Isoprene
- Formula: C5H8
- Molecular weight: 68.1170
- IUPAC Standard InChIKey: RRHGJUQNOFWUDK-UHFFFAOYSA-N
- 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
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Condensed phase thermochemistry data
Go To: Top, 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 |
---|---|---|---|---|---|
ΔcH°liquid | -3158.2 ± 1.6 | kJ/mol | Ccb | Jessup, 1938 | Reanalyzed by Cox and Pilcher, 1970, Original value = -3156.9 ± 1.6 kJ/mol; Corresponding ΔfHºliquid = 47.3 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS |
Quantity | Value | Units | Method | Reference | Comment |
S°liquid | 228.28 | J/mol*K | N/A | Messerly, Todd, et al., 1970 | DH |
S°liquid | 229.2 | J/mol*K | N/A | Warfield and Petree, 1965 | DH |
S°liquid | 229.3 | J/mol*K | N/A | Bekkedahl and Wood, 1937 | DH |
Constant pressure heat capacity of liquid
Cp,liquid (J/mol*K) | Temperature (K) | Reference | Comment |
---|---|---|---|
151.08 | 298.15 | Messerly, Todd, et al., 1970 | T = 12 to 320 K.; DH |
152.5 | 298.15 | Warfield and Petree, 1965 | T = 20 to 300 K. A reexamination of 37BEK/WOO.; DH |
152.6 | 298.2 | Bekkedahl and Wood, 1937 | T = 20 to 300 K.; DH |
Reaction thermochemistry data
Go To: Top, Condensed phase 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:
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- + =
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 1613. ± 21. | kJ/mol | G+TS | Bartmess and McIver Jr., 1979 | gas phase; Between H2O, MeOH. Acid: isoprene; B |
Quantity | Value | Units | Method | Reference | Comment |
ΔrG° | 1586. ± 21. | kJ/mol | IMRB | Bartmess and McIver Jr., 1979 | gas phase; Between H2O, MeOH. Acid: isoprene; B |
By formula: C11H8N4 = C6N4 + C5H8
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 157. ± 3. | kJ/mol | Cm | Rogers, 1971 | solid phase; Heat of formation derived by 77PED/RYL; ALS |
By formula: C6N4 + C5H8 = C11H8N4
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | -157. ± 3. | kJ/mol | Cm | Rogers, 1971 | liquid phase; solvent: Dichloromethane; ALS |
By formula: Ag+ + C5H8 = (Ag+ • C5H8)
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 164. ± 19. | kJ/mol | RAK | Ho, Yang, et al., 1997 | RCD |
Gas phase ion energetics data
Go To: Top, Condensed 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 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)
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
IE (evaluated) | 8.86 ± 0.02 | eV | N/A | N/A | L |
Quantity | Value | Units | Method | Reference | Comment |
Proton affinity (review) | 826.4 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Quantity | Value | Units | Method | Reference | Comment |
Gas basicity | 797.6 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Ionization energy determinations
IE (eV) | Method | Reference | Comment |
---|---|---|---|
8.85 ± 0.02 | PE | Bieri, Burger, et al., 1977 | LLK |
8.85 | EI | Lossing and Traeger, 1975 | LLK |
8.90 ± 0.10 | EI | Puttemans and Delvaux, 1973 | LLK |
8.89 | PE | Beez, Bieri, et al., 1973 | LLK |
8.845 ± 0.005 | PI | Watanabe, Nakayama, et al., 1962 | RDSH |
8.84 ± 0.01 | S | Price and Walsh, 1940 | RDSH |
8.85 | PE | Werstiuk, Clark, et al., 1990 | Vertical value; LL |
8.85 | PE | Masclet, Mouvier, et al., 1981 | Vertical value; LLK |
8.87 | PE | Worley, Webb, et al., 1979 | Vertical value; LLK |
9.04 | PE | Sustmann and Schubert, 1972 | Vertical value; LLK |
Appearance energy determinations
Ion | AE (eV) | Other Products | Method | Reference | Comment |
---|---|---|---|---|---|
C3H3+ | 14.55 ± 0.15 | C2H4+H | EI | Puttemans and Delvaux, 1973 | LLK |
C3H4+ | 12.39 ± 0.12 | C2H4 | EI | Puttemans and Delvaux, 1973 | LLK |
C3H5+ | 14.04 ± 0.10 | C2H2+H | EI | Puttemans and Delvaux, 1973 | LLK |
C3H6+ | 12.76 ± 0.10 | C2H2 | EI | Puttemans and Delvaux, 1973 | LLK |
C4H5+ | 11.44 | CH3 | EI | Lossing and Holmes, 1984 | LBLHLM |
C4H5+ | 11.93 ± 0.10 | CH3 | EI | Puttemans and Delvaux, 1973 | LLK |
C5H5+ | 13.9 | H2+H | EI | Harrison, Haynes, et al., 1965 | RDSH |
C5H7+ | 10.54 | H | EI | Lossing and Traeger, 1975 | LLK |
C5H7+ | 10.54 | H | EI | Holmes, 1974 | LLK |
C5H7+ | 10.93 ± 0.10 | H | EI | Puttemans and Delvaux, 1973 | LLK |
De-protonation reactions
C5H7- + =
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 1613. ± 21. | kJ/mol | G+TS | Bartmess and McIver Jr., 1979 | gas phase; Between H2O, MeOH. Acid: isoprene; B |
Quantity | Value | Units | Method | Reference | Comment |
ΔrG° | 1586. ± 21. | kJ/mol | IMRB | Bartmess and McIver Jr., 1979 | gas phase; Between H2O, MeOH. Acid: isoprene; B |
References
Go To: Top, 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.
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, Condensed phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, References
- Symbols used in this document:
AE Appearance energy Cp,liquid Constant pressure heat capacity of liquid IE (evaluated) Recommended ionization energy S°liquid Entropy of liquid at standard conditions ΔcH°liquid Enthalpy of combustion of liquid 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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