Butane, 2-methyl-

Formula: C₅H₁₂
Molecular weight: 72.1488
IUPAC Standard InChI: InChI=1S/C5H12/c1-4-5(2)3/h5H,4H2,1-3H3
IUPAC Standard InChIKey: QWTDNUCVQCZILF-UHFFFAOYSA-N
CAS Registry Number: 78-78-4
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: iso-Pentane; 1,1,2-Trimethylethane; 2-Methylbutane; iso-C5H12; Ethyldimethylmethane; Isoamylhydride; Exxsol isopentane S; 1,1-Dimethylpropane; Methylbutane; NSC 119476
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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
GT - Glushko Thermocenter, Russian Academy of Sciences, Moscow

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-153.7 ± 0.59	kJ/mol	Ccb	Good, 1970	ALS
Δ_fH°_gas	-154.1 ± 0.96	kJ/mol	Cm	Pilcher and Chadwick, 1967	ALS
Δ_fH°_gas	-154.5 ± 0.84	kJ/mol	Ccb	Prosen and Rossini, 1945	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_gas	-3528.4 ± 0.92	kJ/mol	Cm	Pilcher and Chadwick, 1967	Corresponding Δ_fHº_gas = -154.1 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_gas	-3528.6 ± 0.63	kJ/mol	Cm	Knowlton and Rossini, 1939	Corresponding Δ_fHº_gas = -153.9 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_gas	-3527.6 ± 3.5	kJ/mol	Ccb	Roth and Pahlke, 1936	Reanalyzed by Cox and Pilcher, 1970, Original value = -3529.0 kJ/mol; Corresponding Δ_fHº_gas = -155.0 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS

Constant pressure heat capacity of gas

C_p,gas (J/mol*K)	Temperature (K)	Reference	Comment
84.94	200.	Scott D.W., 1974	Recommended values were obtained from the consistent correlation scheme for alkanes [ Scott D.W., 1974, 2, Scott D.W., 1974]. This approach gives a better agreement with experimental data than the statistical thermodynamics calculations [ Pitzer K.S., 1946, Scott D.W., 1951].; GT
110.37	273.15
118.9 ± 0.4	298.15
119.50	300.
152.88	400.
183.26	500.
210.04	600.
233.05	700.
253.13	800.
270.70	900.
286.19	1000.
299.57	1100.
311.29	1200.
322.17	1300.
330.54	1400.
338.90	1500.

Constant pressure heat capacity of gas

C_p,gas (J/mol*K)	Temperature (K)	Reference	Comment
125.31 ± 0.37	317.20	Scott D.W., 1951	GT
139.12 ± 0.42	358.15
153.64 ± 0.46	402.30
168.36 ± 0.51	449.20
179.62 ± 0.54	487.05

Gas phase ion energetics data

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Data evaluated as indicated in comments:
L - Sharon G. Lias

Data compiled as indicated in comments:
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

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	10.32 ± 0.05	eV	N/A	N/A	L

Ionization energy determinations

IE (eV)	Method	Reference	Comment
10.21	PI	Traeger, Hudson, et al., 1996	T = 0K; LL
10.18	EST	Luo and Pacey, 1992	LL
10.22	PI	Traeger, 1981	LLK
10.3 ± 0.1	PE	Bieri, Burger, et al., 1977	LLK
10.50 ± 0.05	EI	Flesch and Svec, 1973	LLK
10.32	PE	Dewar and Worley, 1969	RDSH
10.32	PI	Watanabe, Nakayama, et al., 1962	RDSH
10.94	PE	Kimura, Katsumata, et al., 1981	Vertical value; LLK
11.0 ± 0.1	PE	Bieri, Burger, et al., 1977	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
C₃H₆⁺	10.66	C₂H₆	PI	Traeger, Hudson, et al., 1996	T = 0K; LL
C₃H₆⁺	10.84 ± 0.025	C₂H₆	PI	Steiner, Giese, et al., 1961	RDSH
C₃H₇⁺	11.06	C₂H₅	PI	Traeger, Hudson, et al., 1996	T = 0K; LL
C₃H₇⁺	11.15 ± 0.05	C₂H₅	PI	Steiner, Giese, et al., 1961	RDSH
C₄H₈⁺	10.72	CH₄	PI	Traeger, Hudson, et al., 1996	T = 0K; LL
C₄H₈⁺	10.74 ± 0.02	CH₄	PI	Steiner, Giese, et al., 1961	RDSH
C₄H₉⁺	10.96	CH₃	PI	Traeger, Hudson, et al., 1996	T = 0K; LL
C₄H₉⁺	10.87	CH₃	PI	Traeger, 1981	LLK
C₄H₉⁺	11.15 ± 0.07	CH₃	PI	Steiner, Giese, et al., 1961	RDSH

IR Spectrum

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Data compiled by: Coblentz Society, Inc.

