Mesitylene

{{chembox |Watchedfields = changed |verifiedrevid = 444009999 |Name = Mesitylene |ImageFileL1_Ref = {{chemboximage|correct|??}} |ImageFileL1 = 1,3,5-Trimethylbenzene.svg |ImageNameL1 = Mesitylene |ImageClassL1 = skin-invert |ImageFileR1 = Mesitylene-3D-vdW.png |ImageNameR1 = Mesitylene |PIN = 1,3,5-Trimethylbenzene<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = The Royal Society of Chemistry | date = 2014 | location = Cambridge | page = 139 | doi = 10.1039/9781849733069-FP001 | isbn = 978-0-85404-182-4}}</ref> |OtherNames = Mesitylene<ref name=iupac2013 /><br />''sym''-Trimethylbenzene |Section1 = {{Chembox Identifiers |ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |ChemSpiderID = 7659 |PubChem = 7947 |KEGG_Ref = {{keggcite|correct|kegg}} |KEGG = C14508 |InChI = 1/C9H12/c1-7-4-8(2)6-9(3)5-7/h4-6H,1-3H3 |InChIKey = AUHZEENZYGFFBQ-UHFFFAOYAK |StdInChI_Ref = {{stdinchicite|correct|chemspider}} |StdInChI = 1S/C9H12/c1-7-4-8(2)6-9(3)5-7/h4-6H,1-3H3 |StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |StdInChIKey = AUHZEENZYGFFBQ-UHFFFAOYSA-N |CASNo_Ref = {{cascite|correct|CAS}} |CASNo = 108-67-8 |UNII_Ref = {{fdacite|correct|FDA}} |UNII = 887L18KQ6X |EINECS = 203-604-4 |UNNumber = 2325 |ChEBI_Ref = {{ebicite|correct|EBI}} |ChEBI = 34833 |SMILES = Cc1cc(cc(c1)C)C }} |Section2 = {{Chembox Properties |C=9|H=12 |Density = 0.8637 g/cm³ at 20 °C |MeltingPtC = −44.8 |BoilingPtC = 164.7 |Appearance = Colorless liquid<ref name=PGCH/> |Odor = Distinctive, aromatic<ref name=PGCH/> |Solubility = 0.002% (20°C)<ref name=PGCH/> |VaporPressure = 2 mmHg (20°C)<ref name=PGCH/> |MagSus = −92.32·10⁻⁶ cm³/mol }} |Section3 = {{Chembox Structure |Dipole = 0.047 D<ref>{{Cite journal |doi = 10.1016/j.atmosenv.2004.01.019| title = Proton transfer reaction rate constants between hydronium ion (H₃O⁺) and volatile organic compounds |year = 2004 |last1 = Zhao| first1 = Jun |last2 = Zhang |first2 = Renyi |journal = Atmospheric Environment |volume = 38 |issue = 14 |pages = 2177–2185 | bibcode = 2004AtmEn..38.2177Z }}</ref> }} |Section7 = {{Chembox Hazards |ExternalSDS = [https://www.sigmaaldrich.com/BE/en/sds/sial/m7200?sdslanguage=en] |FlashPtF = 122 |FlashPt_ref = <ref name=PGCH>{{PGCH|0639}}</ref> |NIOSH_ref = <ref name=PGCH/> |IDLH = N.D. |REL = TWA 25 ppm (125 mg/m³) |PEL = none |GHS_ref = <ref name=PubChem>{{Cite web |last=PubChem |title=Mesitylene |url=https://pubchem.ncbi.nlm.nih.gov/compound/7947 |access-date=2026-05-04 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> |GHSPictograms = {{GHS02}}{{GHS07}}{{GHS09}} |GHSSignalWord = Warning |HPhrases = {{H-phrases|226|335|411}} |PPhrases = {{P-phrases|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_ref = <ref name=PubChem /> |NFPA-H = 2 |NFPA-F = 2 |NFPA-I = 0 }} }}

'''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.<ref name=Ullmanns/>

==Preparation== Mesitylene is prepared by transalkylation of xylene over solid acid catalyst:<ref name=Ullmanns>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}}.</ref> :2&nbsp;C₆H₄(CH₃)₂&nbsp;⇌&nbsp;C₆H₃(CH₃)₃&nbsp;+&nbsp;C₆H₅CH₃ :C₆H₄(CH₃)₂&nbsp;+&nbsp;CH₃OH&nbsp;→&nbsp;C₆H₃(CH₃)₃&nbsp;+&nbsp;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.<ref>{{cite book |last= Cumming |first= W. M. |date= 1937 |title= Systematic organic chemistry (3E) |url= http://www.prepchem.com/synthesis-of-mesitylene/ |location= New York, USA |publisher= D. Van Nostrand Company |page=57 }}</ref>

==Reactions== Oxidation of mesitylene with nitric acid yields trimesic acid, C₆H₃(COOH)₃. Using manganese dioxide, a milder oxidising agent, 3,5-dimethylbenzaldehyde is formed. Mesitylene is oxidised by trifluoroperacetic acid to produce mesitol (2,4,6-trimethylphenol).<ref>{{cite book|pages = 242–243|chapter = Functional Compounds Containing Oxygen, Sulphur or Nitrogen and their Derivatives|chapter-url = https://books.google.com/books?id=XE5VHh7uL_0C&pg=PA242|title = Fluorine in Organic Chemistry|first = Richard D.|last = Chambers|publisher = CRC Press|year = 2004|isbn = 9780849317903}}</ref> Bromination occurs readily, giving mesityl bromide:<ref>{{cite journal|journal=Org. Synth.|year=1931|volume=11|page=24|doi=10.15227/orgsyn.011.0024|title=Bromomesitylene|author=Lee Irvin Smith}}</ref> :(CH₃)₃C₆H₃ + Br₂ → (CH₃)₃C₆H₂Br + HBr

Mesitylene is a ligand in organometallic chemistry, one example being the organomolybdenum complex {{nowrap|[(η⁶-C₆H₃Me₃)Mo(CO)₃]<ref>Girolami, G. S.; Rauchfuss, T. B. and {{ill|Robert Angelici|de|lt=Angelici, R. J.}}, Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA, 1999. {{ISBN|0-93570248-2}}.</ref>}} which can be prepared from molybdenum hexacarbonyl.

