1,4-Dioxin (also referred as dioxin or ''p''-dioxin) is a heterocyclic, organic, non-aromatic compound with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

CHO. There is an

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...

ic form of 1,4-dioxin, 1,2-dioxin (or ''o''-dioxin). 1,2-Dioxin is very unstable due to its

peroxide In chemistry, peroxides are a group of Chemical compound, compounds with the structure , where the R's represent a radical (a portion of a complete molecule; not necessarily a free radical) and O's are single oxygen atoms. Oxygen atoms are joined ...

-like characteristics. The term "dioxin" is most commonly used for a family of derivatives of 1,4-dioxin, known as polychlorinated dibenzodioxins (PCDDs).

Preparation

1,4-Dioxin can be prepared by cycloaddition, namely by the Diels–Alder reaction of furan and maleic anhydride. The

adduct In chemistry, an adduct (; alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is ...

formed has a carbon-carbon double bond, which is converted to an epoxide. The epoxide then undergoes a retro-Diels–Alder reaction, forming 1,4-dioxin and regenerating maleic anhydride.

Derivatives

The word " dioxin" can refer in a general way to compounds which have a dioxin core skeletal structure with

substituent In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. The suffix ''-yl'' is used when naming organic compounds that contain a single bond r ...

molecular groups attached to it. For example, dibenzo-1,4-dioxin is a compound whose structure consists of two benzo- groups fused onto a 1,4-dioxin ring.

Polychlorinated dibenzodioxins

Because of their extreme importance as environmental pollutants, current scientific literature uses the name dioxins commonly for simplification to denote the chlorinated derivatives of dibenzo-1,4-dioxin, more precisely the polychlorinated dibenzodioxins (PCDDs), among which 2,3,7,8-tetrachlorodibenzodioxin (TCDD), a derivative, is the best known. The polychlorinated dibenzodioxins, which can also be classified in the family of halogenated organic compounds, have been shown to bioaccumulate in humans and

wildlife Wildlife refers to domestication, undomesticated animals and uncultivated plant species which can exist in their natural habitat, but has come to include all organisms that grow or live wilderness, wild in an area without being species, introdu ...

due to their

lipophilic Lipophilicity (from Greek language, Greek λίπος "fat" and :wikt:φίλος, φίλος "friendly") is the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such compounds are c ...

properties, and are known

teratogens Teratology is the study of abnormalities of physiological development in organisms during their life span. It is a sub-discipline in medical genetics which focuses on the classification of congenital abnormalities in Dysmorphic feature, dysmor ...

, mutagens, and carcinogens. PCDDs are formed through

combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

bleaching and

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of the secondary sector of the economy. The term may refer ...

processes. The combination of heat and chlorine creates dioxin. Since chlorine is often a part of the Earth's environment, natural ecological activity such as volcanic activity and forest fires can lead to the formation of PCDDs. Nevertheless, PCDDs are mostly produced by human activity. Famous PCDD exposure cases include

Agent Orange Agent Orange is a chemical herbicide and defoliant, one of the tactical uses of Rainbow Herbicides. It was used by the U.S. military as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1962 to 1971. T ...

sprayed over vegetation by the British military in Malaya during the

Malayan Emergency The Malayan Emergency, also known as the Anti–British National Liberation War, was a guerrilla warfare, guerrilla war fought in Federation of Malaya, Malaya between communist pro-independence fighters of the Malayan National Liberation Arm ...

and the U.S. military in Vietnam during the

Vietnam War The Vietnam War (1 November 1955 – 30 April 1975) was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam w ...

, the Seveso disaster, and the poisoning of Viktor Yushchenko. Polychlorinated dibenzofurans are a related class compounds to PCDDs which are often included within the general term "dioxins".

References

{{DEFAULTSORT:Dioxin, 1, 4- Dioxins