Azo compound

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Azo compound

Azo compounds are compounds

Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
bearing the functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
R-N=N-R', in which R and R' can be either aryl

Aryl

In the context of organic molecules, aryl refers to any functional group or substituent derived from a simple aromatic ring, may it be phenyl, thiophene, indole, etc ....
or alkyl

Alkyl

An alkyl is a univalent Radical consisting of carbon and hydrogen atoms, arranged in a chain. The Alkyls form homologous series with the general formula CnH2n+1....
. The N=N group is called an azo group, although the parent compound, HNNH, is called diimide. The more stable derivatives contain two aryl groups. The name azo comes from azote, the French name of nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
that is derived from the Greek a (not) + zoe (to live).

consequence of ?-delocalization, aryl azo compounds have vivid colours, especially reds, oranges, and yellows.

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As dyes and pigments

As a consequence of ?-delocalization, aryl azo compounds have vivid colours, especially reds, oranges, and yellows. Therefore, they are used as dye

Dye

A dye can generally be described as a colored substance that has an Chemical affinity to the Wiktionary:substrate to which it is being applied....
s, azo dyes for example Disperse Orange 1

Disperse Orange 1

Disperse Orange 1 is a dye of the azobenzene class. Disperse Orange 1 contains approximately 25% dye by weight, with the remaining mass consisting of Sodium chloride and other salts....
. Some azo compounds, eg. methyl orange

Methyl orange

Methyl orange is a pH indicator frequently used in titrations.It is often chosen to be used in titrations because of its clear colour change. Because it changes colour at the pH of a mid-strength acid, it is usually used in titrations for acids....
, are used as acid-base indicators due to the different colours of their acid and salt forms. The development of azo dyes was an important step in the development of the chemical industry.

Azo pigments are colorless particles (typically earths or clay

Clay

Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....
s), which have been colored using an azo compound. Azo pigments are important in a variety of paint

Paint

Paint is any liquid, liquifiable, or mastic composition which after application to a Substrate in a thin layer is converted to an opaque solid film....
s including artist's paints. They have excellent coloring properties, again mainly in the yellow to red range, as well as lightfastness. The lightfastness depends not only on the properties of the organic azo compound, but also on the way they have been adsorbed on the pigment carrier. Azo pigments are advantageous because they are non-toxic.

Organic chemistry

Aryl azo compounds

Aryl azo compounds are usually stable, crystalline species. Azobenzene

Azobenzene

Azobenzene is a chemical compound composed of two phenyl rings linked by a azo compound double bond. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of molecules that share the core azobenzene structure, with different chemical functional groups extending from the phenyl rings....
is the prototypical aromatic azo compound. It exists mainly as the trans

Trans

Trans is a Latin noun or prefix, meaning "across", "beyond" or "on the opposite side".Trans may refer to:...
isomer, but upon photolysis, converts to the cis isomer. Aromatic azo compounds can be synthesized by using an azo coupling

Azo coupling

An azo coupling is an organic reaction between a diazonium compound and an aniline, phenol or other aromatic compound which produces an azo compound....
reaction, which entails an electrophilic substitution reaction where a aryl diazonium cation attacks another aryl ring, especially those substituted with electron-releasing groups. Since diazonium salts are often unstable near room temperature, the azo coupling reactions are typically conducted near ice temperatures. The oxidation of hydrazine

Hydrazine

Hydrazine is a chemical compound with the chemical formula N2H4. It is a colourless liquid with an ammonia-like odor and is derived from the same industrial chemistry processes that manufacture ammonia....
s (R-NH-NH-R') also gives azo compounds.

Alkyl azo compounds

Aliphatic azo compounds (R and/or R' = aliphatic) are less commonly encountered than the aryl azo compounds. One example is diethyldiazene, EtN=NEt. At elevated temperatures or upon irradiation

Photochemistry

Photochemistry, a sub-discipline of chemistry, is the study of the interactions between atoms, small molecules, and light . The pillars of photochemistry are UV/VIS spectroscopy, photochemical reactions in organic chemistry and photosynthesis in biochemistry....
, the carbon

Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
-nitrogen (C-N) bonds in certain alkyl azo compounds cleave with the loss of nitrogen gas to generate radicals. Owing to this process, some aliphatic azo compounds are utilized as radical initiator

Radical initiator

In chemistry, radical initiators are substances that can produce radical under mild conditions and promote radical polymerization reactions. These substances generally possess weak bonds—bonds that have small bond dissociation energy....
s. Representative is Azobisisobutylonitrile

Azobisisobutylonitrile

Azobisisobutyronitrile is a toxic compound often used as a foamer in plastics and rubber and as a radical initiator. It is commonly known as AIBN....
(AIBN) which is widely used as an initiator in polymerization. Because of their instability, especially for aliphatic ones, care should be taken with the handling of azo compounds or an explosion

Explosion

An explosion is a sudden increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases....
may occur.

Azo compound

As dyes and pigments

Organic chemistry

Aryl azo compounds

Alkyl azo compounds

See also