Question

what is the name of this hydrocarbon? 1 - methylbutane 2 - methylbutane 2 - methylpropane 3 - methylpropane

Explanation:

1. First, count the longest - carbon chain. Here, the longest carbon - chain has 4 carbon atoms, so the parent alkane is butane.
2. Then, identify the position of the methyl group. The methyl group ($-CH_3$) is attached to the second carbon atom of the butane chain. According to IUPAC nomenclature rules for alkanes, when a methyl group is attached to the second carbon of a butane chain, the name is 2 - methylbutane.

Answer:

B. 2 - methylbutane