Acetylenediol, or ethynediol, is a

chemical substance A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...

with formula HO−C≡C−OH (an

ynol In organic chemistry, an alkynol (shortened to ynol) is an alkyne with a hydroxyl group affixed to one of the two carbon atoms composing the triple bond (). The deprotonated anions of ynols are known as '' ynolates''. An ynol with hydroxyl gro ...

). It is the diol of acetylene. Acetylenediol is unstable in the condensed phase, although its

tautomer Tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert. The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hyd ...

glyoxal Glyoxal is an organic compound with the chemical formula OCHCHO. It is the smallest dialdehyde (a compound with two aldehyde groups). It is a crystalline solid, white at low temperatures and yellow near the melting point (15 °C). The liquid ...

(CHO)₂ is well known.

Detection

Acetylenediol was first observed in the gas-phase by mass spectrometry. The compound was later obtained by photolysis of

squaric acid Squaric acid, also called quadratic acid because its four carbon atoms approximately form a square, is a diprotic organic acid with the chemical formula C4O2(OH)2. The conjugate base of squaric acid is the hydrogensquarate anion ; and the conjug ...

in a solid argon matrix at .

Derivatives

Alkoxide derivatives

Like the diol, most simple ether derivatives are labile.

Di-tert-butoxyacetylene Di-''tert''-butoxyacetylene is the organic compound with the formula (CH3)3COC≡COC(CH3)3. A pale yellow liquid, it is one of the more common dialkoxyacetylenes. Most other dialkoxyacetylenes are very labile. For example, dimethoxyacetylene p ...

is however a distillable liquid.

Acetylenediolate salts

Salts of the acetylenediolate (ethynediolate) dianion ⁻O−C≡C−O⁻ are known. They are not however prepared from ethynediol, but by the reduction of

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

. Potassium acetylenediolate (K₂C₂O₂) was first obtained by

Liebig Justus Freiherr von Liebig (12 May 1803 – 20 April 1873) was a German scientist who made major contributions to agricultural and biological chemistry, and is considered one of the principal founders of organic chemistry. As a professor at t ...

in 1834, from the reaction of

with metallic

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 atmosph ...

;Justus Liebig (1834), Annalen der Chemie und Pharmacie, volume 11, p. 182. Cited by Raymond N. Vrtis et al. (1988), JACS p. 7564. but for a long time the product was assumed to be "potassium carbonyl" (KCO). Over the next 130 years were described the "carbonyls" of

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

(Johannis, 1893), barium (Gunz and Mentrel, 1903), strontium (Roederer, 1906), and

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 ...

, rubidium, and caesium (Pearson, 1933).T. G. Pearson (1933), ''Carbonyls of Lithium, Rubidium and Caesium''. Nature, volume 131, pp. 166–167 (4 February 1933). The reaction was eventually shown to yield a mixture of the potassium acetylenediolate and potassium benzenehexolate .Werner Büchner, E. Weiss (1964) ''Zur Kenntnis der sogenannten «Alkalicarbonyle» IV Über die Reaktion von geschmolzenem Kalium mit Kohlenmonoxid. Helvetica Chimica Acta'', Volume 47 Issue 6, Pages 1415–1423. The structure of these salts was clarified only in 1963 by Büchner and Weiss.Werner Büchner, E. Weiss (1963) ''Zur Kenntnis der sogenannten «Alkalicarbonyle» I Die Kristallstruktur des Kalium-acetylendiolats, KOC≡COK''. Helvetica Chimica Acta, Volume 46 Issue 4, Pages 1121–1127. E. Weiss, Werner Büchner (1963), ''Zur Kenntnis der sogenannten Alkalicarbonyle. II. Die Kristallstrukturen des Rubidium- und Caesium-acetylendiolats, RbOC≡CORb und CsOC≡COCs.'' Zeitschrift für anorganische und allgemeine Chemie, Volume 330 Issue 5-6, Pages 251–258. Acetylenediolates can also be prepared by the rapid reaction of CO and a solution of the corresponding metal in liquid

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

at low temperature. Potassium acetylenediolate is a pale yellow solid that reacts explosively with air, halogens, halogenated hydrocarbons, alcohols, water, and any substance which possesses an acidic hydrogen.Charles Kenneth Taylor (1982), ''The Chemical Behavior of the Alkali Metal Acetylenediolates''. Thesis, Pennsylvania State University; also Technical Memo A642321, Penn State University Park Applied Research Lab. 227 pages.

Coordination complexes

Acetylenediol can form coordination compounds, such as aH(HOC≡COH)(dmpe)₂Clsup>+Cl⁻ where dmpe is bis(dimethylphosphino)ethane.Raymond N. Vrtis, Ch. Pulla Rao, Simon G. Bott, and Stephen J. Lippard (1988), ''Synthesis and Stabilization of Tantalum-Coordinated Dihydroxyacetylene from Two Reductively Coupled Carbon Monoxide Ligands'' J. Am. Chem. Soc., volume 110 issue 22, pp 7564–7566. Acetylenediolate and related anions such as deltate and squarate have been obtained from carbon monoxide under mild conditions by reductive coupling of CO ligands in organouranium complexes.Alistair S. Frey, F. Geoffrey N. Cloke, Peter B. Hitchcock (2008), ''Mechanistic Studies on the Reductive Cyclooligomerisation of CO by U(III) Mixed Sandwich Complexes; the Molecular Structure of U(η-C₈H₆₂)(η-Cp^*)sub>2(μ-η¹:η¹-C₂O₂)'' Journal of the American Chemical Society, volume 130, issue 42, pages 13816–13817.

References