Given two compounds with the molecular formula $C_4{H}_{10}$, one being n-butane and the other being isobutane, what is the relationship between these two compounds?

• A. They are identical compounds.
• B. They are constitutional isomers.
• C. They are diastereomers.
• D. They are enantiomers.

Answer: (B)

Verified step by step guidance

1. Identify the molecular formula of both compounds, which is \(C_4H_{10}\), indicating they are isomers of butane.
2. Recognize that n-butane is a straight-chain alkane, while isobutane (also called methylpropane) is a branched-chain alkane.
3. Understand that compounds with the same molecular formula but different connectivity of atoms are called constitutional (or structural) isomers.
4. Recall that diastereomers and enantiomers are types of stereoisomers, which have the same connectivity but differ in spatial arrangement; since n-butane and isobutane differ in connectivity, they cannot be stereoisomers.
5. Conclude that the relationship between n-butane and isobutane is that they are constitutional isomers.