Isoprene

• Formula: C₅H₈
• Molecular weight: 68.1170
• IUPAC Standard InChI: InChI=1S/C5H8/c1-4-5(2)3/h4H,1-2H2,3H3 Copy

  
• IUPAC Standard InChIKey: RRHGJUQNOFWUDK-UHFFFAOYSA-N Copy
• CAS Registry Number: 78-79-5
• 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: 1,3-Butadiene, 2-methyl-; β-Methylbivinyl; Isopentadiene; 2-Methyl-1,3-butadiene; 2-Methylbutadiene; CH2=C(CH3)CH=CH2; 2-Methylbuta-1,3-diene; 3-Methyl-1,3-butadiene; NSC 9237
• 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
  • Reaction thermochemistry data
  • Gas phase ion energetics data
  • References
  • Notes
• Other data available:
  • Phase change data
  • Henry's Law data
  • Ion clustering data
  • IR Spectrum
  • Mass spectrum (electron ionization)
  • UV/Visible spectrum
  • Gas Chromatography
• Data at other public NIST sites:
  • Microwave spectra (on physics lab web site)
  • Computational Chemistry Comparison and Benchmark Database
  • Gas Phase Kinetics Database
• Options:
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Gas phase 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:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
GT - Glushko Thermocenter, Russian Academy of Sciences, Moscow

Constant pressure heat capacity of gas

Condensed phase 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:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
DH - Eugene S. Domalski and Elizabeth D. Hearing

Constant pressure heat capacity of liquid

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
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
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

C₅H₇^- +  =

By formula: C₅H₇^- + H⁺ = C₅H₈

=  + 

By formula: C₁₁H₈N₄ = C₆N₄ + C₅H₈

 +  =

By formula: C₆N₄ + C₅H₈ = C₁₁H₈N₄

 +  = ( • )

By formula: Ag⁺ + C₅H₈ = (Ag⁺ • C₅H₈)

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
LL - Sharon G. Lias and Joel F. Liebman
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard

View reactions leading to C₅H₈⁺ (ion structure unspecified)

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

C₅H₇^- +  =

By formula: C₅H₇^- + H⁺ = C₅H₈

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.

Fraser and Prosen, 1955
Fraser, F.M.; Prosen, E.J., Heats of combustion and isomerization of six pentadienes and spiropentane, J. Res. NBS, 1955, 54, 143-148. [all data]

Messerly J.F., 1970
Messerly J.F., Chemical thermodynamic properties of the pentadienes. Third law studies, J. Chem. Eng. Data, 1970, 15, 227-232. [all data]

Thermodynamics Research Center, 1997
Thermodynamics Research Center, Selected Values of Properties of Chemical Compounds., Thermodynamics Research Center, Texas A&M University, College Station, Texas, 1997. [all data]

Compton D.A.C., 1977
Compton D.A.C., Conformations of conjugated hydrocarbons. Part 2. A spectroscopic and thermodynamic study of cis- and trans-penta-1,3-diene, J. Chem. Soc. Perkin Trans. 2, 1977, 1311-1315. [all data]

Jessup, 1938
Jessup, R.S., Heat of combustion of isoprene, J. Res. NBS, 1938, 20, 589-597. [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]

Messerly, Todd, et al., 1970
Messerly, J.F.; Todd, S.S.; Guthrie, G.B., Chemical thermodynamic properties of the pentadienes, J. Chem. Eng. Data, 1970, 15, 227-232. [all data]

Warfield and Petree, 1965
Warfield, R.W.; Petree, M.C., Thermodynamic properties of natural rubber and isoprene, Die Makromol. Chemie, 1965, 84, 1-8. [all data]

Bekkedahl and Wood, 1937
Bekkedahl, N.; Wood, L.A., Entropy of isoprene from heat-capacity measurements, J. Res. NBS, 1937, 19, 551-558. [all data]

Bartmess and McIver Jr., 1979
Bartmess, J.E.; McIver Jr., The Gas Phase Acidity Scale in Gas Phase Ion Chemistry, Gas Phase Ion Chemistry, V. 2, M.T. Bowers, Ed., Academic Press, NY, 1979, Ch. 11, Elsevier, 1979. [all data]

Rogers, 1971
Rogers, F.E., Thermochemistry of the Diels-Alder reaction. I. Enthalpy of addition of isoprene to tetracyanoethylene, J. Phys. Chem., 1971, 75, 1734-1737. [all data]

