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Cyclopentadienyl radical


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:
HL - Edward P. Hunter and 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 C5H5+ (ion structure unspecified)

Quantity Value Units Method Reference Comment
Proton affinity (review)831.5kJ/molN/AHunter and Lias, 1998HL
Quantity Value Units Method Reference Comment
Gas basicity799.1kJ/molN/AHunter and Lias, 1998HL

Electron affinity determinations

EA (eV) Method Reference Comment
1.93 ± 0.13D-EABartmess, Scott, et al., 1979value altered from reference due to change in acidity scale; B
1.786 ± 0.020LPESEngelking and Lineberger, 1977B
1.789 ± 0.047LPDMcDonald, Bianchina, et al., 1991B
1.839 ± 0.030LPDRichardson, Stephenson, et al., 1973B
<2.20 ± 0.30EIAEDiDomenico, Harland, et al., 1972From cyclopentadiene; B

Ionization energy determinations

IE (eV) Method Reference Comment
8.41EILossing and Traeger, 1975LLK
8.56EISchissel, McAdoo, et al., 1968RDSH
8.7 ± 0.1EIHarrison, Honnen, et al., 1960RDSH

Anion protonation reactions

cyclopentadienide anion + Hydrogen cation = 1,3-Cyclopentadiene

By formula: C5H5- + H+ = C5H6

Quantity Value Units Method Reference Comment
Deltar1481. ± 9.2kJ/molG+TSBartmess, Scott, et al., 1979gas phase; value altered from reference due to change in acidity scale; B
Deltar1485. ± 12.kJ/molG+TSCumming and Kebarle, 1978gas phase; B
Deltar1495. ± 8.4kJ/molD-EAEngelking and Lineberger, 1977gas phase; B
Quantity Value Units Method Reference Comment
Deltar1455. ± 8.4kJ/molIMREBartmess, Scott, et al., 1979gas phase; value altered from reference due to change in acidity scale; B
Deltar1459. ± 8.4kJ/molIMRECumming and Kebarle, 1978gas phase; B

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:   A


 Energy 
 (cm-1
 Med.   Transition   «lambda»min 
 (nm) 
 «lambda»max 
 (nm) 
 References

To = 29572.166 ± 0.002 gas A-X 306 395 Thrush, 1956
Porter and Ward, 1968
Engleman and Ramsay, 1970
Nelson, Pasternack, et al., 1983
Yu, Foster, et al., 1988
Sun and Bernstein, 1995
Applegate, Bezant, et al., 2001


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

a1' 2 1055 gas LF Sun and Bernstein, 1995
Applegate, Bezant, et al., 2001
e1 8 CH deform. 166 H gas AB LF Thrush, 1956
Porter and Ward, 1968
Engleman and Ramsay, 1970
Yu, Williamson, et al., 1989
Sun and Bernstein, 1995
Applegate, Bezant, et al., 2001
e2' 11 1019 gas LF Sun and Bernstein, 1995
Applegate, Bezant, et al., 2001
12 797 gas AB LF Engleman and Ramsay, 1970
Yu, Williamson, et al., 1989
Sun and Bernstein, 1995
Applegate, Bezant, et al., 2001

State:   X


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

a1' 2 1071 gas LF Applegate, Bezant, et al., 2001
a2' 3 1244 gas LF Applegate, Bezant, et al., 2001
a2 4 681 gas LF Applegate, Bezant, et al., 2001
4 661 vs Ar IR Korolev and Nefedov, 1993
e1' 5 CH stretch 3079 w m Ar IR Korolev and Nefedov, 1993
6 1383 m Ar IR Korolev and Nefedov, 1993
7 1001 gas LF Applegate, Bezant, et al., 2001
e1 8 766 H gas LF Applegate, Bezant, et al., 2001
e2' 10 1320 gas LF Applegate, Bezant, et al., 2001
11 1041 gas LF Applegate, Bezant, et al., 2001
12 872 gas PD LF Engelking and Lineberger, 1977
Nelson, Pasternack, et al., 1983
Yu, Williamson, et al., 1989
Applegate, Bezant, et al., 2001
e2 13 861 H gas LF Applegate, Bezant, et al., 2001
14 576 H gas LF Applegate, Bezant, et al., 2001

Additional references: Jacox, 1994, page 385; Jacox, 1998, page 344; Jacox, 2003, page 364; Liebling and McConnell, 1965; DiMauro, Heaven, et al., 1986

Notes

wWeak
mMedium
vsVery strong
H(1/2)(2nu)
oEnergy separation between the v = 0 levels of the excited and electronic ground states.

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.

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]

Bartmess, Scott, et al., 1979
Bartmess, J.E.; Scott, J.A.; McIver, R.T., Jr., The gas phase acidity scale from methanol to phenol, J. Am. Chem. Soc., 1979, 101, 6047. [all data]

Engelking and Lineberger, 1977
Engelking, P.C.; Lineberger, W.C., Laser photoelectron spectrometry of C5H5-: A determination of the electron affinity and Jahn-Teller coupling in cyclopentadienyl, J. Chem. Phys., 1977, 67, 1412. [all data]

McDonald, Bianchina, et al., 1991
McDonald, R.N.; Bianchina, E.J.; Tung, C.C., Electron Photodetachment of Cyclopentadienylidene Anion Radical in a Flowing Afterglow Apparatus - EA and «DELTA»H(f)-Degrees of Cyclopentadienylide, J. Am. Chem. Soc., 1991, 113, 19, 7115, https://doi.org/10.1021/ja00019a005 . [all data]

