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 N=N group is called an azo functional group, and the R and R' groups of azo compounds are often aromatic or aliphatic. This helps to stabilise the N=N group by making it part of an extended delocalised system. This also has the effect of making many azo compounds coloured, as delocalised or conjugated systems often absorb visible frequencies of light. Chemistry (in Greek: χημεία) is the science of matter that deals with the composition, structure, and properties of substances and with the transformations that they undergo. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... In chemistry, non-aromatic and non-cyclic (acyclic) organic compounds are called aliphatic. ... In ecology functional groups are collections of organisms based on morphological, physiological, behavioral, biochemical, or environmental responses or on trophic criteria. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... In chemistry, non-aromatic and non-cyclic (acyclic) organic compounds are called aliphatic. ...

A typical Azo compound, 4-hydroxyphenylazobenzene, a.k.a. yellow azo dye

The name azo comes from azote, an old name of nitrogen that originates in French and is derived from the Greek a (not) + zoe (to live). Aromatic azo compounds (R = R' = aromatic) are usually stable and have vivid colors such as red, orange, and yellow. Therefore, they are used as dyes, which are called azo dyes. Azobenzene is a typical aromatic azo compound. Their colour originates from absorbance in the visible region of the spectrum due to the delocalization of electrons in the benzene and azo groups forming a conjugated system. General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... Jump to: navigation, search Yarn drying after being dyed in the early American tradition, at Conner Prairie living history museum. ... 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. ... In chemistry, delocalized electrons are electrons in a molecule that do not belong to a single atom or a covalent bond. ... A chemically conjugated system, is a system of atoms covalently bonded with alternating single and double bonds (e. ...

Aliphatic azo compounds (R and/or R' = aliphatic) are rather unstable. At an elevated temperature or by irradiation, two carbon-nitrogen (R-N) bonds are cleaved simultaneously with the loss of nitrogen gas to generate carbon-centered radicals. Owing to this process, some aliphatic azo compounds are utilized as radical initiators. Azobisisobutylonitrile (AIBN) is a typical one and is widely used in industrial processes and in laboratory experiments. General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... 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, also azobisisobutylonitrile, is a toxic white crystalline compound often used as a foamer in plastics and rubber. ...

Aromatic azo compounds can be synthesized by using an azocoupling reaction, that is, an electrophilic substitution reaction on aromatic rings with diazonium salts. Diazonium salts decompose at temperatures warmer than about 5 degrees Celsius, so the reaction must take place in solution under freezing conditions: 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. ...

An oxidation reaction of hydrazine (R-NH-NH-R') also gives an azo compound. The most fundamental reactions in chemistry are the redox processes. ... Hydrazine is a chemical compound with formula N2H4 used as a rocket fuel. ...

Because of their instability, especially for aliphatic ones, care should be taken with the handling of azo compounds or an explosion may occur.