JEE Main · 2021 · 17 Mar 2021 · Shift 1 · Haloalkanes and Haloarenes

The above reaction requires which of the following reaction conditions?

(A) $573 K, 300 atm$
(B) $623 K, Cu, 300 atm$
(C) $573 K, Cu, 300 atm$
(D) $623 K, 300 atm$ ✓ Correct

Answer: (D)

Solution

The scheme is the conversion of chlorobenzene into sodium phenoxide by aqueous sodium hydroxide, the Dow process. A chlorine lone pair is delocalised into the ring, which gives the carbon–chlorine bond partial double-bond character and shortens it, and the

π

electron cloud of the ring also repels the approaching hydroxide. Both effects make the displacement extremely slow under ordinary conditions, so the reaction is forced through by heat and pressure alone, with no metal catalyst. The conditions required are 623 K and 300 atm.

JEE Main · 2021 · 17 Mar 2021 · Shift 1 · Single correct option

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