Simple_aromatic_ring Simple_aromatic_ring

Simple aromatic ring - Definition and Overview
Related Words: Fragrant, Odorant, Savory, Spicy, Sweet

Table of simple aromatic rings

Five-membered rings: Fused five-membered rings:

Furan_simple_structure.png
Image:Furan_simple_structure.png


Furan
Benzofuran_simple_structure.png
Image:Benzofuran_simple_structure.png


Benzofuran
Isobenzofuran_simple_structure.png
Image:Isobenzofuran_simple_structure.png


Isobenzofuran

Pyrrole_simple_structure.png
Image:Pyrrole_simple_structure.png


Pyrrole
Indole_simple_structure.png
Image:Indole_simple_structure.png


Indole
Isoindole_simple_structure.png
Image:Isoindole_simple_structure.png


Isoindole

Thiophene_simple_structure.png
Image:Thiophene_simple_structure.png


Thiophene
Benzothiophene_simple_structure.png
Image:Benzothiophene_simple_structure.png


Benzothiophene
Benzo-c-thiophene_simple_structure.png
Image:Benzo-c-thiophene_simple_structure.png


Benzo[c]thiophene		  

Imidazole_simple_structure.png
Image:Imidazole_simple_structure.png


Imidazole
Benzimidazole_simple_structure.png
Image:Benzimidazole_simple_structure.png


Benzimidazole
Purine_simple_structure.png
Image:Purine_simple_structure.png


Purine

Pyrazole_simple_structure.png
Image:Pyrazole_simple_structure.png


Pyrazole
Indazole_simple_structure.png
Image:Indazole_simple_structure.png


Indazole		  

Oxazole_simple_structure.png
Image:Oxazole_simple_structure.png


Oxazole
Benzoxazole_simple_structure.png
Image:Benzoxazole_simple_structure.png


Benzoxazole		  

Isoxazole_simple_structure.png
Image:Isoxazole_simple_structure.png


Isoxazole
Benzisoxazole_simple_structure.png
Image:Benzisoxazole_simple_structure.png


Benzisoxazole		  

Thiazole_simple_structure.png
Image:Thiazole_simple_structure.png


Thiazole
Benzothiazole_simple_structure.png
Image:Benzothiazole_simple_structure.png


Benzothiazole		  
 
Six-membered rings: Fused six-membered rings:  

Benzene_simple_structure.png
Image:Benzene_simple_structure.png


Benzene
Naphthalene_simple_structure.png
Image:Naphthalene_simple_structure.png


Naphthalene
Anthracene_simple_structure.png
Image:Anthracene_simple_structure.png


Anthracene

Pyridine_simple_structure.png
Image:Pyridine_simple_structure.png


Pyridine
Quinoline_simple_structure.png
Image:Quinoline_simple_structure.png


Quinoline
Isoquinoline_simple_structure.png
Image:Isoquinoline_simple_structure.png


Isoquinoline

Pyrazine_simple_structure.png
Image:Pyrazine_simple_structure.png


Pyrazine
Quinoxaline_simple_structure.png
Image:Quinoxaline_simple_structure.png


Quinoxaline
Acridine_simple_structure.png
Image:Acridine_simple_structure.png


Acridine

Pyrimidine_simple_structure.png
Image:Pyrimidine_simple_structure.png


Pyrimidine
Quinazoline_simple_structure.png
Image:Quinazoline_simple_structure.png


Quinazoline		  

Pyridazine_simple_structure.png
Image:Pyridazine_simple_structure.png


Pyridazine
Cinnoline_simple_structure.png
Image:Cinnoline_simple_structure.png


Cinnoline		  

Simple aromatic rings are aromatic organic compounds (also known as arenes or aromatics) that consist only of conjugated planar ring systems with delocalized pi electron clouds instead of discrete alternating single and double bonds. Typical simple aromatic compounds are benzene and indole.

Simple aromatic rings can be heterocyclic if they contain non-carbon ring atoms, e.g. oxygen, nitrogen, or sulfur.

Simple monocyclic aromatic rings are usually five-membered rings like pyrrole or six-membered rings like pyridine. Fused aromatic rings like naphthalene or purine consist of monocyclic rings that share their connecting bonds.

The nitrogen (N) containing aromatic rings can be separated into non-basic and basic aromatic rings:

  • In the non-basic rings the lone pair of electrons of the nitrogen atom is delocalized and contributes to the aromatic pi electron system. In these compounds the the nitrogen atom is connected to a hydrogen atom. Examples of non-basic nitrogen-containing aromatic rings are pyrrole and indole.
  • In the basic aromatic rings the lone pair of electrons 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 the nitrogen atom is not connected to a hydrogen atom. 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. Under acidic conditions these compounds get protonated and form aromatic cations (e.g. pyridinium).

In the oxygen (O) and sulfur (S) containing aromatic rings one of the electron pairs of the heteroatoms contributes to the aromatic system (similar to the non-basic nitrogen containing rings), while the second lone pair extends in the plane of the ring (similar to the basic nitrogen containing rings).

See also

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