2,4,6-Tri-tert-butylphenol

2,4,6-Tri-tert-butylphenol 2,4,6-Tri-tert-butylphenol structure.svg 150px 2,4,6-Tri-tert-butylphenol 2,4,6-TTBP 732-26-3 correct CAS correct FDA 12902 211-989-5 99J2VIC675 387905 12368 CC(C)(C)C1=CC(=C(C(=C1)C(C)(C)C)O)C(C)(C)C 1S/C18H30O/c1-16(2,3)12-10-13(17(4,5)6)15(19)14(11-12)18(7,8)9/h10-11,19H,1-9H3 PFEFOYRSMXVNEL-UHFFFAOYSA-N 18 30 1 07 09 Warning 302 315 319 410 264 270 273 280 301+312 302+352 305+351+338 321 330 332+313 337+313 362 391 501 2,4,6-Tri-tert-butylphenol (2,4,6-TTBP) is a phenol symmetrically substituted with three tert-butyl groups and thus strongly sterically hindered. 2,4,6-TTBP is a readily oxidizable aromatic compound and a weak acid. It oxidizes to give the deep-blue 2,4,6-tri-tert-butylphenoxy radical.Warren J. J. Tronic T. A. Mayer J. M. Thermochemistry of Proton-Coupled Electron Transfer Reagents and Its Implications Chemical Reviews 2010 110 12 6961–7001 10.1021/cr100085k 20925411 3006073 2,4,6-TTBP is related to 2,6-di-tert-butylphenol, which is widely used as an antioxidant in industrial applications. These compounds are colorless solids.Antioxidants Peter P. Klemchuk 2005 10.1002/14356007.a03_091 Preparation The preparation of 2,4,6-tri-tert-butylphenol has been studied extensively. As early as 1890, Wilhelm Koenigs described the acid-catalyzed reaction of phenol with isobutylene.„auch in diesem Falle [findet] scheinbar eine directe Addition eines ungesättigten Kohlenwasserstoffs an eine aromatische Substanz statt“. W. Koenigs Chem. Ber. Ueber Condensationen ungesättigter Kohlenwasserstoffe mit Phenolen 23 2 3144–3146 1890 German 10.1002/cber.189002302257 https://zenodo.org/record/1425598 Many other reports have appeared.A.R. Hajipour Y. Ghayeb N. Sheikhan A.E. Ruoho Tetrahedron Lett. Brønsted acidic ionic liquid as an efficient and reusable catalyst for one-pot synthesis of 1-amidoalkyl 2-naphthols under solvent-free conditions 50 5649–5651 2009 40 10.1016/j.tetlet.2009.07.116 Yields up to 90% have been reported. Typical side products are the result of incomplete alkylation: 4-tert-butylphenol (4-TBP), 2,4-di-tert-butylphenol (2,4-DTBP), 2,6-di-tert-butylphenol (2,6-DTBP). 2,5-Di-tert-butylphenol (2,5-DTB) has been observed.G.H. Stillson D.W. Sawyer C.K. Hunt The hindered phenols J. Am. Chem. Soc. 67 2 303–307 1945 10.1021/ja01218a045 2,4,6-tri-tert-butylphenol is also found as a by-product in the synthesis of the disubstitution products 2,4-DTBP and 2,6-DTBP, which are more widely used antioxidants. 350px|center|Synthese von 2,4,6-Tri-tert-butylphenol mit Isobuten A synthesis of 2,4,6-tri-tert-butylphenol has been described that is also suitable as a teaching experiment. Methyl tert-butyl ether is used as the alkylating agent and sulfuric acid as catalyst. 2,4,6-TTBP is being obtained in 69% yield.B.G. Somers C.D. Cook J. Chem. Educ. The preparation of 2,4,6-tri-tert-butylphenol 32 6 312 1955 10.1021/ed032p312 350px|center|Synthese von 2,4,6-TTBP mit Methyl-tert-butylether (MTBE) Properties 2,4,6-Tri-tert-butylphenol is a white solid which dissolves in many organic solvents, but not in aqueous or alcoholic alkaline solutions. The green-blue coloring with iron(III)chloride, which is characteristic for phenols, does not occur in 2,4,6-TTBP. The compound is oxidizable in air but practically non-biodegradable.https://www.ec.gc.ca/ese-ees/92E21475-4289-446B-BCDA-E3E71BB93EF2/batch2_732-26-3_en.pdf Environment Canada, Health Canada Screening Assessment for the Challenge, Phenol, 2,4,6-tris(1,1-dimethylethyl)-(2,4,6-tri-tert-butylphenol), CAS Registry Number 732-26-3 November 2008 2017-01-11 As an electron-rich aromatic, 2,4,6-tri-tert-butylphenol can also be easily oxidized electrochemically.J.A. Richards P.E. Whitson D.H. Evans J. Electroanal. Chem. Electrochemical oxidation of 2,4,6-tri-tert-butylphenol 63 3 311–327 1975 German 10.1016/s0022-0728(75)80303-2 In the alkaline, the phenolate anion formed is first oxidized in a reversible reaction to the phenoxy radical. The stable radical is oxidized by further electron withdrawal to the phenoxonium cation, which reacts in water to give 2,4,6-tri-tert-butyl-4-hydroxy-2,5-cyclohexadienone. 