chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...

the descriptor vicinal (from

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

''vicinus'' = neighbor), abbreviated ''vic'', describes any two

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...

s bonded to two adjacent

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...

atoms (i.e., in a 1,2-relationship).

Relation of atoms in a molecule

For example, the

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and b ...

2,3-dibromobutane carries two vicinal

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...

atoms and 1,3-dibromobutane does not. Mostly, the use of the term vicinal is restricted to two ''identical'' functional groups. Likewise in a ''gem-''dibromide the prefix ''gem'', an abbreviation of

geminal In chemistry, the descriptor geminal () refers to the relationship between two atoms or functional groups that are attached to the same atom. A geminal diol, for example, is a diol (a molecule that has two alcohol functional groups) attached t ...

, signals that both bromine atoms are bonded to the ''same'' atom (i.e., in a 1,1-relationship). For example, 1,1-dibromobutane is geminal. While comparatively less common, the term hominal has been suggested as a descriptor for groups in a 1,3-relationship. Like other such descriptors as syn, anti, exo or endo, the description ''vicinal'' helps explain 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 use of the term can also be extended to substituents on aromatic rings.

¹H NMR spectroscopy

In ¹H NMR spectroscopy, the coupling of two hydrogen atoms on adjacent carbon atoms is called vicinal coupling. The vicinal coupling constant is referred to as ³''J'' because the hydrogen atoms couple through three bonds. Depending on the other substituents, the vicinal coupling constant assumes values between 0 and +20 Hz.D. H. Williams, I. Fleming: ''Strukturaufklärung in der organischen Chemie; Eine Einführung in die spektroskopischen Methoden'', 6. überarbeitete Auflage, Georg Thieme Verlag, Stuttgart 1991, S. 105. The dependence of the vicinal coupling constant on the

dihedral angle A dihedral angle is the angle between two intersecting planes or half-planes. In chemistry, it is the clockwise angle between half-planes through two sets of three atoms, having two atoms in common. In solid geometry, it is defined as the un ...

\!\,\phi

is described by the Karplus relation.

References

{{Navbox stereochemistry Molecular geometry Chemical nomenclature

Relation of atoms in a molecule

1H NMR spectroscopy

See also

References

¹H NMR spectroscopy