• Nitro groups are reduced to amino groups using active metals in acid (\( Fe/HCl \)).
• Primary aromatic amines undergo diazotization to form stable diazonium salts at low temperatures.
• Diazonium groups can be replaced by hydrogen (deamination) using mild reducing agents like phosphinic acid (\( H_{3}PO_{2} \)). Step 1: Formation of A (Reduction)
The nitro group in 2-bromo-4-nitrotoluene is reduced to an amino group. Structure A:3-bromo-4-methylaniline (or 2-bromo-4-aminotoluene).
Step 2: Formation of B (Diazotization)
Reaction with \( NaNO_{2} + HCl \) at \( 0-5^{\circ}C \) converts the \( -NH_{2} \) group into a diazonium chloride group (\( -N_{2}^{+}Cl^{-} \)). Structure B:3-bromo-4-methylbenzenediazonium chloride.
Step 3: Formation of C (Deamination)
Treatment with hypophosphorous acid (\( H_{3}PO_{2} \)) and water replaces the \( -N_{2}^{+}Cl^{-} \) group with a Hydrogen atom. The byproduct is phosphorous acid (\( H_{3}PO_{3} \)). Structure C:2-bromotoluene.
The final answer is A: 3-bromo-4-methylaniline, B: 3-bromo-4-methylbenzenediazonium chloride, C: 2-bromotoluene.
