1H-Pyrazole
- Formula: C3H4N2
- Molecular weight: 68.0773
- IUPAC Standard InChI: InChI=1S/C3H4N2/c1-2-4-5-3-1/h1-3H,(H,4,5)
- 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
View 3d structure (requires JavaScript / HTML 5) - Other names: Pyrazole; 1,2-Diazole
- Permanent link for this species. Use this link for bookmarking this species for future reference.
- Information on this page:
- Other data available:
- Data at other public NIST sites:
- Options:
Data at NIST subscription sites:
NIST subscription sites provide data under the NIST Standard Reference Data Program, but require an annual fee to access. The purpose of the fee is to recover costs associated with the development of data collections included in such sites. Your institution may already be a subscriber. Follow the links above to find out more about the data in these sites and their terms of usage.
Gas phase thermochemistry data
Go To: Top, Reaction thermochemistry data, Ion clustering 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 | 42.40 | kcal/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 | 42.9 ± 0.2 | kcal/mol | Ccb | Jimenez, Roux, et al., 1987 | see Jimenez, Roux, et al., 1986; ALS |
| ΔfH°gas | 43.3 ± 2.1 | kcal/mol | Ccb | Bedford, Edmondson, et al., 1962 | ALS |
Reaction thermochemistry data
Go To: Top, Gas phase thermochemistry data, Ion clustering 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:
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° | 353.6 ± 2.4 | kcal/mol | G+TS | Gianola, Ichino, et al., 2006 | gas phase; B |
| ΔrH° | 353.6 ± 2.4 | kcal/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° | 346.4 ± 2.3 | kcal/mol | N/A | Gianola, Ichino, et al., 2006 | gas phase; B |
| ΔrG° | 346.4 ± 2.3 | kcal/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° | 44.7 ± 4.0 | kcal/mol | CIDT | Huang and Rodgers, 2002 | RCD |
+
= (
•
)
By formula: Na+ + C3H4N2 = (Na+ • C3H4N2)
| Quantity | Value | Units | Method | Reference | Comment |
|---|---|---|---|---|---|
| ΔrH° | 30.6 ± 2.2 | kcal/mol | CIDT | Huang and Rodgers, 2002 | RCD |
+
= (
•
)
By formula: K+ + C3H4N2 = (K+ • C3H4N2)
| Quantity | Value | Units | Method | Reference | Comment |
|---|---|---|---|---|---|
| ΔrH° | 20.0 ± 0.8 | kcal/mol | CIDT | Huang and Rodgers, 2002 | RCD |
Ion clustering data
Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry 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 by: Robert C. Dunbar
Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. Searches may be limited to ion clustering reactions. A general reaction search form is also available.
Clustering reactions
+
= (
•
)
By formula: K+ + C3H4N2 = (K+ • C3H4N2)
| Quantity | Value | Units | Method | Reference | Comment |
|---|---|---|---|---|---|
| ΔrH° | 20.0 ± 0.8 | kcal/mol | CIDT | Huang and Rodgers, 2002 |
+
= (
•
)
By formula: Li+ + C3H4N2 = (Li+ • C3H4N2)
| Quantity | Value | Units | Method | Reference | Comment |
|---|---|---|---|---|---|
| ΔrH° | 44.7 ± 4.0 | kcal/mol | CIDT | Huang and Rodgers, 2002 |
+
= (
•
)
By formula: Na+ + C3H4N2 = (Na+ • C3H4N2)
| Quantity | Value | Units | Method | Reference | Comment |
|---|---|---|---|---|---|
| ΔrH° | 30.6 ± 2.2 | kcal/mol | CIDT | Huang and Rodgers, 2002 |
References
Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Ion clustering 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]
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]
Notes
Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Ion clustering data, References
- Symbols used in this document:
ΔfH°gas Enthalpy of formation of gas 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
- The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgment. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the Database.
- Customer support for NIST Standard Reference Data products.