Cyclopentene, 1-methyl-

Formula: C₆H₁₀
Molecular weight: 82.1436
IUPAC Standard InChI: InChI=1S/C6H10/c1-6-4-2-3-5-6/h4H,2-3,5H2,1H3
IUPAC Standard InChIKey: ATQUFXWBVZUTKO-UHFFFAOYSA-N
CAS Registry Number: 693-89-0
Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
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Other names: 1-Methyl-1-cyclopentene; 1-Methylcyclopentene; 1-Methyl-1-cyclopentane; Cyc1opentene,l-methyl-; 1-Cyclopentene, 1-methyl; 1-Methylcyclopentene-1
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Gas phase thermochemistry data

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Data compiled as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
DRB - Donald R. Burgess, Jr.

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-4.39	kJ/mol	Chyd	Allinger, Dodziuk, et al., 1982	ALS
Δ_fH°_gas	-3.6 ± 0.75	kJ/mol	Cm	Fuchs and Peacock, 1979	ALS
Δ_fH°_gas	-2.5	kJ/mol	N/A	Good and Smith, 1969	Value computed using Δ_fH_liquid° value of -36.4±0.6 kj/mol from Good and Smith, 1969 and Δ_vapH° value of 33.9 kj/mol from Labbauf and Rossini, 1961.; DRB
Δ_fH°_gas	-4. ± 2.	kJ/mol	Ccb	Labbauf and Rossini, 1961	Heat of formation derived by Cox and Pilcher, 1970; ALS

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	-36.4 ± 0.63	kJ/mol	Ccb	Good and Smith, 1969	ALS
Δ_fH°_liquid	-37.9 ± 0.67	kJ/mol	Ccb	Labbauf and Rossini, 1961	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-3753.8 ± 0.54	kJ/mol	Ccb	Good and Smith, 1969	Corresponding Δ_fHº_liquid = -36.4 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_liquid	-3752.4 ± 0.59	kJ/mol	Ccb	Labbauf and Rossini, 1961	Corresponding Δ_fHº_liquid = -37.8 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
153.1	298.15	Fuchs and Peacock, 1979	DH

Gas phase ion energetics data

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Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias

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)

Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	816.5	kJ/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	787.1	kJ/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
8.59	EI	Lossing and Traeger, 1975	LLK
8.60 ± 0.01	PE	Rang, Paldoia, et al., 1974	LLK
9.12 ± 0.05	EI	Praet, 1970	RDSH
8.55 ± 0.01	PI	Praet, 1970	RDSH
8.54 ± 0.01	PE	Praet and Delwiche, 1970	RDSH
8.62 ± 0.02	EI	Winters and Collins, 1969	RDSH

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
C₃H₃⁺	13.23 ± 0.21	?	EI	Winters and Collins, 1969	RDSH
C₃H₅⁺	13.7	C₄H₇	EI	Shikhmamedbekova, Aslanov, et al., 1970	RDSH
C₃H₅⁺	14.9 ± 0.1	?	EI	Praet, 1970	RDSH
C₃H₅⁺	12.45 ± 0.13	?	EI	Winters and Collins, 1969	RDSH
C₄H₅⁺	13.14 ± 0.09	?	EI	Winters and Collins, 1969	RDSH
C₄H₆⁺	12.33 ± 0.05	C₂H₄	EI	Praet, 1970	RDSH
C₄H₆⁺	11.02 ± 0.12	?	EI	Winters and Collins, 1969	RDSH
C₅H₅⁺	13.45 ± 0.19	?	EI	Winters and Collins, 1969	RDSH
C₅H₇⁺	8.59	CH₃	EI	Lossing and Traeger, 1975, 2	LLK
C₅H₇⁺	10.19	H	EI	Lossing and Traeger, 1975	LLK
C₅H₇⁺	11.59 ± 0.05	CH₃	EI	Praet, 1970	RDSH
C₅H₇⁺	9.99 ± 0.09	CH₃	EI	Winters and Collins, 1969	RDSH
C₆H₇⁺	12.40 ± 0.17	H₂+H	EI	Winters and Collins, 1969	RDSH
C₆H₉⁺	11.97 ± 0.05	H	EI	Praet, 1970	RDSH
C₆H₉⁺	10.59 ± 0.13	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]

Good and Smith, 1969
Good, W.D.; Smith, N.K., Enthalpies of combustion of toluene, benzene, cyclohexane, cyclohexene, methylcyclopentane, 1-methylcyclopentene, and n-hexane, J. Chem. Eng. Data, 1969, 14, 102-106. [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]

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]

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]

Praet, 1970
Praet, M.-Th., Ionisation et dissociation du 1-methyl-cyclopentene, du methylenecyclopentane et de quelques isomeres par impact d'electrons et de photons, Org. Mass Spectrom., 1970, 4, 65. [all data]

Praet and Delwiche, 1970
Praet, M.-T.; Delwiche, J., Ionization energies of some cyclic molecules, Chem. Phys. Lett., 1970, 5, 546. [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]

Shikhmamedbekova, Aslanov, et al., 1970
Shikhmamedbekova, A.Z.; Aslanov, F.A.; Gadzhiev, M.M.; Gulamova, T.E.; Akhmedova, F.N., Mass spectrometric study of methylene cycloalkenes, Dokl. Phys. Chem., 1970, 26, 34. [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]

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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