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.
Oxidation of alcohols involves formation of carbon oxygen double bond with
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Cleavage of O-H bond and C-H bond
When an alcohol is oxidised, the carbon carrying the –OH group becomes the carbon of a C=O group. For this, two hydrogen atoms are removed: the hydrogen of the O–H group and a hydrogen on that same carbon (the α-hydrogen). So the O–H and C–H bonds both break, and the C=O bond forms in their place:
\( \displaystyle \ce{RCH2-OH} \xrightarrow{[\text{O}]} \ce{RCH=O + H2O} \)
Passing the vapour of a primary or secondary alcohol over heated copper at 573 K gives an aldehyde or a ketone in the same way:
\( \displaystyle \ce{RCH2OH} \xrightarrow{\ce{Cu},\ 573\ \text{K}} \ce{RCHO + H2} \)
A tertiary alcohol has no hydrogen on the carbon carrying –OH, so it does not undergo this oxidation.
Why the other options are incorrect
Option (1) Cleavage of an O-H bond — Incorrect. Breaking only the O–H bond gives an alkoxide ion or an ester (as with sodium or an acid chloride), not a C=O group.
Option (2) Cleavage of C-H bond — Incorrect. If the O–H bond stayed, the oxygen could not form a double bond with carbon.
Option (4) Cleavage of C-C bond — Incorrect. C–C bonds break only under strong conditions (for example hot \( \ce{KMnO4} \) on a tertiary alcohol), giving acids with fewer carbon atoms; this is not the normal oxidation.
NCERT (2026-27 edition):
Oxidation
