1H-Pyrazole
- Formula: C3H4N2
- Molecular weight: 68.0773
- IUPAC Standard InChIKey: WTKZEGDFNFYCGP-UHFFFAOYSA-N
- CAS Registry Number: 288-13-1
- 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: Pyrazole; 1,2-Diazole
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Gas phase thermochemistry data
Go To: Top, Condensed phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data compiled as indicated in comments:
DRB - Donald R. Burgess, Jr.
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔfH°gas | 177.4 | kJ/mol | N/A | Zaheeruddin and Lodhi, 1991 | Value computed using ΔfHsolid° value of 112.4 kj/mol from Zaheeruddin and Lodhi, 1991 and ΔsubH° value of 65.0 kj/mol from Jimenez, Roux, et al., 1987.; DRB |
ΔfH°gas | 179.4 ± 0.8 | kJ/mol | Ccb | Jimenez, Roux, et al., 1987 | see Jimenez, Roux, et al., 1986; ALS |
ΔfH°gas | 181. ± 8.8 | kJ/mol | Ccb | Bedford, Edmondson, et al., 1962 | ALS |
Condensed phase thermochemistry data
Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data compiled as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
DH - Eugene S. Domalski and Elizabeth D. Hearing
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔfH°solid | Ccb | Zaheeruddin and Lodhi, 1991 | uncertain value: 112.38 kJ/mol; ALS | ||
ΔfH°solid | 105.4 ± 0.7 | kJ/mol | Ccb | Jimenez, Roux, et al., 1987 | see Jimenez, Roux, et al., 1986; ALS |
ΔfH°solid | 116.0 ± 4.6 | kJ/mol | Ccb | Bedford, Edmondson, et al., 1962 | Reanalyzed by Cox and Pilcher, 1970, Original value = 118. ± 4.6 kJ/mol; ALS |
Quantity | Value | Units | Method | Reference | Comment |
ΔcH°solid | Ccb | Zaheeruddin and Lodhi, 1991 | uncertain value: -1864.60 kJ/mol; ALS | ||
ΔcH°solid | -1857.6 ± 0.6 | kJ/mol | Ccb | Jimenez, Roux, et al., 1987 | see Jimenez, Roux, et al., 1986; ALS |
ΔcH°solid | -1868.2 ± 4.6 | kJ/mol | Ccb | Bedford, Edmondson, et al., 1962 | Reanalyzed by Cox and Pilcher, 1970, Original value = -1870.8 ± 4.6 kJ/mol; ALS |
ΔcH°solid | -1859. | kJ/mol | Ccb | Zimmerman and Geisenfelder, 1961 | ALS |
Constant pressure heat capacity of solid
Cp,solid (J/mol*K) | Temperature (K) | Reference | Comment |
---|---|---|---|
81.0 | 298.15 | Jimenez, Roux, et al., 1987 | Cp given as 1.19 J/g*K.; DH |
87.9 | 300. | DeWit, Offringa, et al., 1983 | T = 300 to 450 K.; DH |
Reaction thermochemistry 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 compiled as indicated in comments:
B - John E. Bartmess
RCD - Robert C. Dunbar
Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.
Individual Reactions
C3H3N2- + =
By formula: C3H3N2- + H+ = C3H4N2
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 1479. ± 10. | kJ/mol | G+TS | Gianola, Ichino, et al., 2006 | gas phase; B |
ΔrH° | 1479. ± 10. | 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° | 1449. ± 9.6 | kJ/mol | N/A | Gianola, Ichino, et al., 2006 | gas phase; B |
ΔrG° | 1449. ± 9.6 | kJ/mol | IMRE | Taft, Anvia, et al., 1986 | gas phase; value altered from reference due to change in acidity scale; B |
By formula: Li+ + C3H4N2 = (Li+ • C3H4N2)
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 187. ± 17. | kJ/mol | CIDT | Huang and Rodgers, 2002 | RCD |
By formula: Na+ + C3H4N2 = (Na+ • C3H4N2)
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 128. ± 9.2 | kJ/mol | CIDT | Huang and Rodgers, 2002 | RCD |
By formula: K+ + C3H4N2 = (K+ • C3H4N2)
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 84. ± 3. | kJ/mol | CIDT | Huang and Rodgers, 2002 | RCD |
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
Data compiled as indicated in comments:
B - John E. Bartmess
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
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
Proton affinity (review) | 894.1 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Quantity | Value | Units | Method | Reference | Comment |
Gas basicity | 860.5 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Ionization energy determinations
IE (eV) | Method | Reference | Comment |
---|---|---|---|
9.38 ± 0.03 | PE | Lichtenberger, Copenhaver, et al., 1988 | LL |
9.25 ± 0.01 | PI | Main-Bobo, Loesik, et al., 1986 | LBLHLM |
9.27 ± 0.05 | PE | Baker, Betteridge, et al., 1970 | RDSH |
9.15 | PE | Daamen, Oskam, et al., 1979 | Vertical value; LLK |
9.15 | PE | Cradock, Findlay, et al., 1973 | Vertical value; LLK |
Appearance energy determinations
Ion | AE (eV) | Other Products | Method | Reference | Comment |
---|---|---|---|---|---|
CH2N+ | 11.72 ± 0.05 | C2H2N | PI | Main-Bobo, Loesik, et al., 1986 | LBLHLM |
C2H3N+ | 11.76 ± 0.02 | CHN | PI | Main-Bobo, Loesik, et al., 1986 | LBLHLM |
De-protonation reactions
C3H3N2- + =
By formula: C3H3N2- + H+ = C3H4N2
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 1479. ± 10. | kJ/mol | G+TS | Gianola, Ichino, et al., 2006 | gas phase; B |
ΔrH° | 1479. ± 10. | 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° | 1449. ± 9.6 | kJ/mol | N/A | Gianola, Ichino, et al., 2006 | gas phase; B |
ΔrG° | 1449. ± 9.6 | 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 thermochemistry data, Condensed phase thermochemistry data, Reaction thermochemistry data, 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.
