Benzene, hexamethyl-
- Formula: C12H18
- Molecular weight: 162.2713
- IUPAC Standard InChIKey: YUWFEBAXEOLKSG-UHFFFAOYSA-N
- CAS Registry Number: 87-85-4
- 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:
- Other names: Hexamethylbenzene; Mellitene; 1,2,3,4,5,6-Hexamethylbenzene
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Phase change data
Go To: Top, Gas phase ion energetics data, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
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.
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
DH - Eugene S. Domalski and Elizabeth D. Hearing
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
Tboil | 538.2 | K | N/A | Weast and Grasselli, 1989 | BS |
Tboil | 536.85 | K | N/A | Cooper, Crowne, et al., 1967 | Uncertainty assigned by TRC = 0.6 K; TRC |
Quantity | Value | Units | Method | Reference | Comment |
Tfus | 438. ± 3. | K | AVG | N/A | Average of 13 values; Individual data points |
Quantity | Value | Units | Method | Reference | Comment |
Tc | 758. ± 1. | K | N/A | Tsonopoulos and Ambrose, 1995 | |
Tc | 758. | K | N/A | Ambrose, Broderick, et al., 1974 | Uncertainty assigned by TRC = 2. K; TRC |
Tc | 751.15 | K | N/A | Guye and Mallet, 1902 | Uncertainty assigned by TRC = 10. K; crit. temp. greater than this - sample decomposes at this T; TRC |
Quantity | Value | Units | Method | Reference | Comment |
ΔvapH° | 68.6 | kJ/mol | CGC | Zhao, Unhannanant, et al., 2008 | AC |
Quantity | Value | Units | Method | Reference | Comment |
ΔsubH° | 83. ± 7. | kJ/mol | AVG | N/A | Average of 7 values; Individual data points |
Enthalpy of vaporization
ΔvapH (kJ/mol) | Temperature (K) | Method | Reference | Comment |
---|---|---|---|---|
56.8 | 458. | A | Stephenson and Malanowski, 1987 | Based on data from 443. to 537. K.; AC |
Enthalpy of sublimation
ΔsubH (kJ/mol) | Temperature (K) | Method | Reference | Comment |
---|---|---|---|---|
85.2 | 320. | A | Ambrose, Lawrenson, et al., 1976 | Based on data from 303. to 338. K.; AC |
83.2 | 329. | A | Overberger, Steele, et al., 1969 | Based on data from 314. to 364. K.; AC |
Enthalpy of fusion
ΔfusH (kJ/mol) | Temperature (K) | Reference | Comment |
---|---|---|---|
20.63 | 438.7 | Domalski and Hearing, 1996 | See also Spaght, Thomas, et al., 1931.; AC |
Entropy of fusion
ΔfusS (J/mol*K) | Temperature (K) | Reference | Comment |
---|---|---|---|
4.58 | 383.7 | Domalski and Hearing, 1996 | CAL |
47.02 | 438.7 |
Temperature of phase transition
Ttrs (K) | Initial Phase | Final Phase | Reference | Comment |
---|---|---|---|---|
382. | crystaline, III | crystaline, I | Fujiwara, Inaba, et al., 1992 | DH |
439. | crystaline, I | liquid | Fujiwara, Inaba, et al., 1992 | DH |
Enthalpy of phase transition
ΔHtrs (kJ/mol) | Temperature (K) | Initial Phase | Final Phase | Reference | Comment |
---|---|---|---|---|---|
1.100 | 117.5 | crystaline, III | crystaline, II | Fujiwara, Inaba, et al., 1992 | From Atake, Gyoten, et al., 1982; DH |
1.500 | 384.0 | crystaline, II | crystaline, I | Petropavlov, Tsygankova, et al., 1988 | DH |
1.103 | 115.5 | crystaline, II | crystaline, I | Yoshimoto, Fujiwara, et al., 1985 | DH |
0.990 | 117.5 | crystaline, III | crystaline, II | Atake, Gyoten, et al., 1982 | First order transition.; DH |
