Acetylene

• Formula: C₂H₂
• Molecular weight: 26.0373
• IUPAC Standard InChI: InChI=1S/C2H2/c1-2/h1-2H Copy

  
• IUPAC Standard InChIKey: HSFWRNGVRCDJHI-UHFFFAOYSA-N Copy
• CAS Registry Number: 74-86-2
• Chemical structure:
  This structure is also available as a 2d Mol file or as a computed 3d SD file
  The 3d structure may be viewed using Java or Javascript.
• Other names: Ethyne; Ethine; Narcylen; C2H2; Acetylen; UN 1001; Vinylene
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase thermochemistry data
  • Phase change data
  • Reaction thermochemistry data
  • IR Spectrum
  • Mass spectrum (electron ionization)
  • References
  • Notes
• Other data available:
  • Henry's Law data
  • Gas phase ion energetics data
  • Ion clustering data
  • Vibrational and/or electronic energy levels
  • Gas Chromatography
• Data at other public NIST sites:
  • Microwave spectra (on physics lab web site)
  • Electron-Impact Ionization Cross Sections (on physics web site)
  • Gas Phase Kinetics Database
• Options:
  • Switch to SI units

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• NIST / TRC Web Thermo Tables, professional edition (thermophysical and thermochemical data)

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Gas phase thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
DRB - Donald R. Burgess, Jr.
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
GT - Glushko Thermocenter, Russian Academy of Sciences, Moscow

Constant pressure heat capacity of gas

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
    C_p = heat capacity (cal/mol*K)
    H° = standard enthalpy (kcal/mol)
    S° = standard entropy (cal/mol*K)
    t = temperature (K) / 1000.

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Phase change data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
BS - Robert L. Brown and Stephen E. Stein
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director
AC - William E. Acree, Jr., James S. Chickos
CAL - James S. Chickos, William E. Acree, Jr., Joel F. Liebman, Students of Chem 202 (Introduction to the Literature of Chemistry), University of Missouri -- St. Louis

Enthalpy of vaporization

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
    P = vapor pressure (atm)
    T = temperature (K)

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Enthalpy of sublimation

Enthalpy of fusion

Entropy of fusion

Reaction thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
B - John E. Bartmess
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
RCD - Robert C. Dunbar
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
MS - José A. Martinho Simões

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Individual Reactions

C₂H^- +  =

By formula: C₂H^- + H⁺ = C₂H₂

COS⁺ +  = (COS⁺ • )

By formula: COS⁺ + C₂H₂ = (COS⁺ • C₂H₂)

 +  = ( • )

By formula: Co⁺ + C₂H₂ = (Co⁺ • C₂H₂)

Enthalpy of reaction

 +  = ( • )

By formula: Ni⁺ + C₂H₂ = (Ni⁺ • C₂H₂)

Enthalpy of reaction

2 +  =

By formula: 2H₂ + C₂H₂ = C₂H₆

=  + 

By formula: C₇H₈ = C₅H₆ + C₂H₂

C₂Na₂ (cr) + 2 (l) = 2( • 1418) (solution) +  (g)

By formula: C₂Na₂ (cr) + 2H₂O (l) = 2(HNaO • 1418H₂O) (solution) + C₂H₂ (g)

C₂HCs (cr) +  (l) = ( • 1031) (solution) +  (g)

By formula: C₂HCs (cr) + H₂O (l) = (HCsO • 1031H₂O) (solution) + C₂H₂ (g)

C₂HNa (cr) +  (l) = ( • 1418) (solution) +  (g)

By formula: C₂HNa (cr) + H₂O (l) = (HNaO • 1418H₂O) (solution) + C₂H₂ (g)

 +  = ( • )

By formula: Cu⁺ + C₂H₂ = (Cu⁺ • C₂H₂)

Enthalpy of reaction

2 =

By formula: 2C₂H₂ = C₄H₄

Rh⁺ +  = (Rh⁺ • )

