Mesitylene

Mesitylene
Mesitylene
Mesitylene
Mesitylene
Mesitylene
Names
Preferred IUPAC name
1,3,5-Trimethylbenzene
Other names
Mesitylene
sym-Trimethylbenzene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.003.278 Edit this at Wikidata
EC Number
  • 203-604-4
KEGG
UNII
UN number 2325
  • InChI=1S/C9H12/c1-7-4-8(2)6-9(3)5-7/h4-6H,1-3H3 checkY
    Key: AUHZEENZYGFFBQ-UHFFFAOYSA-N checkY
  • InChI=1/C9H12/c1-7-4-8(2)6-9(3)5-7/h4-6H,1-3H3
    Key: AUHZEENZYGFFBQ-UHFFFAOYAK
  • Cc1cc(cc(c1)C)C
Properties
C9H12
Molar mass 120.195 g·mol−1
Appearance Colorless liquid
Odor Distinctive, aromatic
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)
Vapor pressure 2 mmHg (20°C)
−92.32·10−6 cm3/mol
Structure
0.047 D
Hazards
GHS labelling:
GHS02: FlammableGHS07: Exclamation markGHS09: Environmental hazard
Warning
H226, H335, H411
P210, P233, P240, P241, P242, P243, P261, P271, P273, P280, P303+P361+P353, P304+P340, P319, P370+P378, P391, P403+P233, P403+P235, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
2
0
Flash point 50 °C; 122 °F; 323 K
NIOSH (US health exposure limits):
PEL (Permissible)
 none
REL (Recommended)
 TWA 25 ppm (125 mg/m3)
IDLH (Immediate danger)
 N.D.
Safety data sheet (SDS)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkYX markN ?)

Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenzene (hemimellitene). All three compounds have the formula C6H3(CH3)3, which is commonly abbreviated C6H3Me3. Mesitylene is a colorless liquid with sweet aromatic odor. It is a component of coal tar, which is its traditional source. It is a precursor to diverse fine chemicals. The mesityl group (Mes) is a substituent with the formula C6H2Me3 and is found in various other compounds.

Preparation

Mesitylene is prepared by transalkylation of xylene over solid acid catalyst:

2 C6H4(CH3)2 ⇌ C6H3(CH3)3 + C6H5CH3

It can also be prepared by methylation of meta-xylene:

C6H4(CH3)2 + CH3OH → C6H3(CH3)3 + H2O

Although impractical, it could be prepared by trimerization of propyne, also requiring an acid catalyst, which yields a mixture of 1,3,5- and 1,2,4-trimethylbenzenes.

Trimerization of acetone via aldol condensation, which is catalyzed and dehydrated by sulfuric acid is another method of synthesizing mesitylene.

Uses and reactions

Mesitylene undergoes three main types of reactions: substitution at the aromatic C–H, oxidation of the methyl groups, and complexation of the aromatic ring. It also has other niche uses.

Ring substitution

The three methyl-group substituents activate the ring for electrophilic aromatic substitution.

Mesitylene is mainly used as a precursor to 2,4,6-trimethylaniline, a precursor to colorants. This derivative is prepared by selective mononitration of mesitylene, avoiding oxidation of the methyl groups.

Bromination using molecular bromine occurs readily, giving mesityl bromide:

(CH3)3C6H3 + Br2 → (CH3)3C6H2Br + HBr

Laboratory quantities of mesitaldehyde are sometimes prepared from mesitylene in a Gattermann reaction variant.

The arenium ion formed by protonation is stable enough to be isolated as a salt. Mesitylenium tetrakis(pentafluorophenyl)borate is useful as a catalyst for hydrogen/deuterium exchange on other aromatic-ring compounds.

Methyl-group oxidation

Oxidation of mesitylene with nitric acid yields trimesic acid, C6H3(COOH)3. Using manganese dioxide, a milder oxidizing agent, 3,5-dimethylbenzaldehyde is formed. Mesitylene is oxidized by trifluoroperacetic acid to produce mesitol (2,4,6-trimethylphenol).

