Benzene, hexamethyl-

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Gas phase thermochemistry data

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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:
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
Δfgas-18.5 ± 0.60kcal/molCcbColomina, Jimenez, et al., 1989see Boned, Colomina, et al., 1964; ALS
Δfgas-18.7kcal/molN/AParks, West, et al., 1946Value computed using ΔfHsolid° value of -163.3±3.1 kj/mol from Parks, West, et al., 1946 and ΔsubH° value of 85.0 kj/mol from Parks, West, et al., 1946.; DRB

Constant pressure heat capacity of gas

Cp,gas (cal/mol*K) Temperature (K) Reference Comment
44.07200.Draeger, 1985Recommended values are in close agreement with experimental data on S(T). Discrepancies with earlier statistically calculated values [ Hastings S.H., 1957] amount to 16 and 13 J/mol*K in S(T) and Cp(T), respectively.; GT
54.33273.15
57.72 ± 0.1298.15
57.98300.
71.30400.
83.48500.
94.12600.
103.3700.
111.1800.
117.9900.
123.81000.
128.81100.
133.21200.
137.01300.
140.21400.
143.11500.

Reaction thermochemistry data

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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:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias

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

Hexamethyltetracyclo[2.2.0(2,6).0(3,5)]hexane = Benzene, hexamethyl-

By formula: C12H18 = C12H18

Quantity Value Units Method Reference Comment
Δr-82.5 ± 0.8kcal/molCmAdam and Chang, 1969liquid phase; solvent: Pure phase; Heat of isomerization; ALS
Δr-91.2kcal/molEqkOth, 1968liquid phase; Heat of isomerization, see Oth, 1969; ALS
Δr-91.5kcal/molCmOth, 1968liquid phase; solvent: Toluene-d8; Heat of isomerization at 150°C; ALS

Dewar benzene, hexamethyl- = Benzene, hexamethyl-

By formula: C12H18 = C12H18

Quantity Value Units Method Reference Comment
Δr-56.2 ± 0.6kcal/molCmAdam and Chang, 1969liquid phase; solvent: Pure phase; ALS
Δr-59.5kcal/molEqkOth, 1968liquid phase; Heat of isomerization, see Oth, 1969; ALS

C6H7N+ + Benzene, hexamethyl- = (C6H7N+ • Benzene, hexamethyl-)

By formula: C6H7N+ + C12H18 = (C6H7N+ • C12H18)

Bond type: Charge transfer bond (positive ion)

Quantity Value Units Method Reference Comment
Δr17.1kcal/molPHPMSMeot-Ner (Mautner) and El-Shall, 1986gas phase; M
Quantity Value Units Method Reference Comment
Δr24.3cal/mol*KPHPMSMeot-Ner (Mautner) and El-Shall, 1986gas phase; M

Anti-1,2,3,5,6-pentamethyl-4-methylenebicyclo[3.1.0]hex-2-ene = Benzene, hexamethyl-

By formula: C12H18 = C12H18

Quantity Value Units Method Reference Comment
Δr-42.7kcal/molCisoChilds and Mulholland, 1983liquid phase; ALS

Gas phase ion energetics data

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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 ± 0.01eVN/AN/AL
Quantity Value Units Method Reference Comment
Proton affinity (review)205.7kcal/molN/AHunter and Lias, 1998HL
Quantity Value Units Method Reference Comment
Gas basicity199.8kcal/molN/AHunter and Lias, 1998HL

Electron affinity determinations

EA (eV) Method Reference Comment
<0.121 ± 0.017ECDWojnarovits and Foldiak, 1981EA 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
7.85PEHowell, Goncalves, et al., 1984LBLHLM
7.87EIKuznesof, Stafford, et al., 1967RDSH
7.85 ± 0.02PIVilesov, 1961RDSH
7.85PIBralsford, Harris, et al., 1960RDSH
7.8CTSFoster, 1959RDSH
7.95CTSBriegleb and Czekalla, 1959RDSH
7.85PEHowell, Goncalves, et al., 1984Vertical value; LBLHLM
7.9PEKovac, Mohraz, et al., 1980Vertical value; LLK

References

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry 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.

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]

Adam and Chang, 1969
Adam, W.; Chang, J.C., Kinetics and thermochemistry of valence isomerization by differential scanning calorimetry: the case of hexamethylprismane and hexamethyldewarbenzene, Int. J. Chem. Kinet., 1969, 1, 487-492. [all data]

Oth, 1968
Oth, J.F.M., The kinetics and thermochemistry of the thermal rearrangement of hexamethylbicyclo[2.2.0]hexa-2,5-diene (hexamethyldewarbenzene) and of hexamethyltetracyclo[2.2.0,0(2,6).0(3,5)]hexane (hexamethylprismane), Chem. Ber., 1968, 47, 1185-1195. [all data]

Oth, 1969
Oth, J.F.M., The kinetics and thermochemistry of the thermal rearrangement of hexamethyl(Dewar benzene) and of hexamethylprismane, Angew. Chem. Int. Ed. Engl., 1969, 7, 646. [all data]

Meot-Ner (Mautner) and El-Shall, 1986
Meot-Ner (Mautner), M.; El-Shall, M.S., Ionic Charge Transfer Complexes. 1. Cationic Complexes with Delocalized and Partially Localized pi Systems, J. Am. Chem. Soc., 1986, 108, 15, 4386, https://doi.org/10.1021/ja00275a026 . [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]

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, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, References