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	-32.07 ± 0.15	kcal/mol	Ccb	Pittam and Pilcher, 1972	ALS
Δ_fH°_gas	-32.42 ± 0.13	kcal/mol	Cm	Prosen, Maron, et al., 1951	see Prosen and Rossini, 1945, Rossini, 1935; ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_gas	-685.71 ± 0.14	kcal/mol	Ccb	Pittam and Pilcher, 1972	Corresponding Δ_fHº_gas = -32.07 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_gas	-685.37 ± 0.11	kcal/mol	Cm	Prosen, Maron, et al., 1951	see Prosen and Rossini, 1945, Rossini, 1935; Corresponding Δ_fHº_gas = -32.41 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
8.320	50.	Chen S.S., 1975	Recommended values are in good agreement with those calculated by [ Pitzer K.S., 1946].; GT
11.30	100.
14.41	150.
17.17	200.
21.49	273.15
23.10	298.15
23.22	300.
29.739	400.
35.669	500.
40.719	600.
45.000	700.
48.671	800.
51.850	900.
54.601	1000.
57.000	1100.
59.070	1200.
60.880	1300.
62.450	1400.
63.819	1500.

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
19.67 ± 0.01	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
21.50 ± 0.01	273.15
22.76 ± 0.024	293.15
24.061 ± 0.024	313.15
25.423 ± 0.026	333.15
26.209	347.6
26.707 ± 0.026	353.15
26.900	359.4
28.590	387.5
32.751	452.5
36.551	520.9
38.549	561.7
40.559	605.3
44.259	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	47.990	cal/mol*K	N/A	Aston, Kennedy, et al., 1940
S°_liquid	47.49	cal/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 (cal/mol*K)	Temperature (K)	Reference	Comment
30.999	260.	Aston, Kennedy, et al., 1940	T = 20 to 260 K.
30.69	258.3	Parks, Shomate, et al., 1937	T = 79 to 261 K. Value is unsmoothed experimental datum.

Reaction thermochemistry data

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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°	412.9 ± 2.0	kcal/mol	Bran	DePuy, Gronert, et al., 1989	gas phase; B
Δ_rH°	414.7 ± 4.8	kcal/mol	Bran	Peerboom, Rademaker, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	404.3 ± 2.1	kcal/mol	H-TS	DePuy, Gronert, et al., 1989	gas phase; B
Δ_rG°	406.1 ± 4.9	kcal/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°	413.1 ± 2.0	kcal/mol	Bran	DePuy, Gronert, et al., 1989	gas phase; B
Δ_rH°	414.0 ± 2.0	kcal/mol	Bran	DePuy, Bierbaum, et al., 1984	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	405.7 ± 2.1	kcal/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°	-28.15 ± 0.10	kcal/mol	Chyd	Kistiakowsky, Ruhoff, et al., 1935	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -28.39 ± 0.18 kcal/mol; At 355 °K; ALS

= Isobutane

By formula: C₄H₁₀ = C₄H₁₀

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-2.318	kcal/mol	Eqk	Pines, Kvetinskas, et al., 1945	gas phase; Heat of isomerization; ALS

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
0.00086		Q	N/A	missing citation give several references for the Henry's law constants but don't assign them to specific species.
0.00084		L	N/A
0.00081	2700.	L	N/A
0.00085		V	N/A

References

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Reaction thermochemistry data, Henry's Law 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
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_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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