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Gas phase ion energetics data

Go To: Top, 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
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
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
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 C7H8+ (ion structure unspecified)

Quantity Value Units Method Reference Comment
IE (evaluated)8.828 ± 0.001eVN/AN/AL
Quantity Value Units Method Reference Comment
Proton affinity (review)187.4kcal/molN/AHunter and Lias, 1998HL
Quantity Value Units Method Reference Comment
Gas basicity180.8kcal/molN/AHunter and Lias, 1998HL

Proton affinity at 298K

Proton affinity (kcal/mol) Reference Comment
187.0Aue, 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
180.1Aue, 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
8.8276 ± 0.0006TELu, Eiden, et al., 1992LL
8.79PEKlasinc, Kovac, et al., 1983LBLHLM
8.80 ± 0.07EISelim and Helal, 1982LBLHLM
8.83PEKimura, Katsumata, et al., 1981LLK
8.82EIMcLoughlin, Morrison, et al., 1979LLK
8.82PETraeger and McLoughlin, 1978LLK
8.82PITraeger and McLoughlin, 1978LLK
8.82 ± 0.01EQLias and Ausloos, 1978LLK
8.84PEBock, Kaim, et al., 1978LLK
8.82PEBehan, Johnstone, et al., 1976LLK
8.81EIHoffman, 1974LLK
8.80PEMcLean, 1973LLK
8.78 ± 0.02PEMaier and Turner, 1973LLK
8.91CTSKobayashi, Kobayashi, et al., 1973LLK
8.8 ± 0.1EIGilbert, Leach, et al., 1973LLK
8.72PEDebies and Rabalais, 1973LLK
8.67EICooks, Bertrand, et al., 1973LLK
8.82PIStebbings and Taylor, 1972LLK
8.89 ± 0.03EIJohnstone and Mellon, 1972LLK
8.71CTSPitt, 1970RDSH
8.82PEDewar and Worley, 1969RDSH
8.80 ± 0.04EIBock, Seidl, et al., 1968RDSH
8.82 ± 0.02PIAkopyan and Vilesov, 1968RDSH
8.82PIBralsford, Harris, et al., 1960RDSH
8.82 ± 0.01PIWatanabe, 1954RDSH
8.82 ± 0.05SPrice and Walsh, 1947RDSH
8.82PEHowell, Goncalves, et al., 1984Vertical value; LBLHLM
8.85PEKobayashi, 1978Vertical value; LLK
9.00PEKlasinc, Novak, et al., 1978Vertical value; LLK
8.90 ± 0.03PEMarschner and Goetz, 1974Vertical value; LLK
8.82PEBischof, Dewar, et al., 1974Vertical value; LLK
8.85 ± 0.015PEKobayashi and Nagakura, 1972Vertical value; LLK
9.0 ± 0.03PEKlessinger, 1972Vertical value; LLK

Appearance energy determinations

Ion AE (eV) Other Products MethodReferenceComment
C5H5+16.4 ± 0.2C2H2+HEITajima and Tsuchiya, 1973LLK
C5H5+16.7?EIHarrison, Haynes, et al., 1965RDSH
C6H5+13.70CH3EIHoffman, 1974LLK
C6H5+13.7 ± 0.1CH3EIMajer and Patrick, 1962RDSH
C7H7+10.94HTRPIHuang and Dunbar, 1991T = 0K; LL
C7H7+10.70 ± 0.09HEISelim and Helal, 1982LBLHLM
C7H7+10.71HEIMcLoughlin, Morrison, et al., 1979LLK
C7H7+10.71HPITraeger and McLoughlin, 1978LLK
C7H7+10.71 ± 0.03HTETraeger and McLoughlin, 1977LLK
C7H7+11.8HEIHoffman, 1974LLK
C7H7+11.55 ± 0.05HPIAkopyan and Vilesov, 1968RDSH
C7H7+11.7 ± 0.1HEINounou, 1966RDSH
C7H7+[C6H5CH2+]10.7 ± 0.1HPILifshitz, Gotkis, et al., 1993T = 298K; LL
C7H7+[C6H5CH2+]11.1 ± 0.1HPILifshitz, Gotkis, et al., 1993T = 0K; LL
C7H7+[C6H5CH2+]11.1HPILifshitz, Gotkis, et al., 1993, 2T = 0K; LL
C7H7+[C6H5CH2+]11.17 ± 0.10HPIPECOBombach, Dannacher, et al., 1983T = 0K; LBLHLM
C7H7+[C6H5CH2+]11.17 ± 0.10HPIPECOBombach, Dannacher, et al., 1983, 2T = 0K; LBLHLM
C7H7+[c-C7H7+]11.1 ± 0.1HPILifshitz, Gotkis, et al., 1993T = 0K; LL
C7H7+[c-C7H7+]10.7 ± 0.1HPILifshitz, Gotkis, et al., 1993T = 298K; LL
C7H7+[c-C7H7+]11.1HPILifshitz, Gotkis, et al., 1993, 2T = 0K; LL
C7H7+[c-C7H7+]10.52 ± 0.07HPIPECOBombach, Dannacher, et al., 1983T = 0K; LBLHLM
C7H7+[c-C7H7+]10.52 ± 0.10HPIPECOBombach, Dannacher, et al., 1983, 2T = 0K; LBLHLM

