Octane

Formula: C₈H₁₈
Molecular weight: 114.2285
IUPAC Standard InChI: InChI=1S/C8H18/c1-3-5-7-8-6-4-2/h3-8H2,1-2H3
IUPAC Standard InChIKey: TVMXDCGIABBOFY-UHFFFAOYSA-N
CAS Registry Number: 111-65-9
Chemical structure:
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Isotopologues:
Other names: n-Octane; n-C8H18; Oktan; Oktanen; Ottani; UN 1262
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Gas phase thermochemistry data

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Data compiled as indicated in comments:
DRB - Donald R. Burgess, Jr.
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	-208.7	kJ/mol	N/A	Good, 1972	Value computed using Δ_fH_liquid° value of -250.3±1.8 kj/mol from Good, 1972 and Δ_vapH° value of 41.6 kj/mol from Prosen and Rossini, 1945.; DRB
Δ_fH°_gas	-208.4 ± 0.67	kJ/mol	Ccb	Prosen and Rossini, 1945	see Prosen and Rossini, 1944; ALS
Quantity	Value	Units	Method	Reference	Comment
S°_gas	467.06 ± 0.92	J/mol*K	N/A	Scott D.W., 1974	This reference does not contain the original experimental data. Experimental entropy value is based on the results [ Messerly J.F., 1967] for S(liquid).; GT

Constant pressure heat capacity of gas

C_p,gas (J/mol*K)	Temperature (K)	Reference	Comment
232.74 ± 0.47	385.65	Hossenlopp I.A., 1981	Please also see Barrow G.M., 1951.; GT
238.95 ± 0.48	398.15
242.67	405.7
250.59 ± 0.50	423.15
263.02 ± 0.53	448.15
270.70	462.5
274.84 ± 0.55	473.15
285.98 ± 0.57	498.15
295.39	522.7
297.00 ± 0.59	523.15

Constant pressure heat capacity of gas

C_p,gas (J/mol*K)	Temperature (K)	Reference	Comment
144.77	200.	Scott D.W., 1974, 2	Recommended values were obtained from the consistent correlation scheme for alkanes [ Scott D.W., 1974, Scott D.W., 1974, 2]. This approach gives a better agreement with experimental data than the statistical thermodynamics calculation [ Pitzer K.S., 1944, Pitzer K.S., 1946].; GT
175.69	273.15
187.8 ± 0.4	298.15
188.70	300.
239.74	400.
286.81	500.
326.77	600.
360.24	700.
388.28	800.
411.71	900.
431.37	1000.
448.52	1100.
463.17	1200.
476.98	1300.
489.53	1400.
497.90	1500.

References

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Good, 1972
Good, W.D., The enthalpies of combustion and formation of n-octane and 2,2,3,3-tetramethylbutane, J. Chem. Thermodyn., 1972, 4, 709-714. [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]

Prosen and Rossini, 1944
Prosen, E.J.; Rossini, F.D., Heats of combustion of eight normal paraffin hydrocarbons in the liquid state, J. Res. NBS, 1944, 33, 255-272. [all data]

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

Messerly J.F., 1967
Messerly J.F., Low-temperature thermal data for n-pentane, n-heptadecane, and n-octadecane. Revised thermodynamic functions for the n-alkanes, C5-C18, J. Chem. Eng. Data, 1967, 12, 338-346. [all data]

Hossenlopp I.A., 1981
Hossenlopp I.A., Vapor heat capacities and enthalpies of vaporization of five alkane hydrocarbons, J. Chem. Thermodyn., 1981, 13, 415-421. [all data]

Barrow G.M., 1951
Barrow G.M., Experimental vapor heat capacities and heats of vaporization of seven octanes, J. Am. Chem. Soc., 1951, 73, 1824-1826. [all data]

Scott D.W., 1974, 2
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]

Pitzer K.S., 1944
Pitzer K.S., Thermodynamics of gaseous paraffins. Specific heat and related properties, Ind. Eng. Chem., 1944, 36, 829-831. [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]

Notes

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Symbols used in this document:

C_p,gas Constant pressure heat capacity of gas

S°_gas Entropy 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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C_p,gas	Constant pressure heat capacity of gas
S°_gas	Entropy of gas at standard conditions
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions