Tetramethylbutane

Tetramethylbutane

Skeletal formula of tetramethylbutane
Spacefill model of tetramethylbutane
Names
Preferred IUPAC name 2,2,3,3-Tetramethylbutane[1]
Identifiers
CAS Number	594-82-1^Y
3D model (JSmol)	Interactive image
ChemSpider	11185^Y
ECHA InfoCard	100.008.961
EC Number	209-855-6
PubChem CID	11675
UNII	EB34RI15NY^Y
UN number	1325
CompTox Dashboard (EPA)	DTXSID9073204
InChI InChI=1S/C8H18/c1-7(2,3)8(4,5)6/h1-6H3^Y Key: OMMLUKLXGSRPHK-UHFFFAOYSA-N^Y
SMILES CC(C)(C)C(C)(C)C
Properties
Chemical formula	C8H18
Molar mass	114.232 g·mol^−1
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^−1 kg^−1
Thermochemistry
Heat capacity (C)	232.2 J K^−1 mol^−1 (at 2.8 °C)
Std molar entropy (S^⦵298)	273.76 J K^−1 mol^−1
Std enthalpy of formation (ΔfH^⦵298)	−270.3 – −267.9 kJ mol^−1
Std enthalpy of combustion (ΔcH^⦵298)	−5.4526 – −5.4504 MJ mol^−1
Hazards
GHS labelling:
Pictograms
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	Neopentane 2,2-Dimethylbutane 2,3-Dimethylbutane Triptane Tetraethylmethane 2,2,4-Trimethylpentane 2,3,3-Trimethylpentane 2,3,4-Trimethylpentane Tetra-tert-butylmethane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is ^YN ?) Infobox references

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).^[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.