Hydroperoxy radical

Formula: HO₂
Molecular weight: 33.0067
IUPAC Standard InChI: InChI=1S/HO2/c1-2/h1H
IUPAC Standard InChIKey: OUUQCZGPVNCOIJ-UHFFFAOYSA-N
CAS Registry Number: 3170-83-0
Chemical structure:
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Reaction thermochemistry data

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

Data compiled by: John E. Bartmess

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

+ = Hydroperoxy radical

By formula: O₂^- + H⁺ = HO₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	352.99 ± 0.72	kcal/mol	D-EA	Travers, Cowles, et al., 1989	gas phase
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	346.67 ± 0.82	kcal/mol	H-TS	Travers, Cowles, et al., 1989	gas phase

Vibrational and/or electronic energy levels

Go To: Top, Reaction thermochemistry data, References, Notes

Data compiled by: Marilyn E. Jacox

State: B

Energy (cm^-1)	Med.	Transition	λ_min (nm)	λ_max (nm)	References


T_x = 48800	gas	B-X	200	280	Troe, 1969
					Kijewski and Troe, 1971
					Paukert and Johnston, 1972
					Hochanadel, Ghormley, et al., 1972
					Crowley, Simon, et al., 1991

State: A

Energy (cm^-1)	Med.	Transition	λ_min (nm)	λ_max (nm)	References


T_o = 7029.688	gas	A-X	1130	2120	Hunziker and Wendt, 1974
					Becker, Fink, et al., 1974
					Hunziker and Wendt, 1976
					Freedman and Jones, 1976
					Becker, Fink, et al., 1978
					Tuckett, Freedman, et al., 1979
					Fink, Kruse, et al.
					Fink and Ramsay, 1997
					Ramond, Blanksby, et al., 2002

Vib. sym.	No.	Approximate type of mode	cm^-1	Med.	Method	References


a'	1	OH stretch	3268.5	gas	EM	Fink, Kruse, et al.
	2	Bend	1285	gas	EM	Fink, Kruse, et al.
	3	OO stretch	929.068	gas	AB EM	Hunziker and Wendt, 1976 Becker, Fink, et al., 1978 Holstein, Fink, et al., 1983 Fink, Kruse, et al.
	3	OO stretch	929.068	gas	PE	Ramond, Blanksby, et al., 2002

State: X

Vib. sym.	No.	Approximate type of mode	cm^-1		Med.	Method	References


a'	1	OH stretch	3436.20		gas	LD	Yamada, Endo, et al., 1983
	1	OH stretch	3415.1		Ne	IR	Thompson and Jacox, 1989 Jacox and Thompson
	1	OH stretch	3412.5	s	Ar	IR	Milligan and Jacox, 1963 Jacox and Milligan, 1972 Smith and Andrews, 1974
	1	OH stretch	3400		O₂	IR	Bandow and Akimoto, 1985
	2	Bend	1391.75		gas	DL IR	Nagai, Endo, et al., 1981 Burkholder, Hammer, et al., 1992
	2	Bend	1397.8		Ne	IR	Thompson and Jacox, 1989 Jacox and Thompson
	2	Bend	1388.5	vs	Ar	IR	Milligan and Jacox, 1963 Jacox and Milligan, 1972 Smith and Andrews, 1974
	2	Bend	1392		O₂	IR	Bandow and Akimoto, 1985
	3	OO stretch	1097.63		gas	LMR DL	Johns, McKellar, et al., 1978 Buchanan, Thrush, et al., 1983 Zahniser and Stanton, 1984 Nelson and Zahniser, 1991
	3	OO stretch	1097.63		gas	IR PE	Burkholder, Hammer, et al., 1992 Ramond, Blanksby, et al., 2002
	3	OO stretch	1100.3		Ne	IR	Thompson and Jacox, 1989 Jacox and Thompson
	3	OO stretch	1101.1	s	Ar	IR	Milligan and Jacox, 1963 Jacox and Milligan, 1972 Smith and Andrews, 1974
	3	OO stretch	1109		O₂	IR	Bandow and Akimoto, 1985

