Methyl radical

• Formula: CH₃
• Molecular weight: 15.0345
• IUPAC Standard InChI: InChI=1S/CH3/h1H3 Copy

  
• IUPAC Standard InChIKey: WCYWZMWISLQXQU-UHFFFAOYSA-N Copy
• CAS Registry Number: 2229-07-4
• 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.
• Isotopologues:
  • Methyl-d3 radical
  • Methyl-d3 radical
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase ion energetics data
  • Vibrational and/or electronic energy levels
  • References
  • Notes
• Other data available:
  • Gas phase thermochemistry data
  • Reaction thermochemistry data
  • Ion clustering data
• Data at other public NIST sites:
  • 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, 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:
L - Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess
LL - Sharon G. Lias and Joel F. Liebman
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 CH₃⁺ (ion structure unspecified)

Electron affinity determinations

Ionization energy determinations

Appearance energy determinations

Cation De-protonation reactions

CH₂^- +  =

By formula: CH₂^- + H⁺ = CH₃⁺

Vibrational and/or electronic energy levels

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: Marilyn E. Jacox

State:   4f ²E'?

State:   4p ²A₂

State:   3d ²A₁'

State:   3d ²E

State:   3p ²A₂

State:   3s ²A₁'

State:   X

Additional references: Jacox, 1994, page 125; Jacox, 1998, page 214; Jacox, 2003, page 156; Frye, Sears, et al., 1988; Parker, Wang, et al., 1989; Sears, Frye, et al., 1989; Westre and Kelly, 1989; Miller, Burton, et al., 1989; Fawzy, Sears, et al., 1990; Rudolph, Hall, et al., 1996

Notes

References

Go To: Top, 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.

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]

Feldman, Rackwitz, et al., 1977
Feldman, D.; Rackwitz, R.; Kaiser, H.J.; Heincke, E., Photodetachment bei einigen neagtiven molekulionen: P₂-, As₂-, CH₂-, CH₃-, S₃-, Z. Naturforsch. A:, 1977, 32, 600. [all data]

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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]

Page, 1972
Page, F.M., Experimental determination of the electron affinities of inorganic radicals, Adv. Chem. Ser., 1972, 36, 68. [all data]

Page and Goode, 1969
Page, F.M.; Goode, G.C., Negative Ions and the Magnetron., Wiley, NY, 1969. [all data]

Gaines and Page, 1968
Gaines, A.F.; Page, F.M., The Stabilities of Negative Ions.I. The Methyl-, Diphenylmethyl, and Triphenylmethyl Negative Ions, Int. J. Mass Spectrom. Ion Phys., 1968, 1, 4-5, 315, https://doi.org/10.1016/0020-7381(68)85008-9 . [all data]

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Nagano, Y.; Murthy, S.; Beauchamp, J.L., Thermochemical properties and gas-phase ion chemistry of phenylsilane investigated by FT-ICR spectrometry. Identification of parent- and fragment-ion structural isomers by their specific reactivities, J. Am. Chem. Soc., 1993, 115, 10805. [all data]

Houle and Beauchamp, 1979
Houle, F.A.; Beauchamp, J.L., Photoelectron spectroscopy of methyl, ethyl, isopropyl, and tert-butyl radicals. Implications for the thermochemistry and structures of the radicals and their corresponding carbonium ions, J. Am. Chem. Soc., 1979, 101, 4067. [all data]

Reeher, Flesch, et al., 1976
Reeher, J.R.; Flesch, G.D.; Svec, H.J., The mass spectra and ionization potentials of the neutral fragments produced during the electron bombardment of aromatic compounds, Org. Mass Spectrom., 1976, 11, 154. [all data]

Kaposi, Riedel, et al., 1975
Kaposi, O.; Riedel, M.; Sanchez, G.R., Mass-spectrometric study of electron-impact and heterogeneous pyrolytic decomposition of methyl bromide, Acta Chim. Acad. Sci. Hung., 1975, 85, 361. [all data]

Golob, Jonathan, et al., 1973
Golob, L.; Jonathan, N.; Morris, A.; Okuda, M.; Ross, K.J., The first ionization potential of the methyl radical as determined by photoelectron spectroscopy, J. Electron Spectrosc. Relat. Phenom., 1973, 1, 506. [all data]

