Everything about Triazine totally explained
A
triazine is one of three
organic chemicals,
isomeric with each other, whose
empirical formula is
333.
Structure
The triazine structure is a
heterocyclic ring, analogous to the six-membered
benzene ring but with three carbons replaced by nitrogens. The three isomers of triazine are distinguished from each other by the positions of their nitrogen atoms, and are referred to as
1,2,3-triazine,
1,2,4-triazine, and
1,3,5-triazine. Other
aromatic nitrogen heterocycles are
pyridines with 1 ring nitrogen atom,
diazines with 2 nitrogen atoms in the ring and
tetrazines with 4 ring nitrogen atoms. Triazines are weaker
bases than
pyridine.
Uses
The best known 1,3,5-triazine derivative is
melamine with three
amino substituents used in the manufacture of resins. Another triazine extensively used in resins is benzoguanamine. Triazine compounds are often used as the basis for various
herbicides such as
cyanuric chloride (2,4,6-trichloro-1,3,5-triazine). Chlorine-substituted triazines are also used as
reactive dyes. These compounds react through a chlorine group with hydroxyl groups present in
cellulose fibres in nucleophilic substitution, the other triazine positions contain chromophores.
A series of 1,2,4-triazine derivatives known as BTPs have been considered in the
liquid-liquid extraction community as possible
extractants for use in the advanced
nuclear reprocessing of used fuel. BTPs are molecules containing a
pyridine ring bonded to two 1,2,4-triazin-3-yl groups.
Synthesis
1,2,3-Triazines can be synthesized by thermal rearrangement of 2-azidocyclopropenes. 1,2,4-Triazines are prepared from condensation of 1,2-dicarbonyl compounds with amidrazones. A classical triazine synthesis is also the
Bamberger triazine synthesis. Symmetrical 1,3,5-triazines are prepared by
trimerization of
cyanogen chloride or
cyanimide. Benzoguanamine (with one phenyl and 2 amino substituents) is synthesised from
benzonitrile and dicyandiamide in
dimethoxyethane with
potassium hydroxide.
Reactions
Although triazines are aromatic compounds the
resonance energy is much lower than in benzene, and
electrophilic aromatic substitution is difficult but
nucleophilic aromatic substitution more frequent.
2,4,6-Trichloro-1,3,5-triazine is easily hydrolyzed to
cyanuric acid by heating with water at elevated temperatures. 2,4,6-Tris(phenoxy)-1,3,5-triazine reacts with aliphatic amines in
aminolysis, and this reaction can be used to give
dendrimers. Pyrolysis of
melamine under expulsion of
ammonia gives the tri-s-triazine
melem. Cyanuric chloride assists in the
amidation of
carboxylic acids.
The 1,2,4-triazines can react with
electron-rich dienophiles in an
inverse electron demand
Diels-Alder reaction. This forms a bicylic intermediate which normally then extrudes out a molecule of nitrogen gas to form an aromatic ring again. In this way the 1,2,4-triazines can be reacted with
alkynes to form pyridine rings. An alternative to using an alkyne is to use
norbornadiene which can be thought of as a masked alkyne.
Further Information
Get more info on 'Triazine'.
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