NCERT MCQ Solutions for Class 12 Chemistry Chapter 7 Alcohols, Phenols and Ethers

Alcohols are formed when a hydrogen atom in an aliphatic hydrocarbon is replaced by an –OH group.

Phenol contains an –OH group directly attached to a carbon atom of an aromatic system. This carbon is sp² hybridized.

The classification defines primary alcohols as those where the –OH group is attached to a primary carbon atom.

Alcohols with an –OH group bonded to an sp² carbon of a C=C double bond as vinylic alcohols.

Ethers are classified as simple or symmetrical if the alkyl or aryl groups attached to the oxygen atom are the same, like diethyl ether.

According to IUPAC rules described, the parent chain is propane and the –OH group is on carbon 2, hence Propan-2-ol.

Common names for dihydroxy derivatives of benzene, listing Benzene-1,4-diol as Hydroquinone or quinol.

The IUPAC system regards ethers as hydrocarbon derivatives where H is replaced by –OR or –OAr. The larger R group is chosen as the parent hydrocarbon.

In the acid-catalyzed hydration of unsymmetrical alkenes, the addition takes place in accordance with Markovnikov’s rule.

The alcohol formed via hydroboration–oxidation looks as if water was added to the alkene opposite to Markovnikov’s rule.

Reduction of aldehydes yields primary alcohols, while ketones give secondary alcohols.

Grignard reagents react with ketones to produce tertiary alcohols after hydrolysis.

The commercial production of phenol from cumene, involving oxidation to cumene hydroperoxide followed by treatment with dilute acid.

The high boiling points of alcohols and phenols mainly to the presence of intermolecular hydrogen bonding, which is absent in ethers and hydrocarbons.

Electron-releasing alkyl groups decrease acid strength. Therefore, the order is Primary > Secondary > Tertiary.

The greater acidity of phenols by highlighting the resonance stabilization of the phenoxide ion, where the negative charge is delocalized over the aromatic ring, making it more stable than the localized charge on an alkoxide ion.

The reaction of alcohols/phenols with carboxylic acids, acid chlorides or acid anhydrides to form esters is termed esterification.

The relative ease of dehydration follows the order Tertiary > Secondary > Primary, related to the stability of the intermediate carbocations.

The Reimer–Tiemann reaction as introducing a –CHO group at the ortho position of the benzene ring when phenol reacts with chloroform in the presence of sodium hydroxide.

Williamson synthesis is described as the reaction of an alkyl halide with a sodium alkoxide (R–X + R′–ONa → R–O–R′ + NaX).