Potts, Glenn, et al., 1972
Potts, A.W.; Glenn, K.G.; Price, W.C., General discussion, Faraday Discuss. Chem. Soc., 1972, 54, 64. [all data]

Jonathan, 1972
Jonathan, N., General discussion, Faraday Discuss. Chem. Soc., 1972, 54, 64. [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]

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]

Chupka and Lifshitz, 1968
Chupka, W.A.; Lifshitz, C., Photoionization of CH₃⁺; heat of formation of CH₂, J. Chem. Phys., 1968, 48, 1109. [all data]

Elder, Giese, et al., 1962
Elder, F.A.; Giese, C.; Steiner, B.; Inghram, M., Photo-ionization of alkyl free radicals, J. Chem. Phys., 1962, 36, 3292. [all data]

Herzberg and Shoosmith, 1956
Herzberg, G.; Shoosmith, J., Absorption spectrum of free CH₃ and CD₃ radicals, Can. J. Phys., 1956, 34, 523. [all data]

Dyke, Jonathan, et al., 1976
Dyke, J.; Jonathan, N.; Lee, E.; Morris, A., Vacuum ultraviolet photoelectron spectroscopy of transient species, J. Chem. Soc. Faraday Trans. 2, 1976, 72, 1385. [all data]

Koenig, Balle, et al., 1975
Koenig, T.; Balle, T.; Snell, W., Helium(I) photoelectron spectra of organic radicals, J. Am. Chem. Soc., 1975, 97, 662. [all data]

Potts, Glenn, et al., 1972, 2
Potts, A.W.; Glenn, K.G.; Price, W.C., General discussion, Faraday Discuss. Chem. Soc., 1972, 54, 65. [all data]

Waldron, 1956
Waldron, J.D., The ionization and dissociation of methyl radicals on electron impact, Metropolitan Vickers Gaz., 1956, 27, 66. [all data]

Leopold, Murray, et al., 1985
Leopold, D.G.; Murray, K.K.; Miller, A.E.S.; Lineberger, W.C., Methylene: A study of the X3B1 and the 1A1 states by photoelectron spectroscopy of CH₂^- and CD₂^-, J. Chem. Phys., 1985, 83, 4849. [all data]

Hudgens, DiGiuseppe, et al., 1983
Hudgens, J.W.; DiGiuseppe, T.G.; Lin, M.C., Two photon resonance enhanced multiphoton ionization spectroscopy and state assignments of the methyl radical, J. Chem. Phys., 1983, 79, 2, 571, https://doi.org/10.1063/1.445857 . [all data]

Black and Powis, 1988
Black, J.F.; Powis, I., Rotational structure and predissociation dynamics of the methyl 4pz(v=0) Rydberg state investigated by resonance enhanced multiphoton ionization spectroscopy, J. Chem. Phys., 1988, 89, 7, 3986, https://doi.org/10.1063/1.454832 . [all data]

Herzberg, 1961
Herzberg, G., The Bakerian Lecture. The Spectra and Structures of Free Methyl and Free Methylene, Proc. Roy. Soc. (London) A262, 1961, 262, 1310, 291, https://doi.org/10.1098/rspa.1961.0120 . [all data]

Milligan and Jacox, 1967
Milligan, D.E.; Jacox, M.E., Infrared and Ultraviolet Spectroscopic Study of the Products of the Vacuum-Ultraviolet Photolysis of Methane in Ar and N2 Matrices. The Infrared Spectrum of the Free Radical CH3, J. Chem. Phys., 1967, 47, 12, 5146, https://doi.org/10.1063/1.1701772 . [all data]

DiGiuseppe, Hudgens, et al., 1982
DiGiuseppe, T.G.; Hudgens, J.W.; Lin, M.C., Multiphoton ionization of methyl radicals in the gas phase, J. Phys. Chem., 1982, 86, 1, 36, https://doi.org/10.1021/j100390a008 . [all data]

