Question

In the following reaction
${C_6}{H_5}C{H_2}Br\xrightarrow[{{H_3}{O^ + }}]{{Mg,ether}}X$,
The product ‘X’ is
(1) ${C_6}{H_5}C{H_2}OC{H_2}{C_6}{H_5}$
(2) ${C_6}{H_5}C{H_2}OH$
(3) ${C_6}{H_5}C{H_3}$
(4) ${C_6}{H_5}C{H_2}C{H_2}{C_6}{H_5}$

Answer 1

This reaction is an example of Grignard reaction in which we use Grignard reagent. Basically, Grignard reagents are haloalkanes or compounds with halogen atoms bonded to $s{p^3}$ or $s{p^2}$ hybridized carbon atoms. It reacts with magnesium metal to form organo-magnesium halides and Grignard reagents which are highly reactive organometallic reagents produced by treating alkyl or aryl halide with magnesium metal in presence of an anhydrous ether.
For example, they undergo trans-metallation with cadmium chloride to form dialkyl cadmium. We can write the chemical equation for the above chemical reaction as,
$2RMgX + CdC{l_2} \to {R_2}Cd + 2MgXCl$
Where, R represents alkyl or aryl groups.

Complete answer:
We have remembered that the grignard reaction is a chemical reaction in which alkyl, allyl, vinyl or aryl-magnesium halides are added to a carbonyl group in aldehyde or ketone. Hence, this reaction results in forming carbon-carbon bonds.
We can write the completed reaction as,

Now we can discuss about the mechanism of this reaction as,
Stage-1: Formation of new alkyl magnesium compound

In the presence of ether, $Mg$ will react with $Br$ to form an unstable magnesium compound.
Stage-2: Hydrolysis
The new formed compound is quite unstable and it will react with ${H_3}{O^ + }$ to form a benzene alkyl compound –

The ${H^ + }$ will react with $C{H_2}$ to form Methyl benzene and $O{H^ - }$ will react with $MgBr$ to form $MgBrOH$.
The resultant compound which is Methyl benzene can be written as ${C_6}{H_5}C{H_3}$.
Therefore, option 3 is correct.

Note:
With the help of this Grignard reagent we can prepare many organic compounds. Grignard reagents react with carbonyl carbon and ester yields corresponding alcohols.
In industries, Grignard reagent is used to produce Tamoxifen, used to cure cancer.