Video narration
Staring at a haloalkane structure and still unsure which carbon chain to choose, where to start, or how to build the name? Think of a classroom row: choose the row, number from the end nearest the marked seat, then add its label. First, find the longest continuous carbon chain. That becomes the parent chain, and its carbon count gives the alkane name. Second, number from the end nearest the halogen. This prevents numbering from the wrong end. The number attached to the halogen is its locant-the position number. Third, combine the locant, the halogen prefix, and the parent alkane. For chlorine, the prefix is chloro-. Now use CH3-CH(Cl)-CH2-CH3. The continuous chain has four carbons, so the parent is butane. Numbering from the left puts chlorine on carbon 2; from the right, it would be 3, so choose the left. Combine them: 2-chlorobutane. Chain, direction, name: solved.