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

Analysis

To solve this, we need to look at the molecular structure and classification of the two compounds: 2-methylpropane and butane.

Concept Explanation

1. Molecular Formula: • Butane: This is a straight-chain alkane with 4 carbon atoms. Its formula is $C_4H_{10}$. • 2-methylpropane: This is a branched-chain alkane (isobutane). It also has 4 carbon atoms ($3$ in the main chain + $1$ in the methyl group). Its formula is also $C_4H_{10}$.
2. Homologous Series: A homologous series is a group of organic compounds with the same general formula and similar chemical properties. Both butane and 2-methylpropane are alkanes (general formula $C_nH_{2n+2}$).
3. Isomerism: Since they have the same molecular formula but different structural arrangements, they are structural isomers.

Step-by-Step Solution

• Option A: Both compounds have 4 carbon atoms. Therefore, they do not have a different number of carbon atoms. This statement is false.
• Option B: Both are alkanes. Since they belong to the same family of hydrocarbons, they are members of the same homologous series. This statement is true.
• Option C: Boiling points depend on surface area and intermolecular forces. Straight-chain alkanes (butane) have a larger surface area than branched-chain alkanes (2-methylpropane), leading to stronger Van der Waals forces. Thus, they have different boiling points. This statement is false.
• Option D: Isomers in the same homologous series generally exhibit very similar chemical properties because they share the same functional groups. This statement is false.

Conclusion

Exam Tip: Whenever you see two compounds that are isomers of each other, always remember that they will share the same molecular formula and belong to the same homologous series, but they will differ in their physical properties (like boiling point) due to their different shapes!