Acetylenedicarboxylic acid or butynedioic acid is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

dicarboxylic acid In organic chemistry, a dicarboxylic acid is an organic compound containing two carboxyl groups (). The general molecular formula for dicarboxylic acids can be written as , where R can be aliphatic or aromatic. In general, dicarboxylic acids show ...

) with the formula C₄H₂O₄ or . It is a crystalline solid that is soluble in

diethyl ether Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable liq ...

. The removal of two

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

s yields the acetylenedicarboxylate dianion , which consists only of

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

, making it an

oxocarbon anion In chemistry, an oxocarbon anion is a negative ion consisting solely of carbon and oxygen atoms, and therefore having the general formula for some integers ''x'', ''y'', and ''n''. The most common oxocarbon anions are carbonate, , and oxalate, ...

. Partial ionization yields the monovalent

hydrogenacetylenedicarboxylate Acetylenedicarboxylic acid or butynedioic acid is an organic compound (a dicarboxylic acid) with the formula C4H2O4 or . It is a crystalline solid that is soluble in diethyl ether. The removal of two protons yields the acetylenedicarboxylate di ...

anion . The acid was first described in 1877 by Polish chemist Ernest Bandrowski. It can be obtained by treating α,β-dibromo

succinic acid Succinic acid () is a dicarboxylic acid with the chemical formula (CH2)2(CO2H)2. The name derives from Latin ''succinum'', meaning amber. In living organisms, succinic acid takes the form of an anion, succinate, which has multiple biological ro ...

with

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

KOH in

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

. The reaction yields

potassium bromide Potassium bromide ( K Br) 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 US. Its action is due to the bromide ion (sodium bromide is equall ...

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

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

. Acetylenedicarboxylic acid is used in the synthesis of

dimethyl acetylenedicarboxylate Dimethyl acetylenedicarboxylate (DMAD) is an organic compound with the formula CH3O2CC2CO2CH3. It is a di-ester in which the ester groups are conjugated with a C-C triple bond. As such, the molecule is highly electrophilic, and is widely employed ...

, an important laboratory reagent. The acid is commonly traded as a laboratory chemical. It can also be reacted with

sulfur tetrafluoride Sulfur tetrafluoride is the chemical compound with the formula S F4. It is a colorless corrosive gas that releases dangerous HF upon exposure to water or moisture. Despite these unwelcome characteristics, this compound is a useful reagent for t ...

to produce

hexafluoro-2-butyne Hexafluoro-2-butyne (HFB) is a fluorocarbon with the chemical structure CF3C≡CCF3. HFB is a particularly electrophilic acetylene derivative, and hence a potent dienophile for Diels–Alder reactions. HFB is prepared by the action of sulfur te ...

, a powerful dienophile for use in Diels-Alder reactions. Fatty alcohol esters of acetylenedicarboxylic acid can be used for the preparation of phase change materials (PCM).

Anions and salts

Hydrogenacetylenedicarboxylate (often abbreviated as Hadc or HADC) is a monovalent

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

of acetylenedicarboxylic acid with the formula or . The anion can be derived from acetylenedicarboxylic acid by removal of a single

or from the

acetylenedicarboxylate Acetylenedicarboxylic acid or butynedioic acid is an organic compound (a dicarboxylic acid) with the formula C4H2O4 or . It is a crystalline solid that is soluble in diethyl ether. The removal of two protons yields the acetylenedicarboxylate di ...

dianion by addition of a proton. The name is also used for any

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

of this anion. Salts of this anion are of interest in

crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The wor ...

because they contain unusually short and strong

hydrogen bond In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a ...

s. In many crystalline salts (with the exception of the

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...

one), the HADC units form linear chains connected by strong hydrogen bonds. Each carboxylate group is usually planar; but the two groups may lie in different planes due to rotation about the carbon–carbon bonds. They are coplanar in the

hydrated Drinking is the act of ingesting water or other liquids into the body through the mouth, proboscis, or elsewhere. Humans drink by swallowing, completed by peristalsis in the esophagus. The physiological processes of drinking vary widely among ot ...

salts and , nearly coplanar in the

guanidinium Guanidine is the compound with the formula HNC(NH2)2. It is a colourless solid that dissolves in polar solvents. It is a strong base that is used in the production of plastics and explosives. It is found in urine predominantly in patients experien ...

salt , but off by 60° or more in other salts such as anhydrous . Potassium hydrogenacetylenedicarboxylate is a

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

of HADC with chemical formula KC₄HO₄ or , often abbreviated as KHadc. It is often called potassium hydrogen acetylenedicarboxylate or monopotassium acetylenedicarboxylate. The salt can be obtained from acetylenedicarboxylic acid and is a common laboratory starting material for the synthesis of other derivatives of that acid. In the crystalline form, the hydrogenacetylenedicarboxylate anions are joined into linear chains by uncommonly short hydrogen bonds.

Acetylenedicarboxylate (often abbreviated as ADC or adc) is a divalent anion with formula or ₂C–C≡C–CO₂sup>2−; or any

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

thereof. The anion can be derived from acetylenedicarboxylic acid by the loss of two

s. It is one of several oxocarbon anions which, like

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

and

oxalate Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl o ...

, consist solely of

and

. The ADC anion can at as a

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...

organometallic complex Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and s ...

es, such as the blue polymeric complex with

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

( II) and 2,2′-

bipyridine Bipyridines also known as bipyridyls, dipyridyls, and dipyridines, are a family of chemical compounds with the formula (C5H4N)2, consisting of two pyridyl (C5H4N) rings. Pyridine is an aromatic nitrogen-containing heterocycle. Bipyridines are of sig ...

, .

Thallium Thallium is a chemical element with the Symbol (chemistry), symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists W ...

(I) acetylenedicarboxylate (Tl₂C₄O₄) decomposes at 195 °C, leaving a residue of

pyrophoric A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolith ...

thallium powder.

References

{{Reflist Alkyne derivatives Dicarboxylic acids

Anions and salts

See also

References