Acetylenedicarboxylic acid or butynedioic acid is an organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 (a dicarboxylic acid

Dicarboxylic acid

Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R may be an alkyl, alkenyl, alkynyl, or aryl group...

) with the formula C₄H₂O₄ or HO₂C-C≡C-CO₂H. It is a crystalline solid that is soluble in diethyl ether

Diethyl ether

Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

.

The removal of two proton

Proton

The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

s yields the acetylenedicarboxylate

Acetylenedicarboxylate

Acetylenedicarboxylate is a divalent anion with formula C4O42− or [O2C–C≡C–CO2]2−; or any salt or ester thereof. The anion can be derived from acetylenedicarboxylic acid C4H2O4 by the loss of two protons...

 dianion C₄O₄²⁻, which consists only of carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 and oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

, making it an oxocarbon anion

Oxocarbon anion

In chemistry, an oxocarbon anion is a negative ion consisting solely of carbon and oxygen atoms, and therefore having the general formula CxOyn− for some integers x, y, and n....

. Partial ionization yields the monovalent hydrogenacetylenedicarboxylate

Hydrogenacetylenedicarboxylate

Hydrogenacetylenedicarboxylate is a monovalent anion with the formula C4HO4− or HO2C-C≡C-CO2−...

 anion HC₄O₄⁻.

The acid was first described in 1877 by Polish chemist Ernest Bandrowski

Ernest Tytus Bandrowski

Ernest Tytus Bandrowski was a Polish chemist.Bandrowski was professor at the Jagiellonian University starting in 1896. He studied crystalloluminescence and described a number of chemical compounds, such as acetylenedicarboxylic acid....

. It can be obtained by treating α,β-dibromosuccinic acid

Succinic acid

Succinic acid is a dicarboxylic acid. Succinate plays a biochemical role in the citric acid cycle. The name derives from Latin succinum, meaning amber, from which the acid may be obtained....

 with potassium hydroxide

Potassium hydroxide

Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 KOH in methanol

Methanol

Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

 or ethanol

Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

. The reaction yields potassium bromide

Potassium bromide

Potassium bromide is a salt, widely used as an anticonvulsant and a sedative in the late 19th and early 20th centuries, with over-the-counter use extending to 1975 in the United States. Its action is due to the bromide ion...

 and potassium acetylenedicarboxylate. The salts are separated and the latter is treated with sulfuric acid

Sulfuric acid

Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

.

Acetylenedicarboxylic acid is used in the synthesis of dimethyl acetylenedicarboxylate

Dimethyl acetylenedicarboxylate

Dimethyl acetylenedicarboxylate is the organic compound with the formula CH3O2CC2CO2CH3. This ester, which exists as a liquid at room temperature, is highly electrophilic. As such, DMAD, as it is commonly called in the laboratory, is widely employed as a dienophile in cycloaddition reactions,...

, an important laboratory reagent. Both the acid and the monobasic salt potassium hydrogenacetylenedicarboxylate

Potassium hydrogenacetylenedicarboxylate

Potassium hydrogenacetylenedicarboxylate is a potassium salt with chemical formula KC4HO4 or K+·HC4O4−, often abbreviated as KHadc. It is often called potassium hydrogen acetylenedicarboxylate or monopotassium acetylenedicarboxylate....

KC₄HO₄ are commonly traded as laboratory chemicals.