| |||
| Names | |||
|---|---|---|---|
| Preferred IUPAC name 1,3,5-Trimethylbenzene[1] | |||
| Other names Mesitylene[1] sym-Trimethylbenzene | |||
| Identifiers | |||
| |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
| ||
| ECHA InfoCard | 100.003.278 | ||
| EC Number |
| ||
| KEGG |
| ||
| UNII | |||
| UN number | 2325 | ||
| |||
| |||
| Properties | |||
| C9H12 | |||
| Molar mass | 120.19 g/mol | ||
| Appearance | Colorless liquid[2] | ||
| Odor | Distinctive, aromatic[2] | ||
| Density | 0.8637 g/cm3 at 20 °C | ||
| Melting point | −44.8 °C (−48.6 °F; 228.3 K) | ||
| Boiling point | 164.7 °C (328.5 °F; 437.8 K) | ||
| 0.002% (20°C)[2] | |||
| Vapor pressure | 2 mmHg (20°C)[2] | ||
| −92.32·10−6 cm3/mol | |||
| Structure | |||
| 0.047D[3] | |||
| Hazards | |||
| Flash point | 50 °C; 122 °F; 323 K[2] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | none[2] | ||
REL (Recommended) | TWA 25 ppm (125 mg/m3)[2] | ||
IDLH (Immediate danger) | N.D.[2] | ||
| Safety data sheet (SDS) | [1] | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Mesitylene or1,3,5-trimethylbenzene is a derivative ofbenzene with threemethylsubstituents positioned symmetrically around the ring. The other two isomerictrimethylbenzenes are1,2,4-trimethylbenzene (pseudocumene) and1,2,3-trimethylbenzene (hemimellitene). All three compounds have theformula C6H3(CH3)3, which is commonly abbreviated C6H3Me3. Mesitylene is a colorless liquid with sweet aromatic odor. It is a component ofcoal tar, which is its traditional source. It is a precursor to diversefine chemicals. Themesityl group (Mes) is a substituent with the formula C6H2Me3 and is found in various other compounds.[4]
Mesitylene is prepared bytransalkylation ofxylene over solidacid catalyst:[4]
Although impractical, it could be prepared by trimerization ofpropyne, also requiring anacid catalyst, which yields a mixture of 1,3,5- and 1,2,4-trimethylbenzenes.
Trimerization ofacetone viaaldol condensation, which is catalyzed anddehydrated bysulfuric acid is another method of synthesizing mesitylene.[5]
Oxidation of mesitylene withnitric acid yieldstrimesic acid, C6H3(COOH)3. Usingmanganese dioxide, a milderoxidising agent, 3,5-dimethylbenzaldehyde is formed. Mesitylene is oxidised bytrifluoroperacetic acid to producemesitol (2,4,6-trimethylphenol).[6] Bromination occurs readily, givingmesityl bromide:[7]
Mesitylene is aligand inorganometallic chemistry, one example being theorganomolybdenum complex[(η6-C6H3Me3)Mo(CO)3][8] which can be prepared frommolybdenum hexacarbonyl.
Mesitylene is mainly used as a precursor to2,4,6-trimethylaniline, a precursor to colorants. This derivative is prepared by selective mononitration of mesitylene, avoiding oxidation of the methyl groups.[9]
molybdenum_tricarbonyl.png)
Mesitylene is used in the laboratory as a specialty solvent. In the electronics industry, mesitylene has been used as adeveloper for photopatternablesilicones due to its solvent properties.
The threearomatic hydrogen atoms of mesitylene are in identical chemical shift environments. Therefore, they only give a single peak near 6.8 ppm in the1H NMR spectrum; the same is also true for the ninemethyl protons, which give a singlet near 2.3 ppm. For this reason, mesitylene is sometimes used as aninternal standard in NMR samples that contain aromatic protons.[10]
Uvitic acid is obtained by oxidizing mesitylene or by condensingpyruvic acid withbaryta water.[11]
TheGattermann reaction can be simplified by replacing the HCN/AlCl3 combination withzinc cyanide (Zn(CN)2).[12] Although it is highly toxic, Zn(CN)2 is a solid, making it safer to work with than gaseous hydrogen cyanide (HCN).[13] The Zn(CN)2 reacts with the HCl to form the key HCN reactant and ZnCl2 that serves as the Lewis-acid catalystin-situ. An example of the Zn(CN)2 method is the synthesis ofmesitaldehyde from mesitylene.[14]
Mesitylene was first prepared in 1837 byRobert Kane, an Irish chemist, by heating acetone with concentrated sulfuric acid.[15] He named his new substance "mesitylene" because the German chemistCarl Reichenbach had named acetone "mesit" (from the Greek μεσίτης, the mediator),[16] and Kane believed that his reaction had dehydrated mesit, converting it to analkene, "mesitylene".[17] However, Kane's determination of the chemical composition ("empirical formula") of mesitylene was incorrect. The correct empirical formula was provided byAugust W. von Hofmann in 1849.[18] In 1866Adolf von Baeyer gave a correct mesitylene's empirical formula; however, with a wrong structure of tetracyclo[3.1.1.11,3.13,5]nonane.[19] A conclusive proof that mesitylene was trimethylbenzene was provided byAlbert Ladenburg in 1874; however, assuming wrong benzene structure ofprismane.[20]
![Mesitylene by Adolf von Baeyer (tetracyclo[3.1.1.11,3.13,5]nonane)](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aMesitylen_by_Adolf_von_Baeyer.png)
The group (CH3)3C6H2- is calledmesityl (organic group symbol: Mes). Mesityl derivatives, e.g.tetramesityldiiron, are typically prepared from theGrignard reagent (CH3)3C6H2MgBr.[21] Due to its large steric demand, the mesityl group is used as a large blocking group in asymmetric catalysis (to enhance diastereo- or enantioselectivity) and organometallic chemistry (to stabilize low oxidation state or low coordination number metal centers). Larger analogues with even greater steric demand, for example2,6-diisopropylphenyl (Dipp) and the analogously namedTripp ((iPr)3C6H2, Is) andsupermesityl ((tBu)3C6H2, Mes*) groups, may be even more effective toward achieving these goals.
Mesitylene is also a major urbanvolatile organic compound (VOC) which results fromcombustion. It plays a significant role in aerosol andtropospheric ozone formation as well as other reactions inatmospheric chemistry.[citation needed]
{{cite book}}:ISBN / Date incompatibility (help)| International | |
|---|---|
| National | |
| Other | |