1.1284 | 116.48 | crystaline, II | crystaline, I | Frankosky and Aston, 1965 | Entropy obtained as difference of integral of observed Cp over range 115 to 128 K, and integral of extrapolated Cp data.; DH |
1.841 | 383.55 | crystaline, II | crystaline, I | Momotani, Suga, et al., 1956 | DH |
20.585 | 438.35 | crystaline, I | liquid | Momotani, Suga, et al., 1956 | DH |
1.766 | 383.7 | crystaline, II | crystaline, I | Spaght, Thomas, et al., 1932 | DH |
20.640 | 438.7 | crystaline, I | liquid | Spaght, Thomas, et al., 1932 | DH |
1.017 | 108. | crystaline, III | crystaline, II | Huffman, Parks, et al., 1930 | DH |
0.155 | 151. | crystaline, II | crystaline, I | Huffman, Parks, et al., 1930 | DH |
Entropy of phase transition
ΔStrs (J/mol*K) | Temperature (K) | Initial Phase | Final Phase | Reference | Comment |
---|---|---|---|---|---|
9.3 | 117.5 | crystaline, III | crystaline, II | Fujiwara, Inaba, et al., 1992 | From; DH |
3.9 | 384.0 | crystaline, II | crystaline, I | Petropavlov, Tsygankova, et al., 1988 | DH |
9.55 | 115.5 | crystaline, II | crystaline, I | Yoshimoto, Fujiwara, et al., 1985 | DH |
8.3 | 117.5 | crystaline, III | crystaline, II | Atake, Gyoten, et al., 1982 | First; DH |
10.08 | 116.48 | crystaline, II | crystaline, I | Frankosky and Aston, 1965 | Entropy; DH |
4.81 | 383.55 | crystaline, II | crystaline, I | Momotani, Suga, et al., 1956 | DH |
46.86 | 438.35 | crystaline, I | liquid | Momotani, Suga, et al., 1956 | DH |
4.60 | 383.7 | crystaline, II | crystaline, I | Spaght, Thomas, et al., 1932 | DH |
47.0 | 438.7 | crystaline, I | liquid | Spaght, Thomas, et al., 1932 | DH |
9.5 | 108. | crystaline, III | crystaline, II | Huffman, Parks, et al., 1930 | DH |
1.0 | 151. | crystaline, II | crystaline, I | Huffman, Parks, et al., 1930 | DH |
Gas phase ion energetics data
Go To: Top, Phase change data, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias
Data compiled as indicated in comments:
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
B - John E. Bartmess
View reactions leading to C12H18+ (ion structure unspecified)
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
IE (evaluated) | 7.85 ± 0.01 | eV | N/A | N/A | L |
Quantity | Value | Units | Method | Reference | Comment |
Proton affinity (review) | 860.6 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Quantity | Value | Units | Method | Reference | Comment |
Gas basicity | 836.0 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Electron affinity determinations
EA (eV) | Method | Reference | Comment |
---|---|---|---|
<0.121 ± 0.017 | ECD | Wojnarovits and Foldiak, 1981 | EA is an upper limit: Chen and Wentworth, 1989. G3MP2B3 calculations indicate an EA of ca. -0.1 eV, anion unbound.; B |
Ionization energy determinations
IE (eV) | Method | Reference | Comment |
---|---|---|---|
7.85 | PE | Howell, Goncalves, et al., 1984 | LBLHLM |
7.87 | EI | Kuznesof, Stafford, et al., 1967 | RDSH |
7.85 ± 0.02 | PI | Vilesov, 1961 | RDSH |
7.85 | PI | Bralsford, Harris, et al., 1960 | RDSH |
7.8 | CTS | Foster, 1959 | RDSH |
7.95 | CTS | Briegleb and Czekalla, 1959 | RDSH |
7.85 | PE | Howell, Goncalves, et al., 1984 | Vertical value; LBLHLM |
7.9 | PE | Kovac, Mohraz, et al., 1980 | Vertical value; LLK |
References
Go To: Top, Phase change data, Gas phase ion energetics data, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Weast and Grasselli, 1989
