Which of the following statements is true about 2-methylpropane and butane

Analyze the question: We are comparing 2-methylpropane and butane. First, write their structures.

• Butane: CH₃CH₂CH₂CH₃ (straight chain), formula C₄H₁₀
• 2-methylpropane (isobutane): (CH₃)₂CHCH₃ (branched chain), formula C₄H₁₀

They have the same molecular formula but different structures, so they are structural (chain) isomers.

Concept: Isomers share the same molecular formula and the same functional group, but their structures differ. Because both are alkanes, they have similar chemical properties. Their physical properties, such as boiling point, differ slightly.

Checking each option:

• A. Not members of the same homologous series: False. Both are alkanes with the general formula CₙH₂ₙ₊₂.
• B. Same boiling point: False. Butane boils at about 0°C, while 2-methylpropane boils at about -12°C. Branching reduces the surface area for van der Waals forces, which lowers the boiling point.
• C. Different number of carbon atoms: False. Both have 4 carbons.
• D. Same chemical properties: True. Both are saturated alkanes with the same functional group (C–C and C–H single bonds). They undergo the same reactions: combustion and substitution with halogens.

Answer: D

Tip: For isomers, remember this: same formula, same chemical properties (same functional group), different physical properties. Branched isomers have lower boiling points than straight-chain ones.