Methane

• Formula: CH₄
• Molecular weight: 16.0425
• IUPAC Standard InChI: InChI=1S/CH4/h1H4 Copy

  
• IUPAC Standard InChIKey: VNWKTOKETHGBQD-UHFFFAOYSA-N Copy
• CAS Registry Number: 74-82-8
• 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: Marsh gas; Methyl hydride; CH4; Fire Damp; R 50; Biogas; R 50 (refrigerant)
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• Information on this page:
  • Gas phase ion energetics data
  • Mass spectrum (electron ionization)
  • References
  • Notes
• Other data available:
  • Gas phase thermochemistry data
  • Phase change data
  • Reaction thermochemistry data: reactions 1 to 50, reactions 51 to 100, reactions 101 to 112
  • Henry's Law data
  • Ion clustering data
  • IR Spectrum
  • Vibrational and/or electronic energy levels
  • Fluid Properties
• 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
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Gas phase ion energetics data

Go To: Top, Mass spectrum (electron ionization), 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
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

View reactions leading to CH₄⁺ (ion structure unspecified)

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

CH₃^- +  =

By formula: CH₃^- + H⁺ = CH₄

Mass spectrum (electron ionization)

Go To: Top, 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: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

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Additional Data

References

Go To: Top, Gas phase ion energetics data, 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.

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]

Berkowitz, Greene, et al., 1987
Berkowitz, J.; Greene, J.P.; Cho, H.; Ruscic, B., The ionization potentials of CH₄ and CD₄, J. Chem. Phys., 1987, 86, 674. [all data]

Chatham, Hils, et al., 1984
Chatham, H.; Hils, D.; Robertson, R.; Gallagher, A., Total and partial electron collisional ionization cross sections for CH₄, C₂H₆, SiH₄, and Si₂H₆, J. Chem. Phys., 1984, 81, 1770. [all data]

Plessis, Marmet, et al., 1983
Plessis, P.; Marmet, P.; Dutil, R., Ionization and appearance potentials of CH₄ by electron impact, J. Phys. B:, 1983, 16, 1283. [all data]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [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]

Selim and El-Kholy, 1975
Selim, E.T.M.; El-Kholy, S.B., Mass spectrometric ionization and dissociation of methane, Indian J. Pure Appl. Phys., 1975, 13, 233. [all data]

Debies and Rabalais, 1975
Debies, T.P.; Rabalais, J.W., Calculated photoionization cross-sections and angular distributions for the isoelectronic series Ne, HF, H₂O, NH₃, and CH₄, J. Am. Chem. Soc., 1975, 97, 487. [all data]

Rabalais, Debies, et al., 1974
Rabalais, J.W.; Debies, T.P.; Berkosky, J.L.; Huang, J.-T.J.; Ellison, F.O., Calculated photoionization cross sections relative experimental photoionization intensities for a selection of small molecules, J. Chem. Phys., 1974, 61, 516. [all data]

Morrison and Traeger, 1973
Morrison, J.D.; Traeger, J.C., Ionization and dissociation by electron impact. III. CH₄ and SiH₄, Int. J. Mass Spectrom. Ion Phys., 1973, 11, 289. [all data]

Potts and Price, 1972
Potts, A.W.; Price, W.C., The photoelectron spectra of methane, silane germane and stannane, Proc. R. Soc. London A:, 1972, 165. [all data]

Finney and Harrison, 1972
Finney, C.D.; Harrison, A.G., A third-derivative method for determining electron-impact onset potentials, Int. J. Mass Spectrom. Ion Phys., 1972, 9, 221. [all data]

Bergmark, Rabalais, et al., 1972
Bergmark, T.; Rabalais, J.W.; Werme, L.O.; Karlsson, L.; Siegbahn, K., High-resolution electron spectra of methane, thiophene, 2-bromothiphene, and 3-bromothiophene in Electron Spectroscopy, ed. D.A. Shirley (North-Holland Pub. Co., Amsterdam), 1972. [all data]

Rabalais, Bergmark, et al., 1971
Rabalais, J.W.; Bergmark, T.; Werme, L.O.; Karlsson, L.; Siegbahn, K., The Jahn-Teller effect in the electron spectrum of methane, Phys. Scr., 1971, 3, 13. [all data]

Chupka and Berkowitz, 1971
Chupka, W.A.; Berkowitz, J., Photoionization of methane: ionization potential and proton affinity of CH₄, J. Chem. Phys., 1971, 54, 4256. [all data]

Pullen, Carlson, et al., 1970
Pullen, B.P.; Carlson, T.A.; Moddeman, W.E.; Schweitzer, G.K.; Bull, W.E., Photoelectron spectra of methane, silane, germane, methyl fluoride, difluoromethane, and trifluoromethane, J. Chem. Phys., 1970, 53, 768. [all data]

Brundle, Robin, et al., 1970
Brundle, C.R.; Robin, M.B.; Basch, H., Electronic energies and electronic structures of the fluoromethanes, J. Chem. Phys., 1970, 53, 2196. [all data]