CRC Handbook of Data on Organic Compounds, 2nd Editon, Weast,R.C and Grasselli, J.G., ed(s)., CRC Press, Inc., Boca Raton, FL, 1989, 1. [all data]
Cooper, Crowne, et al., 1967
Cooper, A.R.; Crowne, C.W.P.; Farrell, P.G.,
Gas-Liquid Chromatographic Studies of Electron-Donor-Acceptor Systems,
Trans. Faraday Soc., 1967, 63, 447. [all data]
Tsonopoulos and Ambrose, 1995
Tsonopoulos, C.; Ambrose, D.,
Vapor-Liquid Critical Properties of Elements and Compounds. 3. Aromatic Hydrocarbons,
J. Chem. Eng. Data, 1995, 40, 547-558. [all data]
Ambrose, Broderick, et al., 1974
Ambrose, D.; Broderick, B.E.; Townsend, R.,
The Critical Temperatures and Pressures of Thirty Organic Compounds,
J. Appl. Chem. Biotechnol., 1974, 24, 359. [all data]
Guye and Mallet, 1902
Guye, P.A.; Mallet, E.,
Measurement of Critical Constants,
Arch. Sci. Phys. Nat., 1902, 13, 274-296. [all data]
Zhao, Unhannanant, et al., 2008
Zhao, Hui; Unhannanant, Patamaporn; Hanshaw, William; Chickos, James S.,
Enthalpies of Vaporization and Vapor Pressures of Some Deuterated Hydrocarbons. Liquid-Vapor Pressure Isotope Effects,
J. Chem. Eng. Data, 2008, 53, 7, 1545-1556, https://doi.org/10.1021/je800091s
. [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]
Ambrose, Lawrenson, et al., 1976
Ambrose, D.; Lawrenson, I.J.; Sprake, C.H.S.,
The vapour pressure of hexamethylbenzene,
The Journal of Chemical Thermodynamics, 1976, 8, 5, 503-504, https://doi.org/10.1016/0021-9614(76)90071-9
. [all data]
Overberger, Steele, et al., 1969
Overberger, John E.; Steele, William A.; Aston, John G.,
The vapor pressure of hexamethylbenzene the standard entropy of hexamethylbenzene vapor and the barrier to internal rotation,
The Journal of Chemical Thermodynamics, 1969, 1, 6, 535-542, https://doi.org/10.1016/0021-9614(69)90014-7
. [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]
Spaght, Thomas, et al., 1931
Spaght, M.E.; Thomas, S.B.; Parks, G.S.,
Some Heat-Capacity Data on Organic Compounds obtained with a Radiation Calorimeter,
J. Phys. Chem., 1931, 36, 3, 882-888, https://doi.org/10.1021/j150333a009
. [all data]
Fujiwara, Inaba, et al., 1992
Fujiwara, T.; Inaba, A.; Atake, T.; Chihara, H.,
Thermodynamic properties of deuterated hexamethylbenzene and of its solid solutions with the hydrogenated analog. A large isotope effect on the phase transition at the temperature 117 K,
J. Chem. Thermodynam., 1992, 24, 863-881. [all data]
Atake, Gyoten, et al., 1982
Atake, T.; Gyoten, H.; Chihara, H.,
A concealed anomaly at 117.5 K in the heat capacity of hexamethylbenzene,
J. Chem. Phys., 1982, 76(11), 5535-5540. [all data]
Petropavlov, Tsygankova, et al., 1988
Petropavlov, N.N.; Tsygankova, I.G.; Teslenko, L.A.,
Microcalorimetric investigation of polymorphic transitions in organic crystals,
Sov. Phys. Crystallogr., 1988, 33(6), 853-855. [all data]
Yoshimoto, Fujiwara, et al., 1985
Yoshimoto, Y.; Fujiwara, T.; Atake, T.; Chihara, H.,
Solid-solid transition in hexamethylbenzene that depends on thermal history,
Chem. Lett., 1985, (9), 1347-1350. [all data]
Frankosky and Aston, 1965
Frankosky, M.; Aston, J.G.,
The heat capacity and entropy of hexamethylbenzene from 13 to 340 K. An estimate of the internal rotation barrier,
J. Phys. Chem., 1965, 69, 3126-3132. [all data]
