Heptane, 3-methyl-

Formula: C₈H₁₈
Molecular weight: 114.2285
IUPAC Standard InChI: InChI=1S/C8H18/c1-4-6-7-8(3)5-2/h8H,4-7H2,1-3H3
IUPAC Standard InChIKey: LAIUFBWHERIJIH-UHFFFAOYSA-N
CAS Registry Number: 589-81-1
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.
Isotopologues:
- 2-C2D5-Hexane
- 2-C2H5-Hexane-d13
Stereoisomers:
- (S)-3-methylheptane
Other names: 3-Methylheptane; 2-Ethylhexane
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- Gas Phase Kinetics Database
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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	-50.82 ± 0.27	kcal/mol	Ccb	Prosen and Rossini, 1945	ALS
Quantity	Value	Units	Method	Reference	Comment
S°_gas	111.35 ± 0.20	cal/mol*K	N/A	Finke H.L., 1973	GT

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
31.709	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 good agreement with experimental data available for alkanes. However, large uncertainties could be expected at high temperatures.; GT
41.181	273.15
44.4 ± 0.1	298.15
44.651	300.
57.400	400.
68.791	500.
78.401	600.
86.599	700.
93.499	800.
99.300	900.
104.30	1000.
108.60	1100.
112.40	1200.
116.00	1300.
119.00	1400.
122.00	1500.

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	-60.35 ± 0.27	kcal/mol	Ccb	Prosen and Rossini, 1945	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-1306.92 ± 0.31	kcal/mol	Ccb	Prosen and Rossini, 1945	Corresponding Δ_fHº_liquid = -60.32 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
S°_liquid	86.66	cal/mol*K	N/A	Finke and Messerly, 1973	Thermodynamic properties calculated from a Debye function at 10 K.; DH

Constant pressure heat capacity of liquid

C_p,liquid (cal/mol*K)	Temperature (K)	Reference	Comment
59.799	298.15	Finke and Messerly, 1973	T = 10 to 380 K.; DH
59.670	298.15	Osborne and Ginnings, 1947	T = 293 to 318 K.; DH

Phase change data

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Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director
AC - William E. Acree, Jr., James S. Chickos
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
T_boil	392. ± 1.	K	AVG	N/A	Average of 27 out of 28 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
T_fus	152. ± 1.	K	AVG	N/A	Average of 15 out of 16 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
T_triple	152.65	K	N/A	Finke and Messerly, 1973, 2	Uncertainty assigned by TRC = 0.008 K; by exatroplation to 1/f = 0; TRC
Quantity	Value	Units	Method	Reference	Comment
T_c	563.6 ± 0.5	K	N/A	Daubert, 1996
T_c	563.7	K	N/A	Majer and Svoboda, 1985
T_c	563.60	K	N/A	McMicking and Kay, 1965	Uncertainty assigned by TRC = 0.4 K; TRC
Quantity	Value	Units	Method	Reference	Comment
P_c	25.2 ± 0.4	atm	N/A	Daubert, 1996
P_c	25.127	atm	N/A	McMicking and Kay, 1965	Uncertainty assigned by TRC = 0.4000 atm; TRC
Quantity	Value	Units	Method	Reference	Comment
V_c	0.464	l/mol	N/A	Daubert, 1996
Quantity	Value	Units	Method	Reference	Comment
ρ_c	2.15 ± 0.04	mol/l	N/A	Daubert, 1996
ρ_c	2.15	mol/l	N/A	McMicking and Kay, 1965	Uncertainty assigned by TRC = 0.04 mol/l; TRC
Quantity	Value	Units	Method	Reference	Comment
Δ_vapH°	9.532	kcal/mol	N/A	Majer and Svoboda, 1985
Δ_vapH°	9.51 ± 0.05	kcal/mol	C	An, Hu, et al., 1987	AC
Δ_vapH°	9.51	kcal/mol	N/A	Reid, 1972	AC
Δ_vapH°	9.51 ± 0.02	kcal/mol	C	Osborne and Ginnings, 1947, 2	AC
Δ_vapH°	9.520	kcal/mol	C	Osborne and Ginnings, 1947	ALS

