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.
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name
2,2-Dimethylbutane[2] | |||
| Other names
Neohexane,[1] 22DMB
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| 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 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 | ||
| -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: | |||
   
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| Danger | |||
| H225, H304, H315, H336, H411 | |||
| P210, P261, P273, P301+P310, P331 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | −29 °C (−20 °F; 244 K) | ||
| 425 °C (797 °F; 698 K) | |||
| Explosive limits | 1.2–7.7% | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible)
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none[3] | ||
| 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
editButlerov'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
editNeohexane 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
edit- Methylbutane (isopentane)
- 2-Methylpentane (isohexane)
References
edit- ^ Haynes, William M. (2010). Handbook of Chemistry and Physics (91 ed.). Boca Raton, Florida, USA: CRC Press. p. 3-194. ISBN 978-1-43982077-3.
- ^ "2,2-DIMETHYLBUTANE - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification and Related Records. Retrieved 9 March 2012.
- ^ NIOSH Pocket Guide to Chemical Hazards. "#0323". National Institute for Occupational Safety and Health (NIOSH).
- ^ Philosophical Magazine. Taylor & Francis. 1876.
- ^ Журнал Русского физико-химического общества (in Russian). Тип-ія Б. Демакова. 1872.
- ^ "2,2-dimethylbutane". National Center for Biotechnology Information. 18 July 2015. Retrieved 20 July 2015.
- ^ Rabo, J. A.; Pickert, P. E.; Mays, R. L. (1961). "Pentane and Hexane Isomerization". Industrial & Engineering Chemistry. 53 (9). American Chemical Society (ACS): 733–736. doi:10.1021/ie50621a029. ISSN 0019-7866.
- ^ Den Hartog, A. J.; Rek, P. J. M.; Botman, M. J. P.; De Vreugd, C.; Ponec, V. (1988). "Reactions of 2,2-dimethylbutane on platinum-rhenium/alumina catalysts. Effect of sulfur and chlorine on the selectivity". Langmuir. 4 (5). American Chemical Society (ACS): 1100–1103. doi:10.1021/la00083a006. ISSN 0743-7463.
- ^ Brown, Ronald; Kemball, Charles; McDougall, Gordon S. (1995). "Exchange reactions of 2,2-dimethylpentane, 2,2-dimethylbutane and 2,2-dimethylpropane over Pt/SiO2 and Rh/SiO2". Journal of the Chemical Society, Faraday Transactions. 91 (7). Royal Society of Chemistry (RSC): 1131. doi:10.1039/ft9959101131. ISSN 0956-5000.
- ^ "Hazardous Substance Fact Sheet - 2,2-Dimethylbutane" (PDF). New Jersey Department of Health. June 2008. Retrieved 2 July 2021.
- ^ "2,2-Dimethylbutane". Consumer Products Information Database. 2021. Retrieved 2 July 2021.
- ^ Burch, R.; Paál, Z. (1994). "The use of 2,2-dimethylbutane (neohexane) as a probe molecule of metal catalysts". Applied Catalysis A: General. 114 (1). Elsevier BV: 9–33. doi:10.1016/0926-860x(94)85106-9. ISSN 0926-860X.