By formula: Rh⁺ + C₂H₂ = (Rh⁺ • C₂H₂)

Enthalpy of reaction

 +  = ( • )

By formula: Cr⁺ + C₂H₂ = (Cr⁺ • C₂H₂)

Enthalpy of reaction

 +  = ( • )

By formula: Ti⁺ + C₂H₂ = (Ti⁺ • C₂H₂)

Enthalpy of reaction

 +  = ( • )

By formula: La⁺ + C₂H₂ = (La⁺ • C₂H₂)

Enthalpy of reaction

 +  = ( • )

By formula: Sc⁺ + C₂H₂ = (Sc⁺ • C₂H₂)

Enthalpy of reaction

 +  = ( • )

By formula: V⁺ + C₂H₂ = (V⁺ • C₂H₂)

Enthalpy of reaction

 +  = ( • )

By formula: Y⁺ + C₂H₂ = (Y⁺ • C₂H₂)

Enthalpy of reaction

 +  = C₂H₂Br^-

By formula: Br^- + C₂H₂ = C₂H₂Br^-

C₂Ag₂ (cr) + 2( • 12.3) (solution) =  (aq) + 2 (cr)

By formula: C₂Ag₂ (cr) + 2(HCl • 12.3H₂O) (solution) = C₂H₂ (aq) + 2AgCl (cr)

(CAS Reg. No. 25012-81-1 • 4294967295) +  = CAS Reg. No. 25012-81-1

By formula: (CAS Reg. No. 25012-81-1 • 4294967295C₂H₂) + C₂H₂ = CAS Reg. No. 25012-81-1

 +  = ( • )

By formula: Al⁺ + C₂H₂ = (Al⁺ • C₂H₂)

=  + 

By formula: C₂H₂Cl₂ = C₂H₂ + Cl₂

=  + 

By formula: C₂H₃Cl = C₂H₂ + HCl

 +  =

By formula: C₅H₆ + C₂H₂ = C₇H₈

C₂H₂⁺ +  = (C₂H₂⁺ • )

By formula: C₂H₂⁺ + C₂H₂ = (C₂H₂⁺ • C₂H₂)

 +  = ( • )

By formula: Fe⁺ + C₂H₂ = (Fe⁺ • C₂H₂)

=  + 

By formula: C₂H₂I₂ = C₂H₂ + I₂

C₂H₂I₂ =  + 

By formula: C₂H₂I₂ = C₂H₂ + I₂

IR Spectrum

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Data compiled by: Coblentz Society, Inc.

• GAS (50 mmHg DILUTED TO A TOTAL PRESSURE OF 600 mmHg WITH N2); DOW KBr FOREPRISM; DIGITIZED BY NIST FROM HARD COPY (FROM TWO SEGMENTS); 4 cm^-1 resolution

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

• gas

Mass spectrum (electron ionization)

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

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Additional Data

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, IR Spectrum, Mass spectrum (electron ionization), Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [all data]

Manion, 2002
Manion, J.A., Evaluated Enthalpies of Formation of the Stable Closed Shell C1 and C2 Chlorinated Hydrocarbons, J. Phys. Chem. Ref. Data, 2002, 31, 1, 123-172, https://doi.org/10.1063/1.1420703 . [all data]

Gurvich, Veyts, et al., 1991
Thermodynamic Properties of Individual Substances, 4th edition, Volume 2, Gurvich, L.V.; Veyts, I.V.; Alcock, C.B.;, ed(s)., Hemisphere, New York, 1991. [all data]

Wagman, Kilpatrick, et al., 1945
Wagman, D.D.; Kilpatrick, J.E.; Pitzer, K.S.; Rossini, F.D., Heats, equilibrium constants, and free energies of formation of the acetylene hydrocarbons through the pentynes, to 1,500° K, J. Res. NBS, 1945, 35, 467-496. [all data]

