VICINAL (CHEMISTRY)

In chemistry 'vicinal' (from Latin ''vicinus'' = neighbour) stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not.
Likewise in a ''gem-dibromide'' the prefix 'gem', an abbreviation of geminal, signals that both bromine atoms are bonded to the ''same'' atom. For example, 1,1-dibromobutane is geminal.
Like other such concepts as syn, anti, exo or endo the description ''vicinal'' helps explaining how different parts of a molecule are related to each other either structurally or spatially. The vicinal adjective is sometimes restricted to those molecules with two ''identical'' functional groups. The term can also be extended to substituents on aromatic rings.