Additional references: Jacox, 1994, page 49; Jacox, 1998, page 153; Jacox, 2003, page 43; Radford, Evenson, et al., 1974; Hougen, 1975; Hougen, Radford, et al., 1975; Beers and Howard, 1975; Beers and Howard, 1976; Saito, 1977; Tuckett, Freedman, et al., 1979, 2; McKellar, 1979; Barnes, Brown, et al., 1980; Charo and De Lucia, 1982; Saito, Endo, et al., 1983; Lubic, Amano, et al., 1984; Uehara, Kawaguchi, et al., 1985; Sears, Takacs, et al., 1986; Chance, Park, et al., 1995; Chance, Ramsay, et al., 2001; Fink and Ramsay, 2002; DeSain, Ho, et al., 2003; Wang and Andrews, 2005; Fink and Ramsay, 2006

Notes

Strong

Very strong

Energy separation between the v = 0 levels of the excited and electronic ground states.

Energy separation between the band maximum of the excited electronic state and the v = 0 level of the ground state.

References

Go To: Top, Reaction thermochemistry data, Vibrational and/or electronic energy levels, Notes

Travers, Cowles, et al., 1989
Travers, M.J.; Cowles, D.C.; Ellison, G.B., Reinvestigation of the Electron Affinities of O2 and NO, Chem. Phys. Lett., 1989, 164, 5, 449, https://doi.org/10.1016/0009-2614(89)85237-6 . [all data]

Troe, 1969
Troe, J., Ber. Bunsenges. Phys. Chem., 1969, 73, 946. [all data]

Kijewski and Troe, 1971
Kijewski, H.; Troe, J., Study of the pyrolysis of H2O2 in the presence of H2and CO by use of UV absorption of HO2, Int. J. Chem. Kinet., 1971, 3, 3, 223, https://doi.org/10.1002/kin.550030304 . [all data]

Paukert and Johnston, 1972
Paukert, T.T.; Johnston, H.S., Spectra and Kinetics of the Hydroperoxyl Free Radical in the Gas Phase, J. Chem. Phys., 1972, 56, 6, 2824, https://doi.org/10.1063/1.1677613 . [all data]

Hochanadel, Ghormley, et al., 1972
Hochanadel, C.J.; Ghormley, J.A.; Ogren, P.J., Absorption Spectrum and Reaction Kinetics of the HO2 Radical in the Gas Phase, J. Chem. Phys., 1972, 56, 9, 4426, https://doi.org/10.1063/1.1677885 . [all data]

Crowley, Simon, et al., 1991
Crowley, J.N.; Simon, F.G.; Burrows, J.P.; Moortgat, G.K.; Jenkin, M.E.; Cox, R.A., The HO2 radical UV absorption spectrum measured by molecular modulation, UV/diode-array spectroscopy, J. Photochem. Photobiol. A: Chem., 1991, 60, 1, 1, https://doi.org/10.1016/1010-6030(91)90001-A . [all data]

Hunziker and Wendt, 1974
Hunziker, H.E.; Wendt, H.R., Near infrared absorption spectrum of HO2, J. Chem. Phys., 1974, 60, 11, 4622, https://doi.org/10.1063/1.1680949 . [all data]

Becker, Fink, et al., 1974
Becker, K.H.; Fink, E.H.; Langen, P.; Schurath, U., Near infrared emission bands of the HO2 radical, J. Chem. Phys., 1974, 60, 11, 4623, https://doi.org/10.1063/1.1680950 . [all data]

Hunziker and Wendt, 1976
Hunziker, H.E.; Wendt, H.R., Electronic absorption spectra of organic peroxyl radicals in the near infrared, J. Chem. Phys., 1976, 64, 8, 3488, https://doi.org/10.1063/1.432606 . [all data]

Freedman and Jones, 1976
Freedman, P.A.; Jones, W.J., J. Chem. Soc., 1976, Faraday Trans. 2 72, 207. [all data]