500px|center|Elektrochemische Oxidation von 2,4,6-TTBP In acidic media, the hydroxydienone is dealkylated with the cleavage of the tert-butyl group in the 4-position to the 2,6-di-tert-butylhydroquinone, which is oxidized to the end product 2,6-di-tert-butyl-1,4-benzoquinone. 350px|center|Dealkylierung zum 1,4-Benzochinon The oxidation of 2,4,6-tri-tert-butylphenol in the alkaline to the intensely blue-colored phenoxy radical can also occur with potassium ferricyanide.C.D. Cook D.A. Kuhn P. Fianu J. Am. Chem. Soc. Oxidation of hindered phenols. IV. Stable phenoxy radicals 78 9 2002–2005 1956 10.1021/ja01590a067 The 2,4,6-tri-tert-butylphenoxy radical forms blue crystals on cooling to −70 °C which are stable at room temperature for several weeks and only gradually turn yellow. The phenoxy radical reacts with oxygen as a diradical to form a 4,4'-linked peroxide forming yellow crystals.C.D. Cook R.C. Woodworth J. Am. Chem. Soc. Oxidation of hindered phenols. II. The 2,4,6-Tri-t-butylphenoxy radical 75 24 6242–6244 1953 10.1021/ja01120a040 600px|center|Oxidation von 2,4,6-TTBP mit Hexacyanoferrat (III) zum Peroxid Applications The electron-rich 2,4,6-tri-tert-butylphenol can easily be oxidized to the phenoxy radical, which in the 4-position adds phenols,US 3410878 Preparation of quinol ethers 1968-11-12 H.-D. BeckerE. Müller K. Ley G. Schlechte Chem. Ber. Über Sauerstoffradikale, VIII. Über Dehydrierung von Phenolen 90 11 2660–2672 1957 German 10.1002/cber.19570901136 as well as alcohols and thiolsUS 3895069 Process for the preparation of 2,4,6-trialkyl-4-alkylthio or 4-alkoxycyclohexadi-2,5-ene-1-ones 1975-7-15 J.H. Atkinson, D. Clark to the corresponding cyclohexadienones. The cyclohexadienones, also referred to in the literature as de Chinolether, cleave the 4-position tert-butyl group upon heating under acidic conditions and aromatizes back to the substituted phenol. The reaction can be used for the synthesis of 2,6-di-tert-butyl-4-methoxyphenol, which is frequently used as an antioxidant. 600px|center|Synthese von 2,6-Di-tert-butyl-4-methoxyphenol aus 2,4,6-TTBP 2,4,6-TTBP is used as stabilizers, free-radical scavengers and antioxidants in technical applications, such as in fuels, hydraulic fluids and lubricating oils, as well as in elastomeric and thermoplastic polymers. Because of its pronounced persistence, its high tendency for bioaccumulation and aquatic toxicity, 2,4,6-TTBP is only of low industrial use and is even forbidden, for example, in Japan. The phenoxy radical of 2,4,6-TTBP is also described as a sterically demanding protecting group in a reagent for the transfer of a nucleophilic dimethylaminomethyl group [(CH3)2-N-CH2-] to form tertiary amines.D. Seebach T. Hassel Angew. Chem. 2,4,6-Tri-tert-butylphenoxy (TBPO) als sterisch wirksame Carbonylschutzgruppe — Ein neues nucleophiles Dimethylaminomethylierungsmittel 90 4 296–297 1978 German 10.1002/ange.19780900422 1978AngCh..90..296S Regulation On January 23, 2024, on the basis of its being toxic for reproduction and being persistent, bioaccumulative, and toxic (PBT), 2,4,6-TTBP was added to EU REACH's Candidate List of Substances of Very High Concern (SVHC) for Authorization.Candidate List of substances of very high concern for Authorisation - ECHA https://echa.europa.eu/candidate-list-table 2024-01-24 echa.europa.eu en-GB References Category:Alkylphenols Category:Tert-butyl compounds