One synthesis of uvitic acid obtains the product by oxidizing mesitylene.

Ring complexation

Structure of (mesitylene)molybdenum tricarbonyl, [(η6-C6H3Me3)Mo(CO)3]

Mesitylene is a ligand in organometallic chemistry, one example being the organomolybdenum complex [(η6-C6H3Me3)Mo(CO)3] which can be prepared from molybdenum hexacarbonyl.

Niche uses

Mesitylene is used in the laboratory as a specialty solvent. In the electronics industry, mesitylene has been used as a developer for photopatternable silicones due to its solvent properties.

The three aromatic hydrogen atoms of mesitylene are in identical chemical shift environments. Therefore, they only give a single peak near 6.8 ppm in the 1H NMR spectrum; the same is also true for the nine methyl protons, which give a singlet near 2.3 ppm. For this reason, mesitylene is sometimes used as an internal standard in NMR samples that contain aromatic protons.

History

Mesitylene was first prepared in 1837 by Robert Kane, an Irish chemist, by heating acetone with concentrated sulfuric acid. He named his new substance "mesitylene" because the German chemist Carl Reichenbach had named acetone "mesit" (from the Greek μεσίτης, the mediator), and Kane believed that his reaction had dehydrated mesit, converting it to an alkene, "mesitylene". However, Kane's determination of the chemical composition ("empirical formula") of mesitylene was incorrect. An accurate elemental analysis was provided by August W. von Hofmann in 1849, although von Hofmann also mistook the empirical formula because he used a then-current atomic weight of 6 for carbon. In 1866 Adolf von Baeyer gave a correct empirical formula, but proposed a tetracyclo[3.1.1.11,3.13,5]nonane structure:

Mesitylene by Adolf von Baeyer (tetracyclo[3.1.1.11,3.13,5]nonane)

Finally, Albert Ladenburg provided conclusive proof that mesitylene was trimethylbenzene in 1874, which he wrote in terms of Ladenburg benzene (see Benzene § Ring formula):

Mesitylene by Albert Ladenburg (1,2,6-trimethylprismane)

Mesityl group

Mesityl substituents are employed to produce a stable analogue of the elusive PbH2:(C6H3-2,6-(mesityl)2)PbH dimer

The group (CH3)3C6H2- is called mesityl (organic group symbol: Mes). 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). Transition metal mesityl derivatives, e.g. tetramesityldiiron, are typically prepared from the Grignard reagent (CH3)3C6H2MgBr.

Larger analogues with even greater steric demand, for example 2,6-diisopropylphenyl (Dipp) and the analogously named Tripp ((iPr)3C6H2, Is) and supermesityl ((tBu)3C6H2, Mes*) groups, may be even more effective toward achieving these goals.