Enthalpy of vaporization

Δ_vapH (kcal/mol)	Temperature (K)	Method	Reference	Comment
8.045	392.1	N/A	Majer and Svoboda, 1985
9.58	301.	A	Stephenson and Malanowski, 1987	Based on data from 286. to 393. K.; AC
9.94	271.	IP	Stephenson and Malanowski, 1987	Based on data from 238. to 286. K. See also Osborn and Douslin, 1974.; AC
9.15	331.	MM	Willingham, Taylor, et al., 1945	Based on data from 316. to 393. K.; AC

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
P = vapor pressure (atm)
T = temperature (K)

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Temperature (K)	A	B	C	Reference	Comment
238. to 288.	4.50677	1568.919	-40.686	Osborn and Douslin, 1974	Coefficents calculated by NIST from author's data.
315.82 to 392.96	4.01864	1331.53	-60.555	Williamham, Taylor, et al., 1945

Enthalpy of fusion

Δ_fusH (kcal/mol)	Temperature (K)	Reference	Comment
2.789	152.6	Domalski and Hearing, 1996	AC

Enthalpy of phase transition

ΔH_trs (kcal/mol)	Temperature (K)	Initial Phase	Final Phase	Reference	Comment
2.7949	152.6574	crystaline, I	liquid	Finke and Messerly, 1973	DH

Entropy of phase transition

ΔS_trs (cal/mol*K)	Temperature (K)	Initial Phase	Final Phase	Reference	Comment
1.832	152.6574	crystaline, I	liquid	Finke and Messerly, 1973	DH

In addition to the Thermodynamics Research Center (TRC) data available from this site, much more physical and chemical property data is available from the following TRC products:

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

= Heptane, 3-methyl-

By formula: C₈H₁₈ = C₈H₁₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-0.61 ± 0.19	kcal/mol	Ciso	Prosen and Rossini, 1945, 2	liquid phase; Calculated from ΔHc

+ = Heptane, 3-methyl-

By formula: C₈H₁₆ + H₂ = C₈H₁₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-29.8 ± 0.1	kcal/mol	Chyd	Rogers, Dejroongruang, et al., 1992	liquid phase; solvent: Cyclohexane

= Heptane, 3-methyl-

By formula: C₈H₁₈ = C₈H₁₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	0.45 ± 0.10	kcal/mol	Eqk	Roganov, Kabo, et al., 1972	gas phase; At 1368 K

References

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

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]

Finke H.L., 1973
Finke H.L., 3-Methylpentane and 3-methylheptane: low-temperature thermodynamic properties, J. Chem. Thermodyn., 1973, 5, 247-257. [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]

Finke and Messerly, 1973
Finke, H.L.; Messerly, J.F., 3-Methylpentane and 3-methylheptane: low-temperature thermodynamic properties, J. Chem. Thermodynam., 1973, 5, 247-257. [all data]

Osborne and Ginnings, 1947
Osborne, N.S.; Ginnings, D.C., Measurements of heat of vaporization and heat capacity of a number of hydrocarbons, J. Res. NBS, 1947, 39, 453-477. [all data]

Finke and Messerly, 1973, 2
Finke, H.L.; Messerly, J.F., 3-Methylpentane and 3-Methylheptane: Low-temperature Thermo. Properties properties, J. Chem. Thermodyn., 1973, 5, 247. [all data]

Daubert, 1996
Daubert, T.E., Vapor-Liquid Critical Properties of Elements and Compounds. 5. Branched Alkanes and Cycloalkanes, J. Chem. Eng. Data, 1996, 41, 365-372. [all data]

Majer and Svoboda, 1985
Majer, V.; Svoboda, V., Enthalpies of Vaporization of Organic Compounds: A Critical Review and Data Compilation, Blackwell Scientific Publications, Oxford, 1985, 300. [all data]

McMicking and Kay, 1965
McMicking, J.H.; Kay, W.B., Vapor Pressures and Saturated Liquid and Vapor Densities of The Isomeric Heptanes and Isomeric Octanes, Proc., Am. Pet. Inst., Sect. 3, 1965, 45, 75-90. [all data]