De-protonation reactions

C7H7- + Hydrogen cation = Toluene

By formula: C7H7- + H+ = C7H8

Quantity Value Units Method Reference Comment
Δr382.33 ± 0.45kcal/molD-EAGunion, Gilles, et al., 1992gas phase; Kim, Wenthold, et al., 1999, with LN2 cooling of the ion, gives the same EA; B
Δr380.8 ± 2.1kcal/molG+TSBartmess, Scott, et al., 1979gas phase; value altered from reference due to change in acidity scale; B
Δr379.2 ± 2.1kcal/molG+TSGal, Decouzon, et al., 2001gas phase; B
Δr377.0 ± 3.5kcal/molCIDTGraul and Squires, 1990gas phase; B
Δr384.5 ± 7.1kcal/molG+TSBohme and Young, 1971gas phase; B
Quantity Value Units Method Reference Comment
Δr373.7 ± 2.0kcal/molIMREBartmess, Scott, et al., 1979gas phase; value altered from reference due to change in acidity scale; B
Δr372.1 ± 2.0kcal/molIMREGal, Decouzon, et al., 2001gas phase; B
Δr377.4 ± 7.0kcal/molIMRBBohme and Young, 1971gas 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, . [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]

Lu, Eiden, et al., 1992
Lu, K.-T.; Eiden, G.C.; Weisshaar, J.C., Toluene cation: nearly free rotation of the methyl group, J. Phys. Chem., 1992, 96, 9742. [all data]

Klasinc, Kovac, et al., 1983
Klasinc, L.; Kovac, B.; Gusten, H., Photoelectron spectra of acenes. Electronic structure and substituent effects, Pure Appl. Chem., 1983, 55, 289. [all data]

Selim and Helal, 1982
Selim, E.T.M.; Helal, A.I., The study of C1-C3 monosubstituted alkyl benzenes by the inverse convolution of first differential ionization efficiency curves, Org. Mass Spectrom., 1982, 17, 539. [all data]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]

McLoughlin, Morrison, et al., 1979
McLoughlin, R.G.; Morrison, J.D.; Traeger, J.C., Photoionization of the C-1 - C-4 monosubstituted alkyl benzenes: Thermochemistry of [C7H7]+ and [C8H9]+ formation, Org. Mass Spectrom., 1979, 14, 104. [all data]

Traeger and McLoughlin, 1978
Traeger, J.C.; McLoughlin, R.G., A photoionization study of the energetics of C7H7+ ion formed from C7H8 precursors, Int. J. Mass Spectrom. Ion Phys., 1978, 27, 319. [all data]

Lias and Ausloos, 1978
Lias, S.G.; Ausloos, P.J., eIonization energies of organic compounds by equilibrium measurements, J. Am. Chem. Soc., 1978, 100, 6027. [all data]

Bock, Kaim, et al., 1978
Bock, H.; Kaim, W.; Rohwer, H.E., Die hyperkonjugative Stabilisierung von p-Xylol-Radikalkationen durch (H3C)3Si-Substituenten, Chem. Ber., 1978, 111, 3573. [all data]

Behan, Johnstone, et al., 1976
Behan, J.M.; Johnstone, R.A.W.; Bentley, T.W., An evaluation of empirical methods for calculating the ionization potentials of substituted benzenes, Org. Mass Spectrom., 1976, 11, 207. [all data]

Hoffman, 1974
Hoffman, M.K., Hidden rearrangements in the mass spectral decomposition of cycloheptatriene, Z. Naturforsch. A:, 1974, 29, 1077. [all data]

McLean, 1973
McLean, R.A.N., The bonding of a silicon atom with a phenyl ring: The photoelectron spectrum of phenylsilane, Can. J. Chem., 1973, 51, 2089. [all data]

Maier and Turner, 1973
Maier, J.P.; Turner, D.W., Steric inhibition of resonance studied by molecular photoelectron spectroscopy. Part 2. Phenylethylenes, J. Chem. Soc. Faraday Trans. 2, 1973, 69, 196. [all data]

