Which compound is formed when a secondary alcohol is oxidized?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Ketone
Oxidation of an alcohol removes the H of the −OH group and an H from the carbon carrying it, forming a C=O group. The product depends on how many hydrogens that carbon has:
Primary alcohol (\( \ce{RCH2OH} \)) → aldehyde, and further to carboxylic acid.
Secondary alcohol (\( \ce{R2CHOH} \)) → ketone; the carbonyl carbon now carries two alkyl groups and no H, so it is not oxidised further under normal conditions.
Tertiary alcohol (\( \ce{R3COH} \)): no H on the carbinol carbon, so no oxidation under normal conditions.
\( \displaystyle \ce{CH3CH(OH)CH3} \xrightarrow{\ce{CrO3}} \ce{CH3COCH3} \)
Why the other options are incorrect
Option (2) Aldehyde — Incorrect. An aldehyde is formed by oxidation of a primary alcohol.
Option (3) Alkene — Incorrect. An alkene is formed by dehydration (loss of water, e.g. with conc. \( \ce{H2SO4} \)), not by oxidation.
Option (4) Carboxylic acid — Incorrect. Carboxylic acids come from oxidation of primary alcohols (through the aldehyde); a secondary alcohol gives an acid only by cleavage of C–C bonds under drastic conditions.
NCERT (2026-27 edition):
Chemical Reactions – “… 4. Oxidation: Oxidation of alcohols involves the formation of a carbon-oxygen double bond with cleavage of an O-H and C-H bonds. Such a cleavage and formation of bonds occur in oxidation reactions. These are also known as dehydrogenation reactions as these involve loss of dihydrogen from an alcohol molecule. Depending on the oxidising agent used, a primary alcohol is oxidised to an aldehyde which in turn is oxidised to a carboxylic acid. … Secondary alcohols are oxidised to ketones by chromic anhyride (CrO3). Tertiary alcohols do not undergo oxidation reaction.”