Question

Identify the major product formed from the following reaction:

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Aromatic amines first form diazonium salts with \(NaNO_2/HCl\) at \(273K\). Sandmeyer reaction replaces the diazonium group by halogen. The aryl halide then forms a Grignard reagent with \(Mg/dry\ ether\), and treatment with \(D_3O^+\) gives deuterated arene.

Answer 1

The Correct Option is A

Step 1: Diazotization of \(p\)-toluidine.
The given compound is \(p\)-toluidine, which contains \(-NH_2\) and \(-CH_3\) groups at para positions.
On treatment with \[ NaNO_2/HCl,\ 273K \] the \(-NH_2\) group is converted into a diazonium salt.
\[ p\text{-}CH_3C_6H_4NH_2 \rightarrow p\text{-}CH_3C_6H_4N_2^+Cl^- \]

Step 2: Sandmeyer reaction.
The diazonium salt reacts with \[ Cu_2Cl_2 \] and the diazonium group is replaced by chlorine.
Thus, the product formed is \[ p\text{-}CH_3C_6H_4Cl \] This compound is \(p\)-chlorotoluene.

Step 3: Formation of Grignard reagent.
On reaction with magnesium in dry ether, \[ p\text{-}CH_3C_6H_4Cl \] forms an aryl magnesium chloride compound.
\[ p\text{-}CH_3C_6H_4Cl + Mg \rightarrow p\text{-}CH_3C_6H_4MgCl \]

Step 4: Reaction with \(D_3O^+\).
Grignard reagents react with \(D_3O^+\) to give deuterated hydrocarbons.
Therefore, \[ p\text{-}CH_3C_6H_4MgCl + D_3O^+ \rightarrow p\text{-}CH_3C_6H_4D \] Thus, deuterium replaces the Grignard group position, which is para to the methyl group.

Step 5: Final conclusion.
The major product is \[ \boxed{p\text{-deuterotoluene}} \] Hence, the correct option is \[ \boxed{(1)} \]