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) Copy

  
• IUPAC Standard InChIKey: WTKZEGDFNFYCGP-UHFFFAOYSA-N Copy
• 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
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase thermochemistry data
  • Condensed phase thermochemistry data
  • Phase change data
  • Reaction thermochemistry data
  • Gas phase ion energetics data
  • Ion clustering data
  • IR Spectrum
  • Mass spectrum (electron ionization)
  • Gas Chromatography
  • References
  • Notes
• Other data available:
  • UV/Visible spectrum
• Data at other public NIST sites:
  • Gas Phase Kinetics Database
• Options:
  • Switch to calorie-based units

Data at NIST subscription sites:

• NIST / TRC Web Thermo Tables, professional edition (thermophysical and thermochemical data)

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, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, IR Spectrum, Mass spectrum (electron ionization), Gas Chromatography, 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

Condensed phase thermochemistry data

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, IR Spectrum, Mass spectrum (electron ionization), Gas Chromatography, 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

Constant pressure heat capacity of solid

Phase change data

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, IR Spectrum, Mass spectrum (electron ionization), Gas Chromatography, 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:
BS - Robert L. Brown and Stephen E. Stein
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
DRB - Donald R. Burgess, Jr.
AC - William E. Acree, Jr., James S. Chickos
DH - Eugene S. Domalski and Elizabeth D. Hearing

Enthalpy of sublimation

Enthalpy of fusion

Entropy of fusion

Reaction thermochemistry data

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Gas phase ion energetics data, Ion clustering data, IR Spectrum, Mass spectrum (electron ionization), Gas Chromatography, 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

 +  = ( • )

By formula: Li⁺ + C₃H₄N₂ = (Li⁺ • C₃H₄N₂)

 +  = ( • )

By formula: Na⁺ + C₃H₄N₂ = (Na⁺ • C₃H₄N₂)

 +  = ( • )

By formula: K⁺ + C₃H₄N₂ = (K⁺ • C₃H₄N₂)

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Ion clustering data, IR Spectrum, Mass spectrum (electron ionization), Gas Chromatography, 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

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

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

C₃H₃N₂^- +  =

By formula: C₃H₃N₂^- + H⁺ = C₃H₄N₂

Ion clustering data

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, IR Spectrum, Mass spectrum (electron ionization), Gas Chromatography, 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)

 +  = ( • )

By formula: Li⁺ + C₃H₄N₂ = (Li⁺ • C₃H₄N₂)

 +  = ( • )

By formula: Na⁺ + C₃H₄N₂ = (Na⁺ • C₃H₄N₂)

IR Spectrum

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, Mass spectrum (electron ionization), Gas Chromatography, 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: Coblentz Society, Inc.

Condensed Phase Spectrum

Notice: This spectrum may be better viewed with a Javascript and HTML 5 enabled browser.

For Zoom

1.) Enter the desired X axis range (e.g., 100, 200)

2.) Check here for automatic Y scaling

3.) Press here to zoom

Notice: Except where noted, spectra from this collection were measured on dispersive instruments, often in carefully selected solvents, and hence may differ in detail from measurements on FTIR instruments or in other chemical environments. More information on the manner in which spectra in this collection were collected can be found here.

Notice: Concentration information is not available for this spectrum and, therefore, molar absorptivity values cannot be derived.

Additional Data

Mass spectrum (electron ionization)

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, IR Spectrum, Gas Chromatography, 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: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

Notice: This spectrum may be better viewed with a Javascript and HTML 5 enabled browser.

For Zoom

1.) Enter the desired X axis range (e.g., 100, 200)

2.) Check here for automatic Y scaling

3.) Press here to zoom

Additional Data

Gas Chromatography

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, IR Spectrum, Mass spectrum (electron ionization), 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: NIST Mass Spectrometry Data Center, William E. Wallace, director

Kovats' RI, non-polar column, isothermal

View large format table.