Heinze, Heberle, et al., 1994
Heinze, J.; Heberle, N.; Kohse-Hoinghaus, K., The CH3 3pz2A2´´ ← X 2A2´´ 000 band at temperatures up to 1700 K investigated by REMPI spectroscopy, Chem. Phys. Lett., 1994, 223, 4, 305, https://doi.org/10.1016/0009-2614(94)00469-2 . [all data]

Zhang, Zhang, et al., 2005
Zhang, B.; Zhang, J.; Liu, K., Imaging the "missing" bands in the resonance-enhanced multiphoton ionization detection of methyl radical, J. Chem. Phys., 2005, 122, 10, 104310, https://doi.org/10.1063/1.1859277 . [all data]

Fu, Hu, et al., 2005
Fu, H.B.; Hu, Y.J.; Bernstein, E.R., IR/UV double resonant spectroscopy of the methyl radical: Determination of ν[sub 3] in the 3p[sub z] Rydberg state, J. Chem. Phys., 2005, 123, 23, 234307, https://doi.org/10.1063/1.2135772 . [all data]

Callear and Metcalfe, 1976
Callear, A.B.; Metcalfe, M.P., Oscillator strengths of the bands of the B2 A´1---X2 A´´2 system of CD3 and a spectroscopic measurement of the recombination rate comparison with CH3, Chem. Phys., 1976, 14, 2, 275, https://doi.org/10.1016/0301-0104(76)80045-6 . [all data]

Westre, Gansberg, et al., 1992
Westre, S.G.; Gansberg, T.E.; Kelly, P.B.; Ziegler, L.D., Structure and dynamics of higher vibronic levels in the methyl radical Rydberg 3s state, J. Phys. Chem., 1992, 96, 9, 3610, https://doi.org/10.1021/j100188a012 . [all data]

Settersten, Farrow, et al., 2003
Settersten, T.B.; Farrow, R.L.; Gray, J.A., Coherent infrared--ultraviolet double-resonance spectroscopy of CH3, Chem. Phys. Lett., 2003, 370, 1-2, 204, https://doi.org/10.1016/S0009-2614(03)00062-9 . [all data]

Holt, McCurdy, et al., 1984
Holt, P.L.; McCurdy, K.E.; Weisman, R.B.; Adams, J.S.; Engel, P.S., Transient CARS spectroscopy of the ν1 band of methyl radical, J. Chem. Phys., 1984, 81, 7, 3349, https://doi.org/10.1063/1.448000 . [all data]

Kelly and Westre, 1988
Kelly, P.B.; Westre, S.G., Resonance Raman spectroscopy of the methyl radical, Chem. Phys. Lett., 1988, 151, 3, 253, https://doi.org/10.1016/0009-2614(88)85284-9 . [all data]

Triggs, Zahedi, et al., 1992
Triggs, N.E.; Zahedi, M.; Nibler, J.W.; DeBarber, P.; Valentini, J.J., High resolution study of the ν1 vibration of CH3 by coherent Raman photofragment spectroscopy, J. Chem. Phys., 1992, 96, 3, 1822, https://doi.org/10.1063/1.462083 . [all data]

Zahedi, Harrison, et al., 1994
Zahedi, M.; Harrison, J.A.; Nibler, J.W., 266 nm CH3I photodissociation: CH3 spectra and population distributions by coherent Raman spectroscopy, J. Chem. Phys., 1994, 100, 6, 4043, https://doi.org/10.1063/1.466342 . [all data]

Hadrich, Hefter, et al., 1996
Hadrich, S.; Hefter, S.; Pfelzer, B.; Doerk, T.; Jauernik, P.; Uhlenbusch, J., Determination of the absolute Raman cross section of methyl, Chem. Phys. Lett., 1996, 256, 1-2, 83, https://doi.org/10.1016/0009-2614(96)00411-3 . [all data]

Tan, Winer, et al., 1972
Tan, L.Y.; Winer, A.M.; Pimentel, G.C., Infrared Spectrum of Gaseous Methyl Radical by Rapid Scan Spectroscopy, J. Chem. Phys., 1972, 57, 9, 4028, https://doi.org/10.1063/1.1678876 . [all data]

Yamada, Hirota, et al., 1981
Yamada, C.; Hirota, E.; Kawaguchi, K., Diode laser study of the ν2 band of the methyl radical, J. Chem. Phys., 1981, 75, 11, 5256, https://doi.org/10.1063/1.441991 . [all data]

