Benzene, pentamethyl-

Formula: C₁₁H₁₆
Molecular weight: 148.2447
IUPAC Standard InChI: InChI=1S/C11H16/c1-7-6-8(2)10(4)11(5)9(7)3/h6H,1-5H3
IUPAC Standard InChIKey: BEZDDPMMPIDMGJ-UHFFFAOYSA-N
CAS Registry Number: 700-12-9
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: Pentamethylbenzene; 1,2,3,4,5-Pentamethylbenzene; Benzene, 1,2,3,4,5-pentamethyl-
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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
DRB - Donald R. Burgess, Jr.
GT - Glushko Thermocenter, Russian Academy of Sciences, Moscow

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-67.2 ± 2.2	kJ/mol	Ccb	Colomina, Jimenez, et al., 1989	see Boned, Colomina, et al., 1964; ALS
Δ_fH°_gas	-57.7	kJ/mol	N/A	Parks, West, et al., 1946	Value computed using Δ_fH_solid° value of -135.1±2.6 kj/mol from Parks, West, et al., 1946 and Δ_subH° value of 77.4 kj/mol from Colomina, Jimenez, et al., 1989.; DRB

Constant pressure heat capacity of gas

C_p,gas (J/mol*K)	Temperature (K)	Reference	Comment
162.3	200.	Draeger, 1985	There is an appreciable difference between values of S(T) and Cp(T) for tetra-, penta-, and hexamethylbenzene from earlier statistical thermodynamics calculation [ Hastings S.H., 1957] and those obtained by [ Draeger, 1985] (up to 5, 9, and 16 J/mol*K, respectively). Results [ Draeger, 1985] are more reliable and they agree with experimental data for hexamethylbenzene.; GT
199.7	273.15
212.5 ± 0.4	298.15
213.4	300.
264.4	400.
311.4	500.
352.3	600.
387.4	700.
417.5	800.
443.4	900.
465.6	1000.
484.8	1100.
501.3	1200.
515.6	1300.
527.9	1400.
538.7	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_cH°_liquid	-6475.6 ± 6.3	kJ/mol	Ccb	Banse and Parks, 1933	Reanalyzed by Cox and Pilcher, 1970, Original value = -6470.64 kJ/mol; Corresponding Δ_fHº_liquid = -139.7 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_solid	-144.6 ± 2.2	kJ/mol	Ccb	Colomina, Jimenez, et al., 1989	see Boned, Colomina, et al., 1964; ALS
Δ_fH°_solid	-135.1 ± 2.6	kJ/mol	Ccb	Parks, West, et al., 1946	Reanalyzed by Cox and Pilcher, 1970, Original value = -135.7 ± 0.04 kJ/mol; ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_solid	-6470.6 ± 1.6	kJ/mol	Ccb	Colomina, Jimenez, et al., 1989	see Boned, Colomina, et al., 1964; Corresponding Δ_fHº_solid = -144.7 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_solid	-6480.1 ± 2.6	kJ/mol	Ccb	Parks, West, et al., 1946	Reanalyzed by Cox and Pilcher, 1970, Original value = -6479.6 ± 2.6 kJ/mol; Corresponding Δ_fHº_solid = -135.1 kJ/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
S°_{solid,1 bar}	294.1	J/mol*K	N/A	Huffman, Parks, et al., 1931	crystaline, I phase; Extrapolation below 90 K, 102.9 J/mol*K.; DH

Constant pressure heat capacity of solid

C_p,solid (J/mol*K)	Temperature (K)	Reference	Comment
210.5	298.15	Colomina, Jimenez, et al., 1989	DH
270.3	298.1	Eibert, 1944	crystaline, I phase; T = 25 to 200°C, equations only, in t°C. Cp(c) = 0.3914 + 0.001760t cal/gK (25 to 40°C); Cp(liq) = 0.432 + 0.000425 t cal/gK (55 to 200°C).; DH
267.3	303.	Ferry and Thomas, 1933	T = 303 to 393 K.; DH
251.0	283.8	Huffman, Parks, et al., 1931	crystaline, I phase; T = 92 to 304 K. Value is unsmoothed experimental datum.; DH

Phase change data

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Data compiled as indicated in comments:
BS - Robert L. Brown and Stephen E. Stein
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
DRB - Donald R. Burgess, Jr.
DH - Eugene S. Domalski and Elizabeth D. Hearing
CAL - James S. Chickos, William E. Acree, Jr., Joel F. Liebman, Students of Chem 202 (Introduction to the Literature of Chemistry), University of Missouri -- St. Louis

Quantity	Value	Units	Method	Reference	Comment
T_boil	510. ± 20.	K	AVG	N/A	Average of 10 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
T_fus	326. ± 3.	K	AVG	N/A	Average of 17 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Δ_subH°	71.60 ± 0.10	kJ/mol	C	Sabbah, Tabet, et al., 1994	ALS
Δ_subH°	71.6 ± 0.1	kJ/mol	C	Sabbah, Tabet, et al., 1994	AC
Δ_subH°	77.4 ± 0.4	kJ/mol	V	Colomina, Jimenez, et al., 1989	see Boned, Colomina, et al., 1964; ALS
Δ_subH°	77.4	kJ/mol	N/A	Colomina, Jimenez, et al., 1989	DRB
Δ_subH°	77.4 ± 0.4	kJ/mol	ME	Colomina, Jimenez, et al., 1989	Based on data from 296. to 313. K.; AC

