Arsonic acids are a subset of

organoarsenic compound Organoarsenic chemistry is the chemistry of compounds containing a chemical bond between arsenic and carbon. A few organoarsenic compounds, also called "organoarsenicals," are produced industrially with uses as insecticides, herbicides, and fungic ...

s defined as

oxyacid An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bonded to oxygen that can dissociate to produce ...

s where a

pentavalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of a ...

arsenic atom is bonded to two

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy g ...

s, a third oxygen atom (this one with a double bond), and an organic

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 ...

. The

salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

s of arsonic acids are called arsonates. Like all arsenic-containing compounds, arsonic acids are toxic and

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...

ic to humans.

Arsonic acid Arsonic acid is the simplest of the arsonic acids. It is a hypothetical compound, although the tautomeric arsenious acid (As(OH)3) is well established. In contrast to the instability of HAsO(OH)2, the phosphorus compound with analogous stoichi ...

refers to , the case where the substituent is a single hydrogen atom. The other arsonic acids can simply be viewed as hydrocarbyl derivatives of this base case.

Arsenic acid Arsenic acid or trihydrogen arsenate is the chemical compound with the formula . More descriptively written as , this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as ...

results when the substituent is a hydroxyl group.

Methylarsonic acid Methylarsonic acid is an organoarsenic compound with the formula CH3AsO3H2. It is a colorless, water-soluble solid. Salts of this compound, e.g. disodium methyl arsonate, have been widely used in as herbicides and fungicides in growing cotton an ...

results when the substituent is a methyl group.

Phenylarsonic acid Phenylarsonic acid is the chemical compound with the formula C6H5AsO(OH)2, commonly abbreviated PhAsO3H2. This colourless solid is an organic derivative of arsenic acid, AsO(OH)3, where one OH group has been replaced by a phenyl group. The compo ...

results when the substituent is a

phenyl group In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula C6 H5, and is often represented by the symbol Ph. Phenyl group is closely related to benzene and can be viewed as a benzene ring, minus a hydrogen ...

Syntheses

The Béchamp reaction is used to produce

arsonic acids Arsonic acids are a subset of organoarsenic compounds defined as oxyacids where a pentavalent arsenic atom is bonded to two hydroxyl groups, a third oxygen atom (this one with a double bond), and an organic substituent. The salts/conjugate base ...

from activated aromatic substrates. The reaction is an

electrophilic aromatic substitution Electrophilic aromatic substitution is an organic reaction in which an atom that is attached to an aromatic system (usually hydrogen) is replaced by an electrophile. Some of the most important electrophilic aromatic substitutions are aromatic ni ...

, using

arsenic acid Arsenic acid or trihydrogen arsenate is the chemical compound with the formula . More descriptively written as , this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as ...

as the electrophile. The reaction proceeds according to this idealized stoichiometry: :

Uses

Poultry feed

Arsanilic acid Arsanilic acid, also known as aminophenyl arsenic acid or aminophenyl arsonic acid, is an organoarsenic compound, an amino derivative of phenylarsonic acid whose amine group is in the 4-position. A crystalline powder introduced medically in the l ...

carbarsone Carbarsone is an organoarsenic compound used as an antiprotozoal drug for treatment of amebiasis and other infections. It was available for amebiasis in the United States as late as 1991. Thereafter, it remained available as a turkey feed additi ...

nitarsone Nitarsone is an organoarsenic compound that is used in poultry production as a feed additive to increase weight gain, improve feed efficiency, and prevent histomoniasis (blackhead disease). It is marketed as Histostat by Zoetis. Nitarsone once ...

, and roxarsone were formerly used in poultry feed in order to promote growth and increase feed conversion. In addition,

and

can also prevent histomoniasis. However, concern grew over whether or not the arsenic would be ingested by humans when they ate the poultry. In 2013, a study found that chickens who were fed roxarsone and other arsenic-containing feed additives tended to show elevated levels of arsenic in

breast meat Poultry () are domesticated birds kept by humans for their eggs, their meat or their feathers. These birds are most typically members of the superorder Galloanserae (fowl), especially the order Galliformes (which includes chickens, quails, ...

—three times as high—compared to chickens that were not fed any arsenical feed additives. On September of that year,

Zoetis Zoetis Inc. (/zō-EH-tis/) is an American drug company, the world's largest producer of medicine and vaccinations for pets and livestock. The company was a subsidiary of Pfizer, the world's largest drug maker, but with Pfizer's spinoff of its ...

and

Fleming Laboratories Fleming may refer to: Places Australia *Fleming, Northern Territory, a town and a locality Canada * Fleming, Saskatchewan * Fleming Island (Saskatchewan) Egypt * Fleming (neighborhood), a neighborhood in Alexandria Greenland * Fleming Fjord ...

, the drugs' sponsors, voluntarily withdrew the FDA approvals for

arsanilic acid Arsanilic acid, also known as aminophenyl arsenic acid or aminophenyl arsonic acid, is an organoarsenic compound, an amino derivative of phenylarsonic acid whose amine group is in the 4-position. A crystalline powder introduced medically in the l ...

, and roxarsone, leaving only

approved until its approval for use in animal feed was withdrawn by the FDA in 2015.

Medicine

Difetarsone Difetarsone is an antiprotozoal agent. Various studies have shown it to be particularly effective against ''Trichuris trichiura'', commonly known as the whipworm. Prior to the drugs use in the early 1970s, there were few effective treatments for th ...

and

can be used to treat protozoal infections and

Entamoeba histolytica ''Entamoeba histolytica'' is an anaerobic parasitic amoebozoan, part of the genus ''Entamoeba''. Predominantly infecting humans and other primates causing amoebiasis, ''E. histolytica'' is estimated to infect about 35-50 million people worldwid ...

infections.

can also be used to treat

whipworm ''Trichuris trichiura, Trichocephalus trichiuris'' or whipworm, is a parasitic roundworm (a type of helminth) that causes trichuriasis (a type of helminthiasis which is one of the neglected tropical diseases) when it infects a human large intes ...

infections.

was discovered to treat

sleeping sickness African trypanosomiasis, also known as African sleeping sickness or simply sleeping sickness, is an insect-borne parasitic infection of humans and other animals. It is caused by the species ''Trypanosoma brucei''. Humans are infected by two typ ...

in the early 1900s, but its usage in humans was discontinued after it was found to be too toxic. Acetarsol is an anti-infective.

List

is technically not an arsonic acid because the substituent is a hydroxyl group, not a hydrocarbyl group, so arsenic acid has three hydroxyl groups bound to the arsenic atom, while arsonic acids only have two.

References

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