Question

Consider the following statements:
(A) Propanal and Propanone are functional isomers.
(B) Ethoxyethane and methoxypropane are metameres.
(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.
In the light of the above statements, choose the correct option.

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

Hint:

For isomerism, functional isomers differ in functional groups, metameres have different alkyl groups attached to the same functional group, and chain isomers differ in the carbon chain arrangement.

Answer 1

The Correct Option is C

To determine the correct answer, let's analyze each of the given statements:

1. (A) Propanal and Propanone are functional isomers.
   • Propanal (CH₃CH₂CHO) and Propanone (CH₃COCH₃) have the same molecular formula (C₃H₆O) but differ in the functional groups. Propanal is an aldehyde and Propanone is a ketone.
   • Thus, they are functional isomers.
2. (B) Ethoxyethane and methoxypropane are metameres.
   • Ethoxyethane (C₂H₅-O-C₂H₅) and methoxypropane (CH₃-O-CH₂CH₂CH₃) have the same molecular formula (C₄H₁₀O) and belong to the same homologous series (ethers), but differ in the alkyl groups attached to the oxygen atom.
   • This type of isomerism is called metamerism.
3. (C) But-2-ene shows optical isomerism.
   • Optical isomerism typically occurs in chiral molecules that have an asymmetrical carbon atom.
   • But-2-ene is symmetrical and does not have chiral centers, thus it does not exhibit optical isomerism. It can, however, exhibit geometrical (cis-trans) isomerism.
4. (D) But-1-ene and But-2-ene are functional isomers.
   • But-1-ene and But-2-ene are both alkenes with the same molecular formula (C₄H₈) but differ in the position of the double bond.
   • This is an example of position isomerism, not functional isomerism.
5. (E) Pentane and 2,2-dimethylpropane are chain isomers.
   • Pentane (CH₃(CH₂)₃CH₃) and 2,2-dimethylpropane (C(CH₃)₄) have the same molecular formula (C₅H₁₂), but differ in the carbon chain arrangement.
   • This is an example of chain isomerism.

Based on this analysis, the correct statements are (A), (B), and (E). Therefore, the correct answer is: A, B, E only.