Gurvich, Veyts, et al., 1989
Gurvich, L.V.; Veyts, I.V.; Alcock, C.B., Thermodynamic Properties of Individual Substances, 4th ed.; Vols. 1 and 2, Hemisphere, New York, 1989. [all data]

Buckingham and Donaghy, 1982
Buckingham, J.; Donaghy, S.M., Dictionary of Organic Compounds: Fifth Edition, Chapman and Hall, New York, 1982, 1. [all data]

Maass and Wright, 1921
Maass, O.; Wright, C.H., SOME PHYSICAL PROPERTIES OF HYDROCARBONS CONTAINING TWO AND THREE CARBON ATOMS., J. Am. Chem. Soc., 1921, 43, 5, 1098-1111, https://doi.org/10.1021/ja01438a013 . [all data]

Morehouse and Maass, 1931
Morehouse, F.R.; Maass, O., The Preparationa and Physical Properties of Ethyl and Methyl Acetylene, Can. J. Res., 1931, 5, 306. [all data]

Maass and Russell, 1918
Maass, O.; Russell, J., Unsaturation and molecular compound formation, J. Am. Chem. Soc., 1918, 40, 1561-1573. [all data]

McIntosh, 1907
McIntosh, D., The physical properties of liquid and solid acetylene., J. Phys. Chem., 1907, 11, 306-17. [all data]

Clark and Din, 1950
Clark, A.M.; Din, F., Equilibria Between Solid, Liquid, and Gaseous Phases at Low Temperature binary systems acetylene - carbon dioxide, acetylene - ethylene and acetylene - ethane, Trans. Faraday Soc., 1950, 46, 901. [all data]

Tsonopoulos and Ambrose, 1996
Tsonopoulos, C.; Ambrose, D., Vapor-Liquid Critical Properties of Elements and Compounds. 6. Unsaturated Aliphatic Hydrocarbons, J. Chem. Eng. Data, 1996, 41, 645-656. [all data]

Goloborod'ko and Khodeeva, 1972
Goloborod'ko, N.P.; Khodeeva, S.M., Russ. J. Phys. Chem. (Engl. Transl.), 1972, 46, 235-7. [all data]

Khodeeva, 1966
Khodeeva, S.M., Visual Observation of Gas-Gas Mixture, Russ. J. Phys. Chem. (Engl. Transl.), 1966, 40, 1061-3. [all data]

Stephenson and Malanowski, 1987
Stephenson, Richard M.; Malanowski, Stanislaw, Handbook of the Thermodynamics of Organic Compounds, 1987, https://doi.org/10.1007/978-94-009-3173-2 . [all data]

Reid, 1972
Reid, Robert C., Handbook on vapor pressure and heats of vaporization of hydrocarbons and related compounds, R. C. Wilhort and B. J. Zwolinski, Texas A Research Foundation. College Station, Texas(1971). 329 pages.$10.00, AIChE J., 1972, 18, 6, 1278-1278, https://doi.org/10.1002/aic.690180637 . [all data]

Ambrose and Townsend, 1964
Ambrose, D.; Townsend, R., Vapour pressure of acetylene, Trans. Faraday Soc., 1964, 60, 1025, https://doi.org/10.1039/tf9646001025 . [all data]

Ambrose, 1956
Ambrose, D., The vapour pressures and critical temperatures of acetylene and carbon dioxide, Trans. Faraday Soc., 1956, 52, 772, https://doi.org/10.1039/tf9565200772 . [all data]

Boublik, Fried, et al., 1984
Boublik, T.; Fried, V.; Hala, E., The Vapour Pressures of Pure Substances: Selected Values of the Temperature Dependence of the Vapour Pressures of Some Pure Substances in the Normal and Low Pressure Region, 2nd ed., Elsevier, New York, 1984, 972. [all data]

Ambrose and Townsend, 1964, 2
Ambrose, D.; Townsend, R., Vapour Pressure of Acetylene, Trans. Faraday Soc., 1964, 60, 1025-1029, https://doi.org/10.1039/tf9646001025 . [all data]