GAS (100 mmHg, N2 ADDED, TOTAL PRESSURE 600 mmHg); DOW KBr FOREPRISM-GRATING; DIGITIZED BY COBLENTZ SOCIETY (BATCH II) FROM HARD COPY; 2 cm^-1 resolution

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

References

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Good, 1970
Good, W.D., The enthalpies of combustion and formation of the isomeric pentanes, J. Chem. Thermodyn., 1970, 2, 237-244. [all data]

Pilcher and Chadwick, 1967
Pilcher, G.; Chadwick, J.D.M., Measurements of heats of combustion by flame calorimetry. Part 4.-n-Pentane, isopentane, neopentane, Trans. Faraday Soc., 1967, 63, 2357-2361. [all data]

Prosen and Rossini, 1945
Prosen, E.J.; Rossini, F.D., Heats of combustion and formation of the paraffin hydrocarbons at 25° C, J. Res. NBS, 1945, 263-267. [all data]

Knowlton and Rossini, 1939
Knowlton, J.W.; Rossini, F.D., Heats of combustion of tetramethylmethane and 2-methylbutane, J. Res. NBS, 1939, 22, 415-424. [all data]

Roth and Pahlke, 1936
Roth, W.A.; Pahlke, H., Sekundare eichsubstanz fur verbrennungscalorimeter fur gase und dampfe. Die verbrennungswarme von isopentandampf, Angew. Chem., 1936, 49, 618-619. [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]

Scott D.W., 1974
Scott D.W., Chemical Thermodynamic Properties of Hydrocarbons and Related Substances. Properties of the Alkane Hydrocarbons, C1 through C10 in the Ideal Gas State from 0 to 1500 K. U.S. Bureau of Mines, Bulletin 666, 1974. [all data]

Scott D.W., 1974, 2
Scott D.W., Correlation of the chemical thermodynamic properties of alkane hydrocarbons, J. Chem. Phys., 1974, 60, 3144-3165. [all data]

Pitzer K.S., 1946
Pitzer K.S., The entropies and related properties of branched paraffin hydrocarbons, Chem. Rev., 1946, 39, 435-447. [all data]

Scott D.W., 1951
Scott D.W., Rotational isomerism and thermodynamic functions of 2-methylbutane and 2,3-dimethylbutane. Vapor heat capacity and heat of vaporization of 2-methylbutane, J. Am. Chem. Soc., 1951, 73, 1707-1712. [all data]

Traeger, Hudson, et al., 1996
Traeger, J.C.; Hudson, C.E.; McAdoo, D.J., A photoionization study of the ion-neutral complexes [CH₃CH⁺CH₃CH₂CH₃] and [CH₃CH₂CH⁺CH₃CH₃] in the gas phase: Formation, H-transfer and C-C bond formation between partners, and channeling of energy into dissociation, J. Am. Soc. Mass Spectrom., 1996, 7, 73. [all data]

Luo and Pacey, 1992
Luo, Y.-R.; Pacey, P.D., Effects of alkyl substitution on ionization energies of alkanes and haloalkanes and on heats of formation of their molecular cations. Part 2. Alkanes and chloro-, bromo- and iodoalkanes, Int. J. Mass Spectrom. Ion Processes, 1992, 112, 63. [all data]

Traeger, 1981
Traeger, J.C., Heat of formation of sec-butyl cation in the gas phase, Org. Mass Spectrom., 1981, 16, 193. [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]

Flesch and Svec, 1973
Flesch, G.D.; Svec, H.J., Fragmentation reactions in the mass spectrometer for C₂-C₅ alkanes, J. Chem. Soc. Faraday Trans. 2, 1973, 69, 1187. [all data]

Dewar and Worley, 1969
Dewar, M.J.S.; Worley, S.D., Photoelectron spectra of molecules. I. Ionization potentials of some organic molecules and their interpretation, J. Chem. Phys., 1969, 50, 654. [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]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]

Steiner, Giese, et al., 1961
Steiner, B.; Giese, C.F.; Inghram, M.G., Photoionization of alkanes. Dissociation of excited molecular ions, J. Chem. Phys., 1961, 34, 189. [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, IR Spectrum, References

Symbols used in this document:

AE	Appearance energy
C_p,gas	Constant pressure heat capacity of gas
IE (evaluated)	Recommended ionization energy
Δ_cH°_gas	Enthalpy of combustion of gas at standard conditions
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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