What does the prefix "iso-" indicate in organic chemistry nomenclature?

In organic chemistry nomenclature, the prefix "iso-" signifies that a compound has a branched chain structure. This prefix is commonly used to denote that the compound contains a specific branching pattern as opposed to being a simple straight-chain (or linear) isomer.

For example, in the case of alkanes, "iso-" often refers to the presence of a methyl group on the second carbon of a four-carbon chain, resulting in a branched structure such as isobutane. This distinguishes it from its straight-chain counterpart, butane, which has no branching.

The "iso-" prefix conveys important structural information, indicating that the molecular architecture includes a branch that can affect the compound's physical and chemical properties, such as boiling points and reactivity. Understanding the significance of the "iso-" prefix is essential in organic nomenclature to accurately identify and communicate about different isomeric forms of organic compounds.