Acetylenediol, or ethynediol, is a chemical substance with formula HO−C≡C−OH (an ynol). It is the diol of acetylene. Acetylenediol is unstable in the condensed phase, although its tautomerism glyoxal (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 in a
Matrix isolation at .
Recently, this molecule was synthesized in interstellar ice analogs composed of
carbon monoxide (CO) and
water (H
2O) upon exposure to energetic electrons and detected upon sublimation by isomer-selective photoionization reflectron time-of-flight mass spectrometry.
Derivatives
Alkoxide derivatives
Like the diol, most simple ether derivatives are labile. Di-tert-butoxyacetylene 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. Potassium acetylenediolate (K
2C
2O
2) was first obtained by Liebig in 1834, from the reaction of
carbon monoxide with metallic
potassium;
[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 (Johannis, 1893),
barium (Gunz and Mentrel, 1903),
strontium (Roederer, 1906), and
lithium,
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» IV1 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 at low temperature.[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 TaH(HOC≡COH)(dmpe)
2Cl
+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 Deltic acid 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-C8H6{Si'Pr3-1,4}2)(η-Cp*)2(μ-η1:η1-C2O2) Journal of the American Chemical Society, volume 130, issue 42, pages 13816–13817. ]
See also
