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Cyclopentadienyl radical


Gas phase ion energetics 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 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)198.7kcal/molN/AHunter and Lias, 1998HL
Quantity Value Units Method Reference Comment
Gas basicity191.0kcal/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
Deltar353.9 ± 2.2kcal/molG+TSBartmess, Scott, et al., 1979gas phase; value altered from reference due to change in acidity scale; B
Deltar354.9 ± 2.9kcal/molG+TSCumming and Kebarle, 1978gas phase; B
Deltar357.2 ± 2.0kcal/molD-EAEngelking and Lineberger, 1977gas phase; B
Quantity Value Units Method Reference Comment
Deltar347.7 ± 2.0kcal/molIMREBartmess, Scott, et al., 1979gas phase; value altered from reference due to change in acidity scale; B
Deltar348.7 ± 2.0kcal/molIMRECumming and Kebarle, 1978gas phase; B

References

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


Notes

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