vicinally

Vicinally is an adverb used in chemistry to describe the relative positions of two atoms or functional groups within a molecule. Specifically, when two atoms or groups are said to be vicinal, it means they are located on adjacent carbon atoms. This arrangement is common in organic chemistry and is often relevant to the reactivity of a molecule. For example, vicinal dihalides, which have two halogen atoms on adjacent carbons, are known to undergo dehydrohalogenation to form alkenes. The term vicinal comes from the Latin word "vicinus," meaning "neighboring." Understanding vicinal relationships is crucial for predicting reaction pathways and the properties of organic compounds. It is distinct from geminal, where two atoms or groups are attached to the same carbon atom, and isolated, where they are separated by two or more carbon atoms.