Diazine
Diazines are heterocyclic aromatic chemical compounds. They belong to the organic compounds, and have a six-membered ring system which contains two nitrogen atoms as hetero atoms, and thus include the azines.
The term Diazines can be derived from the systematic Hantzsch - Widman nomenclature.
There are three isomeric parent systems are formulated - pyridazine (1,2- diazine ), pyrimidine (1,3- diazine ) and pyrazine (1,4- diazine ) - whose empirical formula C4H4N2 is.
Pyrimidine
Pyrazine
Occurrence
Diazines can be found in a number of natural products. For example, the nucleobases of DNA and RNA have a purine or pyrimidine skeleton.
Production
Pyridazines
For the preparation of pyridazines, a double condensation reaction can be used. For this purpose, a 1,4- dicarbonyl compound is reacted with hydrazine. Hydrazine condenses this gradually split off water per one particle to the carbonyl. The diimine formed therefrom can now, for example, be dehydrated on a palladium - charcoal catalyst and be flavored.
Pyrimidines
Pyrimidines can be obtained with amidines from the acid-catalyzed reaction of 1,3- dicarbonyl compounds. In the first step, the amino function fused to a ketone. The second step consists of a further condensation with subsequent aromatization, wherein the ring is formed. In both condensation steps a particle of water is split off ever. To this reaction both ketones and aldehydes are used as carbonyl components.
Pyrazines
Pyrazines can be synthesized by the reaction of carbonyl compounds, which are brominated in α - position. The diimine thus obtained can be flavored by oxidation.
A further possibility consists in the oxidation of the corresponding piperazines.
Properties
Diazines belong to the group of aromatic nitrogen bases. The two nitrogen atoms reduce the electron density in the ring system so strong that often only poorly or not run at them electrophilic aromatic substitutions. The willingness to electrophilic substitution can be increased by the introduction of electron-donating substituents.