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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
L - Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess
MM - Michael M. Meot-Ner (Mautner)
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 C5H6+ (ion structure unspecified)

Quantity Value Units Method Reference Comment
IE (evaluated)8.57 ± 0.01eVN/AN/AL
Quantity Value Units Method Reference Comment
Proton affinity (review)196.4kcal/molN/AHunter and Lias, 1998HL
Quantity Value Units Method Reference Comment
Gas basicity190.8kcal/molN/AHunter and Lias, 1998HL

Proton affinity at 298K

Proton affinity (kcal/mol) Reference Comment
197.9Aue, Guidoni, et al., 2000Experimental literature data re-evaluated by the authors using ab initio protonation entropies; MM

Gas basicity at 298K

Gas basicity (review) (kcal/mol) Reference Comment
190.8Aue, Guidoni, et al., 2000Experimental literature data re-evaluated by the authors using ab initio protonation entropies; MM

Ionization energy determinations

IE (eV) Method Reference Comment
8.44PEKiselev, Sakhabutdinov, et al., 1992LL
8.58 ± 0.02PEBieri, Burger, et al., 1977LLK
8.56 ± 0.01EIHolmes and McGillivray, 1971LLK
8.57 ± 0.01PIDerrick, Asbrink, et al., 1971LLK
8.57 ± 0.01PIDemeo and El-Sayed, 1970RDSH
9.0EIHedaya, Kent, et al., 1968RDSH
8.55PIDewar and Worley, 1968RDSH
8.53PEKiselev, Sakhabutdinov, et al., 1992Vertical value; LL
8.61PEBock and Kaim, 1980Vertical value; LLK
8.6PECradock, Ebsworth, et al., 1975Vertical value; LLK
8.56PECradock, Findlay, et al., 1974Vertical value; LLK

Appearance energy determinations

Ion AE (eV) Other Products MethodReferenceComment
C5H5+12.62HEIOccolowitz and White, 1968RDSH
C5H5+12.9HEIHarrison, Haynes, et al., 1965RDSH
C5H5+11.9 ± 0.5HEIDorman, 1965RDSH
C5H5+12.6HEIHarrison, Honnen, et al., 1960RDSH

De-protonation reactions

cyclopentadienide anion + Hydrogen cation = 1,3-Cyclopentadiene

By formula: C5H5- + H+ = C5H6

Quantity Value Units Method Reference Comment
Δr353.9 ± 2.2kcal/molG+TSBartmess, Scott, et al., 1979gas phase; value altered from reference due to change in acidity scale; B
Δr354.9 ± 2.9kcal/molG+TSCumming and Kebarle, 1978gas phase; B
Δr357.2 ± 2.0kcal/molD-EAEngelking and Lineberger, 1977gas phase; B
Quantity Value Units Method Reference Comment
Δr347.7 ± 2.0kcal/molIMREBartmess, Scott, et al., 1979gas phase; value altered from reference due to change in acidity scale; B
Δr348.7 ± 2.0kcal/molIMRECumming and Kebarle, 1978gas phase; B


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]

Aue, Guidoni, et al., 2000
Aue, D.H.; Guidoni, M.; Betowski, L.D., Ab initio calculated gas-phase basicities of polynuclear aromatic hydrocarbons, Int. J. Mass Spectrom., 2000, 201, 283. [all data]

Kiselev, Sakhabutdinov, et al., 1992
Kiselev, V.D.; Sakhabutdinov, A.G.; Shakirov, I.M.; Zverev, V.V.; Konovalov, A.I., Bis reactants in Diels-Alder reactions. VII. Preparation and properties of polyadducts of reactions of bis(polymethylcyclopentadienes) and bis(maleimides), Zh. Org. Khim., 1992, 28, 2244. [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]

Holmes and McGillivray, 1971
Holmes, J.L.; McGillivray, D., The mass spectra of isomeric hydrocarbons-I: Norbornene and nortricyclene; The mechanisms and energetics of their fragmentations, Org. Mass Spectrom., 1971, 5, 1349. [all data]

Derrick, Asbrink, et al., 1971
Derrick, P.J.; Asbrink, L.; Edqvist, O.; Jonsson, B.-O.; Lindholm, E., Rydberg series in small molecules. XIII. Photoelectron spectroscopy and electronic structure of cyclopentadiene, Intern. J. Mass Spectrom. Ion Phys., 1971, 6, 203. [all data]

Demeo and El-Sayed, 1970
Demeo, D.A.; El-Sayed, M.A., Ionization potential and structure of olefins, J. Chem. Phys., 1970, 52, 2622. [all data]

Hedaya, Kent, et al., 1968
Hedaya, E.; Kent, M.E.; McNeil, D.W.; Lossing, F.P.; McAllister, T., The thermal rearrangement of phenylnitrene to cyanocyclopentadiene, Tetrahedron Lett., 1968, 30, 3415. [all data]

Dewar and Worley, 1968
Dewar, M.J.S.; Worley, S.D., Ionization potential of cis-1,3-butadiene, J. Chem. Phys., 1968, 49, 2454. [all data]

Bock and Kaim, 1980
Bock, H.; Kaim, W., Radical ions. 37. Ionization and one-electron oxidation of electron-rich silylalkyl olefins, J. Am. Chem. Soc., 1980, 102, 4429. [all data]

Cradock, Ebsworth, et al., 1975
Cradock, S.; Ebsworth, E.A.V.; Moretto, H.; Rankin, D.W.H., Photoelectron spectra and fluxional behaviour in some σ-cyclopentadienes, J. Chem. Soc. Dalton Trans., 1975, 390. [all data]

Cradock, Findlay, et al., 1974
Cradock, S.; Findlay, R.H.; Palmer, M.H., Bonding in methyl- and silyl-cyclopentadiene compounds: a study by photoelectron spectroscopy ab initio molecular-orbital calculations, J. Chem. Soc. Dalton Trans., 1974, 1650. [all data]

Occolowitz and White, 1968
Occolowitz, J.L.; White, G.L., Energetic considerations in the assignment of some fragment ion structures, Australian J. Chem., 1968, 21, 997. [all data]

Harrison, Haynes, et al., 1965
Harrison, A.G.; Haynes, P.; McLean, S.; Meyer, F., The mass spectra of methyl-substituted cyclopentadienes, J. Am. Chem. Soc., 1965, 87, 5099. [all data]

Dorman, 1965
Dorman, F.H., Second differential ionization-efficiency curves for fragment ions by electron impact, J. Chem. Phys., 1965, 43, 3507. [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]

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]

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]

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]


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