1H-Imidazole
- Formula: C3H4N2
- Molecular weight: 68.0773
- IUPAC Standard InChI: InChI=1S/C3H4N2/c1-2-5-3-4-1/h1-3H,(H,4,5)
- IUPAC Standard InChIKey: RAXXELZNTBOGNW-UHFFFAOYSA-N
- CAS Registry Number: 288-32-4
- Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
The 3d structure may be viewed using Java or Javascript. - Other names: Imidazole; Glyoxalin; Glyoxaline; Imidazol; Imutex; Methanimidamide, N,N'-1,2-ethenediyl-; Miazole; 1,3-Diaza-2,4-cyclopentadiene; 1,3-Diazole; Formamidine, N,N'-vinylene-; Iminazole; IMD; Pyrro(b)monazole; USAF EK-4733; NSC 60522
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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
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 ± 0.01 | eV | N/A | N/A | L |
| Quantity | Value | Units | Method | Reference | Comment |
| Proton affinity (review) | 942.8 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
| Quantity | Value | Units | Method | Reference | Comment |
| Gas basicity | 909.2 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Ionization energy determinations
| IE (eV) | Method | Reference | Comment |
|---|---|---|---|
| 8.81 ± 0.01 | PI | Main-Bobo, Loesik, et al., 1986 | LBLHLM |
| 9.12 | EI | Klebe, Houte, et al., 1972 | LLK |
| 8.96 | PE | Ramsey, 1979 | Vertical value; LLK |
| 8.78 | PE | Cradock, Findlay, et al., 1973 | Vertical value; LLK |
Appearance energy determinations
| Ion | AE (eV) | Other Products | Method | Reference | Comment |
|---|---|---|---|---|---|
| CH2N+ | 11.67 ± 0.05 | C2H2N | PI | Main-Bobo, Loesik, et al., 1986 | LBLHLM |
| C2H2N+ | 13.2 | HCN | EI | Klebe, Houte, et al., 1972 | LLK |
| C2H3N2+ | 11.48 ± 0.02 | CH | PI | Main-Bobo, Loesik, et al., 1986 | LBLHLM |
| C3H3N2+ | 12.8 | H | EI | Klebe, Houte, et al., 1972 | LLK |
De-protonation reactions
+
=
By formula: C3H3N2- + H+ = C3H4N2
| Quantity | Value | Units | Method | Reference | Comment |
|---|---|---|---|---|---|
| ΔrH° | 1464.1 ± 3.0 | kJ/mol | G+TS | Gianola, Ichino, et al., 2005 | gas phase; B |
| ΔrH° | 1465. ± 8.8 | kJ/mol | G+TS | Taft, Anvia, et al., 1986 | gas phase; value altered from reference due to change in acidity scale; B |
| Quantity | Value | Units | Method | Reference | Comment |
| ΔrG° | 1433.4 ± 1.7 | kJ/mol | IMRE | Gianola, Ichino, et al., 2005 | gas phase; B |
| ΔrG° | 1434. ± 8.4 | kJ/mol | IMRE | Taft, Anvia, et al., 1986 | gas 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
Go To: Top, Gas phase ion energetics data, References
- Symbols used in this document:
AE Appearance energy IE (evaluated) Recommended ionization energy ΔrG° Free energy of reaction at standard conditions ΔrH° Enthalpy of reaction at standard conditions - Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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