Ho, Yang, et al., 1997
Ho, Y.-P.; Yang, Y.-C.; Klippenstein, S.J.; Dunbar, R.C., Binding Energies of Ag+ and Cd+ Complexes from Analysis of Radiative Association Kinetics, J. Phys. Chem. A, 1997, 101, 18, 3338, https://doi.org/10.1021/jp9637284 . [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]

Bieri, Burger, et al., 1977
Bieri, G.; Burger, F.; Heilbronner, E.; Maier, J.P., Valence ionization enrgies of hydrocarbons, Helv. Chim. Acta, 1977, 60, 2213. [all data]

Lossing and Traeger, 1975
Lossing, F.P.; Traeger, J.C., Stabilization in cyclopentadienyl, cyclopentenyl, and cyclopentyl cations, J. Am. Chem. Soc., 1975, 97, 1579. [all data]

Puttemans and Delvaux, 1973
Puttemans, J.-P.; Delvaux, J.C., Ionisation et fragmentation d'isomeres C₅H₈ sous impact electronique. Spiropentane - methylenecyclobutane - isoprene, Ing. Chim. Brussell, 1973, 55(267-8), 7. [all data]

Beez, Bieri, et al., 1973
Beez, M.; Bieri, G.; Bock, H.; Heilbronner, E., The ionization potentials of butadiene, hexatriene, andtheir methyl derivatives: evidence for through space interaction between double bond π-orbitals and non-bonded pseudo-π orbitals of methyl groups?, Helv. Chim. Acta, 1973, 56, 1028. [all data]

Watanabe, Nakayama, et al., 1962
Watanabe, K.; Nakayama, T.; Mottl, J., Ionization potentials of some molecules, J. Quant. Spectry. Radiative Transfer, 1962, 2, 369. [all data]

Price and Walsh, 1940
Price, W.C.; Walsh, A.D., The absorption spectra of conjugated dienes in the vacuum ultra-violet (1), Proc. Roy. Soc. (London), 1940, A174, 220. [all data]

Werstiuk, Clark, et al., 1990
Werstiuk, N.H.; Clark, K.B.; Leigh, W.J., Conformational analysis and structure elucidation of 2,3-dimethyl and 2,4-dimethyl-2,4-hexadienes by AM1 and He(I) ultraviolet photoelectron spectroscopy, Can. J. Chem., 1990, 68, 2078. [all data]

Masclet, Mouvier, et al., 1981
Masclet, P.; Mouvier, G.; Bocquet, J.F., Effets electroniques et effets steriques dus a la substitution alcoyle dans les dienes conjugues, J. Chim. Phys., 1981, 78, 99. [all data]

Worley, Webb, et al., 1979
Worley, S.D.; Webb, T.R.; Gibson, D.H.; Ong, T.-S., On the electronic structures of cyclobutadiene trimethylenemethane, J. Organomet. Chem., 1979, 168, 16. [all data]

Sustmann and Schubert, 1972
Sustmann, R.; Schubert, R., Photoelektronenspektroskopische bestimmung von substituenten-effekten. I. Subtituierte butadiene, Tetrahedron Lett., 1972, 27, 2739. [all data]

Lossing and Holmes, 1984
Lossing, F.P.; Holmes, J.L., Stabilization energy and ion size in carbocations in the gas phase, J. Am. Chem. Soc., 1984, 106, 6917. [all data]

Harrison, Haynes, et al., 1965
Harrison, A.G.; Haynes, P.; McLean, S.; Meyer, F., The mass spectra of methyl-substituted cyclopentadienes, J. Am. Chem. Soc., 1965, 87, 5099. [all data]

Holmes, 1974
Holmes, J.L., The mass spectra of isomeric hydrocarbons - II: The C₅H₈ isomers, spiropentane, cyclopentene, 1,3-pentadiene and isoprene; the mechanisms and energetics of their fragmentations, Org. Mass Spectrom., 1974, 8, 247. [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,gas	Constant pressure heat capacity of gas
  Cp,liquid	Constant pressure heat capacity of liquid
  IE (evaluated)	Recommended ionization energy
  S°gas	Entropy of gas at standard conditions
  S°liquid	Entropy of liquid at standard conditions
  ΔcH°gas	Enthalpy of combustion of gas at standard conditions
  ΔcH°liquid	Enthalpy of combustion of liquid at standard conditions
  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
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