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
  • Gas phase ion energetics data
  • IR Spectrum
  • Gas Chromatography
  • References
  • Notes
• Other data available:
  • Henry's Law data
  • Ion clustering data
  • Mass spectrum (electron ionization)
  • Vibrational and/or electronic energy levels
• 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:
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Data at NIST subscription sites:

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

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Gas phase thermochemistry data

Go To: Top, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, IR Spectrum, Gas Chromatography, References, Notes

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 (J/mol*K)
    H° = standard enthalpy (kJ/mol)
    S° = standard entropy (J/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 (bar)
    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

Gas phase ion energetics 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 evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
LL - Sharon G. Lias and Joel F. Liebman

View reactions leading to C₂H₂⁺ (ion structure unspecified)

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

C₂H^- +  =

By formula: C₂H^- + H⁺ = C₂H₂

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

Gas Chromatography

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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

Kovats' RI, non-polar column, isothermal

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Kovats' RI, non-polar column, custom temperature program

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Normal alkane RI, non-polar column, temperature ramp

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Normal alkane RI, non-polar column, custom temperature program

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References

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, IR Spectrum, Gas Chromatography, Notes

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

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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]

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Notes

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• Symbols used in this document:
  

  AE	Appearance energy
  Cp,gas	Constant pressure heat capacity of gas
  IE (evaluated)	Recommended ionization energy
  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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