Structure and numbering of the imidazole, benzothiazole, oxazole and tetrazole

 Here’s an overview of the structure and numbering for imidazole, benzothiazole, oxazole, and tetrazole, along with examples for each:

1. Imidazole

• Structure: Imidazole is a five-membered heterocyclic compound with two non-adjacent nitrogen atoms. The ring structure consists of three carbon atoms and two nitrogen atoms, with the nitrogens being part of the ring system.

• Numbering: The ring is numbered such that one nitrogen is at position 1 and the other is at position 3. The carbon atoms are numbered 2, 4, and 5, respectively.

  Example: Imidazole itself, with the structure:

  N

 / \

C   C

 \ / \

  C   N

2. Benzothiazole

• Structure: Benzothiazole is a fused ring system that combines a benzene ring (a six-membered aromatic ring) with a thiazole ring (a five-membered ring with one sulfur and one nitrogen).

• Numbering: In benzothiazole, the thiazole ring is fused to the benzene ring. The numbering starts from the sulfur atom in the thiazole ring, which is designated as position 1, and the nitrogen as position 3. The benzene ring is fused to this structure with its carbons numbered sequentially.

  Example: Benzothiazole itself, with the structure:

    N

   / \

C6H5-C

   \ / 

    S

3. Oxazole

• Structure: Oxazole is a five-membered heterocyclic compound with one oxygen and one nitrogen atom. The ring structure includes three carbon atoms, one oxygen, and one nitrogen.

• Numbering: The numbering starts with the oxygen atom at position 1 and the nitrogen atom at position 3. The remaining carbon atoms are numbered 2, 4, and 5.

  Example: Oxazole itself, with the structure:

  O

 / \

C   C

 \ / \

  C   N

4. Tetrazole

• Structure: Tetrazole is a five-membered ring containing four nitrogen atoms and one carbon atom.

• Numbering: The numbering starts with the carbon atom at position 1. The four nitrogen atoms are then numbered consecutively around the ring.

  Example: Tetrazole itself, with the structure:

  N

 / \

N   C

 \ / \

  N   N

These structures and numbering conventions are crucial for understanding the chemistry and reactivity of these heterocyclic compounds.