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. 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. 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. Many other reports have appeared. 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. 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. 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. 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. As an electron-rich aromatic, 2,4,6-tri-tert-butylphenol can also be easily oxidized electrochemically. 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. 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. 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. 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. 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, as well as alcohols and thiols to the corresponding cyclohexadienones. The cyclohexadienones, also referred to in the literature as , cleave the 4-position tert-butyl group upon heating under acidic conditions and