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Isoprene

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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
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
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard

View reactions leading to C5H8+ (ion structure unspecified)

Quantity Value Units Method Reference Comment
IE (evaluated)8.86 ± 0.02eVN/AN/AL
Quantity Value Units Method Reference Comment
Proton affinity (review)826.4kJ/molN/AHunter and Lias, 1998HL
Quantity Value Units Method Reference Comment
Gas basicity797.6kJ/molN/AHunter and Lias, 1998HL

Ionization energy determinations

IE (eV) Method Reference Comment
8.85 ± 0.02PEBieri, Burger, et al., 1977LLK
8.85EILossing and Traeger, 1975LLK
8.90 ± 0.10EIPuttemans and Delvaux, 1973LLK
8.89PEBeez, Bieri, et al., 1973LLK
8.845 ± 0.005PIWatanabe, Nakayama, et al., 1962RDSH
8.84 ± 0.01SPrice and Walsh, 1940RDSH
8.85PEWerstiuk, Clark, et al., 1990Vertical value; LL
8.85PEMasclet, Mouvier, et al., 1981Vertical value; LLK
8.87PEWorley, Webb, et al., 1979Vertical value; LLK
9.04PESustmann and Schubert, 1972Vertical value; LLK

Appearance energy determinations

Ion AE (eV) Other Products MethodReferenceComment
C3H3+14.55 ± 0.15C2H4+HEIPuttemans and Delvaux, 1973LLK
C3H4+12.39 ± 0.12C2H4EIPuttemans and Delvaux, 1973LLK
C3H5+14.04 ± 0.10C2H2+HEIPuttemans and Delvaux, 1973LLK
C3H6+12.76 ± 0.10C2H2EIPuttemans and Delvaux, 1973LLK
C4H5+11.44CH3EILossing and Holmes, 1984LBLHLM
C4H5+11.93 ± 0.10CH3EIPuttemans and Delvaux, 1973LLK
C5H5+13.9H2+HEIHarrison, Haynes, et al., 1965RDSH
C5H7+10.54HEILossing and Traeger, 1975LLK
C5H7+10.54HEIHolmes, 1974LLK
C5H7+10.93 ± 0.10HEIPuttemans and Delvaux, 1973LLK

De-protonation reactions

C5H7- + Hydrogen cation = Isoprene

By formula: C5H7- + H+ = C5H8

Quantity Value Units Method Reference Comment
Deltar1613. ± 21.kJ/molG+TSBartmess and McIver Jr., 1979gas phase; Between H2O, MeOH. Acid: isoprene; B
Quantity Value Units Method Reference Comment
Deltar1586. ± 21.kJ/molIMRBBartmess and McIver Jr., 1979gas phase; Between H2O, MeOH. Acid: isoprene; 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]

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]

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]

Puttemans and Delvaux, 1973
Puttemans, J.-P.; Delvaux, J.C., Ionisation et fragmentation d'isomeres C5H8 sous impact electronique. Spiropentane - methylenecyclobutane - isoprene, Ing. Chim. Brussell, 1973, 55(267-8), 7. [all data]

Beez, Bieri, et al., 1973
Beez, M.; Bieri, G.; Bock, H.; Heilbronner, E., The ionization potentials of butadiene, hexatriene, andtheir methyl derivatives: evidence for through space interaction between double bond «pi»-orbitals and non-bonded pseudo-«pi» orbitals of methyl groups?, Helv. Chim. Acta, 1973, 56, 1028. [all data]

Watanabe, Nakayama, et al., 1962
Watanabe, K.; Nakayama, T.; Mottl, J., Ionization potentials of some molecules, J. Quant. Spectry. Radiative Transfer, 1962, 2, 369. [all data]

Price and Walsh, 1940
Price, W.C.; Walsh, A.D., The absorption spectra of conjugated dienes in the vacuum ultra-violet (1), Proc. Roy. Soc. (London), 1940, A174, 220. [all data]

Werstiuk, Clark, et al., 1990
Werstiuk, N.H.; Clark, K.B.; Leigh, W.J., Conformational analysis and structure elucidation of 2,3-dimethyl and 2,4-dimethyl-2,4-hexadienes by AM1 and He(I) ultraviolet photoelectron spectroscopy, Can. J. Chem., 1990, 68, 2078. [all data]

Masclet, Mouvier, et al., 1981
Masclet, P.; Mouvier, G.; Bocquet, J.F., Effets electroniques et effets steriques dus a la substitution alcoyle dans les dienes conjugues, J. Chim. Phys., 1981, 78, 99. [all data]

Worley, Webb, et al., 1979
Worley, S.D.; Webb, T.R.; Gibson, D.H.; Ong, T.-S., On the electronic structures of cyclobutadiene trimethylenemethane, J. Organomet. Chem., 1979, 168, 16. [all data]

Sustmann and Schubert, 1972
Sustmann, R.; Schubert, R., Photoelektronenspektroskopische bestimmung von substituenten-effekten. I. Subtituierte butadiene, Tetrahedron Lett., 1972, 27, 2739. [all data]

Lossing and Holmes, 1984
Lossing, F.P.; Holmes, J.L., Stabilization energy and ion size in carbocations in the gas phase, J. Am. Chem. Soc., 1984, 106, 6917. [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]

Holmes, 1974
Holmes, J.L., The mass spectra of isomeric hydrocarbons - II: The C5H8 isomers, spiropentane, cyclopentene, 1,3-pentadiene and isoprene; the mechanisms and energetics of their fragmentations, Org. Mass Spectrom., 1974, 8, 247. [all data]

Bartmess and McIver Jr., 1979
Bartmess, J.E.; McIver Jr., The Gas Phase Acidity Scale in Gas Phase Ion Chemistry, Gas Phase Ion Chemistry, V. 2, M.T. Bowers, Ed., Academic Press, NY, 1979, Ch. 11, Elsevier, 1979. [all data]


Notes

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