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Tetramethylbutane

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Tetramethylbutane
Skeletal formula of tetramethylbutane
Spacefill model of tetramethylbutane
Names
Preferred IUPAC name 2,2,3,3-Tetramethylbutane
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.008.961 Edit this at Wikidata
EC Number
  • 209-855-6
PubChem CID
UNII
UN number 1325
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C8H18/c1-7(2,3)8(4,5)6/h1-6H3Key: OMMLUKLXGSRPHK-UHFFFAOYSA-N
SMILES
  • CC(C)(C)C(C)(C)C
Properties
Chemical formula C8H18
Molar mass 114.232 g·mol
Appearance White, opaque, waxy crystals
Odor Odorless
Melting point 98 to 104 °C; 208 to 219 °F; 371 to 377 K
Boiling point 106.0 to 107.0 °C; 222.7 to 224.5 °F; 379.1 to 380.1 K
Henry's law
constant (kH) 		2.9 nmol Pa kg
Thermochemistry
Heat capacity (C) 232.2 J K mol (at 2.8 °C)
Std molar
entropy (S298) 		273.76 J K mol
Std enthalpy of
formation (ΔfH298) 		−270.3 – −267.9 kJ mol
Std enthalpy of
combustion (ΔcH298) 		−5.4526 – −5.4504 MJ mol
Hazards
GHS labelling:
Pictograms GHS02: FlammableGHS07: Exclamation markGHS08: Health hazardGHS09: Environmental hazard
Signal word Danger
Hazard statements H228, H304, H315, H336, H410
Precautionary statements P210, P240, P241, P261, P264, P271, P273, P280, P301+P310, P302+P352, P304+P340, P312, P321, P331, P332+P313, P362, P370+P378, P391, P403+P233, P405, P501
Flash point 4 °C (39 °F; 277 K)
Explosive limits 1–?%
Related compounds
Related alkanes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). ☒N verify (what is  ?) Infobox references
Chemical compound

Tetramethylbutane, sometimes called hexamethylethane, is a hydrocarbon with formula C8H18 or (H3C-)3C-C(-CH3)3. It is the most heavily branched and most compact of the octane isomers, the only one with a butane (C4) backbone. Because of its highly symmetrical structure, it has a very high melting point and a short liquid range; in fact, it is the smallest saturated acyclic hydrocarbon that appears as a solid at a room temperature of 25 °C. (Among cyclic hydrocarbons, cubane, C8H8 is even smaller and is also solid at room temperature.) It is also the most stable C8H18 isomer, with a heat of formation 4.18 kcal/mol (17.5 kJ/mol) lower than that of n-octane, a fact that has been attributed to stabilizing dispersive interactions (electron correlation) between the methyl groups (protobranching).

The compound can be obtained from ethyl bromide, tert-butyl bromide, and magnesium metal in the presence of manganese(II) ions. Despite conditions amenable to the formation of a Grignard reagent, organomagnesium compounds are believed not the active species. Instead, they transmetalate to organomanganese compounds, which then decompose to tert-butyl radicals, which dimerize.

The full IUPAC name of the compound is 2,2,3,3-tetramethylbutane, but the numbers are superfluous in this case because there is no other possible arrangement of "tetramethylbutane".

References

  1. "Hexamethylethane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification and Related Information. Retrieved 11 March 2012.
  2. Joyce, Justin P.; Shores, Matthew P.; Rappè, Anthony K. (2020-07-29). "Protobranching as repulsion-induced attraction: a prototype for geminal stabilization". Physical Chemistry Chemical Physics. 22 (29): 16998–17006. Bibcode:2020PCCP...2216998J. doi:10.1039/D0CP02193H. ISSN 1463-9084. PMID 32676632. S2CID 220606477.
  3. M. S. KHARASCH; J. W. HANCOCK; W. NUDENBERG; P. O. TAWNEY (1956). "Factors Influencing the Course and Mechanism of Grignard Reactions. XXII. The Reaction of Grignard Reagents with Alkyl Halides and Ketones in the Presence of Manganous Salts". Journal of Organic Chemistry. 21 (3): 322–327. doi:10.1021/jo01109a016.
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