Zaheeruddin and Lodhi, 1991
Zaheeruddin, M.; Lodhi, Z.H.,
Enthalpies of formation of some cyclic compounds,
Phys. Chem. (Peshawar Pak.), 1991, 10, 111-118. [all data]
Jimenez, Roux, et al., 1987
Jimenez, P.; Roux, M.V.; Turrion, C.,
Thermochemical properties of N-heterocyclic compounds. I. Enthalpies of combustion, vapour pressures and enthalpies of sublimation, and enthalpies of formation of pyrazole, imidazole, indazole, and benzimidazole,
J. Chem. Thermodyn., 1987, 19, 985-992. [all data]
Jimenez, Roux, et al., 1986
Jimenez, P.; Roux, M.V.; Turrion, C.; Gomis, F.,
Thermochemical properties of some N-heterocyclic compounds,
J. Calorim. Anal. Therm. Thermodyn. Chim., 1986, 17, 469-470. [all data]
Bedford, Edmondson, et al., 1962
Bedford, A.F.; Edmondson, P.B.; Mortimer, C.T.,
Heats of formation and bond energies. Part VI. n-Butyliso-butyraldimine, n-butylisobutylamine, pyrazole, and imidazole,
J. Chem. Soc., 1962, 2927-2931. [all data]
Cox and Pilcher, 1970
Cox, J.D.; Pilcher, G.,
Thermochemistry of Organic and Organometallic Compounds, Academic Press, New York, 1970, 1-636. [all data]
Zimmerman and Geisenfelder, 1961
Zimmerman, H.; Geisenfelder, H.,
Uber die Mesomerieenergie von Azolen,
Z. Electrochem., 1961, 65, 368-371. [all data]
DeWit, Offringa, et al., 1983
DeWit, H.G.M.; Offringa, J.C.A.; De Kruif, C.G.; Van Miltenburg, J.C.,
Thermodynamic properties of molecular organic crystals containing nitrogen, oxygen and sulfur. III. Molar heat capacities measured by differential scanning calorimetry,
Thermochim. Acta, 1983, 65, 43-51. [all data]
Gianola, Ichino, et al., 2006
Gianola, A.J.; Ichino, T.; Kato, S.; Bierbaum, V.M.; Lineberger, W.C.,
Thermochemical studies of pyrazolide,
J. Phys. Chem. A, 2006, 110, 27, 8457-8466, https://doi.org/10.1021/jp057499+
. [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]
Huang and Rodgers, 2002
Huang, H.; Rodgers, M.T.,
Sigma versus Pi interactions in alkali metal ion binding to azoles: Threshold collision-induced dissociation and ab initio theory studies,
J. Phys. Chem. A, 2002, 106, 16, 4277, https://doi.org/10.1021/jp013630b
. [all data]
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]
Lichtenberger, Copenhaver, et al., 1988
Lichtenberger, D.L.; Copenhaver, A.S.; Gray, H.B.; Marshall, J.L.; Hopkins, M.D.,
Valence electronic structure of bis(Pyrazolyl)-bridged iridium dicarbonyl dimers. Electronic effects of 3,5-dimethylpyraxzolyl substitution on metal-metal interactions,
Inorg. Chem., 1988, 27, 4488. [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]
Baker, Betteridge, et al., 1970
Baker, A.D.; Betteridge, D.; Kemp, N.R.; Kirby, R.E.,
Application of photoelectron spectrometry to pesticide analysis. Photoelectron spectra of fivemembered heterocycles and related molecules,
Anal. Chem., 1970, 42, 1064. [all data]
Daamen, Oskam, et al., 1979
Daamen, H.; Oskam, A.; Stufkens, D.J.; Waaijers, H.W.,
Bonding properties of group VIB metal pentacarbonyl azole complexes studied by electronic absorption, photoelectron, 13C NMR and vibrational spectroscopy,
Inorg. Chim. Acta, 1979, 34, 253. [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]
Notes
Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, References
- Symbols used in this document:
AE Appearance energy Cp,solid Constant pressure heat capacity of solid ΔcH°solid Enthalpy of combustion of solid at standard conditions ΔfH°gas Enthalpy of formation of gas at standard conditions ΔfH°solid Enthalpy of formation of solid at standard conditions 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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