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1H-Imidazole

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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
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

Quantity Value Units Method Reference Comment
IE (evaluated)8.81 ± 0.01eVN/AN/AL
Quantity Value Units Method Reference Comment
Proton affinity (review)942.8kJ/molN/AHunter and Lias, 1998HL
Quantity Value Units Method Reference Comment
Gas basicity909.2kJ/molN/AHunter and Lias, 1998HL

Ionization energy determinations

IE (eV) Method Reference Comment
8.81 ± 0.01PIMain-Bobo, Loesik, et al., 1986LBLHLM
9.12EIKlebe, Houte, et al., 1972LLK
8.96PERamsey, 1979Vertical value; LLK
8.78PECradock, Findlay, et al., 1973Vertical value; LLK

Appearance energy determinations

Ion AE (eV) Other Products MethodReferenceComment
CH2N+11.67 ± 0.05C2H2NPIMain-Bobo, Loesik, et al., 1986LBLHLM
C2H2N+13.2HCNEIKlebe, Houte, et al., 1972LLK
C2H3N2+11.48 ± 0.02CHPIMain-Bobo, Loesik, et al., 1986LBLHLM
C3H3N2+12.8HEIKlebe, Houte, et al., 1972LLK

De-protonation reactions

imidazolide anion + Hydrogen cation = 1H-Imidazole

By formula: C3H3N2- + H+ = C3H4N2

Quantity Value Units Method Reference Comment
Deltar1464.1 ± 3.0kJ/molG+TSGianola, Ichino, et al., 2005gas phase; B
Deltar1465. ± 8.8kJ/molG+TSTaft, Anvia, et al., 1986gas phase; value altered from reference due to change in acidity scale; B
Quantity Value Units Method Reference Comment
Deltar1433.4 ± 1.7kJ/molIMREGianola, Ichino, et al., 2005gas phase; B
Deltar1434. ± 8.4kJ/molIMRETaft, Anvia, et al., 1986gas phase; value altered from reference due to change in acidity scale; 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]

Main-Bobo, Loesik, et al., 1986
Main-Bobo, J.; Loesik, S.; Gase, W.; Baer, T.; Mommers, A.; Holmes, J., The thermochemistry and dissociation dynamics of internal-energy selected pyrazole and imidazole ions, J. Am. Chem. Soc., 1986, 108, 677. [all data]

Klebe, Houte, et al., 1972
Klebe, K.J.; Houte, J.J.V.; Thuijl, J.V., Loss of HCN and H from the molecular ion of imidazole, Org. Mass Spectrom., 1972, 6, 1363. [all data]

Ramsey, 1979
Ramsey, B.G., Substituent effects on imidazole basicity and photoelectron spectroscopy determined ionization energies, J. Org. Chem., 1979, 44, 2093. [all data]

Cradock, Findlay, et al., 1973
Cradock, S.; Findlay, R.H.; Palmer, M.H., The molecular energy levels of the azoles: A study by photoelectron spectroscopy and ab initio molecular orbital calculations, Tetrahedron, 1973, 29, 2173. [all data]

Gianola, Ichino, et al., 2005
Gianola, A.J.; Ichino, T.; Hoenigman, R.L.; Kato, S.; Bierbaum, V.M.; Lineberger, W.C., Photoelectron spectra and ion chemistry of imidazolide, J. Phys. Chem. A, 2005, 109, 50, 11504-11514, https://doi.org/10.1021/jp053566o . [all data]

Taft, Anvia, et al., 1986
Taft, R.W.; Anvia, F.; Taagepera, M.; Catalan, J.; Elgueroy, J., Electrostatic proximity effects in the relative basicities of pyrazole, imidazole, pyridazine, and pyrimidine, J. Am. Chem. Soc., 1986, 108, 3237. [all data]


Notes

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