Wormhoudt and McCurdy, 1989
Wormhoudt, J.; McCurdy, K.E., A measurement of the strength of the ν2 band of CH3, Chem. Phys. Lett., 1989, 156, 1, 47, https://doi.org/10.1016/0009-2614(89)87078-2 . [all data]

Stancu, Ropcke, et al., 2005
Stancu, G.D.; Ropcke, J.; Davies, P.B., Line strengths and transition dipole moment of the ν[sub 2] fundamental band of the methyl radical, J. Chem. Phys., 2005, 122, 1, 014306, https://doi.org/10.1063/1.1812755 . [all data]

Snelson, 1970
Snelson, A., Infrared matrix isolation spectrum of the methyl radical produced by pyrolysis of methyl iodide and dimethyl mercury, J. Phys. Chem., 1970, 74, 3, 537, https://doi.org/10.1021/j100698a011 . [all data]

Jacox, 1977
Jacox, M.E., Matrix isolation study of the infrared spectrum and structure of the CH3 free radical, J. Mol. Spectrosc., 1977, 66, 2, 272, https://doi.org/10.1016/0022-2852(77)90217-X . [all data]

Lee and Lee, 2011
Lee, Y.-F.; Lee, Y.-P., Infrared absorption of CH3SO2 observed upon irradiation of a p-H2 matrix containing CH3I and SO2, J. Chem. Phys., 2011, 1334, 12, 124314, https://doi.org/10.1063/1.3567117 . [all data]

Amano, Bernath, et al., 1982
Amano, T.; Bernath, P.F.; Yamada, C.; Endo, Y.; Hirota, E., Difference frequency laser spectroscopy of the ν3 band of the CH3 radical, J. Chem. Phys., 1982, 77, 11, 5284, https://doi.org/10.1063/1.443797 . [all data]

Tanarro, Sanz, et al., 1994
Tanarro, I.; Sanz, M.M.; Bermejo, D.; Domingo, C.; Santos, J., Double modulation-high resolution infrared spectroscopic technique: The ν3 band of the CH3 radical and excited states of CH4 in a hollow cathode discharge, J. Chem. Phys., 1994, 100, 1, 238, https://doi.org/10.1063/1.466991 . [all data]

Tanarro, Sanz, et al., 1994, 2
Tanarro, I.; Sanz, M.M.; Domingo, C.; Bermejo, D.; Santos, J.; Domenech, J.L., Transition dipole moment of the .nu.3 band of CH3, J. Phys. Chem., 1994, 98, 23, 5862, https://doi.org/10.1021/j100074a009 . [all data]

Bethardy and Macdonald, 1995
Bethardy, G.A.; Macdonald, R.G., Direct measurement of the transition dipole moment of the v3 asymmetric C--H stretching vibration of the CH3 radical, J. Chem. Phys., 1995, 103, 8, 2863, https://doi.org/10.1063/1.470499 . [all data]

Davis, Anderson, et al., 1997
Davis, S.; Anderson, D.T.; Duxbury, G.; Nesbitt, D.J., Jet-cooled molecular radicals in slit supersonic discharges: Sub-Doppler infrared studies of methyl radical, J. Chem. Phys., 1997, 107, 15, 5661, https://doi.org/10.1063/1.474259 . [all data]

Scherer, Aniolek, et al., 1997
Scherer, J.J.; Aniolek, K.W.; Cernansky, N.P.; Rakestraw, D.J., Determination of methyl radical concentrations in a methane/air flame by infrared cavity ringdown laser absorption spectroscopy, J. Chem. Phys., 1997, 107, 16, 6196, https://doi.org/10.1063/1.474284 . [all data]

Kawaguchi, 2001
Kawaguchi, K., High-resolution Fourier transform infrared spectra of the CH, Can. J. Phys., 2001, 79, 2-3, 449, https://doi.org/10.1139/p00-093 . [all data]

Pacansky and Bargon, 1975
Pacansky, J.; Bargon, J., Low temperature photochemical studies on acetyl benzoyl peroxide. Observation of methyl and phenyl radicals by matrix isolation infrared spectroscopy, J. Am. Chem. Soc., 1975, 97, 23, 6896, https://doi.org/10.1021/ja00856a066 . [all data]