==Applications== 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.<ref name=Booth>{{cite encyclopedia|author=Gerald Booth|title=Nitro Compounds, Aromatic|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2007|publisher=Wiley-VCH|location=Weinheim|doi=10.1002/14356007.a17_411|isbn=978-3527306732}}</ref>

===Niche uses=== [[File:(Mesitylene)molybdenum tricarbonyl.png|left|thumb|150px|class=skin-invert-image|Structure of (mesitylene)molybdenum tricarbonyl, [(η⁶-C₆H₃Me₃)Mo(CO)₃] ]] 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.<ref>{{Cite web|url=http://chemicalland21.com/industrialchem/organic/MESITYLENE.htm|title=Mesitylene (1,3,5-Trimethyl Benzene)}}</ref>

One synthesis of uvitic acid obtains the product by oxidizing mesitylene.<ref>{{cite web|title=Definition of uvitic acid|url=http://www.merriam-webster.com/dictionary/uvitic%20acid|publisher=merriam-webster.com|accessdate=31 October 2016}}</ref>

Laboratory quantities of mesitaldehyde are sometimes prepared from mesitylene in a Gattermann reaction variant.<ref>{{OrgSynth| last1 =Fuson | first1=R. C. | last2=Horning |first2=E. C. |last3=Rowland |first3=S. P.|last4=Ward |first4=M. L.| title = Mesitaldehyde| collvol = 3| collvolpages = 549| year = 1955| doi=10.15227/orgsyn.023.0057}}</ref>

==History== Mesitylene was first prepared in 1837 by Robert Kane, an Irish chemist, by heating acetone with concentrated sulfuric acid.<ref>Robert Kane (1839) [https://archive.org/details/bub_gb_AuIcAQAAMAAJ/page/n589 <!-- pg=99 --> "On a series of combinations derived from pyroacetic spirit] [acetone]" ''Transactions of the Royal Irish Academy'', vol. 18, pages 99–125.</ref> He named his new substance "mesitylene" because the German chemist Carl Reichenbach had named acetone "mesit" (from the Greek μεσίτης, the mediator),<ref>Reichenbach's research is excerpted in: C. Reichenbach (1834) [https://books.google.com/books?id=P0s9AAAAcAAJ&pg=PA298 "Ueber Mesit (Essiggeist) und Holzgeist"] (On mesit (spirit of vinegar) and wood spirits), ''Annalen der Pharmacie'', vol. 10, no. 3, pages 298–314.</ref> and Kane believed that his reaction had dehydrated mesit, converting it to an alkene, "mesitylene".<ref>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, [https://archive.org/details/bub_gb_atXNAAAAMAAJ/page/n110 page 102], footnote 2.</ref> 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.<ref>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, [https://books.google.com/books?id=oKAwAAAAYAAJ&pg=PA104 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.</ref> In 1866 Adolf von Baeyer gave a correct empirical formula, but proposed a tetracyclo[3.1.1.1^1,3.1^3,5]nonane structure:<ref>Adolf von Baeyer (1866) [https://books.google.com/books?id=yYlKAAAAYAAJ&pg=RA1-PA297 "Ueber die Condensationsproducte des Acetons"] (On condensation products of acetone), ''Annalen der Chemie und Pharmacie'', vol. 140, pages 297–306.</ref> ::[[File:Mesitylen by Adolf von Baeyer.png|120px|Mesitylene by Adolf von Baeyer (tetracyclo[3.1.1.1^1,3.1^3,5]nonane)]] Finally, Albert Ladenburg provided conclusive proof that mesitylene was trimethylbenzene in 1874, which he wrote in terms of Ladenburg benzene (see {{slink|Benzene|Ring formula}}):<ref>Albert Ladenburg (1874) "Ueber das Mesitylen" (On mesitylene), ''Berichte der deutschen chemischen Gesellschaft'', vol. 7, pages 1133–1137. {{doi| 10.1002/cber.18740070261}}</ref> ::120px|Mesitylene by Albert Ladenburg (1,2,6-trimethylprismane)

==Mesityl group== {{See also|Tetramesityl compounds}} The group (CH₃)₃C₆H₂- is called '''mesityl''' (organic group symbol: Mes). Mesityl derivatives, e.g. tetramesityldiiron, are typically prepared from the Grignard reagent (CH₃)₃C₆H₂MgBr.<ref>{{cite journal|title=Isoodurene|author=Lee Irvin Smith|journal=Org. Synth.|year=1931|volume=11|page=66|doi=10.15227/orgsyn.011.0066}}</ref> 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 example 2,6-diisopropylphenyl (Dipp) and the analogously named '''Tripp''' ((ⁱPr)₃C₆H₂, Is) and '''supermesityl''' ((''^t''Bu)₃C₆H₂, Mes*) groups, may be even more effective toward achieving these goals.

==Safety and the environment== Mesitylene is also a major urban volatile organic compound (VOC) which results from combustion. It plays a significant role in aerosol and tropospheric ozone formation as well as other reactions in atmospheric chemistry.{{citation needed|date=August 2022}}

==References== <references/>

{{Authority control}} {{Hydrocarbons}}

Category:Hydrocarbon solvents Category:Alkylbenzenes Category:C3-Benzenes Category:Aromatic solvents