Tetramethylbutane

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Tetramethylbutane
Skeletal formula of tetramethylbutane Tetramethylbutane skeletal.png
Skeletal formula of tetramethylbutane
Spacefill model of tetramethylbutane Tetramethylbutane 3D 1.png
Spacefill model of tetramethylbutane
Names
Preferred IUPAC name
2,2,3,3-Tetramethylbutane [1]
Identifiers
3D model (JSmol)
ChemSpider
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EC Number
  • 209-855-6
PubChem CID
UNII
UN number 1325
  • InChI=1S/C8H18/c1-7(2,3)8(4,5)6/h1-6H3 Yes check.svgY
    Key: OMMLUKLXGSRPHK-UHFFFAOYSA-N Yes check.svgY
  • CC(C)(C)C(C)(C)C
Properties
C8H18
Molar mass 114.232 g·mol−1
AppearanceWhite, 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
2.9 nmol Pa−1 kg−1
Thermochemistry
232.2 J K−1 mol−1 (at 2.8 °C)
Std molar
entropy
(S298)
273.76 J K−1 mol−1
−270.3 – −267.9 kJ mol−1
−5.4526 – −5.4504 MJ mol−1
Hazards
GHS labelling:
GHS-pictogram-flamme.svg GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H228, H304, H315, H336, H410
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 [77 °F], 100 kPa).
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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, norbornane, C7H12 and norbornene, C7H10 are even smaller and are 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). [2]

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 to be the active species. Instead, they transmetalate to organomanganese compounds, which then decompose to tert-butyl radicals, which dimerize. [3]

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.