Nitrobenzene is converted into 1,3-dibromobenzene. Which sequence works?

A(i) $Br X_{2} / FeBr X_{3}$ ; (ii) $Sn / HCl$ ; (iii) $NaNO X_{2}$ / dil. $HCl$ , 273-278 K; (iv) $CuBr / HBr$
B(i) $Sn / HCl$ ; (ii) $NaNO X_{2}$ / dil. $HCl$ , 273-278 K; (iii) $CuBr / HBr$ ; (iv) $Br X_{2} / FeBr X_{3}$
C(i) $Br X_{2} / FeBr X_{3}$ ; (ii) $Sn / HCl$ ; (iii) $NaNO X_{2}$ / dil. $HCl$ , 273-278 K; (iv) $H X_{3} PO X_{2}$
D(i) $Sn / HCl$ ; (ii) $Br X_{2}$ water; (iii) $NaNO X_{2}$ / dil. $HCl$ , 273-278 K; (iv) $H X_{3} PO X_{2}$

Answer: A

The meta-directing

NO X_{2}

must be used for the first bromination: nitrobenzene gives 1-bromo-3-nitrobenzene, and

Sn / HCl

gives 3-bromoaniline. Diazotisation and Sandmeyer bromination then give 1,3-dibromobenzene. Brominating after the amine or bromobenzene stage gives ortho/para products, and

H X_{3} PO X_{2}

in place of

CuBr

would give bromobenzene or 1,3,5-tribromobenzene.

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Nitrobenzene is converted into 1,3-dibromobenzene. Which sequence works?

Answer: A

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