vicinal

In chemistry , vicinal (usually abbreviated as vic , from the Latin vicinus "neighbor") means that two functional groups (e.g. halogens such as fluorine , chlorine or bromine ) are bound to two neighboring carbon atoms . The use of the term vicinal is usually restricted to two identical functional groups.

	Comparison of vicinal with geminal and isolated substitution patterns
	Alkane	geminal	vicinal	isolated
methane			does not exist	does not exist
Ethane				does not exist
propane
Red marked substituents on selected dibromoalkanes.

The term vicinal is also used to describe trisubstituted benzene and heterocycles. 1,2,3-trimethylbenzene is z. B. designated as vic -trimethylbenzene.

Further terms describing the relative arrangement of two functional groups are geminal and α and β positions .

¹ H-NMR spectroscopy: maleic acid dimethyl ester (above) with two blue- marked vicinal cis protons on adjacent carbon atoms. Fumaric acid dimethyl ester (bottom) with two green marked trans vicinal protons on adjacent carbon atoms. The vicinal coupling constant ³ J _cis is less than ³ J _trans .

¹ H-NMR spectroscopy

In ¹ H- NMR spectroscopy , the coupling of two hydrogen atoms located on adjacent carbon atoms is referred to as vicinal coupling . The vicinal coupling constant is referred to as ³ J because the hydrogen atoms couple with each other through three bonds. Depending on the other substituents, the vicinal coupling constant assumes values ​​between 0 and +20 Hz. The dependence of the vicinal coupling constant on the dihedral angle is described by the Karplus relationship . ${\displaystyle \!\,\phi }$

Individual evidence

1. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 6: T-Z. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1988, ISBN 3-440-04516-1 , p. 4511.
2. ^ Brockhaus ABC Chemie , VEB F. A. Brockhaus Verlag, Leipzig 1965, p. 1502.
3. ^ DH Williams, I. Fleming: Structure clarification in organic chemistry; An introduction to spectroscopic methods , 6th revised edition, Georg Thieme Verlag, Stuttgart 1991, p. 105.