), this salt is then neutralized with dilute HCl producing benzoic acid (C₆H₅CO₂H).
