Read the passage carefully and answer the questions based on the passage:
Alcohols are versatile compounds as they can act as both nucleophile and electrophiles. They undergo reactions based on cleavage of O-H and C-O bonds. The cleavage of O-H bond reflects the acidic character of alcohols. However they are weaker acids than water, phenol and carboxylic acids. Alkoxide ion formed by loss of proton from the OH group of alcohols react with water to form the corresponding conjugate acid-base pair. They act as Bronsted base due to presence of unshared electron pairs on oxygen. Both alcohols and phenol react with carboxylic acids, acid chlorides and anhydrides to form esters. The introduction of acetyl group in alcohols or phenol is known as acetylation. Alcohols react with hydrogen halides to form alkyl halides which form the basis of Lucas test. They also undergo acid catalyzed dehydration to form alkenes. Alcohols can be easily oxidized with variety of oxidizing agents. The nature of the product depends on the type of oxidizing agent and the nature of alcohol.
Pyridinium chlorochromate is used for:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Conversion of primary alcohol to aldehyde
Oxidation of a primary alcohol goes in two stages: first to an aldehyde, then to a carboxylic acid. Strong oxidising agents in water (acidified \( \ce{KMnO4} \)) take it all the way to the acid. To stop at the aldehyde, a mild oxidising agent in an anhydrous medium is needed.
Pyridinium chlorochromate (PCC), used in a non-aqueous solvent, is such a reagent: it stops at the aldehyde.
\( \displaystyle \ce{CH3-CH=CH-CH2OH} \xrightarrow{\text{PCC}} \ce{CH3-CH=CH-CHO} \)
So PCC is used for the conversion of a primary alcohol to an aldehyde.
Why the other options are incorrect
Option (1) Dehydration of primary alcohol — Incorrect. Dehydration (loss of water to give an alkene) needs a protic acid such as concentrated \( \ce{H2SO4} \) at about 443 K; PCC is an oxidising agent, not a dehydrating agent.
Option (3) Conversion of secondary alcohol to carboxylic acids — Incorrect. A secondary alcohol is oxidised to a ketone, not to a carboxylic acid; the carbon chain would have to break to give an acid.
Option (4) Conversion of Primary alcohols to carboxylic acids — Incorrect. This needs a strong oxidising agent such as acidified potassium permanganate; PCC stops at the aldehyde stage.
NCERT (2026-27 edition):
Oxidation – …
