JEE Main · 2008 · 27 Apr 2008 · Offline · Hydrocarbons

Phenol, when it first reacts with concentrated sulphuric acid and then with concentrated nitric acid, gives

(A)2,4,6-trinitrobenzene
(B)o-nitrophenol✓ Correct
(C)p-nitrophenol
(D)nitrobenzene

Answer: (B)

Solution

Concentrated sulphuric acid first sulphonates phenol, and because the bulky sulphonic acid group goes mainly to the para position it effectively blocks that site. Nitration with concentrated nitric acid then enters the ortho position, and in the course of the reaction the sulphonic acid group is hydrolysed off, so the product isolated is

o

-nitrophenol. The sulphonation thus serves as a temporary blocking step that steers the nitro group ortho.

JEE Main · 2008 · 27 Apr 2008 · Offline · Single correct option

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