An, Hu, et al., 1987
An, Xuwu; Hu, Riheng; Wang, Hu; Wu, Mali; Zou, Yongkuang, Enthalpies of Vaporization of α- and β-Pinene, Acta Phys. Chim. Sin., 1987, 3, 6, 668-671, https://doi.org/10.3866/PKU.WHXB19870621 . [all data]

Reid, 1972
Reid, Robert C., Handbook on vapor pressure and heats of vaporization of hydrocarbons and related compounds, R. C. Wilhort and B. J. Zwolinski, Texas A Research Foundation. College Station, Texas(1971). 329 pages.$10.00, AIChE J., 1972, 18, 6, 1278-1278, https://doi.org/10.1002/aic.690180637 . [all data]

Osborne and Ginnings, 1947, 2
Osborne, Nathan S.; Ginnings, Defoe C., Measurements of heat of vaporization and heat capacity of a number of hydrocarbons, J. RES. NATL. BUR. STAN., 1947, 39, 5, 453-17, https://doi.org/10.6028/jres.039.031 . [all data]

Stephenson and Malanowski, 1987
Stephenson, Richard M.; Malanowski, Stanislaw, Handbook of the Thermodynamics of Organic Compounds, 1987, https://doi.org/10.1007/978-94-009-3173-2 . [all data]

Osborn and Douslin, 1974
Osborn, Ann G.; Douslin, Donald R., Vapor-pressure relations for 15 hydrocarbons, J. Chem. Eng. Data, 1974, 19, 2, 114-117, https://doi.org/10.1021/je60061a022 . [all data]

Willingham, Taylor, et al., 1945
Willingham, C.B.; Taylor, W.J.; Pignocco, J.M.; Rossini, F.D., Vapor pressures and boiling points of some paraffin, alkylcyclopentane, alkylcyclohexane, and alkylbenzene hydrocarbons, J. RES. NATL. BUR. STAN., 1945, 35, 3, 219-17, https://doi.org/10.6028/jres.035.009 . [all data]

Williamham, Taylor, et al., 1945
Williamham, C.B.; Taylor, W.J.; Pignocco, J.M.; Rossini, F.D., Vapor Pressures and Boiling Points of Some Paraffin, Alkylcyclopentane, Alkylcyclohexane, and Alkylbenzene Hydrocarbons, J. Res. Natl. Bur. Stand. (U.S.), 1945, 35, 3, 219-244, https://doi.org/10.6028/jres.035.009 . [all data]

Domalski and Hearing, 1996
Domalski, Eugene S.; Hearing, Elizabeth D., Heat Capacities and Entropies of Organic Compounds in the Condensed Phase. Volume III, J. Phys. Chem. Ref. Data, 1996, 25, 1, 1, https://doi.org/10.1063/1.555985 . [all data]

Prosen and Rossini, 1945, 2
Prosen, E.J.; Rossini, F.D., Heats of isomerization of the 18 octanes, J. Res. NBS, 1945, 34, 163-174. [all data]

Rogers, Dejroongruang, et al., 1992
Rogers, D.W.; Dejroongruang, K.; Samuel, S.D.; Fang, W.; Zhao, Y., Enthalpies of hydrogenation of the octenes and the methylheptenes, J. Chem. Thermodyn., 1992, 24, 561-565. [all data]

Roganov, Kabo, et al., 1972
Roganov, G.N.; Kabo, G.Ya.; Andreevskii, D.N., Thermodynamics of the isomerization of methylpentanes and methylheptanes, Neftekhimiya, 1972, 12, 495-500. [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
P_c	Critical pressure
S°_gas	Entropy of gas at standard conditions
S°_liquid	Entropy of liquid at standard conditions
T_boil	Boiling point
T_c	Critical temperature
T_fus	Fusion (melting) point
T_triple	Triple point temperature
V_c	Critical volume
ΔH_trs	Enthalpy of phase transition
ΔS_trs	Entropy of phase transition
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_fusH	Enthalpy of fusion
Δ_rH°	Enthalpy of reaction at standard conditions
Δ_vapH	Enthalpy of vaporization
Δ_vapH°	Enthalpy of vaporization at standard conditions
ρ_c	Critical density

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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