pentamethylbenzene
{{Chembox
| verifiedrevid = 443812488
| ImageFileL1 = Pentamethylbenzene.svg
| ImageNameL1 =
| ImageFileR1 = Pentamethylbenzene-3D-balls.png
| ImageNameR1 =
| PIN = 1,2,3,4,5-Pentamethylbenzene
| OtherNames = Pentamethylbenzene
|Section1={{Chembox Identifiers
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG =
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 700-12-9
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = H6JLD3AI98
| ChEBI = 38998
| PubChem = 12784
| ChemSpiderID = 12259
| InChI = 1/C11H16/c1-7-6-8(2)10(4)11(5)9(7)3/h6H,1-5H3
| InChIKey = BEZDDPMMPIDMGJ-UHFFFAOYAT
| SMILES = Cc1cc(C)c(C)c(C)c1C
| StdInChI = 1S/C11H16/c1-7-6-8(2)10(4)11(5)9(7)3/h6H,1-5H3
| StdInChIKey = BEZDDPMMPIDMGJ-UHFFFAOYSA-N
}}
|Section2={{Chembox Properties
| C=11 | H=16
| Appearance =
| Density = 0.917 g/cm3
| MeltingPtC = 54.4
| BoilingPtC = 232
| SolubleOther = soluble
| Solvent = organic solvents
}}
|Section3={{Chembox Hazards
| MainHazards = Flammable
| FlashPt =
| AutoignitionPt =
}}
}}
Pentamethylbenzene is an organic compound with the formula C6H(CH3)5. It is a colourless solid with a sweet odor. The compound is classified as an aromatic hydrocarbon. It is a relatively easily oxidized benzene derivative, with E1/2 of 1.95 V vs NHE.{{cite journal|doi=10.1021/ja00326a014|title=Electron transfer from aromatic hydrocarbons and their pi-complexes with metals. Comparison of the standard oxidation potentials and vertical ionization potentials|journal=Journal of the American Chemical Society|volume=106|issue=14|pages=3968–3976|year=1984|last1=Howell|first1=J. O.|last2=Goncalves|first2=J. M.|last3=Amatore|first3=C.|last4=Klasinc|first4=L.|last5=Wightman|first5=R. M.|last6=Kochi|first6=J. K.}}
Synthesis and reactions
It is obtained as a minor product in the Friedel–Crafts methylation of xylene to durene (1,2,4,5-tetramethylbenzene).{{OrgSynth|first = Lee Irvin|last = Smith |year = 1930|title = Durene|collvol = 2|collvolpages = 248|volume = 10|pages = 32|prep = CV2P0248|doi = 10.15227/orgsyn.010.0032}} Like durene, pentamethylbenzene is rather electron-rich and undergoes electrophilic substitution readily.{{Ullmann|first1 = Karl|last1 = Griesbaum|first2 = Arno|last2 = Behr|first3 = Dieter|last3 = Biedenkapp|first4 = Heinz-Werner|last4 = Voges|first5 = Dorothea|last5 = Garbe|first6 = Christian|last6 = Paetz|first7 = Gerd|last7 = Collin|first8 = Dieter|last8 = Mayer|first9 = Hartmut|last9 = Höke|title = Hydrocarbons|year = 2002|doi = 10.1002/14356007.a13_227}} Indeed, it is used as a scavenger for carbocations.{{OrgSynth|title = Trichloroboron-Promoted Deprotection of Phenolic Benzyl Ether Using Pentamethylbenzene as a Non Lewis-Basic Cation Scavenger|first1 = Shun|last1 = Okaya|first2 = Keiichiro|last2 = Okuyama|first3 = Kentaro|last3 = Okano|first4 = Hidetoshi|last4 = Tokuyama|year = 2016|volume = 93|pages = 63-74|prep = v93p0063|doi = 10.15227/orgsyn.093.0063}}
Pentamethylbenzene has been observed as an intermediate in the formation of hexamethylbenzene from phenol{{cite journal|doi = 10.1021/jo01037a517|year = 1963|last1 = Landis|first1 = Phillip S.|last2 = Haag|first2 = Werner O.|journal = Journal of Organic Chemistry|volume = 28|issue = 2|pages = 585|title = Formation of Hexamethylbenzene from Phenol and Methanol}} and alkylation of durene or pentamethylbenzene has been reported as a suitable starting material for the synthesis of hexamethylbenzene.