2-Butyne

• Formula: C₄H₆
• Molecular weight: 54.0904
• IUPAC Standard InChI: InChI=1S/C4H6/c1-3-4-2/h1-2H3 Copy

  
• IUPAC Standard InChIKey: XNMQEEKYCVKGBD-UHFFFAOYSA-N Copy
• CAS Registry Number: 503-17-3
• 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: But-2-yne; Dimethylacetylene; CH3C≡CCH3; Crotonylene; UN 1144
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Phase change data
  • Gas phase ion energetics data
  • Vibrational and/or electronic energy levels
  • References
  • Notes
• Other data available:
  • Gas phase thermochemistry data
  • Condensed phase thermochemistry data
  • Reaction thermochemistry data
  • IR Spectrum
  • Mass spectrum (electron ionization)
  • Gas Chromatography
• Data at other public NIST sites:
  • Microwave spectra (on physics lab web site)
  • Computational Chemistry Comparison and Benchmark Database
  • Gas Phase Kinetics Database
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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
DH - Eugene S. Domalski and Elizabeth D. Hearing
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

Enthalpy of vaporization

Entropy of vaporization

Enthalpy of sublimation

Enthalpy of fusion

Entropy of fusion

Gas phase ion energetics data

Go To: Top, Phase change data, Vibrational and/or electronic energy levels, References, Notes

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
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

View reactions leading to C₄H₆⁺ (ion structure unspecified)

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

C₄H₅^- +  =

By formula: C₄H₅^- + H⁺ = C₄H₆

Vibrational and/or electronic energy levels

Go To: Top, Phase change data, Gas phase ion energetics data, References, Notes

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

Data compiled by: Takehiko Shimanouchi

Symmetry:   D'_3h     Symmetry Number σ = 6

Source: Shimanouchi, 1972

Notes

References

Go To: Top, Phase change data, Gas phase ion energetics data, Vibrational and/or electronic energy levels, Notes

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

Pomerantz, Fookson, et al., 1954
Pomerantz, P.; Fookson, A.; Mears, T.W.; Rothberg, S.; Howard, F.L., Synthesis and Physical Properties of Several Acetylenic Hydrocarbons, J. Res. Natl. Bur. Stand. (U. S.), 1954, 52, 51. [all data]

Boord, Greenlee, et al., 1946
Boord, C.E.; Greenlee, K.W.; Perilstein, W.L., The Synthesis, Purification and Prop. of Hydrocarbons of Low Mol. Weight, Am. Pet. Inst. Res. Proj. 45, Eighth Annu. Rep., Ohio State Univ., June 30, 1946. [all data]

Henne and Greenlee, 1945
Henne, A.L.; Greenlee, K.W., Preparation and Physical Constants of Acetylenic Compounds, J. Am. Chem. Soc., 1945, 67, 484-5. [all data]

Heisig and Davis, 1935
Heisig, G.B.; Davis, H.M., Physical Constants of Dimethylacetylene, J. Am. Chem. Soc., 1935, 57, 339-40. [all data]

Yost, Osborne, et al., 1941
Yost, D.M.; Osborne, D.W.; Garner, C.S., The Heat Capacity, Entropy, and Heats of Transition, Fusion, and Vaporization of Dimethylacetylene. Free Rotation in the Dimethylacetylene Molecule, J. Am. Chem. Soc., 1941, 63, 3492. [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]

Yost, Osborne, et al., 1941, 2
Yost, D.M.; Osborne, D.W.; Garner, C.S., The heat capacity, entropy, and heats of transition, fusion, and vaporization of dimethylacetylene. Free rotation in the dimethylacetylene molecule, J. Am. Chem. Soc., 1941, 63, 3492-3496. [all data]

Osborne, Garner, et al., 1940
Osborne, D.W.; Garner, C.S.; Yost, D.M., The entropy of dimethylacetylene from low temperature calorimetric measurements. Free rotation in the dimethylacetylene molecule, J. Chem. Phys., 1940, 8, 131. [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]

Yost, Osborne, et al., 1941, 3
Yost, D.M.; Osborne, D.W.; Garner, C.S., The heat capacity, entropy, and heats of transition, fusion, and vaporization of dimethylacetylene. Free rotation in the dimethylacetylene molecule, J. Am. Chem. Soc., 1941, 63, 3492-34. [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]

Acree, 1991
Acree, William E., Thermodynamic properties of organic compounds: enthalpy of fusion and melting point temperature compilation, Thermochimica Acta, 1991, 189, 1, 37-56, https://doi.org/10.1016/0040-6031(91)87098-H . [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Bieri, Burger, et al., 1977
Bieri, G.; Burger, F.; Heilbronner, E.; Maier, J.P., Valence ionization enrgies of hydrocarbons, Helv. Chim. Acta, 1977, 60, 2213. [all data]

Carlier, Dubois, et al., 1975
Carlier, P.; Dubois, J.E.; Masclet, P.; Mouvier, G., Spectres de photoelectrons des alcynes, J. Electron Spectrosc. Relat. Phenom., 1975, 7, 55. [all data]

Ensslin, Bock, et al., 1974
Ensslin, W.; Bock, H.; Becker, G., Photoelectron spectra and molecular properties. XXX. π interactions in H₃Si- H₃C-substituted acetylenes, J. Am. Chem. Soc., 1974, 96, 2757. [all data]

Brogli, Heilbronner, et al., 1973
Brogli, F.; Heilbronner, E.; Hornung, V.; Kloster-Jensen, E., 230. Die photoelektronen-spektren methyl-substituierter Acetylene, Helv. Chim. Acta, 1973, 56, 2171. [all data]

Lossing, 1972
Lossing, F.P., Free radicals by mass spectrometry. XLV. Ionization potentials and heats of formation of C₃H₃, C₃H₅, and C₄H₇ radicals and ions, Can. J. Chem., 1972, 50, 3973. [all data]

Bieri and Asbrink, 1980
Bieri, G.; Asbrink, L., 30.4-nm He(II) photoelectron spectra of organic molecules, J. Electron Spectrosc. Relat. Phenom., 1980, 20, 149. [all data]

Coats and Anderson, 1957
Coats, F.H.; Anderson, R.C., Thermodynamic data from electron-impact measurements on acetylene and substituted acetylenes, J. Am. Chem. Soc., 1957, 79, 1340. [all data]

Gal, Decouzon, et al., 2001
Gal, J.F.; Decouzon, M.; Maria, P.C.; Gonzalez, A.I.; Mo, O.; Yanez, M.; El Chaouch, S.; Guillemin, J.C., Acidity trends in alpha,beta-unsaturated alkanes, silanes, germanes, and stannanes, J. Am. Chem. Soc., 2001, 123, 26, 6353-6359, https://doi.org/10.1021/ja004079j . [all data]

Shimanouchi, 1972
Shimanouchi, T., Tables of Molecular Vibrational Frequencies Consolidated Volume I, National Bureau of Standards, 1972, 1-160. [all data]

Notes

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• Symbols used in this document:
  

  AE	Appearance energy
  IE (evaluated)	Recommended ionization energy
  Tboil	Boiling point
  Tfus	Fusion (melting) point
  Ttriple	Triple point temperature
  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
  ΔvapH°	Enthalpy of vaporization at standard conditions
  ΔvapS	Entropy of vaporization

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