Question

The compound X is:
${C_6}{H_6} + CO + HCl\xrightarrow{{AnhydrousAlC{l_3}}}X + HCl$
A.${C_6}{H_5}C{H_3}$
B.${C_6}{H_5}C{H_2}Cl$
C.${C_6}{H_5}CHO$
D.${C_6}{H_5}COOH$

Answer 1

Benzene is an aromatic compound. Aromatic compounds undergo substitution reactions easily. Benzene undergoes electrophilic substitution reaction when treated with carbon monoxide and hydrochloric acid in presence of anhydrous aluminum trichloride to give benzaldehyde.

Complete answer:
Aromatic compounds are the compounds that are cyclic, planar, conjugation of pi electrons and obeying Huckel’s rule. Huckel’s rule is given by $\left( {4n + 2} \right)\pi$ electrons, where n is a whole number. Benzene obeys all the above conditions and can be called an aromatic compound. Aromatic compounds undergo substitution reactions.
Benzene undergoes electrophilic substitution reaction when treated with carbon monoxide and hydrochloric acid in presence of anhydrous aluminum chloride to give benzaldehyde. The hydrogen atom in benzene is substituted by the aldehyde group.
This reaction is known as the Gattermann Koch reaction. Anhydrous aluminum trichloride is a Lewis acid as it accepts an electron pair. In this reaction anhydrous aluminum trichloride acts as a catalyst.
The reaction will be as follows:
${C_6}{H_6} + CO + HCl\xrightarrow{{AnhydrousAlC{l_3}}}{C_6}{H_5}CHO + HCl$
The product formed in the above reaction is benzaldehyde and hydrochloric acid. Benzaldehyde is the derivative of benzene and also an aromatic compound. As the aldehyde group is attached to the benzene ring the compound can be called benzaldehyde.
The compound X is benzaldehyde.
Hence option C is the correct answer.

Note:
In the above reaction the product is benzaldehyde, it was prepared by the Gattermann Koch reaction. The catalyst is aluminum trichloride. Sometimes, copper chloride can be used as a catalyst. The hydrogen cyanide can also be used in place of carbon monoxide for the preparation of aldehydes.