The product(s) of the following reaction sequence is(are) (see structure) i) Acetic anhydride/pyridine ii) $\mathrm{KBrO}_{3}/\mathrm{HBr}$ iii) $\mathrm{H}_{3}\mathrm{O}^{+}$, heat iv) $\mathrm{NaNO}_{2}/\mathrm{HCl}$, 273-278 K v) $\mathrm{Cu}/\mathrm{HBr}$

JEE Advanced · 2016 · 22 May 2016 · Paper 1 · Compounds Containing Nitrogen

The product(s) of the following reaction sequence is(are)

(see structure)

i) Acetic anhydride/pyridine
ii)

KBrO_{3} / HBr

iii)

H_{3} O^{+}

, heat
iv)

NaNO_{2} / HCl

, 273-278 K
v)

Cu / HBr

(A)(see structure)
(B)(see structure)
✓ Correct
(C)(see structure)
(D)(see structure)

Answer: (B)

Solution

Starting with aniline: (i) acetylation protects the amino group as acetanilide; (ii) bromination occurs at ortho and para positions (acetamido is ortho/para directing), giving 4-bromoacetanilide as major product; (iii) hydrolysis removes the acetyl group, giving 4-bromoaniline; (iv) diazotization converts the amino group to diazonium salt; (v) Sandmeyer reaction replaces the diazonium group with Br, giving 1,4-dibromobenzene. Thus, the product is (B).

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JEE Advanced · 2016 · 22 May 2016 · Paper 1 · Compounds Containing Nitrogen

Solution

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