Kobayashi, Kobayashi, et al., 1973
Kobayashi, H.; Kobayashi, M.; Kaizu, Y., Molecular complexes of arenetricarbonylchromium, Bull. Chem. Soc. Jpn., 1973, 46, 3109. [all data]

Gilbert, Leach, et al., 1973
Gilbert, J.R.; Leach, W.P.; Miller, J.R., Ionisation appearance potential measurements in arene chromium tricarbonyls, J. Organomet. Chem., 1973, 49, 219. [all data]

Debies and Rabalais, 1973
Debies, T.P.; Rabalais, J.W., Photoelectron spectra of substituted benzenes. II. Seven valence electron substituents, J. Electron Spectrosc. Relat. Phenom., 1973, 1, 355. [all data]

Cooks, Bertrand, et al., 1973
Cooks, R.G.; Bertrand, M.; Beynon, J.H.; Rennekamp, M.E.; Setser, D.W., Energy partitioning data as an ion structure probe. Substituted anisoles, J. Am. Chem. Soc., 1973, 95, 1732. [all data]

Stebbings and Taylor, 1972
Stebbings, W.L.; Taylor, J.W., Photoionization mass spectrometry. II. Contrasting fragmentation of toluene by photons and by electrons, Int. J. Mass Spectrom. Ion Phys., 1972, 9, 471. [all data]

Johnstone and Mellon, 1972
Johnstone, R.A.W.; Mellon, F.A., Electron-impact ionization and appearance potentials, J. Chem. Soc. Faraday Trans. 2, 1972, 68, 1209. [all data]

Pitt, 1970
Pitt, C.G., Hyperconjugation: An alternative to the concept of the pπ-dπ bond in Group IV chemistry, J. Organomet. Chem., 1970, 23, 35. [all data]

Dewar and Worley, 1969
Dewar, M.J.S.; Worley, S.D., Photoelectron spectra of molecules. I. Ionization potentials of some organic molecules and their interpretation, J. Chem. Phys., 1969, 50, 654. [all data]

Bock, Seidl, et al., 1968
Bock, H.; Seidl, H.; Fochler, M., d-Orbitaleffekte in silicium-substituierten π-Elektronensystemen. X. Vertikale Ionisierungsenergien von Alkyl- und Silyl-benzolen, Chem. Ber., 1968, 101, 2815. [all data]

Akopyan and Vilesov, 1968
Akopyan, M.E.; Vilesov, F.I., Mass-spectrometric investigation of the photo-ionization of benzene and its methyl derivatives, Khim. Vysokikh Energ., 1968, 2, 107, In original 89. [all data]

Bralsford, Harris, et al., 1960
Bralsford, R.; Harris, P.V.; Price, W.C., The effect of fluorine on the electronic spectra and ionization potentials of molecules, Proc. Roy. Soc. (London), 1960, A258, 459. [all data]

Watanabe, 1954
Watanabe, K., Photoionization and total absorption cross section of gases. I. Ionization potentials of several molecules. Cross sections of NH3 and NO, J. Chem. Phys., 1954, 22, 1564. [all data]

Price and Walsh, 1947
Price, W.C.; Walsh, A.D., The absorption spectra of benzene derivatives in the vacuum ultra-violet. I, Proc. Roy. Soc. (London), 1947, A191, 22. [all data]

Howell, Goncalves, et al., 1984
Howell, J.O.; Goncalves, J.M.; Amatore, C.; Klasinc, L.; Wightman, R.M.; Kochi, J.K., Electron transfer from aromatic hydrocarbons and their π-complexes with metals. Comparison of the standard oxidation potentials and vertical ionization potentials, J. Am. Chem. Soc., 1984, 106, 3968. [all data]

Kobayashi, 1978
Kobayashi, T., A simple general tendency in photoelectron angular distributions of some monosubstituted benzenes, Phys. Lett., 1978, 69, 105. [all data]

Klasinc, Novak, et al., 1978
Klasinc, L.; Novak, I.; Scholz, M.; Kluge, G., Photoelektronenspektren substituierter Pyridine und Benzole und ihre Interpretation durch die CNDO/SWW-Methode, Croat. Chem. Acta, 1978, 51, 43. [all data]

Marschner and Goetz, 1974
Marschner, F.; Goetz, H., Korrelation zwischen photoelektronen- und elektronen-spektren. III. Eine methode zur deutung der PE- und UV-spektren vom toluol, Tetrahedron, 1974, 30, 3451. [all data]

Bischof, Dewar, et al., 1974
Bischof, P.K.; Dewar, M.J.S.; Goodman, D.W.; Jones, T.B., Photoelectron spectra of molecules. VI. Hyperconjugation versus pπ-dπ bonding in group IVb compounds, J. Organomet. Chem., 1974, 82, 89. [all data]

