2025 O Level Chem P1 Q35 — Organic Chemistry / Isomers Solution
Question
Pent-2-ene has the structure CH₃CH=CHCH₂CH₃. Four other hydrocarbons are shown. Which hydrocarbons are structural isomers of pent-2-ene?
Correct answer: B
Video Solution
Explanation
Answer: B. Structural isomers have the same molecular formula but different arrangements of atoms. Pent-2-ene has the molecular formula \(\text{C}_5\text{H}_{10}\) (5 carbons, 10 hydrogens — an alkene).
Check each structure's molecular formula:
Structure 1 (3-methylbut-1-ene): C₅H₁₀ ✓
Structure 2 (3-methylpent-2-ene): C₆H₁₂ ✗ (one carbon too many)
Structure 3 (2-methylbut-1-ene): C₅H₁₀ ✓
Structure 4 (pent-1-ene): C₅H₁₀ ✓
Structures 1, 3 and 4 share the molecular formula with pent-2-ene → option B.
Get the Sec 3 / Sec 4 recording package
Every O Level Pure Chemistry TYS MCQ solution video, plus full Sec 3 / Sec 4 topic recordings.
Find out more