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 molecular formula given is \( C_5H_{12} \), which corresponds to an alkane with 5 carbon atoms. To identify the structure, follow these steps: 1. The base chain has 4 carbon atoms, which corresponds to butane. 2. A methyl group (-\( CH_3 \)) is attached to the second carbon of the butane chain, making it a branched chain. The IUPAC naming convention dictates that the parent chain (butane) should be numbered such that the substituent (methyl group) gets the lowest possible number. Hence, the correct name for this compound is 2-methylbutane. Thus, the IUPAC name of the compound is \( \boxed{2 \, \text{Methylbutane}} \).