Enthalpy of vaporization

Δ_vapH (kJ/mol)	Temperature (K)	Method	Reference	Comment
57.8	353.	A	Stephenson and Malanowski, 1987	Based on data from 338. to 503. K.; AC

Enthalpy of fusion

Δ_fusH (kJ/mol)	Temperature (K)	Reference	Comment
10.67	328.2	Domalski and Hearing, 1996	AC
10.670	328.2	Eibert, 1944	DH

Entropy of fusion

Δ_fusS (J/mol*K)	Temperature (K)	Reference	Comment
32.5	328.2	Eibert, 1944	DH

Entropy of fusion

Δ_fusS (J/mol*K)	Temperature (K)	Reference	Comment
6.67	296.8	Domalski and Hearing, 1996	CAL
32.51	328.2	Domalski and Hearing, 1996	CAL

Enthalpy of phase transition

ΔH_trs (kJ/mol)	Temperature (K)	Initial Phase	Final Phase	Reference	Comment
1.799	296.35	crystaline, II	crystaline, I	Ferry and Thomas, 1933	DH
12.343	327.45	crystaline, I	liquid	Ferry and Thomas, 1933	DH
1.979	296.8	crystaline, II	crystaline, I	Huffman, Parks, et al., 1931	DH

Entropy of phase transition

ΔS_trs (J/mol*K)	Temperature (K)	Initial Phase	Final Phase	Reference	Comment
6.7	296.8	crystaline, II	crystaline, I	Huffman, Parks, et al., 1931	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

= Benzene, pentamethyl-

By formula: C₁₁H₁₆ = C₁₁H₁₆

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-136. ± 3.	kJ/mol	Ciso	Childs and Mulholland, 1983	liquid phase

References

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Colomina, Jimenez, et al., 1989
Colomina, M.; Jimenez, P.; Roux, M.V.; Turrion, C., Thermochemical properties of 1,2,4,5-tetramethylbenzene, pentamethylbenzene, and hexamethylbenzene, J. Chem. Thermodyn., 1989, 21, 275-281. [all data]

Boned, Colomina, et al., 1964
Boned, M.L.; Colomina, M.; Perez-Ossorio, R.; Turrion, C., Investigaciones termoquimicas sobre los polimetilbencenos superiores, Anal. Fisc. Quim. B, 1964, 60, 459-468. [all data]

Parks, West, et al., 1946
Parks, G.S.; West, T.J.; Naylor, B.F.; Fujii, P.S.; McClaine, L.A., Thermal data on organic compounds. XXIII. Modern combustion data for fourteen hydrocarbons and five polyhydroxy alcohols, J. Am. Chem. Soc., 1946, 68, 2524-2527. [all data]

Draeger, 1985
Draeger, J.A., The methylbenzenes II. Fundamental vibrational shifts, statistical thermodynamic functions, and properties of formation, J. Chem. Thermodyn., 1985, 17, 263-275. [all data]

Hastings S.H., 1957
Hastings S.H., Thermodynamic properties of selected methylbenzenes from 0 to 1000 K, J. Phys. Chem., 1957, 61, 730-735. [all data]

Banse and Parks, 1933
Banse, H.; Parks, G.S., Thermal data on organic compounds. XII. The heats of combustion of nine hydrocarbons, J. Am. Chem. Soc., 1933, 55, 3223-3227. [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]

Huffman, Parks, et al., 1931
Huffman, H.M.; Parks, G.S.; Barmore, M., Thermal data on organic compounds. X. Further studies on the heat capacities, entropies and free energies of hydrocarbons, J. Am. Chem. Soc., 1931, 53, 3876-3888. [all data]

Eibert, 1944
Eibert, J., Thesis Washington University (St. Louis), 1944. [all data]

Ferry and Thomas, 1933
Ferry, J.D.; Thomas, S.B., Some heat capacity data for durene, pentamethylbenzene, stilbene, and dibenzyl, J. Phys. Chem., 1933, 37, 253-255. [all data]

Sabbah, Tabet, et al., 1994
Sabbah, R.; Tabet, D.; Belaadi, S., Enthalpie de sublimation ou vaporisation de quelques derives methyles du benzene, Thermochim. Acta, 1994, 247, 193-199. [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]

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]

Childs and Mulholland, 1983
Childs, R.F.; Mulholland, D.L., Thermochemical relationships between some bicyclohexenyl and benzenium cations, J. Am. Chem. Soc., 1983, 105, 96-99. [all data]

Notes

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Symbols used in this document:

C_p,gas	Constant pressure heat capacity of gas
C_p,solid	Constant pressure heat capacity of solid
S°_{solid,1 bar}	Entropy of solid at standard conditions (1 bar)
T_boil	Boiling point
T_fus	Fusion (melting) point
ΔH_trs	Enthalpy of phase transition
ΔS_trs	Entropy of phase transition
Δ_cH°_liquid	Enthalpy of combustion of liquid at standard conditions
Δ_cH°_solid	Enthalpy of combustion of solid at standard conditions
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_fH°_solid	Enthalpy of formation of solid at standard conditions
Δ_fusH	Enthalpy of fusion
Δ_fusS	Entropy of fusion
Δ_rH°	Enthalpy of reaction at standard conditions
Δ_subH°	Enthalpy of sublimation at standard conditions
Δ_vapH	Enthalpy of vaporization

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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