Identify \(S\) and \(T\):
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (D) and (B)
Follow the sequence one reaction at a time and name each product.
First, benzene is converted to benzaldehyde by the Gattermann-Koch reaction (CO and HCl with anhydrous AlCl3/CuCl). Then KMnO4 oxidises the –CHO group to –COOH. So P is benzoic acid, structure (C).
\( \ce{C6H6 + CO + HCl} \xrightarrow{\text{anhyd. AlCl}_3/\text{CuCl}} \ce{C6H5CHO + HCl} \)
\( \ce{C6H5CHO + [O]} \xrightarrow{\ce{KMnO4}} \ce{C6H5COOH} \)
Thionyl chloride replaces the –OH of the acid by Cl. So Q is benzoyl chloride, structure (E).
\( \ce{C6H5COOH + SOCl2 -> C6H5COCl + SO2 ^ + HCl ^} \)
Methanol reacts with the acid chloride to give an ester. So R is methyl benzoate, structure (A).
\( \ce{C6H5COCl + CH3OH -> C6H5COOCH3 + HCl} \)
LiAlH4 reduces the ester to two alcohols: the acyl part becomes a primary alcohol and methanol is set free. So S is benzyl alcohol, structure (D).
\( \ce{C6H5COOCH3} \xrightarrow{\text{(i) LiAlH}_4\text{, (ii) H}_3\text{O}^+} \ce{C6H5CH2OH + CH3OH} \)
Ammonia reacts with benzoyl chloride (Q) to give the amide. So T is benzamide, structure (B).
\( \ce{C6H5COCl + 2NH3 -> C6H5CONH2 + NH4Cl} \)