Becker, Fink, et al., 1978
Becker, K.H.; Fink, E.H.; Leiss, A.; Schurath, U., A study of the near infrared emission bands of the hydroperoxyl radical at medium resolution, Chem. Phys. Lett., 1978, 54, 1, 191, https://doi.org/10.1016/0009-2614(78)85694-2 . [all data]

Tuckett, Freedman, et al., 1979
Tuckett, R.P.; Freedman, P.A.; Jones, W.J., The emission bands of HO, Mol. Phys., 1979, 37, 2, 379, https://doi.org/10.1080/00268977900100331 . [all data]

Fink, Kruse, et al.
Fink, E.H.; Kruse, H.; Ramsay, D.A., Paper WF2, 42nd Symposium on Molecular Spectroscopy, Columbus, Ohio, June 1987.. [all data]

Fink and Ramsay, 1997
Fink, E.H.; Ramsay, D.A., High-Resolution Study of theÃ2A´ → X2A´´ Transition of HO2: Analysis of the 000--000 Band, J. Mol. Spectrosc., 1997, 185, 2, 304, https://doi.org/10.1006/jmsp.1997.7401 . [all data]

Ramond, Blanksby, et al., 2002
Ramond, R.M.; Blanksby, S.J.; Kato, S.; Bierbaum, V.M.; Davico, G.E.; Schwartz, R.L.; Lineberger, W.C.; Ellison, G.B., Heat of Formation of the Hydroperoxyl Radical HOO Via Negative Ion Studies, J. Phys. Chem. A, 2002, 106, 42, 9641, https://doi.org/10.1021/jp014614h . [all data]

Holstein, Fink, et al., 1983
Holstein, K.J.; Fink, E.H.; Zabel, F., The ν3 vibration of electronically excited HO2(A2A´), J. Mol. Spectrosc., 1983, 99, 1, 231, https://doi.org/10.1016/0022-2852(83)90307-7 . [all data]

Yamada, Endo, et al., 1983
Yamada, C.; Endo, Y.; Hirota, E., Difference frequency laser spectroscopy of the ν1 band of the HO2 radical, J. Chem. Phys., 1983, 78, 7, 4379, https://doi.org/10.1063/1.445321 . [all data]

Thompson and Jacox, 1989
Thompson, W.E.; Jacox, M.E., The vibrational spectra of molecular ions isolated in solid neon. II. O+4 and O-4, J. Chem. Phys., 1989, 91, 7, 3826, https://doi.org/10.1063/1.456868 . [all data]

Jacox and Thompson
Jacox, M.E.; Thompson, W.E., J. Phys. Chem. A 117. [all data]

Milligan and Jacox, 1963
Milligan, D.E.; Jacox, M.E., Infrared Spectroscopic Evidence for the Species HO2, J. Chem. Phys., 1963, 38, 11, 2627, https://doi.org/10.1063/1.1733562 . [all data]

Jacox and Milligan, 1972
Jacox, M.E.; Milligan, D.E., Spectrum and structure of the HO2 free radical, J. Mol. Spectrosc., 1972, 42, 3, 495, https://doi.org/10.1016/0022-2852(72)90225-1 . [all data]

Smith and Andrews, 1974
Smith, D.W.; Andrews, L., Argon matrix infrared spectra and vibrational analysis of the hydroperoxyl and deuteroperoxyl free radicals, J. Chem. Phys., 1974, 60, 1, 81, https://doi.org/10.1063/1.1680809 . [all data]

Bandow and Akimoto, 1985
Bandow, H.; Akimoto, H., Photochemistry of ketene in oxygen/argon matrixes and in solid oxygen at 11 K, J. Phys. Chem., 1985, 89, 5, 845, https://doi.org/10.1021/j100251a026 . [all data]

Nagai, Endo, et al., 1981
Nagai, K.; Endo, Y.; Hirota, E., Diode laser spectroscopy of the HO2 ν2 band, J. Mol. Spectrosc., 1981, 89, 2, 520, https://doi.org/10.1016/0022-2852(81)90044-8 . [all data]

