Isobutane

Formula: C₄H₁₀
Molecular weight: 58.1222
IUPAC Standard InChI: InChI=1S/C4H10/c1-4(2)3/h4H,1-3H3
IUPAC Standard InChIKey: NNPPMTNAJDCUHE-UHFFFAOYSA-N
CAS Registry Number: 75-28-5
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: Propane, 2-methyl-; Trimethylmethane; 1,1-Dimethylethane; 2-Methylpropane; iso-C4H10; i-Butane; UN 1969; R 600a; tert-Butane; A 31; Methylpropane; A 31 (hydrocarbon)
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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	-134.2 ± 0.63	kJ/mol	Ccb	Pittam and Pilcher, 1972	ALS
Δ_fH°_gas	-135.6 ± 0.54	kJ/mol	Cm	Prosen, Maron, et al., 1951	see Prosen and Rossini, 1945, Rossini, 1935; ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_gas	-2869.0 ± 0.59	kJ/mol	Ccb	Pittam and Pilcher, 1972	Corresponding Δ_fHº_gas = -134.2 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_gas	-2867.6 ± 0.46	kJ/mol	Cm	Prosen, Maron, et al., 1951	see Prosen and Rossini, 1945, Rossini, 1935; Corresponding Δ_fHº_gas = -135.6 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
34.81	50.	Chen S.S., 1975	Recommended values are in good agreement with those calculated by [ Pitzer K.S., 1946].; GT
47.28	100.
60.29	150.
71.84	200.
89.91	273.15
96.65	298.15
97.15	300.
124.43	400.
149.24	500.
170.37	600.
188.28	700.
203.64	800.
216.94	900.
228.45	1000.
238.49	1100.
247.15	1200.
254.72	1300.
261.29	1400.
267.02	1500.

Constant pressure heat capacity of gas

C_p,gas (J/mol*K)	Temperature (K)	Reference	Comment
82.30 ± 0.06	243.15	Ernst G., 1970	Other experimental values of heat capacity [ Sage B.H., 1937, Sage B.H., 1938] are less accurate, see [ Chen S.S., 1975]. Please also see Dailey B.P., 1943, Wacker P.F., 1947.; GT
89.97 ± 0.06	273.15
95.21 ± 0.10	293.15
100.67 ± 0.10	313.15
106.37 ± 0.11	333.15
109.66	347.6
111.74 ± 0.11	353.15
112.55	359.4
119.62	387.5
137.03	452.5
152.93	520.9
161.29	561.7
169.70	605.3
185.18	692.7

Condensed phase thermochemistry data

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Data compiled by: Eugene S. Domalski and Elizabeth D. Hearing

Quantity	Value	Units	Method	Reference	Comment
S°_liquid	200.79	J/mol*K	N/A	Aston, Kennedy, et al., 1940
S°_liquid	198.7	J/mol*K	N/A	Parks, Shomate, et al., 1937	Extrapolation below 67 K, 44.02 J/mol*K.

Constant pressure heat capacity of liquid

C_p,liquid (J/mol*K)	Temperature (K)	Reference	Comment
129.70	260.	Aston, Kennedy, et al., 1940	T = 20 to 260 K.
128.4	258.3	Parks, Shomate, et al., 1937	T = 79 to 261 K. Value is unsmoothed experimental datum.

Reaction thermochemistry data

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, References, Notes

Data compiled as indicated in comments:
B - John E. Bartmess
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

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Individual Reactions

C₄H₉^- + = Isobutane

By formula: C₄H₉^- + H⁺ = C₄H₁₀

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1728. ± 8.4	kJ/mol	Bran	DePuy, Gronert, et al., 1989	gas phase; B
Δ_rH°	1735. ± 20.	kJ/mol	Bran	Peerboom, Rademaker, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1692. ± 8.8	kJ/mol	H-TS	DePuy, Gronert, et al., 1989	gas phase; B
Δ_rG°	1699. ± 21.	kJ/mol	H-TS	Peerboom, Rademaker, et al., 1992	gas phase; B

C₄H₉^- + = Isobutane

By formula: C₄H₉^- + H⁺ = C₄H₁₀

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1728. ± 8.4	kJ/mol	Bran	DePuy, Gronert, et al., 1989	gas phase; B
Δ_rH°	1732. ± 8.4	kJ/mol	Bran	DePuy, Bierbaum, et al., 1984	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1697. ± 8.8	kJ/mol	H-TS	DePuy, Gronert, et al., 1989	gas phase; B

+ = Isobutane

By formula: C₄H₈ + H₂ = C₄H₁₀

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-117.8 ± 0.42	kJ/mol	Chyd	Kistiakowsky, Ruhoff, et al., 1935	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -118.78 ± 0.75 kJ/mol; At 355 °K; ALS

