JEE MainChemistryAmines
The correct sequence of reagents to synthesize 3,5-dibromotoluene from p -toluidine is:
Options
- A(i) Br ₂ (aq) (ii) NaNO ₂ , HCl, 273 K (iii) H ₃ PO ₂ , H ₂ O
- B(i) NaNO ₂ , HCl, 273 K (ii) CuBr, HBr (iii) Br ₂ , FeBr ₃
- C(i) Br ₂ (aq) (ii) NaNO ₂ , HCl, 273 K (iii) CuBr, HBr
- D(i) ( CH ₃ CO )₂ O (ii) Br ₂ , FeBr ₃ (iii) H ₃ O ^+ (iv) NaNO ₂ , HCl, 273 K (v) H ₃ PO ₂ , H ₂ O
Correct answer
A. (i) Br ₂ (aq) (ii) NaNO ₂ , HCl, 273 K (iii) H ₃ PO ₂ , H ₂ O
Step-by-step solution
To synthesize 3,5-dibromotoluene from p -toluidine, we must place two bromine atoms meta to the methyl group. This cannot be achieved by direct bromination of toluene or p -bromotoluene due to the ortho/para directing nature of the methyl and bromo groups. 1. The strongly activating - NH ₂ group in p -toluidine directs electrophilic aromatic substitution to its ortho positions. Treatment with aqueous bromine ( Br ₂ (aq) ) yields 2,6-dibromo-4-methylaniline. 2. To obtain the target meta-substituted product, the - NH