Van Den Dool and Kratz RI, non-polar column, temperature ramp

View large format table.

References

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, IR Spectrum, Mass spectrum (electron ionization), Gas Chromatography, 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]

Weast and Grasselli, 1989
CRC Handbook of Data on Organic Compounds, 2nd Editon, Weast,R.C and Grasselli, J.G., ed(s)., CRC Press, Inc., Boca Raton, FL, 1989, 1. [all data]

Lecat, 1947
Lecat, M., Some azeotropes of which one constituant is heterocyclic nitrogen, Ann. Soc. Sci. Bruxelles, Ser. 1, 1947, 61, 73. [all data]

Hilgeman, Mouroux, et al., 1989
Hilgeman, F.R.; Mouroux, F.Y.N.; Mok, D.; Holan, M.K., Phase Diagrams of Binary Solid Azole Systems, J. Chem. Eng. Data, 1989, 34, 220. [all data]

De Wit, Offringa, et al., 1983
De Wit, H.G.M.; Offringa, J.C.A.; De Kruif, C.G.; van Miltenburg, J.C., Thremodynamic properties of molecular organic crystals containing nitrogen, oxygen and sulfur. III. molar heat capacities measured by DSC. scanning calorimetry., Thermochim. Acta, 1983, 65, 43. [all data]

De Wit, Van Miltenburg, et al., 1983
De Wit, H.G.M.; Van Miltenburg, J.C.; De Kruif, C.G., Thermodynamic properties of molecular organic crystals containing nitrogen, oxygen, and sulphur 1. Vapour pressures and enthalpies of sublimation, The Journal of Chemical Thermodynamics, 1983, 15, 7, 651-663, https://doi.org/10.1016/0021-9614(83)90079-4 . [all data]

Hilgeman, Mouroux, et al., 1989, 2
Hilgeman, F.R.; Mouroux, F.Y.N.; Mok, D.; Holan, M.K., Phase diagrams of binary solid azole systems, J. Chem. Eng. Data, 1989, 34, 220-222. [all data]

Domalski and Hearing, 1996
Domalski, Eugene S.; Hearing, Elizabeth D., Heat Capacities and Entropies of Organic Compounds in the Condensed Phase. Volume III, J. Phys. Chem. Ref. Data, 1996, 25, 1, 1, https://doi.org/10.1063/1.555985 . [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]

Zhuravleva, 2000
Zhuravleva, I.L., Evaluation of the polarity and boiling points of nitrogen-containing heterocyclic compounds by gas chromatography, Russ. Chem. Bull. (Engl. Transl.), 2000, 49, 2, 325-328, https://doi.org/10.1007/BF02494682 . [all data]

Golovnya, Kuz'menko, et al., 1999
Golovnya, R.V.; Kuz'menko, T.E.; Zhuravleva, I.L., Gas chromatographic indicator of the ability of five- and six-membered heterocyclic nitrogen-containing compounds for self-association in pure liquids, Russ. Chem. Bull. (Engl. Transl.), 1999, 48, 4, 726-729, https://doi.org/10.1007/BF02496256 . [all data]

Peng, Ding, et al., 1988
Peng, C.T.; Ding, S.F.; Hua, R.L.; Yang, Z.C., Prediction of Retention Indexes I. Structure-Retention Index Relationship on Apolar Columns, J. Chromatogr., 1988, 436, 137-172, https://doi.org/10.1016/S0021-9673(00)94575-8 . [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, IR Spectrum, Mass spectrum (electron ionization), Gas Chromatography, References

• Symbols used in this document:
  

  AE	Appearance energy
  Cp,solid	Constant pressure heat capacity of solid
  Tboil	Boiling point
  Tfus	Fusion (melting) point
  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
  ΔfusH	Enthalpy of fusion
  ΔfusS	Entropy of fusion
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ΔsubH	Enthalpy of sublimation
  ΔsubH°	Enthalpy of sublimation 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.