Kobayashi and Nagakura, 1972
Kobayashi, T.; Nagakura, S., Photoelectron spectra of nitro-compounds, Chem. Lett., 1972, 903. [all data]

Klessinger, 1972
Klessinger, M., Ionization potentials of substituted benzenes, Angew. Chem. Int. Ed. Engl., 1972, 11, 525. [all data]

Tajima and Tsuchiya, 1973
Tajima, S.; Tsuchiya, T., Energetics consideration of C5H5+ ions produced from various precursors by electron impact, Bull. Chem. Soc. Jpn., 1973, 46, 3291. [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]

Majer and Patrick, 1962
Majer, J.R.; Patrick, C.R., Electron impact on some halogenated aromatic compounds, J. Chem. Soc. Faraday Trans., 1962, 58, 17. [all data]

Huang and Dunbar, 1991
Huang, F.-S.; Dunbar, R.C., Time-resolved photodissociation of toluene ion [Eo(C6H5CH3+ Ü C7H7+ + H)=2.11 eV; cited data derived using evaluated IP for toluene. Modeling uncertainties give considerable latitude in the assignment of kinetic parameters.], Int. J. Mass Spectrom. Ion Processes, 1991, 109, 151. [all data]

Traeger and McLoughlin, 1977
Traeger, J.C.; McLoughlin, R.G., Threshold photoionization and dissociation of toluene and cycloheptatriene, J. Am. Chem. Soc., 1977, 99, 7351. [all data]

Nounou, 1966
Nounou, P., Etude des composes aromatiques par spectrometrie de masse. I. Mesure des potentials d'ionisation et d'apparition par la methode du potential retardateur et interpretation des courbes d'ionisation differentielle, J. Chim. Phys., 1966, 63, 994. [all data]

Lifshitz, Gotkis, et al., 1993
Lifshitz, C.; Gotkis, Y.; Ioffe, A.; Laskin, J.; Shaik, S., Is the tropylium ion (Tr+) formed from toluene at its thermochemical threshold?, Int. J. Mass Spectrom. Ion Processes, 1993, 125, R7. [all data]

Lifshitz, Gotkis, et al., 1993, 2
Lifshitz, C.; Gotkis, Y.; Laskin, J.; Ioffe, A.; Shaik, S., Threshold formation of benzylium (Bz+) and tropylium (Tr+) from toluene. Nonstatistical behavior in Franck-Condon gaps, J. Phys. Chem., 1993, 97, 12291. [all data]

Bombach, Dannacher, et al., 1983
Bombach, R.; Dannacher, J.; Stadelmann, J.-P., Energy and time dependence of the decay processes of toluene molecular cations, J. Am. Chem. Soc., 1983, 105, 4205. [all data]

Bombach, Dannacher, et al., 1983, 2
Bombach, R.; Dannacher, J.; Stadelmann, J.-P., The rate-energy functions for the formation of tropylium and benzylium ions from toluene molecular cations, Chem. Phys. Lett., 1983, 95, 259. [all data]

Gunion, Gilles, et al., 1992
Gunion, R.F.; Gilles, M.K.; Polak, M.L.; Lineberger, W.C., Ultraviolet Photoelectron Spectroscopy of the Phenide, Benzyl, and Phenoxide Anions., Int. J. Mass Spectrom. Ion Proc., 1992, 117, 601, . [all data]

Kim, Wenthold, et al., 1999
Kim, J.B.; Wenthold, P.G.; Lineberger, W.C., Ultraviolet photoelectron spectroscopy of o-, m-, and p-halobenzyl anions, J. Phys. Chem. A, 1999, 103, 50, 10833-10841, . [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]

Gal, Decouzon, et al., 2001
Gal, J.F.; Decouzon, M.; Maria, P.C.; Gonzalez, A.I.; Mo, O.; Yanez, M.; El Chaouch, S.; Guillemin, J.C., Acidity trends in alpha,beta-unsaturated alkanes, silanes, germanes, and stannanes, J. Am. Chem. Soc., 2001, 123, 26, 6353-6359, . [all data]

Graul and Squires, 1990
Graul, S.T.; Squires, R.R., Gas-Phase Acidities Derived from Threshold Energies for Activated Reactions, J. Am. Chem. Soc., 1990, 112, 7, 2517, . [all data]

Bohme and Young, 1971
Bohme, D.K.; Young, L.B., Electron affinities from thermal proton transfer reactions: C6H5 and C6H5CH2, Can. J. Chem., 1971, 49, 2918. [all data]


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