Ambrose, 1956, 2
Ambrose, D., The Vapour Pressures and Critical Temperatures of Acetylene and Carbon Dioxide, Trans. Faraday Soc., 1956, 52, 772-781, https://doi.org/10.1039/tf9565200772 . [all data]

Jones, 1960
Jones, A.H., Sublimation Pressure Data for Organic Compounds., J. Chem. Eng. Data, 1960, 5, 2, 196-200, https://doi.org/10.1021/je60006a019 . [all data]

Stull, 1947
Stull, Daniel R., Vapor Pressure of Pure Substances. Organic and Inorganic Compounds, Ind. Eng. Chem., 1947, 39, 4, 517-540, https://doi.org/10.1021/ie50448a022 . [all data]

Burbo, 1943
Burbo, P.Z., Russ. J. Phys. Chem., 1943, 7, 286. [all data]

Miskiewicz, Rieser, et al., 2010
Miskiewicz, Stefan; Rieser, Klaus; Dorfmüller, Thomas, Thermodynamische Untersuchungen an kondensierten Phasen, Berichte der Bunsengesellschaft für physikalische Chemie, 2010, 80, 5, 395-405, https://doi.org/10.1002/bbpc.19760800504 . [all data]

Miskiewicz, Rieser, et al., 1976
Miskiewicz, S.; Rieser, K.; Dorfmuller, T., Thermodynamische Untersuchungen an kondensierten Phasen, Ber. Bunsen-Ges. Physik. Chem., 1976, 80, 5, 395, https://doi.org/10.1002/bbpc.19760800504 . [all data]

Graul S.T. and Bowers, 1991
Graul S.T.; Bowers, M.T., Dynamics of Metastable Dissociation and Photodissociation of the Gas Phase Cluster Ion (OCS.C2H2)+, J. Phys. Chem., 1991, 95, 21, 8328, https://doi.org/10.1021/j100174a055 . [all data]

Orlando, Friedman, et al., 1990
Orlando, T.M.; Friedman, A.; Maier, J.P., Photodissociation Spectroscopy of the [OCS C2H2]+ Cluster, J. Chem. Phys., 1990, 92, 12, 7365, https://doi.org/10.1063/1.458222 . [all data]

Surya, Ranatunga, et al., 1997
Surya, P.I.; Ranatunga, D.R.A.; Freiser, B.S., Infrared Multiphoton Dissociation of MC4H6+ [M=Fe, Co or Ni: C4H6=1,3-butadiene or (C2H2)(C2H4), J. Am. Chem. Soc., 1997, 119, 14, 3351, https://doi.org/10.1021/ja963200c . [all data]

Armentrout and Kickel, 1994
Armentrout, P.B.; Kickel, B.L., Gas Phase Thermochemistry of Transition Metal Ligand Systems: Reassessment of Values and Periodic Trends, in Organometallic Ion Chemistry, B. S. Freiser, ed, 1994. [all data]

Conn, Kistiakowsky, et al., 1939
Conn, J.B.; Kistiakowsky, G.B.; Smith, E.A., Heats of organic reactions. VIII. Some further hydrogenations, including those of some acetylenes, J. Am. Chem. Soc., 1939, 61, 1868-1876. [all data]

Cox and Pilcher, 1970
Cox, J.D.; Pilcher, G., Thermochemistry of Organic and Organometallic Compounds, Academic Press, New York, 1970, 1-636. [all data]

Walsh and Wells, 1975
Walsh, R.; Wells, J.M., The enthalpy of formation of bicyclo[2,2,1]hepta-2,5-diene. Thermodynamic functions of bicyclo[2,2,1]heptane and bicyclo[2,2,1]hepta-2,5-diene, J. Chem. Thermodyn., 1975, 7, 149-154. [all data]