References

  1. 1 2 Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 139. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. 1 2 3 4 5 6 "#0639". NIOSH Pocket Guide to Chemical Hazards. National Institute for Occupational Safety and Health.
  3. ↑ Zhao, Jun; Zhang, Renyi (2004). "Proton transfer reaction rate constants between hydronium ion (H3O+) and volatile organic compounds". Atmospheric Environment. 38 (14): 2177–2185. Bibcode:2004AtmEn..38.2177Z. doi:10.1016/j.atmosenv.2004.01.019.
  4. 1 2 PubChem. "Mesitylene". pubchem.ncbi.nlm.nih.gov. Retrieved 2026-05-04.
  5. 1 2 Karl Griesbaum, Arno Behr, Dieter Biedenkapp, Heinz-Werner Voges, Dorothea Garbe, Christian Paetz, Gerd Collin, Dieter Mayer, Hartmut Höke “Hydrocarbons” in Ullmann's Encyclopedia of Industrial Chemistry 2002 Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_227.
  6. ↑ Cumming, W. M. (1937). Systematic organic chemistry (3E). New York, USA: D. Van Nostrand Company. p. 57.
  7. ↑ Gerald Booth (2007). "Nitro Compounds, Aromatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a17_411. ISBN 978-3527306732.
  8. ↑ Lee Irvin Smith (1931). "Bromomesitylene". Org. Synth. 11: 24. doi:10.15227/orgsyn.011.0024.
  9. ↑ Fuson, R. C.; Horning, E. C.; Rowland, S. P.; Ward, M. L. (1955). "Mesitaldehyde". Organic Syntheses. doi:10.15227/orgsyn.023.0057; Collected Volumes, vol. 3, p. 549.
  10. ↑ Duttwyler, Simon; Butterfield, Anna M.; Siegel, Jay S. (2013). "Arenium Acid Catalyzed Deuteration of Aromatic Hydrocarbons". The Journal of Organic Chemistry. 78 (5): 2134–2138. doi:10.1021/jo302201a. PMID 23163918.
  11. ↑ Duttwyler, Simon; Butterfield, Anna M.; Siegel, Jay S. (2013). "Arenium Acid Catalyzed Deuteration of Aromatic Hydrocarbons". The Journal of Organic Chemistry. 78 (5): 2134–2138. doi:10.1021/jo302201a. PMID 23163918.
  12. ↑ Chambers, Richard D. (2004). "Functional Compounds Containing Oxygen, Sulphur or Nitrogen and their Derivatives". Fluorine in Organic Chemistry. CRC Press. pp. 242–243. ISBN 9780849317903.
  13. ↑ "Definition of uvitic acid". merriam-webster.com. Retrieved 31 October 2016.
  14. ↑ Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J. [de], Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA, 1999. ISBN 0-93570248-2.
  15. ↑ "Mesitylene (1,3,5-Trimethyl Benzene)". Archived from the original on March 18, 2006.
  16. ↑ Robert Kane (1839) "On a series of combinations derived from pyroacetic spirit [acetone]" Transactions of the Royal Irish Academy, vol. 18, pages 99–125.
  17. ↑ Reichenbach's research is excerpted in: C. Reichenbach (1834) "Ueber Mesit (Essiggeist) und Holzgeist" (On mesit (spirit of vinegar) and wood spirits), Annalen der Pharmacie, vol. 10, no. 3, pages 298–314.
  18. ↑ For an explanation of the original of the name "mesitylene", see also: Henry E. Roscoe, A Treatise on Chemistry (New York, New York: D. Appleton and Co., 1889), vol. III, page 102, footnote 2.
  19. ↑ A.W. Hofmann (1849) "On the composition of mesitilole [mesitylene], and some of its derivatives", The Quarterly Journal of the Chemical Society of London, vol. 2, pages 104–115. The empirical formula for mesitylene stated in Hofmann's paper is C18H12; once the modern atomic weight (12) is used in Hofmann's calculations, his results give the correct empirical formula of C9H12.
  20. ↑ Adolf von Baeyer (1866) "Ueber die Condensationsproducte des Acetons" (On condensation products of acetone), Annalen der Chemie und Pharmacie, vol. 140, pages 297–306.
  21. ↑ Albert Ladenburg (1874) "Ueber das Mesitylen" (On mesitylene), Berichte der deutschen chemischen Gesellschaft, vol. 7, pages 1133–1137. doi:10.1002/cber.18740070261
  22. ↑ Queen, Joshua D.; Fettinger, James C.; Power, Philip P. (2019). "Two quasi-stable lead(II) hydrides at ambient temperature". Chemical Communications. 55 (69): 10285–10287. doi:10.1039/c9cc05106f. PMID 31396611.
  23. ↑ Lee Irvin Smith (1931). "Isoodurene". Org. Synth. 11: 66. doi:10.15227/orgsyn.011.0066.