(a) Account for the following:
(i) o-Nitrophenol is more steam volatile than p-nitrophenol.
(ii) t-Butyl chloride on heating with sodium methoxide gives 2-methylpropene instead of t-butyl methyl ether.
(b) Write the reactions involved in:
(i) the Reimer–Tiemann reaction
(ii) Friedel–Crafts alkylation of phenol
(c) Give a simple chemical test to distinguish between ethanol and phenol.
(i) o-Nitrophenol is more steam volatile than p-nitrophenol.
(ii) t-Butyl chloride on heating with sodium methoxide gives 2-methylpropene instead of t-butyl methyl ether.
(b) Write the reactions involved in:
(i) the Reimer–Tiemann reaction
(ii) Friedel–Crafts alkylation of phenol
(c) Give a simple chemical test to distinguish between ethanol and phenol.
Solution
(a)(i) The o-isomer chelates internally (–OH···ON–), so its molecules stay single and escape with steam; p-nitrophenol hydrogen-bonds between molecules and is retained.
(ii) With the hindered t-butyl chloride, methoxide acts as a base, not a nucleophile — E2 elimination gives (CH)C=CH rather than the S2 ether.
(b)(i)
(ii)
(c) Neutral FeCl: phenol → violet colour; ethanol → none.
(ii) With the hindered t-butyl chloride, methoxide acts as a base, not a nucleophile — E2 elimination gives (CH)C=CH rather than the S2 ether.
(b)(i)
(ii)
(c) Neutral FeCl: phenol → violet colour; ethanol → none.
CBSE Class 12 Board · Subjective