How do you name a branched alkane?

To name a branched alkane properly, it's essential to identify the longest continuous carbon chain, which serves as the backbone of the molecule. This chain defines the base name of the alkane and its suffix, such as "-ane" for alkanes. Once the longest chain is established, it's important to number this chain to provide the correct locations for any substituents that branch off. The substituents, which are groups attached to the main carbon chain, need to be named and their positions indicated using the numbering from the longest chain. This method ensures clarity and consistency in naming, facilitating communication among chemists.

Using only the longest carbon chain without considering substituents (the first option) overlooks the importance of the entire molecular structure. Naming all substituents first (the third option) takes away from the systematic approach needed to establish the primary structure of the molecule. Relying solely on common names (the fourth option) may not adequately describe the compound, especially for more complex branched alkanes, as these names can often be ambiguous or inconsistent. Thus, the correct method leverages systematic nomenclature principles to provide a clear and standardized name for the branched alkane.