1,4-Dioxin (also referred as dioxin or ''p''-dioxin) is a heterocyclic,

organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

, non-aromatic compound with the chemical formula CHO. There is an

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

ic form of 1,4-dioxin,

1,2-dioxin 1,2-Dioxin is a heterocyclic, organic, antiaromatic compound with the chemical formula CHO. It is an isomeric form of 1,4-dioxin (or ''p''-dioxin). Due to its peroxide In chemistry, peroxides are a group of compounds with the structure ...

(or ''o''-dioxin). 1,2-Dioxin is very unstable due to its peroxide-like characteristics. The term "dioxin" is most commonly used for a family of derivatives of dioxin, known as

polychlorinated dibenzodioxins Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of long-lived polyhalogenated compound, polyhalogenated organic compounds that are primarily anthropogenic, and contribute toxic, Persistent organic pollutant, persistent org ...

(PCDDs).

Preparation

1,4-Dioxin can be prepared by cycloaddition, namely by the

Diels–Alder reaction In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a peric ...

furan Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans. Furan is a colorless, flammable, highly ...

and maleic anhydride. The adduct formed has a carbon-carbon double bond, which is converted to an epoxide. The epoxide then undergoes a

retro-Diels–Alder reaction The retro-Diels–Alder reaction (rDA reaction) is the reverse of the Diels–Alder (DA) reaction, a +2cycloelimination. It involves the formation of a diene and dienophile from a cyclohexene. It can be accomplished spontaneously with heat, or wit ...

, forming 1,4-dioxin and regenerating maleic anhydride. Synthesis-of-1,4-dioxin-1994-2D-skeletal

Derivatives

The word "

dioxin Dioxin may refer to: * 1,2-Dioxin or 1,4-Dioxin, two unsaturated heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the molecular formula C4H4O2 *Dibenzo-1,4-dioxin, the parent compound also known as ...

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

substituent A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as ''side ...

molecular groups attached to it. For example,

dibenzo-1,4-dioxin Dibenzo-1,4-dioxin, also dibenzodioxin or dibenzo-''p''-dioxin (dibenzo-''para''-dioxin), is a polycyclic heterocyclic organic compound in which two benzene rings are connected by a 1,4-dioxin ring. Its molecular formula is C12H8O2. The two ox ...

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

(PCDDs), among which

2,3,7,8-tetrachlorodibenzodioxin 2,3,7,8-Tetrachlorodibenzo-''p-''dioxin (TCDD) is a polychlorinated dibenzo''-p-''dioxin (sometimes shortened, though inaccurately, to simply 'dioxin')Tuomisto, Jouko (2019) Dioxins and dioxin-like compounds: toxicity in humans and animals, s ...

(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 due to their lipophilic properties, and are known teratogens, mutagens, and carcinogens. PCDDs are formed through combustion, chlorine bleaching and manufacturing processes. The combination of heat and chlorine creates dioxin. Since chlorine is often a part of the Earth's

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

, 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 use" 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 1961 to 1971. It ...

sprayed over vegetation by the

British military The British Armed Forces, also known as His Majesty's Armed Forces, are the military forces responsible for the defence of the United Kingdom, its Overseas Territories and the Crown Dependencies. They also promote the UK's wider interests, su ...

in Malaya during the

Malayan Emergency The Malayan Emergency, also known as the Anti–British National Liberation War was a guerrilla war fought in British Malaya between communist pro-independence fighters of the Malayan National Liberation Army (MNLA) and the military forces o ...

and the

U.S. military The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is the ...

in Vietnam during the Vietnam War, the

Seveso disaster Seveso (; lmo, label= Lombard, Séves ) is a town and ''comune'' in the Province of Monza and Brianza, in the Region of Lombardy. The economy of the town has traditionally been based on the furniture industry. Its name comes from the river of ...

, 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

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