2,2-Dimethylbutane

2,2-Dimethylbutane, trivially known as neohexane at William Odling's 1876 suggestion,^[4] is an organic compound with formula C₆H₁₄ or (H₃C-)₃-C-CH₂-CH₃. It is therefore an alkane, indeed the most compact and branched of the hexane isomers — the only one with a quaternary carbon and a butane (C₄) backbone.

2,2-Dimethylbutane

Stereo, skeletal formula of 2,2-dimethylbutane with some implicit hydrogens shown
Ball stick model of 2,2-dimethylbutane Spacefill model of 2,2-dimethylbutane
Names
Preferred IUPAC name 2,2-Dimethylbutane[1]
Other names Neohexane,[2] 22DMB
Identifiers
CAS Number	75-83-2 Y
3D model (JSmol)	Interactive image
Beilstein Reference	1730736
ChEMBL	ChEMBL142735 Y
ChemSpider	6163 Y
ECHA InfoCard	100.000.825
EC Number	200-906-8
PubChem CID	6403
RTECS number	EJ9300000
UNII	07L56L3MP2 N
UN number	1208
CompTox Dashboard (EPA)	DTXSID4025111
InChI InChI=1S/C6H14/c1-5-6(2,3)4/h5H2,1-4H3 Y Key: HNRMPXKDFBEGFZ-UHFFFAOYSA-N Y
SMILES CCC(C)(C)C
Properties
Chemical formula	C6H14
Molar mass	86.178 g·mol−1
Appearance	Colorless liquid
Odor	Odorless
Density	649 mg mL−1
Melting point	−102 to −98 °C; −152 to −145 °F; 171 to 175 K
Boiling point	49.7 to 49.9 °C; 121.4 to 121.7 °F; 322.8 to 323.0 K
log P	3.51
Vapor pressure	36.88 kPa (at 20 °C)
Henry's law constant (kH)	6.5 nmol Pa−1 kg−1
Magnetic susceptibility (χ)	−76.24·10−6 cm3/mol
Refractive index (nD)	1.369
Thermochemistry
Heat capacity (C)	189.67 J K−1 mol−1
Std molar entropy (S⦵298)	272.00 J K−1 mol−1
Std enthalpy of formation (ΔfH⦵298)	−214.4 – −212.4 kJ mol−1
Std enthalpy of combustion (ΔcH⦵298)	−4.1494 – −4.1476 MJ mol−1
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H304, H315, H336, H411
Precautionary statements	P210, P261, P273, P301+P310, P331
NFPA 704 (fire diamond)	1 3 0
Flash point	−29 °C (−20 °F; 244 K)
Autoignition temperature	425 °C (797 °F; 698 K)
Explosive limits	1.2–7.7%
NIOSH (US health exposure limits):
PEL (Permissible)	none[3]
Related compounds
Related alkanes	Neopentane 2,3-Dimethylbutane Triptane Tetramethylbutane 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

Synthesis

Butlerov's student V. Goryainov originally discovered neohexane in 1872 by cross-coupling of zinc ethyl with tert-butyl iodide.^[5]

2,2-Dimethylbutane can be synthesised by the hydroisomerisation of 2,3-dimethylbutane using an acid catalyst.^[6]

It can also be synthesised by isomerization of n-pentane in the presence of a catalyst containing combinations of one or more of palladium, platinum, rhodium and rhenium on a matrix of zeolite, alumina, silicon dioxide or other materials. Such reactions create a mixture of final products including isopentane, n-hexane, 3-methylpentane, 2-methylpentane, 2,3-dimethylbutane and 2,2-dimethylbutane. Since the composition of the final mixture is temperature dependant the desired final component can be obtained choice of catalyst and by combinations of temperature control and distillations.^[7][8][9]

Uses

Neohexane is used as a high-octane anti-knock additive in gasoline and in the manufacture of agricultural chemicals.^[10] It is also used in a number of commercial, automobile and home maintenance products, such as adhesives, electronic contact cleaners and upholstery polish sprays.^[11]

In laboratory settings, it is commonly used as a probe molecule in techniques which study the active sites of metal catalysts. Such catalysts are used in hydrogen-deuterium exchange, hydrogenolysis, and isomerization reactions. It is well suited to this purpose as 2,2-dimethylbutane contains both an isobutyl and an ethyl group.^[12]

See also

• Methylbutane (isopentane)
• 2-Methylpentane (isohexane)