= Isobutane

By formula: C₄H₁₀ = C₄H₁₀

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-9.699	kJ/mol	Eqk	Pines, Kvetinskas, et al., 1945	gas phase; Heat of isomerization; ALS

References

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Reaction thermochemistry data, Notes

Pittam and Pilcher, 1972
Pittam, D.A.; Pilcher, G., Measurements of heats of combustion by flame calorimetry. Part 8.-Methane, ethane, propane, n-butane and 2-methylpropane, J. Chem. Soc. Faraday Trans. 1, 1972, 68, 2224-2229. [all data]

Prosen, Maron, et al., 1951
Prosen, E.J.; Maron, F.W.; Rossini, F.D., Heats of combustion, formation, and insomerization of ten C₄ hydrocarbons, J. Res. NBS, 1951, 46, 106-112. [all data]

Prosen and Rossini, 1945
Prosen, E.J.; Rossini, F.D., Heats of formation and combustion of 1,3-butadiene and styrene, J. Res. NBS, 1945, 34, 59-63. [all data]

Rossini, 1935
Rossini, F.D., Heat of combustion of isobutane, J. Res. NBS, 1935, 15, 357-361. [all data]

Chen S.S., 1975
Chen S.S., Ideal gas thermodynamic properties and isomerization of n-butane and isobutane, J. Phys. Chem. Ref. Data, 1975, 4, 859-869. [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]

Ernst G., 1970
Ernst G., Ideal and real gas state heat capacities Cp of C3H8, i-C4H10, C2F5Cl, CH2ClCF3, CF2ClCFCl2, and CHF2Cl, J. Chem. Thermodyn., 1970, 2, 787-791. [all data]

Sage B.H., 1937
Sage B.H., Phase equilibria in hydrocarbon systems. XX. Isobaric heat capacity of gaseous propane, n-butane, isobutane, and n-pentane, Ind. Eng. Chem., 1937, 29, 1309-1314. [all data]

Sage B.H., 1938
Sage B.H., Phase equilibrium in hydrocarbon systems. Thermodynamic properties of isobutane, Ind. Eng. Chem., 1938, 30, 673-681. [all data]

Dailey B.P., 1943
Dailey B.P., Heat capacities and hindered rotation in n-butane and isobutane, J. Am. Chem. Soc., 1943, 65, 44-46. [all data]

Wacker P.F., 1947
Wacker P.F., Heat capacities of gaseous oxygen, isobutane, and 1-butene from -30 to +90 C, J. Res. Nat. Bur. Stand., 1947, 38, 651-659. [all data]

Aston, Kennedy, et al., 1940
Aston, J.G.; Kennedy, R.M.; Schumann, S.C., The heat capacity and entropy, heats of fusion and vaporization and the vapor pressure of isobutane, J. Am. Chem. Soc., 1940, 62, 2059-2063. [all data]

Parks, Shomate, et al., 1937
Parks, G.S.; Shomate, C.H.; Kennedy, W.D.; Crawford, B.L., Jr., The entropies of n-butane and isobutane, with some heat capacity data for isobutane, J. Chem. Phys., 1937, 5, 359-363. [all data]

DePuy, Gronert, et al., 1989
DePuy, C.H.; Gronert, S.; Barlow, S.E.; Bierbaum, V.M.; Damrauer, R., The Gas Phase Acidities of the Alkanes, J. Am. Chem. Soc., 1989, 111, 6, 1968, https://doi.org/10.1021/ja00188a003 . [all data]

Peerboom, Rademaker, et al., 1992
Peerboom, R.A.L.; Rademaker, G.J.; Dekoning, L.J.; Nibbering, N.M.M., Stabilization of Cycloalkyl Carbanions in the Gas Phase, Rapid Commun. Mass Spectrom., 1992, 6, 6, 394, https://doi.org/10.1002/rcm.1290060608 . [all data]

DePuy, Bierbaum, et al., 1984
DePuy, C.H.; Bierbaum, V.M.; Damrauer, R., Relative Gas-Phase Acidities of the Alkanes, J. Am. Chem. Soc., 1984, 106, 4051. [all data]

Kistiakowsky, Ruhoff, et al., 1935
Kistiakowsky, G.B.; Ruhoff, J.R.; Smith, H.A.; Vaughan, W.E., Heats of organic reactions. II. Hydrogenation of some simpler olefinic hydrocarbons, J. Am. Chem. Soc., 1935, 57, 876-882. [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]

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
Δ_cH°_gas	Enthalpy of combustion of gas at standard conditions
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_rG°	Free energy of reaction 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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