1,2,4-Trimethylbenzene, also known as pseudocumene, is an organic compound with the chemical formula C6H3(CH3)3. Classified as an aromatic hydrocarbon, it is a flammable colorless liquid with a strong odor. It is nearly insoluble in water but soluble in organic solvents. It occurs naturally in coal tar and petroleum (about 3%). It is one of the three isomers of trimethylbenzene.
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name
1,2,4-Trimethylbenzene | |||
| Other names
Pseudocumene, Asymmetrical trimethylbenzene, ψ-Cumene | |||
| Identifiers | |||
3D model (JSmol) |
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| 1903005 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.002.216 | ||
| EC Number |
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| KEGG | |||
PubChem CID |
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| RTECS number |
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| UNII | |||
| UN number | 1993 2325 | ||
CompTox Dashboard (EPA) |
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| Properties | |||
| C9H12 | |||
| Molar mass | 120.19 g/mol | ||
| Appearance | Colorless liquid | ||
| Density | 0.8761 g/cm3 | ||
| Melting point | −43.78 °C (−46.80 °F; 229.37 K) | ||
| Boiling point | 169 to 171 °C (336 to 340 °F; 442 to 444 K) | ||
| -101.6·10−6 cm3/mol | |||
| Hazards | |||
| GHS labelling: | |||
   | |||
| Warning | |||
| H226, H315, H319, H332, H335, H411 | |||
| P210, P233, P240, P241, P242, P243, P261, P264, P271, P273, P280, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P370+P378, P391, P403+P233, P403+P235, P405, P501 | |||
| Flash point | 44.4 °C (111.9 °F; 317.5 K) | ||
| Explosive limits | 0.9%–6.4%[2] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) |
none[2] | ||
| Safety data sheet (SDS) | Sigma-Aldrich MSDS | ||
| Related compounds | |||
Related compounds |
1,2,3-Trimethylbenzene; 1,3,5-Trimethylbenzene | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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History
In 1849, Charles Blachford Mansfield rectified coal tar and identified fractions which he hypothesized to be cumole and cymole. The latter fraction boiled slightly above 170°C and had specific density of 0.857.[3]
In 1862, Warren De la Rue and Hugo Müller (1833-1915) proposed the term pseudocumole for the fractions heavier than xylole.[4]
When three years later American chemist Cyrus Warren (1824-1891) attempted to reproduce Mansfield's results, he determined that the oil boiling at 170° has the same formula as cumole, not cymole, and suggested to name it isocumole.[5]
The structure of the compound was determined by Th. Ernst and Wilhelm Rudolph Fittig, who first prepared it from bromoxylene and iodomethane in 1866 by a Wurtz–Fittig reaction developed two years earlier.[6]
In the next year, Fittig et al. adopted the pseudocumol terminology,[7] in 1869 Fittig and B. Wackenroder proved that the fraction is a mixture of mesitylene with another trimethylbenzene, for which the name of pseudocumol was retained,[8] and in 1886 Oscar Jacobsen showed that the third trimethylbenzene he discovered earlier is also present.[9]
Production
Industrially, it is isolated from the C9 aromatic hydrocarbon fraction during petroleum distillation. Approximately 40% of this fraction is 1,2,4-trimethylbenzene. It is also generated by methylation of toluene and xylenes and the disproportionation of xylene over aluminosilicate catalysts.[10]
Uses
Pseudocumene is a precursor to mellitic anhydride, from which high performance polymers are made. It is also used as a sterilizing agent and in the making of dyes, perfumes and resins. Another use is as a gasoline additive.[11]
Scintillator
1,2,4-Trimethylbenzene dissolved in mineral oil is used as a liquid scintillator[12] in particle physics experiments such as NOνA and Borexino.
See also
References
External links
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