Question

Petroleum ether (Hydrocarbon Petroleum ether; a mixture of pentane, hexane…etc.) is not really an “Ether”. Petroleum ether and ether are two very different chemicals. State one advantage of using ether over the petroleum ether when preparing benzoic acid via Grignard reaction.

Answer 1

Preparation of phenyl magnesium bromide from bromo benzene & Mg metal using diethyl ether as the solvent under anhydrous conditions.

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Here diethyl ether used as a solvent because the lone pairs of electrons on oxygen help stabilize the partial +ve charge on Mg in the grignard reagent & facilitate its formation. It works as a solvent in nucleophilic addition reactions because the ether functional gp is unreactive with most reactants.

C6H5Br + Mg= C6H5MgBr

bromobenzene phenylmagnesium bromide

C6H5MgBr + CO2= C6H5COOH

benzoicacid   

it reacts with CO2 followed by hydrolysis.