Richardson, Stephenson, et al., 1973
Richardson, J.H.; Stephenson, L.M.; Brauman, J.I., Photodetachment of electrons from large molecular systems: Cyclopentadienide and methylcyclopentadienide ions. An upper limit to the electron affinities of C5H5 and CH3C5H4, J. Chem. Phys., 1973, 59, 5068. [all data]

DiDomenico, Harland, et al., 1972
DiDomenico, A.; Harland, P.W.; Franklin, J.L., Negative ion formation and negative ion-molecule reactions in cyclopentadiene, J. Chem. Phys., 1972, 56, 5299. [all data]

Lossing and Traeger, 1975
Lossing, F.P.; Traeger, J.C., Stabilization in cyclopentadienyl, cyclopentenyl, and cyclopentyl cations, J. Am. Chem. Soc., 1975, 97, 1579. [all data]

Schissel, McAdoo, et al., 1968
Schissel, P.; McAdoo, D.J.; Hedaya, E.; McNeil, D.W., Flash vacuum pyrolysis. III. Formation and ionization of cyclopentadienyl, cyclopentadienyl nickel, and dihydrofulvalene (dicyclopentadienyl) derived from nickelocene, J. Chem. Phys., 1968, 49, 5061. [all data]

Harrison, Honnen, et al., 1960
Harrison, A.G.; Honnen, L.R.; Dauben, H.J., Jr.; Lossing, F.P., Free radicals by mass spectrometry. XX. Ionization potentials of cyclopentadienyl and cycloheptatrienyl radicals, J. Am. Chem. Soc., 1960, 82, 5593. [all data]

Cumming and Kebarle, 1978
Cumming, J.B.; Kebarle, P., Summary of gas phase measurements involving acids AH. Entropy changes in proton transfer reactions involving negative ions. Bond dissociation energies D(A-H) and electron affinities EA(A), Can. J. Chem., 1978, 56, 1. [all data]

Thrush, 1956
Thrush, B.A., Spectrum of the Cyclopentadienyl Radical, Nature, 1956, 178, 4525, 155, https://doi.org/10.1038/178155a0 . [all data]

Porter and Ward, 1968
Porter, G.; Ward, B., The Photolytic Preparation of Cyclopentadienyl and Phenyl Nitrene from Benzene Derivatives, Proc. Roy. Soc. (London) A303, 1968, 303, 1473, 139, https://doi.org/10.1098/rspa.1968.0044 . [all data]

Engleman and Ramsay, 1970
Engleman, R., Jr.; Ramsay, D.A., Electronic absorption spectrum of the cyclopentadienyl radical (C, Can. J. Phys., 1970, 48, 8, 964, https://doi.org/10.1139/p70-125 . [all data]

Nelson, Pasternack, et al., 1983
Nelson, H.H.; Pasternack, L.; McDonald, J.R., Excitation and emission spectra of the 2A´´2 «8637» --> 2E´´1 system of the gas-phase cyclopentadienyl radical, Chem. Phys., 1983, 74, 2, 227, https://doi.org/10.1016/0301-0104(83)80025-1 . [all data]

Yu, Foster, et al., 1988
Yu, L.; Foster, S.C.; Williamson, J.M.; Heaven, M.C.; Miller, T.A., Rotationally resolved electronic spectrum of jet-cooled cyclopentadienyl radical, J. Phys. Chem., 1988, 92, 15, 4263, https://doi.org/10.1021/j100326a004 . [all data]

Sun and Bernstein, 1995
Sun, S.; Bernstein, E.R., Vibronic structure of the cyclopentadienyl radical and its nonrigid van der Waals cluster with nitrogen, J. Chem. Phys., 1995, 103, 11, 4447, https://doi.org/10.1063/1.470633 . [all data]

Applegate, Bezant, et al., 2001
Applegate, B.E.; Bezant, A.J.; Miller, T.A., The Jahn--Teller and related effects in the cyclopentadienyl radical. II. Vibrational analysis of the A [sup 2]A[sub 2][sup ´´]--X [sup 2]E[sub 1][sup ´´] electronic transition, J. Chem. Phys., 2001, 114, 11, 4869, https://doi.org/10.1063/1.1348276 . [all data]

Yu, Williamson, et al., 1989
Yu, L.; Williamson, J.M.; Miller, T.A., Rotationally resolved electronic spectrum of jet-cooled deuterated cyclopentadienyl radical, Chem. Phys. Lett., 1989, 162, 6, 431, https://doi.org/10.1016/0009-2614(89)87003-4 . [all data]

Korolev and Nefedov, 1993
Korolev, V.A.; Nefedov, O.M., Izv. Akad. Nauk, 1993, Ser. Khim., 1497. [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]

Liebling and McConnell, 1965
Liebling, G.R.; McConnell, H.M., Study of Molecular Orbital Degeneracy in C5H5, J. Chem. Phys., 1965, 42, 11, 3931, https://doi.org/10.1063/1.1695862 . [all data]

DiMauro, Heaven, et al., 1986
DiMauro, L.F.; Heaven, M.; Miller, T.A., Lifetimes of the lowest excited states of the cyclopentadienyl and the monomethylcyclopentadienyl radicals, Chem. Phys. Lett., 1986, 124, 6, 489, https://doi.org/10.1016/0009-2614(86)85061-8 . [all data]


Notes

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