Yellow azo dye

Azo compounds are compounds bearing the functional group R-N=N-R', in which R and R' can be either aryl or alkyl. 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 that is derived from the Greek a (not) + zoe (to live). Image File history File links 4-hydroxyphenylazobenzene. ... Image File history File links 4-hydroxyphenylazobenzene. ... A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by mass. ... In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... In the context of organic molecules, aryl refers to any member of the set of functional groups or substituents that are derived from a simple aromatic ring. ... An alkyl is a univalent radical containing only carbon and hydrogen atoms arranged in a chain. ... In chemistry, azo compounds generally have a molecular formula of the form R-N=N-R, in which R and R can be either aromatic or aliphatic. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ...

As dyes and pigments

As a consequence of п-delocalization, aryl azo compounds have vivid colours, especially reds, oranges, and yellows. Therefore, they are used as dyes, azo dyes for example Disperse Orange 1. Some azo compounds, eg. methyl orange, 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. In chemistry, delocalized electrons are electrons in a molecule that do not belong to a single atom or a covalent bond. ... Look up dye in Wiktionary, the free dictionary. ... Methyl Orange is a pH indicator frequently used in titrations. ...

Azo pigments are colorless particles (typically earths or clays), which have been colored using an azo compound. Azo pigments are important in a variety of paints 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. For other uses, see Clay (disambiguation). ... For other uses, see Paint (disambiguation). ...

Organic chemistry

Aryl azo compounds

Aryl azo compounds are usually stable, crystalline species. Azobenzene is the prototypical aromatic azo compound. It exists mainly as the trans isomer, but upon photolysis, converts to the cis isomer. Aromatic azo compounds can be synthesized by using an azo coupling reaction, which entails an electrophilic substitution reaction where a aryl diazonium cation attacks another aryl ring, especially those substituted with electron-releasing groups.^[1] Since diazonium salts are often unstable near room temperature, the azo coupling reactions are typically conducted near ice temperatures. The oxidation of hydrazines (R-NH-NH-R') also gives azo compounds.^[2] Azobenzene is a chemical compound composed of two phenyl rings and one N-N double bond, the former of which are bridged by the latter. ... Trans is a Latin noun or prefix, meaning across, beyond or on the opposite side [of] . It is the opposite of cis, which means on the same side [of]. In chemistry, a double bond (or ring) not subject to free rotation in which the greater radical on both ends is... CIS usually refers to: Commonwealth of Independent States, a modern-day political entity consisting of 11 former Soviet Union Republics CIS is also an acronym for: Canadian Interuniversity Sport Cancer Information Service Carcinoma in situ Centre for Independent Studies Center for Immigration Studies Chinese International School Cisalpino Citizenship & Immigration Services... An azo coupling is an organic reaction between a diazonium compound and an aniline or a phenol. ... An electrophilic aromatic substitution is a chemical reaction in which a hydrogen atom of an aromatic ring is replaced by an electrophile. ... In chemistry, azo compounds generally have a molecular formula of the form R-N=N-R, in which R and R can be either aromatic or aliphatic. ... The most fundamental reactions in chemistry are the redox processes. ... Hydrazine is the chemical compound with formula N2H4. ...

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.^[3] At elevated temperatures or upon irradiation, the carbon-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 initiators. Representative is Azobisisobutylonitrile (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 may occur. Photochemistry is the study of the interaction of light and chemicals. ... For other uses, see Carbon (disambiguation). ... In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical reactions. ... Azobisisobutyronitrile is a toxic compound often used as a foamer in plastics and rubber and as a radical initiator. ...

See also

• Azo coupling
• Ponceau 4R
• Ponceau S

An azo coupling is an organic reaction between a diazonium compound and an aniline or a phenol. ... Ponceau 4R Ponceau 4R (also known as Food Red 7, C.I. 16255, Cochineal Red A, New Coccine, Acid Red 18, SX purple) is a colourant that may be added to foods to induce a colour change. ... Ponceau S Ponceau S, Acid Red 112, or C.I. 27195 is a sodium salt of a diazo dye that may be used to prepare a stain for rapid reversible detection of protein bands on nitrocellulose or PVDF membranes (Western blotting), as well as on cellulose acetate membranes. ...

References

1. ^ H. T. Clarke and W. R. Kirner (1941). "Methyl Red". Org. Synth.; Coll. Vol. 1: 374. 
2. ^ March, J. “Advanced Organic Chemistry” $th Ed. J. Wiley and Sons, 1992: New York. ISBN 0-471-60180-2.
3. ^ Ohme, R.; Preuschhof, H.; Heyne, H.-U. (1988). "Azoethane". Org. Synth.; Coll. Vol. 6: 78.