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The 5-membered ring compounds containing two heteroatoms, at least one of which is nitrogen, are collectively called the azoles. Thiazoles and isothiazoles contain a sulfur and a nitrogen atom in the ring. Dithioles have two sulfur atoms. A large group of 5-membered ring compounds with three or more heteroatoms also exists.
The initially formed nitrogen-centered radical abstracts a H-atom mostly from the δ-position and thus 5-membered rings are formed predominantly. Formation of 6-membered rings is also possible, but relatively rare, and in majority of cases is observed in rigid cyclic systems.
Hexazine (also known as hexaazabenzene) is a hypothetical allotrope of nitrogen composed of 6 nitrogen atoms arranged in a ring-like structure analogous to that of benzene. As a neutrally charged species, it would be the final member of the azabenzene (azine) series, in which all of the methine groups of the benzene molecule have been replaced ...
Simple aromatic rings can be heterocyclic if they contain non-carbon ring atoms, for example, oxygen, nitrogen, or sulfur. They can be monocyclic as in benzene, bicyclic as in naphthalene, or polycyclic as in anthracene. Simple monocyclic aromatic rings are usually five-membered rings like pyrrole or six-membered rings like pyridine.
Pyrimidine (C 4 H 4 N 2; / p ɪ ˈ r ɪ. m ɪ ˌ d iː n, p aɪ ˈ r ɪ. m ɪ ˌ d iː n /) is an aromatic, heterocyclic, organic compound similar to pyridine (C 5 H 5 N). [3] One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring.
In Hantzsch–Widman nomenclature, an azine is an heterocyclic compound containing a 6-membered aromatic ring. It is an analog of a benzene ring in which one or more of the carbon atoms has been replaced by a nitrogen atom, [1] and thus is also called an azabenzene.
It contains a six-membered ring with two adjacent nitrogen atoms. [3] It is a colorless liquid with a boiling point of 208 °C. It is isomeric with two other diazine (C 4 H 4 N 2) rings, pyrimidine and pyrazine.
A ring forming reaction or ring-closing reaction in organic chemistry is an umbrella term for a variety of reactions that introduce one or more rings into a molecule. A heterocycle forming reaction is a reaction that introduces a new heterocycle. [1] [2] Important classes of ring forming reactions include annulations [3] and cycloadditions ...