Burkholder, Hammer, et al., 1992
Burkholder, J.B.; Hammer, P.D.; Howard, C.J.; Towle, J.P.; Brown, J.M., Fourier transform spectroscopy of the ν2 and ν3 bands of HO2, J. Mol. Spectrosc., 1992, 151, 2, 493, https://doi.org/10.1016/0022-2852(92)90582-9 . [all data]

Johns, McKellar, et al., 1978
Johns, J.W.C.; McKellar, A.R.W.; Riggin, M., Laser magnetic resonance spectroscopy of the ν3 fundamental band of HO2 at 9.1 μm, J. Chem. Phys., 1978, 68, 9, 3957, https://doi.org/10.1063/1.436308 . [all data]

Buchanan, Thrush, et al., 1983
Buchanan, J.W.; Thrush, B.A.; Tyndall, G.S., The absolute intensity of the ν3 band of HO2, Chem. Phys. Lett., 1983, 103, 2, 167, https://doi.org/10.1016/0009-2614(83)87487-9 . [all data]

Zahniser and Stanton, 1984
Zahniser, M.S.; Stanton, A.C., A measurement of the vibrational band strength for the ν3 band of the HO2 radical, J. Chem. Phys., 1984, 80, 10, 4951, https://doi.org/10.1063/1.446517 . [all data]

Nelson and Zahniser, 1991
Nelson, D.D., Jr.; Zahniser, M.S., Diode laser spectroscopy of the ν3 vibration of the HO2 radical, J. Mol. Spectrosc., 1991, 150, 2, 527, https://doi.org/10.1016/0022-2852(91)90247-8 . [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]

Radford, Evenson, et al., 1974
Radford, H.E.; Evenson, K.M.; Howard, C.J., HO2 detected by laser magnetic resonance, J. Chem. Phys., 1974, 60, 8, 3178, https://doi.org/10.1063/1.1681503 . [all data]

Hougen, 1975
Hougen, J.T., The assignment of molecular infrared spectra from a laser magnetic resonance spectrometer, J. Mol. Spectrosc., 1975, 54, 3, 447, https://doi.org/10.1016/0022-2852(75)90172-1 . [all data]

Hougen, Radford, et al., 1975
Hougen, J.T.; Radford, H.E.; Evenson, K.M.; Howard, C.J., Analysis of the laser magnetic resonance spectrum of HO2, J. Mol. Spectrosc., 1975, 56, 2, 210, https://doi.org/10.1016/0022-2852(75)90236-2 . [all data]

Beers and Howard, 1975
Beers, Y.; Howard, C.J., The microwave spectrum of HO2 near 65 GHz, J. Chem. Phys., 1975, 63, 10, 4212, https://doi.org/10.1063/1.431191 . [all data]

Beers and Howard, 1976
Beers, Y.; Howard, C.J., The spectrum of DO2 near 60 GHz and the structure of the hydroperoxyl radical, J. Chem. Phys., 1976, 64, 4, 1541, https://doi.org/10.1063/1.432375 . [all data]

Saito, 1977
Saito, S., Microwave spectrum of the HO2 radical, J. Mol. Spectrosc., 1977, 65, 2, 229, https://doi.org/10.1016/0022-2852(77)90190-4 . [all data]

Tuckett, Freedman, et al., 1979, 2
Tuckett, R.P.; Freedman, P.A.; Jones, W.J., The near infra-red emission band of DO, Mol. Phys., 1979, 37, 2, 403, https://doi.org/10.1080/00268977900100341 . [all data]

McKellar, 1979
McKellar, A.R.W., Laser magnetic resonance spectroscopy of the ν2 fundamental band of DO2 at 9.8 μm, J. Chem. Phys., 1979, 71, 1, 81, https://doi.org/10.1063/1.438060 . [all data]

Barnes, Brown, et al., 1980
Barnes, C.E.; Brown, J.M.; Radford, H.E., The EPR and LMR spectra of the DO2 radical: Determination of ground-state parameters, J. Mol. Spectrosc., 1980, 84, 1, 179, https://doi.org/10.1016/0022-2852(80)90252-0 . [all data]