Momotani, Suga, et al., 1956
Momotani, M.; Suga, H.; Seki, S.; Nitta, I.,
Phase transitions in crystals composed of organic molecules with methyl groups at the molecular periperies, Proceed. National Academy of Sci. (India), XXV(Section A,
part, 1956, II), 74-82. [all data]
Spaght, Thomas, et al., 1932
Spaght, M.E.; Thomas, S.B.; Parks, G.S.,
Some heat capacity data on organic compounds obtained with a radiation calorimeter,
J. Phys. Chem., 1932, 36, 882-888. [all data]
Huffman, Parks, et al., 1930
Huffman, H.M.; Parks, G.S.; Daniels, A.C.,
Thermal data on organic compounds. VII. The heat capacities, entropies and free energies of twelve aromatic hydrocarbons,
J. Am. Chem. Soc., 1930, 52, 1547-1558. [all data]
Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G.,
Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update,
J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018
. [all data]
Wojnarovits and Foldiak, 1981
Wojnarovits, L.; Foldiak, G.,
Electron capture detection of aromatic hydrocarbons,
J. Chromatogr. Sci., 1981, 206, 511. [all data]
Chen and Wentworth, 1989
Chen, E.C.M.; Wentworth, W.E.,
Experimental Determination of Electron Affinities of Organic Molecules,
Mol. Cryst. Liq. Cryst., 1989, 171, 271. [all data]
Howell, Goncalves, et al., 1984
Howell, J.O.; Goncalves, J.M.; Amatore, C.; Klasinc, L.; Wightman, R.M.; Kochi, J.K.,
Electron transfer from aromatic hydrocarbons and their π-complexes with metals. Comparison of the standard oxidation potentials and vertical ionization potentials,
J. Am. Chem. Soc., 1984, 106, 3968. [all data]
Kuznesof, Stafford, et al., 1967
Kuznesof, P.M.; Stafford, F.E.; Shriver, D.F.,
Electron impact ionization potentials of methyl-substituted borazines,
J. Phys. Chem., 1967, 71, 1939. [all data]
Vilesov, 1961
Vilesov, F.I.,
Photoionisation of organic vapours in the vacuum ultra-violet,
Zh. Fiz. Khim., 1961, 35, 2010, In original 986. [all data]
Bralsford, Harris, et al., 1960
Bralsford, R.; Harris, P.V.; Price, W.C.,
The effect of fluorine on the electronic spectra and ionization potentials of molecules,
Proc. Roy. Soc. (London), 1960, A258, 459. [all data]
Foster, 1959
Foster, R.,
Ionization potentials of electron donors,
Nature (London), 1959, 183, 1253. [all data]
Briegleb and Czekalla, 1959
Briegleb, G.; Czekalla, J.,
Die Bestimmung von lonisierungsenergien aus den Spektren von Elektronenubergangskomplexen,
Z.Elektrochem., 1959, 63, 6. [all data]
Kovac, Mohraz, et al., 1980
Kovac, B.; Mohraz, M.; Heilbronner, E.; Boekelheide, V.; Hopf, H.,
Photoelectron spectra of the cyclophanes,
J. Am. Chem. Soc., 1980, 102, 4314. [all data]
Notes
Go To: Top, Phase change data, Gas phase ion energetics data, References
- Symbols used in this document:
EA Electron affinity IE (evaluated) Recommended ionization energy Tboil Boiling point Tc Critical temperature Tfus Fusion (melting) point Ttrs Temperature of phase transition ΔHtrs Enthalpy of phase transition ΔStrs Entropy of phase transition ΔfusH Enthalpy of fusion ΔfusS Entropy of fusion ΔsubH Enthalpy of sublimation ΔsubH° Enthalpy of sublimation at standard conditions ΔvapH Enthalpy of vaporization ΔvapH° Enthalpy of vaporization at standard conditions - Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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