Question

Consider the following statements:
[(A)] Propanal and propanone are functional isomers
[(B)] Ethoxyethane and methoxypropane are metamers
[(C)] But-2-ene shows optical isomerism
[(D)] But-1-ene and but-2-ene are functional isomers
[(E)] Pentane and 2,2-dimethylpropane are chain isomers The correct statements are:

• A. A, B, D only
• B. B, C, D only
• C. A, B, E only
• D. A, B, D, E only

Hint:

To identify types of isomerism:
Functional isomers differ in functional groups
Metamers differ in alkyl groups around a polyvalent atom
Optical isomerism requires chirality
Positional isomerism involves change in position of functional group or double bond

Answer 1

The Correct Option is C

[(A)] Correct — Propanal (aldehyde) and propanone (ketone) have the same molecular formula but different functional groups.
[(B)] Correct — Ethoxyethane and methoxypropane are ethers differing in alkyl group distribution, hence metamers.
[(C)] Incorrect — But-2-ene shows geometrical (cis–trans) isomerism, not optical isomerism.
[(D)] Incorrect — But-1-ene and but-2-ene are positional isomers, not functional isomers.
[(E)] Correct — Pentane and 2,2-dimethylpropane differ in carbon chain arrangement, hence chain isomers.