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

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	-178.2 ± 0.88	kJ/mol	Ccb	Good, 1970	Reanalyzed by Pedley, Naylor, et al., 1986, Original value = -178.9 ± 0.59 kJ/mol; ALS
Δ_fH°_liquid	-179.3 ± 0.84	kJ/mol	Ccb	Prosen and Rossini, 1945	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-3504.4 ± 0.84	kJ/mol	Ccb	Good, 1970	Reanalyzed by Pedley, Naylor, et al., 1986, Original value = -3503.6 ± 0.46 kJ/mol; Corresponding Δ_fHº_liquid = -178.2 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_liquid	-3503.3 ± 0.75	kJ/mol	Ccb	Prosen and Rossini, 1945	Corresponding Δ_fHº_liquid = -179.3 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
S°_liquid	260.41	J/mol*K	N/A	Guthrie and Huffman, 1943	DH
S°_liquid	261.04	J/mol*K	N/A	Schumann, Aston, et al., 1942	DH
S°_liquid	254.4	J/mol*K	N/A	Parks, Huffman, et al., 1930	Extrapolation below 90 K, 57.49 J/mol*K.; DH

Constant pressure heat capacity of liquid

C_p,liquid (J/mol*K)	Temperature (K)	Reference	Comment
164.5	298.3	Czarnota, 1988	T = 289 to 299 K. p = 0.1 MPa. Unsmoothed experimental datum. Cp values provided over the pressure range 0.1 to 820 MPa.; DH
164.85	298.15	Guthrie and Huffman, 1943	T = 13 to 300 K.; DH
169.41	290.	Schumann, Aston, et al., 1942	T = 20 to 290 K.; DH
157.3	275.8	Parks, Huffman, et al., 1930	T = 80 to 276 K. Value is unsmoothed experimental datum.; DH

Reaction thermochemistry data

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

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

+ = Butane, 2-methyl-

By formula: H₂ + C₅H₁₀ = C₅H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-126.95	kJ/mol	Chyd	Dolliver, Gresham, et al., 1937	gas phase; At 355 °K
Δ_rH°	-118.2 ± 0.42	kJ/mol	Chyd	Kistiakowsky, Ruhoff, et al., 1936	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -119.2 ± 1.5 kJ/mol; At 355 K

+ = Butane, 2-methyl-

By formula: H₂ + C₅H₁₀ = C₅H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-126.3 ± 0.3	kJ/mol	Chyd	Dolliver, Gresham, et al., 1937	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -126.9 ± 0.3 kJ/mol; At 355 °K

= Butane, 2-methyl-

By formula: C₅H₁₂ = C₅H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-7.786	kJ/mol	Eqk	Pines, Kvetinskas, et al., 1945	gas phase; Heat of isomerization

+ = Butane, 2-methyl-

By formula: H₂ + C₅H₁₀ = C₅H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-111.6 ± 0.3	kJ/mol	Chyd	Kistiakowsky, Ruhoff, et al., 1936	gas phase

Henry's Law data

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Data compiled by: Rolf Sander

Henry's Law constant (water solution)

k_H(T) = k°_H exp(d(ln(k_H))/d(1/T) ((1/T) - 1/(298.15 K)))
k°_H = Henry's law constant for solubility in water at 298.15 K (mol/(kg*bar))
d(ln(k_H))/d(1/T) = Temperature dependence constant (K)

k°_H (mol/(kg*bar))	d(ln(k_H))/d(1/T) (K)	Method	Reference	Comment
0.00072		Q	N/A	missing citation give several references for the Henry's law constants but don't assign them to specific species.
0.00073		L	N/A

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]

Pedley, Naylor, et al., 1986
Pedley, J.B.; Naylor, R.D.; Kirby, S.P., Thermochemical Data of Organic Compounds, Chapman and Hall, New York, 1986, 1-792. [all data]

Guthrie and Huffman, 1943
Guthrie, G.B., Jr.; Huffman, H.M., Thermal data. XVI. The heat capacity and entropy of isopentane. The absence of a reported anomaly, J. Am. Chem. Soc., 1943, 65, 1139-1143. [all data]

Schumann, Aston, et al., 1942
Schumann, S.C.; Aston, J.G.; Sagenkahn, M., The heat capacity and entropy, heats of fusion and vaporization and the vapor pressures of isopentane, J. Am. Chem. Soc., 1942, 64, 1039-1043. [all data]

Parks, Huffman, et al., 1930
Parks, G.S.; Huffman, H.M.; Thomas, S.B., Thermal data on organic compounds. VI. The heat capacities, entropies and free energies of some saturated, non-benzenoid hydrocarbons, J. Am. Chem. Soc., 1930, 52, 1032-1041. [all data]

Czarnota, 1988
Czarnota, I., Heat capacity of 2-methylbutane at high pressures, J. Chem. Thermodynam., 1988, 20, 457-462. [all data]

Dolliver, Gresham, et al., 1937
Dolliver, M.a.; Gresham, T.L.; Kistiakowsky, G.B.; Vaughan, W.E., Heats of organic reactions. V. Heats of hydrogenation of various hydrocarbons, J. Am. Chem. Soc., 1937, 59, 831-841. [all data]

Kistiakowsky, Ruhoff, et al., 1936
Kistiakowsky, G.B.; Ruhoff, J.R.; Smith, H.A.; Vaughan, W.E., Heats of organic reactions. III. Hydrogenation of some higher olefins, J. Am. Chem. Soc., 1936, 58, 137-145. [all data]

Pines, Kvetinskas, et al., 1945
Pines, H.; Kvetinskas, B.; Kassel, L.S.; Ipatieff, V.N., Determination of equilibrium constants for butanes and pentanes, J. Am. Chem. Soc., 1945, 67, 631-637. [all data]

Notes

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Symbols used in this document:

C_p,gas	Constant pressure heat capacity of gas
C_p,liquid	Constant pressure heat capacity of liquid
S°_liquid	Entropy of liquid at standard conditions
d(ln(k_H))/d(1/T)	Temperature dependence parameter for Henry's Law constant
k°_H	Henry's Law constant at 298.15K
Δ_cH°_gas	Enthalpy of combustion of gas at standard conditions
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
Δ_rH°	Enthalpy of reaction at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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