Charo and De Lucia, 1982
Charo, A.; De Lucia, F.C., The millimeter and submillimeter spectrum of HO2: The effects of unpaired electronic spin in a light asymmetric rotor, J. Mol. Spectrosc., 1982, 94, 2, 426, https://doi.org/10.1016/0022-2852(82)90018-2 . [all data]

Saito, Endo, et al., 1983
Saito, S.; Endo, Y.; Hirota, E., The microwave spectrum of the DO2 radical, J. Mol. Spectrosc., 1983, 98, 1, 183, https://doi.org/10.1016/0022-2852(83)90208-4 . [all data]

Lubic, Amano, et al., 1984
Lubic, K.G.; Amano, T.; Uehara, H.; Kawaguchi, K.; Hirota, E., The ν1 band of the DO2 radical by difference frequency laser and diode laser spectroscopy: The equilibrium structure of the hydroperoxyl radical, J. Chem. Phys., 1984, 81, 11, 4826, https://doi.org/10.1063/1.447508 . [all data]

Uehara, Kawaguchi, et al., 1985
Uehara, H.; Kawaguchi, K.; Hirota, E., Diode laser spectroscopy of the ν3 and ν2 fundamental bands of DO2, J. Chem. Phys., 1985, 83, 11, 5479, https://doi.org/10.1063/1.449668 . [all data]

Sears, Takacs, et al., 1986
Sears, T.J.; Takacs, G.A.; Howard, C.J.; Crownover, R.L.; Helminger, P.; De Lucia, F.C., Rotational spectroscopy of DO2 by FIR LMR and millimeter-wave absorption, J. Mol. Spectrosc., 1986, 118, 1, 103, https://doi.org/10.1016/0022-2852(86)90228-6 . [all data]

Chance, Park, et al., 1995
Chance, K.V.; Park, K.; Evenson, K.M.; Zink, L.R.; Stroh, F., Far-Infrared Spectrum of HO2, J. Mol. Spectrosc., 1995, 172, 2, 407, https://doi.org/10.1006/jmsp.1995.1188 . [all data]

Chance, Ramsay, et al., 2001
Chance, K.V.; Ramsay, D.A.; Fink, E.H., Improved Molecular Constants for the Ground State of DO2, J. Mol. Spectrosc., 2001, 207, 1, 123, https://doi.org/10.1006/jmsp.2001.8310 . [all data]

Fink and Ramsay, 2002
Fink, E.H.; Ramsay, D.A., High-Resolution Study of the Atilde;2A´→X2A´´ Transition of DO2: Analysis of the 000--000 Band, J. Mol. Spectrosc., 2002, 216, 2, 322, https://doi.org/10.1006/jmsp.2002.8621 . [all data]

DeSain, Ho, et al., 2003
DeSain, J.D.; Ho, A.D.; Taatjes, C.A., High-resolution diode laser absorption spectroscopy of the O--H stretch overtone band (2,0,0)←(0,0,0) of the HO2 radical, J. Mol. Spectrosc., 2003, 219, 1, 163, https://doi.org/10.1016/S0022-2852(03)00022-5 . [all data]

Wang and Andrews, 2005
Wang, X.; Andrews, L., Infrared Spectrum of Hg(OH), Inorg. Chem., 2005, 44, 1, 108, https://doi.org/10.1021/ic048673w . [all data]

Fink and Ramsay, 2006
Fink, E.H.; Ramsay, D.A., Analysis of perturbations in the state of HO2, J. Mol. Struct., 2006, 795, 1-3, 155, https://doi.org/10.1016/j.molstruc.2005.11.045 . [all data]

Notes

Go To: Top, Reaction thermochemistry data, Vibrational and/or electronic energy levels, References

Symbols used in this document:

Δ_rG° Free energy of reaction at standard conditions

Δ_rH° Enthalpy of reaction at standard conditions
Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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Δ_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions