Cyclopentene, 3-methyl-

Formula: C₆H₁₀
Molecular weight: 82.1436
IUPAC Standard InChI: InChI=1S/C6H10/c1-6-4-2-3-5-6/h2,4,6H,3,5H2,1H3
IUPAC Standard InChIKey: CXOZQHPXKPDQGT-UHFFFAOYSA-N
CAS Registry Number: 1120-62-3
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.
Stereoisomers:
- (R)-3-methylcyclopentene
Other names: 3-Methylcyclopentene; 3-Methylcyclopentene-1; 3-Methyl-1-cyclopentene
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Gas phase thermochemistry data

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Data compiled by: Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	9.67	kJ/mol	Chyd	Allinger, Dodziuk, et al., 1982
Δ_fH°_gas	7.36 ± 0.71	kJ/mol	Cm	Fuchs and Peacock, 1979
Δ_fH°_gas	8. ± 2.	kJ/mol	Ccb	Labbauf and Rossini, 1961	Heat of formation derived by Cox and Pilcher, 1970

Condensed phase thermochemistry data

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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
Δ_fH°_liquid	-24.9 ± 1.8	kJ/mol	Ccb	Labbauf and Rossini, 1961	Reanalyzed by Cox and Pilcher, 1970, Original value = -23.8 ± 0.63 kJ/mol; ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-3766.5 ± 0.54	kJ/mol	Ccb	Labbauf and Rossini, 1961	Corresponding Δ_fHº_liquid = -23.7 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS

Constant pressure heat capacity of liquid

C_p,liquid (J/mol*K)	Temperature (K)	Reference	Comment
152.3	298.15	Fuchs and Peacock, 1979	DH

Gas phase ion energetics data

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Data compiled as indicated in comments:
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

View reactions leading to C₆H₁₀⁺ (ion structure unspecified)

Ionization energy determinations

IE (eV)	Method	Reference	Comment
8.95	EI	Lossing and Traeger, 1975	LLK
8.95 ± 0.01	PE	Rang, Paldoia, et al., 1974	LLK
8.99 ± 0.04	EI	Winters and Collins, 1969	RDSH
8.98 ± 0.05	PE	McAlduff, Caramella, et al., 1978	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
C₃H₃⁺	13.24 ± 0.32	?	EI	Winters and Collins, 1969	RDSH
C₃H₅⁺	12.28 ± 0.17	?	EI	Winters and Collins, 1969	RDSH
C₄H₅⁺	12.69 ± 0.20	?	EI	Winters and Collins, 1969	RDSH
C₄H₆⁺	10.69 ± 0.07	?	EI	Winters and Collins, 1969	RDSH
C₅H₅⁺	13.35 ± 0.05	?	EI	Winters and Collins, 1969	RDSH
C₅H₇⁺	8.95	CH₃	EI	Lossing and Traeger, 1975, 2	LLK
C₅H₇⁺	10.03	CH₃	EI	Lossing and Traeger, 1975	LLK
C₅H₇⁺	9.67 ± 0.11	CH₃	EI	Winters and Collins, 1969	RDSH
C₅H₇⁺	10.52	CH₃	EI	Pignataro, Cassuto, et al., 1967	RDSH
C₆H₇⁺	11.75 ± 0.04	H₂+H	EI	Winters and Collins, 1969	RDSH
C₆H₉⁺	10.35 ± 0.17	H	EI	Winters and Collins, 1969	RDSH

References

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Allinger, Dodziuk, et al., 1982
Allinger, N.L.; Dodziuk, H.; Rogers, D.W.; Naik, S.N., Heats of hydrogenation and formation of some 5-membered ring compounds by molecular mechanics calculations and direct measurements, Tetrahedron, 1982, 38, 1593-1597. [all data]

Fuchs and Peacock, 1979
Fuchs, R.; Peacock, L.A., Heats of vaporization and gaseous heats of formation of some five- and six-membered ring alkenes, Can. J. Chem., 1979, 57, 2302-2304. [all data]

Labbauf and Rossini, 1961
Labbauf, A.; Rossini, F.D., Heats of combustion, formation, and hydrogenation of 14 selected cyclomonoolefin hydrocarbons, J. Phys. Chem., 1961, 65, 476-480. [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]

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]

Rang, Paldoia, et al., 1974
Rang, S.; Paldoia, P.; Talvari, A., Ionization potentials of unsaturated hydrocarbons. 2. Mono-substituted cyclopentenes and cyclohexenes, Eesti. NSV Tead. Akad. Toim., 1974, 354. [all data]

Winters and Collins, 1969
Winters, R.E.; Collins, J.H., Mass spectrometric studies of structural isomers. II.Mono- and bicyclic C₆H₁₀ molecules, Org. Mass Spectrom., 1969, 2, 299. [all data]

McAlduff, Caramella, et al., 1978
McAlduff, E.J.; Caramella, P.; Houk, K.N., Photoelectron spectra of 3-substituted cyclopentenes. Correlations between ionization potentials and cycloaddition regioselectivity, J. Am. Chem. Soc., 1978, 100, 105. [all data]

Lossing and Traeger, 1975, 2
Lossing, F.P.; Traeger, J.C., Free radicals by mass spectrometry XLVI. Heats of formation of C₅H₇ and C₅H₉ radicals and cations., J. Am. Chem. Soc., 1975, 19, 9. [all data]

Pignataro, Cassuto, et al., 1967
Pignataro, S.; Cassuto, A.; Lossing, F.P., Free radicals by mass spectrometry. XXXVI. Ionization potentials of conjugated and nonconjugated radicals, J. Am. Chem. Soc., 1967, 89, 3693. [all data]

Notes

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Symbols used in this document:

AE	Appearance energy
C_p,liquid	Constant pressure heat capacity of liquid
Δ_cH°_liquid	Enthalpy of combustion of liquid at standard conditions
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_fH°_liquid	Enthalpy of formation of liquid at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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