Azo compound

Source: Wikipedia, the free encyclopedia.
"Azene" redirects here. Not to be confused with the polycyclic hydrocarbons known as "acenes" or the acyclic saturated hydronitrogens known as "azanes".
General chemical formula of azo compounds

Azo compounds are

alkyl
groups).

Ancient Greek
ἀ- (a-) 'not', and ζωή (zōē) 'life').

Many textile and leather articles are dyed with azo dyes and pigments.[2]

Aryl azo compounds

cis
isomer.

Aromatic azo compounds can be synthesized by

electron-donating groups:[3][4]

Ar
N+2 + Ar'H → ArN=NAr' + H+

Since

azoxy
intermediate:

ArNO2 + Ar'NH2 → ArN(O)=NAr' + H2O
ArN(O)=NAr' + C6H12O6 → ArN=NAr' + C6H10O6 + H2O

For textile dying, a typical nitro coupling partner would be disodium 4,4′-dinitrostilbene-2,2′-disulfonate. Typical aniline partners are shown below.[6]

An orange azo dye Solvent Yellow 7

As a consequence of

+R and some CD-R
discs use blue azo dye as the recording layer. The commercial success of azo dyes motivated the development of azo compounds in general.

Alkyl azo compounds

See also:
Diazo group

free-radical polymerizations and other radical-induced reactions. It achieves this initiation by decomposition, eliminating a molecule of nitrogen
gas to form two 2-cyanoprop-2-yl radicals:

For instance a mixture of styrene and maleic anhydride in toluene will react if heated, forming the copolymer upon addition of AIBN.

A simple dialkyl diazo compound is diethyldiazene, CH3CH2−N=N−CH2CH3, which can be synthesized through a variant of the Ramberg–Bäcklund reaction.[7] Because of their instability, aliphatic azo compounds pose the risk of explosion.

AIBN is produced by converting acetone cyanohydrin to the hydrazine derivative followed by oxidation:[8]

2 (CH3)2C(CN)OH + N2H4 → [(CH3)2C(CN)]2N2H2 + 2 H2O
[(CH3)2C(CN)]2N2H2 + Cl2 → [(CH3)2C(CN)]2N2 + 2 HCl

Safety and regulation

Many azo pigments are non-toxic, although some, such as

basal cell carcinoma.[10]

European regulation

Certain azo dyes can break down under reductive conditions to release any of a group of defined aromatic amines. Consumer goods which contain listed aromatic amines originating from azo dyes were prohibited from manufacture and sale in European Union countries in September 2003. As only a small number of dyes contained an equally small number of amines, relatively few products were affected.[2]

See also

References

  1. doi:10.1351/goldbook.A00560
  2. ^ a b European Ban on Certain Azo Dyes Archived 2012-08-13 at the Wayback Machine, Dr. A. Püntener and Dr. C. Page, Quality and Environment, TFL
  3. ISBN 0-387-95468-6
    .
  4. ^ H. T. Clarke; W. R. Kirner (1941). "Methyl Red". Organic Syntheses; Collected Volumes, vol. 1, p. 374.
  5. ISBN 978-0-471-60180-7
    .
  6. doi:10.1002/14356007.a03_245
    .
  7. ^ Ohme, R.; Preuschhof, H.; Heyne, H.-U. (1988). "Azoethane". Organic Syntheses; Collected Volumes, vol. 6, p. 78.
  8. doi:10.1002/14356007.a13_177
    .
  9. ^ Tucson University. "Health & Safety in the Arts, A Searchable Database of Health & Safety Information for Artists". Tucson University Studies. Archived from the original on 2009-05-10.
  10. S2CID 34959909
    .
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