Consider the following statements with reference to alcohols. Choose the correct statements.
(A) Dehydration of tertiary alcohols using Cu-metal at 573 K forms an alkene.
(B) p-Nitrophenol is steam volatile so it can be distilled over o-nitrophenol.
(C) Friedel-Crafts acylation of anisole forms 4-methoxyacetophenone as the major product.
(D) During esterification of an alcohol with a carboxylic acid in presence of an acid, removal of water is essential.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (C) and (D) only.
The statements test four different reactions of alcohols, phenols and ethers:
(A) Dehydration of tertiary alcohols using Cu-metal at 573 K forms an alkene. — Correct. Over heated copper, 1° alcohols are dehydrogenated to aldehydes and 2° alcohols to ketones, but a 3° alcohol has no H on the carbinol carbon, so it is dehydrated to an alkene.
\( \displaystyle \ce{(CH3)3C-OH} \xrightarrow{\ce{Cu},\ 573\ \mathrm{K}} \ce{(CH3)2C=CH2 + H2O} \)
(B) p-Nitrophenol is steam volatile so it can be distilled over o-nitrophenol. — Incorrect. o-Nitrophenol is steam volatile because of intramolecular hydrogen bonding. p-Nitrophenol has intermolecular hydrogen bonding, which associates its molecules, so it is not steam volatile.
(C) Friedel-Crafts acylation of anisole forms 4-methoxyacetophenone as the major product. — Correct. –\( \ce{OCH3} \) is an ortho/para directing group, and the para product is major because the ortho position is crowded.
\( \displaystyle \ce{C6H5OCH3 + CH3COCl} \xrightarrow{\text{anhyd. }\ce{AlCl3}} \text{4-methoxyacetophenone (major)} + \text{2-methoxyacetophenone} \)
(D) During esterification of an alcohol with a carboxylic acid in presence of an acid, removal of water is essential. — Correct. Esterification is reversible; water is removed as it forms to shift the equilibrium towards the ester.
\( \displaystyle \ce{RCOOH + R'OH <=> RCOOR' + H2O}\quad\text{(acid catalyst)} \)