CBSE 2026 · Region 3 · Set 1 · Q30 · 4 marks

Alcohols have higher boiling points than other compounds, namely hydrocarbons, ethers and haloalkanes of comparable molecular masses. On oxidation, primary alcohols yield aldehydes with mild oxidizing agents and carboxylic acids with strong oxidizing agents. Secondary alcohols yield ketones on oxidation while tertiary alcohols are resistant to oxidation. Ethers may be prepared by dehydration of alcohols and Williamson synthesis. The C - O bond in ethers can be cleaved by hydrogen halides. The presence of - OH group in phenols activates the aromatic ring towards electrophilic substitution and directs the incoming group to ortho and para positions due to resonance effect. In presence of NaOH , phenol generates phenoxide ion which is even more reactive than phenol. Thus, in alkaline medium, phenol undergoes Kolbe's reaction.

(a)

Name the reagents used in the following reactions :

(i)

Oxidation of a primary alcohol to aldehyde

(ii)

Oxidation of a primary alcohol to carboxylic acid []

(b)

Write the reaction involved in Kolbe's reaction.

(c)

(i)OR(c)

Why are tertiary alcohols resistant to oxidation ?

CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.