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Johnson, G.K.; van Deventer, E.H.; Ackerman, J.P.; Hubbard, W.N.; Osborne, D.W.; Flotow, H.L., J. Chem. Thermodyn., 1973, 5, 57. [all data]

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Reppe, W.; Schlichting, O.; Klager, K.; Toepel, T., Cyclisierende Polymerisation von Acetylen I Uber Cyclooctatetraen, Justus Liebigs Ann. Chem., 1948, 1-93. [all data]

Chen and Armetrout, 1995
Chen, Y.M.; Armetrout, P.B., Activation of C2H6, C3H8, and c-C3H6 by Gas-Phase Rh+ and the Thermochemistry of Rh-Ligand Complexes, J. Am. Chem. Soc., 1995, 117, 36, 9291, https://doi.org/10.1021/ja00141a022 . [all data]

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Wild, D.A.; Milley, P.J.; Loh, Z.M.; Wolynec, P.P.; Weiser, P.S.; Bieske, E.J., Structural and Energetic Properties of the Br--C2H2 Anion Complex from Rotationally Resolved Mid-infrared Spectra And ab initio Calculations, J. Chem. Phys., 2000, 113, 3, 1075, https://doi.org/10.1063/1.481919 . [all data]

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Ervin, Gronert, et al., 1990
Ervin, K.M.; Gronert, S.; Barlow, S.E.; Gilles, M.K.; Harrison, A.G.; Bierbaum, V.M.; DePuy, C.H.; Lin, W.C., Bonds Strengths of Ethylene and Acetylene, J. Am. Chem. Soc., 1990, 112, 15, 5750, https://doi.org/10.1021/ja00171a013 . [all data]

Stockigt, Schwarz, et al., 1996
Stockigt, D.; Schwarz, J.; Schwarz, H., Theoretical and Experimental Studies on the Bond Dissociation Energies of Al(methane)+, Al(acetylene)+, Al(ethene)+, and Al(ethane)+, J. Phys. Chem., 1996, 100, 21, 8786, https://doi.org/10.1021/jp960060k . [all data]

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Laursen, S.L.; Pimentel, G.C., Matrix-induced intersystem crossing in the photochemistry of the 1,2-dichloroethenes, J. Phys. Chem., 1989, 93, 2328-2333. [all data]

Lacher, Gottlieb, et al., 1962
Lacher, J.R.; Gottlieb, H.B.; Park, J.D., Reaction heats of organic compounds. Part 2.-Heat of addition of hydrogen chloride to acetylene, Trans. Faraday Soc., 1962, 58, 2348-2351. [all data]

Ono and Ng, 1982
Ono, Y.; Ng, C.Y., A Study of the Unimolecular Decomposition of the (C2H2)2+ Complex, J. Chem. Phys., 1982, 77, 6, 2947, https://doi.org/10.1063/1.444216 . [all data]

Furuyama, Golden, et al., 1968
Furuyama, S.; Golden, D.M.; Benson, S.W., The thermochemistry of the gas-phase equilibria trans-1,2-diiodoethylene = acetylene + I₂ and trans-1,2-diiodoethylene = cis-1,2-diiodoethylene, J. Phys. Chem., 1968, 72, 3204-3208. [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, IR Spectrum, Mass spectrum (electron ionization), References

• Symbols used in this document:
  

  Cp,gas	Constant pressure heat capacity of gas
  Pc	Critical pressure
  Ptriple	Triple point pressure
  S°gas,1 bar	Entropy of gas at standard conditions (1 bar)
  T	Temperature
  Tboil	Boiling point
  Tc	Critical temperature
  Tfus	Fusion (melting) point
  Ttriple	Triple point temperature
  Vc	Critical volume
  ΔfH°gas	Enthalpy of formation of gas at standard conditions
  ΔfusH	Enthalpy of fusion
  ΔfusS	Entropy of fusion
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ΔsubH	Enthalpy of sublimation
  ΔvapH	Enthalpy of vaporization
  ρc	Critical density

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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