Basic aromatic ring

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Basic aromatic ring systems
Pyridine structure.png
Pyridine
Quinoline structure.png
Quinoline
Isoquinoline structure.png
Isoquinoline
Acridin.svg
Acridine
Pyrazine structure.png
Pyrazine
Quinoxaline structure.png
Quinoxaline
Imidazole structure.png
Imidazole
Benzimidazole structure.png
Benzimidazole
Purine structure.png
Purine
Pyrazole structure.png
Pyrazole
Indazole structure.png
Indazole
Pyrimidine structure.png
Pyrimidine
Quinazoline structure.png
Quinazoline
Pyridazine structure.png
Pyridazine
Cinnoline structure.png
Cinnoline

Basic aromatic rings are aromatic rings in which the lone pair of electrons of a ring-nitrogen atom is not part of the aromatic system and extends in the plane of the ring. This lone pair is responsible for the basicity of these nitrogenous bases, similar to the nitrogen atom in amines. In these compounds the nitrogen atom is not connected to a hydrogen atom. Basic aromatic compounds get protonated and form aromatic cations (e.g. pyridinium) under acidic conditions. Typical examples of basic aromatic rings are pyridine or quinoline. Several rings contain basic as well as non-basic nitrogen atoms, e.g. imidazole and purine.

In non-basic aromatic rings the lone pair of electrons of the nitrogen atom is delocalized and contributes to the aromatic pi electron system. In these compounds the nitrogen atom is connected to a hydrogen atom. Examples of non-basic nitrogen-containing aromatic rings are pyrrole and indole.

The basic aromatic rings purines and pyrimidines are nucleobases found in DNA and RNA.

See also[edit]