Question

Which of the following is the correct IUPAC name for the compound with the molecular formula \( C_5H_{12} \) that contains a branched chain with a methyl group attached to the second carbon of a butane chain?

• A. 2-Methylbutane
• B. 3-Methylbutane
• C. 2-Ethylpropane
• D. Pentane

Hint:

When naming branched alkanes, always choose the longest continuous chain as the parent chain and number it such that the substituent groups get the lowest possible numbers.

Answer 1

The Correct Option is A

The provided molecular formula is \( C_5H_{12} \), indicating an alkane with five carbon atoms. The structural identification proceeds as follows: 1. A four-carbon atom chain forms the base structure, identified as butane. 2. A methyl group (-\( CH_3 \)) is attached to the second carbon of this butane chain, resulting in a branched structure. According to IUPAC nomenclature, the parent chain (butane) must be numbered to assign the lowest possible locant to the substituent (methyl group). Therefore, the correct name for this compound is 2-methylbutane. The IUPAC name of the compound is \( \boxed{2 \, \text{Methylbutane}} \).