Q1. [1] § 4.2.2 Chains, Branches and Rings
Given below are the structures of some hydrocarbons. Select the two structures which are related to each other from the given options :
(i) H–C–C–C=C–H (but-1-ene type structure)
(ii) H–C–C–C–C–H (butane type structure)
(iii) H–C–C–C–C–H (another butane-type structure)
(iv) Cl–C–C–C=C–H (chloro-but-1-ene type structure)
- (A) (i) and (iv)
- (B) (ii) and (iv)
- (C) (ii) and (iii)
- (D) (i) and (iii)
Previously asked in CBSE board exam
2025 31/3/1 Q4
Generated by claude-sonnet-4-6 · 2026-06-15 06:47 · grounding rag
Model Answer
(C) (ii) and (iii)
Structures (ii) and (iii) both have the molecular formula C₄H₁₀ (butane) but different carbon skeletons — they are structural isomers.
Explanation
Structural isomers have the same molecular formula but different structures. (ii) is n-butane (straight chain) and (iii) is isobutane (branched chain) — both C₄H₁₀. Structure (i) is but-1-ene (C₄H₈, unsaturated), and (iv) has a Cl substituent, making it a haloalkane with a different molecular formula. Examiners expect you to identify identical molecular formula + different structure = structural isomers.
If a question refers to an image, map, graph or diagram that is not shown here, find the actual CBSE question paper on the CBSE website:
cbse.gov.in.