Momose, Miki, et al., 1995
Momose, T.; Miki, M.; Uchida, M.; Shimizu, T.; Yoshizawa, I.; Shida, T., Infrared spectroscopic studies on photolysis of methyl iodide and its clusters in solid parahydrogen, J. Chem. Phys., 1995, 103, 4, 1400, https://doi.org/10.1063/1.469763 . [all data]

Tam, Macler, et al., 1997
Tam, S.; Macler, M.; Fajardo, M.E., Matrix isolation spectroscopy of laser ablated carbon species in Ne, D[sub 2], and H[sub 2] matrices, J. Chem. Phys., 1997, 106, 22, 8955, https://doi.org/10.1063/1.474028 . [all data]

Hoshina, Fushitani, et al., 2011
Hoshina, H.; Fushitani, M.; Momose, T., Infrared spectroscopy of rovibrational transitions of methyl radicals (CH3, CD3) in solid parahydrogen, J. Mol. Spectrosc., 2011, 268, 1-2, 164, https://doi.org/10.1016/j.jms.2011.04.014 . [all data]

Jacox, 1994
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules, American Chemical Society, Washington, DC, 1994, 464. [all data]

Jacox, 1998
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules: supplement A, J. Phys. Chem. Ref. Data, 1998, 27, 2, 115-393, https://doi.org/10.1063/1.556017 . [all data]

Jacox, 2003
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules: supplement B, J. Phys. Chem. Ref. Data, 2003, 32, 1, 1-441, https://doi.org/10.1063/1.1497629 . [all data]

Frye, Sears, et al., 1988
Frye, J.M.; Sears, T.J.; Leitner, D., Diode laser spectroscopy of the ν2 band of CD3, J. Chem. Phys., 1988, 88, 9, 5300, https://doi.org/10.1063/1.454588 . [all data]

Parker, Wang, et al., 1989
Parker, D.H.; Wang, Z.W.; Janssen, M.H.M.; Chandler, D.W., Laser ionization spectroscopy of CD3 via the 3pz 2A'2 Rydberg state, J. Chem. Phys., 1989, 90, 1, 60, https://doi.org/10.1063/1.456466 . [all data]

Sears, Frye, et al., 1989
Sears, T.J.; Frye, J.M.; Spirko, V.; Kraemer, W.P., Extended measurements of the ν2 band of CD3 and the determination of the vibrational potential function for methyl, J. Chem. Phys., 1989, 90, 4, 2125, https://doi.org/10.1063/1.456006 . [all data]

Westre and Kelly, 1989
Westre, S.G.; Kelly, P.B., Examination of CD3 vibrational structure by resonance Raman spectroscopy, J. Chem. Phys., 1989, 90, 12, 6977, https://doi.org/10.1063/1.456273 . [all data]

Miller, Burton, et al., 1989
Miller, J.T.; Burton, K.A.; Weisman, R.B.; Wu, W.-X.; Engel, P.S., Cars spectroscopy of gas phase CD3, Chem. Phys. Lett., 1989, 158, 3-4, 179, https://doi.org/10.1016/0009-2614(89)87317-8 . [all data]

Fawzy, Sears, et al., 1990
Fawzy, W.M.; Sears, T.J.; Davies, P.B., Infrared diode laser spectroscopy of the ν3 fundamental of the CD3 radical, J. Chem. Phys., 1990, 92, 12, 7021, https://doi.org/10.1063/1.458242 . [all data]

Rudolph, Hall, et al., 1996
Rudolph, R.N.; Hall, G.E.; Sears, T.J., Measurement of the ν3 fundamental transition moment and vibrational relaxation rates of the CD3 radical, J. Chem. Phys., 1996, 105, 18, 7889, https://doi.org/10.1063/1.472704 . [all data]

Notes

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

• Symbols used in this document:
  

  AE	Appearance energy
  EA	Electron affinity
  IE (evaluated)	Recommended ionization energy
  ΔfH(+) ion,0K	Enthalpy of formation of positive ion at 0K
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions

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