2,2-Dimethylbutane
Chemical compound
From Wikipedia, the free encyclopedia
2,2-Dimethylbutane, trivially known as neohexane at William Odling's 1876 suggestion,[9] 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.
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| Names | |||
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| Preferred IUPAC name
2,2-Dimethylbutane[1] | |||
| Other names
Neohexane,[2] 22DMB | |||
| Identifiers | |||
3D model (JSmol) |
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| 1730736 | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.000.825 | ||
| EC Number |
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PubChem CID |
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| RTECS number |
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| UNII | |||
| UN number | 1208 | ||
CompTox Dashboard (EPA) |
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| Properties | |||
| C6H14 | |||
| Molar mass | 86.178 g·mol−1 | ||
| Appearance | Colorless liquid | ||
| Odor | Odorless | ||
| Density | 649 g/L | ||
| 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 | ||
| −76.24·10−6 cm3/mol | |||
Refractive index (nD) |
1.3688[3] | ||
| 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:[4] | |||
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| Danger | |||
| H225, H304, H315, H336, H411 | |||
| P210, P233, P240, P241, P242, P243, P261, P264, P271, P273, P280, P301+P316, P302+P352, P303+P361+P353, P304+P340, P319, P321, P331, P332+P317, P362+P364, P370+P378, P391, P403+P233, P403+P235, P405, P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | −48 °C (−54 °F; 225 K)[6] closed cup | ||
| 405 °C (761 °F; 678 K)[7] | |||
| Explosive limits | 1.2–7.7% | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) |
none[8] | ||
| Related compounds | |||
Related alkanes |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Synthesis
Butlerov's student V. Goryainov originally discovered neohexane in 1872 by cross-coupling of zinc ethyl with tert-butyl iodide.[10]
2,2-Dimethylbutane can be synthesised by the hydroisomerisation of 2,3-dimethylbutane using an acid catalyst.[11]
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.[12][13][14]
Uses
Neohexane is used as a high-octane anti-knock additive in gasoline and in the manufacture of agricultural chemicals.[15] It is also used in a number of commercial, automobile and home maintenance products, such as adhesives, electronic contact cleaners and upholstery polish sprays.[16]
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.[17]
See also
- Methylbutane (isopentane)
- 2-Methylpentane (isohexane)