What type of structure is indicated by the prefix "iso-" in organic nomenclature?

The prefix "iso-" in organic nomenclature indicates a branched structure. Specifically, it refers to compounds that have a similar carbon skeleton as a straight-chain version but with a distinct branching pattern. For example, isobutane has a four-carbon structure with a branching at the second carbon, as opposed to butane, which is a straight-chain structure.

The use of "iso-" typically signifies that the molecule consists of a straight-chain backbone with a methyl group branching off, creating a more compact molecular shape. This is an important feature in organic chemistry, as the presence of branching can significantly affect the physical and chemical properties of the compound, such as boiling points and reactivity. Understanding these naming conventions helps in identifying structural characteristics in organic compounds.