Lossing and Semeluk, 1969
Lossing, F.P.; Semeluk, G.P., Threshold ionization efficiency curves for monoenergetic electron impact on H₂, D₂, CH₄ and CD₄, Intern. J. Mass Spectrom. Ion Phys., 1969, 2, 408. [all data]

Williams and Hamill, 1968
Williams, J.M.; Hamill, W.H., Ionization potentials of molecules and free radicals and appearance potentials by electron impact in the mass spectrometer, J. Chem. Phys., 1968, 49, 4467. [all data]

Villarejo, Stockbauer, et al., 1968
Villarejo, D.; Stockbauer, R.; Inghram, M.G., Measurement of threshold electrons in the photoionization of small molecules, Bull. Am. Phys. Soc., 1968, 13, 39. [all data]

Cermak, 1968
Cermak, V., Penning ionization electron spectroscopy. I. Determination of ionization potentials of polyatomic molecules, Collection Czech. Chem. Commun., 1968, 33, 2739. [all data]

Baker, Baker, et al., 1968
Baker, A.D.; Baker, C.; Brundle, C.R.; Turner, D.W., The electronic structures of methane, ethane, ethylene and formaldehyde studied by high-resolution molecular photoelectron spectroscopy, Intern. J. Mass Spectrom. Ion Phys., 1968, 1, 285. [all data]

Brehm, 1966
Brehm, B., Massenspektrometrische Untersuchung der Photoionisation von Molekulen, Z. Naturforsch., 1966, 21a, 196. [all data]

Nicholson, 1965
Nicholson, A.J.C., Photoionization-efficiency curves. II. False and genuine structure, J. Chem. Phys., 1965, 43, 1171. [all data]

Dibeler, Krauss, et al., 1965
Dibeler, V.H.; Krauss, M.; Reese, R.M.; Harllee, F.N., Mass-spectrometric study of photoionization. III. Methane and methane-d₄, J. Chem. Phys., 1965, 42, 3791. [all data]

Melton and Hamill, 1964
Melton, C.E.; Hamill, W.H., Appearance potentials by the retarding potential-difference method for secondary ions produced by excited-neutral, excited ion-neutral, and ion-neutral reactions, J. Chem. Phys., 1964, 41, 1469. [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]

Harshbarger, Robin, et al., 1973
Harshbarger, W.R.; Robin, M.B.; Lassettre, E.N., The electron impact spectra of the fluoromethanes, J. Electron Spectrosc. Relat. Phenom., 1973, 1, 319. [all data]

McCulloh and Dibeler, 1976
McCulloh, K.E.; Dibeler, V.H., Enthalpy of formation of methyl and methylene radicals of photoionization studies of methane and ketene, J. Chem. Phys., 1976, 64, 4445. [all data]

Chupka, 1968
Chupka, W.A., Mass-spectrometric study of the photoionization of methane, J. Chem. Phys., 1968, 48, 2337. [all data]

Stockbauer, 1977
Stockbauer, R., A threshold photoelectron-photoion coincidence mass spectrometer for measureing ion kinetic energy release on fragmentation, Int. J. Mass Spectrom. Ion Processes, 1977, 25, 89. [all data]

Lossing and Semeluk, 1970
Lossing, F.P.; Semeluk, G.P., Free radicals by mass spectrometry. XLII.Ionization potentials and ionic heats of formation for C₁-C₄ alkyl radicals, Can. J. Chem., 1970, 48, 955. [all data]

Locht, Olivier, et al., 1979
Locht, R.; Olivier, J.L.; Momigny, J., Dissociative autoionization as a mechanism for the proton formation from methane and methane-d₄ by low energy electron impact, Chem. Phys., 1979, 43, 425. [all data]

Appell and Kubach, 1971
Appell, J.; Kubach, C., On the formation of energetic protons by electron impact on methane, Chem. Phys. Lett., 1971, 11, 486. [all data]

Ellison, Engelking, et al., 1978
Ellison, G.B.; Engelking, P.C.; Lineberger, W.C., An experimental determination of the geometry and electron affinity of CH₃, J. Am. Chem. Soc., 1978, 100, 2556. [all data]

Graul and Squires, 1990
Graul, S.T.; Squires, R.R., Gas-Phase Acidities Derived from Threshold Energies for Activated Reactions, J. Am. Chem. Soc., 1990, 112, 7, 2517, https://doi.org/10.1021/ja00163a007 . [all data]

Bohme, Lee-Ruff, et al., 1972
Bohme, D.K.; Lee-Ruff, E.; Young, L.B., Acidity order of selected bronsted acids in the gas phase at 300K, J. Am. Chem. Soc., 1972, 94, 5153. [all data]

Check, Faust, et al., 2001
Check, C.E.; Faust, T.O.; Bailey, J.M.; Wright, B.J.; Gilbert, T.M.; Sunderlin, L.S., Addition of Polarization and Diffuse Functions to the LANL2DZ Basis Set for P-Block Elements, J. Phys. Chem. A,, 2001, 105, 34, 8111, https://doi.org/10.1021/jp011945l . [all data]

Notes

Go To: Top, Gas phase ion energetics data, Mass spectrum (electron ionization), References

• Symbols used in this document:
  

  AE	Appearance energy
  IE (evaluated)	Recommended ionization energy
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions

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