128-39-2Relevant articles and documents
Oxidation of 2,6-Di-tert-butylphenol by Molecular Oxygen. 2. Catalysis by Cobaltous Polyamine Chelates through Their (μ-Peroxo)- and (μ-Peroxo)(μ-hydroxo)dicobalt(III) Complexes
Bedell, Stephen A.,Martell, Arthur E.
, p. 7909 - 7913 (1985)
The oxidation of 2,6-di-tert-butylphenol by molecular oxygen is catalyzed by the cobaltous chelates of tetraethylenepentamine (TETREN), dipicolyldiethylenetriamine (PYDIEN), and 1,4,10,13-tetraaza-7-thiatridecane (TATTD), through their (μ-peroxo)dicobalt(III) complexes and by those of dipicolylethylenediamine (PYEN), tris(aminoethyl)amine (TREN), and triethylenetetramine (TRIEN) through their (μ-hydroxo)(μ-peroxo)dicobalt(III) complexes.Reaction products are identified as the oxidative coupling product 3,3'5,5'-tetra-tert-butyldiphenoquinone and the partial oxygen insertion product, 2,6-di-tert-butylbenzoquinone.The rates of reaction of the substrate as well as the formation of products are shown to be first order with respect to the concentrations of both the cobalt-dioxygen complex and the substrate.The reaction with (4+) does not occur in the absence of free molecular oxygen in solution and occurs at a reduced rate under air relative to oxygen.
Bolton et al.
, p. 3415 (1968)
Tertiary butylation of phenol on Cu1-xCoxFe 2O4: Catalysis and structure-activity correlation
Mathew, Thomas,Rao, Bollapragada S.,Gopinath, Chinnakonda S.
, p. 107 - 116 (2004)
A systematic study of catalytic tertiary butylation of phenol was carried out with isobutene as a function of temperature, feed composition, time on stream, space velocity, and catalyst composition on Cu1-xCo xFe2O4 (x=0 to 1) system. Tertiary butylation of phenol gives three products, namely, 2-tert-butyl phenol, 4-tert-butyl phenol, and 2,4-di-tert-butyl phenol. The phenol conversion and selectivity of these products depend on the reaction parameters. A good correlation was found between the activity, in terms of phenol conversion and various product selectivities for this reaction, and the acid-base properties of the catalysts. High activity is achieved with x=0.5 composition, illustrating the importance of a 1:1 combination of Cu and Co and the necessity for optimum concentrations of acid-base centers for this reaction. A reaction mechanism involving the interaction of phenoxide from phenol and the tert-butyl cation from isobutene on Cu1-xCoxFe2O4 is proposed. X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopic analysis of fresh and spent catalysts revealed a partial reduction of metal ions due to reaction. Valence band studies clearly revealed an increase in the overlap of metal ion 3d bands from fresh to spent catalysts as reflected from a large decrease in the energy gap between them. The better catalytic results observed with x=0.5 are attributed to an optimum distribution of Cu species with heteroatom neighbors, maximum overlap between the Cu and Co 3d bands, and intermediate acid-base character.
Synthesis and structural characterization of a 4-coordinate molybdenum(VI) dioxo diaryloxide, MoO2(O-2,6-t-Bu2C6H3)2·Ho-2,6-t-Bu2C6H3
Hanna, Tracy A.,Incarvito, Christopher D.,Rheingold, Arnold L.
, p. 630 - 631 (2000)
The facile solution synthesis and spectroscopic and structural characterization of 4-coordinate MoO2(OAr)2. ArOH (1) where Ar = 2,6-di-tert-butylphenyl are described. MoO2(O-2,6-t-Bu2C6H3)2·HO-2,6-t-Bu2C6H3 (1) was synthesized by addition of LiOAr to MoO2Cl2 in CH3CN. Yields are reduced by concurrent oxidation of the phenolic anion to form 3,3',5,5'-tetra-tert-butyl-4,4'-diphenoquinone (4). Relatively strong Mo=O double bonds and p-electron donation from the aryloxide oxygens appear to compensate for the unsaturation of the pseudotetrahedral metal center.
Alkylation of Phenols with tert-Butanol Catalyzed by H-Form of Y Zeolites with a Hierarchical Porous Structure
Bayguzina,Makhiyanova,Khazipova,Khusnutdinov
, p. 1554 - 1559 (2019/10/14)
tert-Butyl-substituted phenols have been synthesized via the reaction of phenol, o-, m-, and p-cresols with tert-butanol under the action of CBr4-promoted Y-zeolites in the H-form with a hierarchical porous structure.
Ambident Reactivity of Phenolate Anions Revisited: A Quantitative Approach to Phenolate Reactivities
Mayer, Robert J.,Breugst, Martin,Hampel, Nathalie,Ofial, Armin R.,Mayr, Herbert
, p. 8837 - 8858 (2019/07/08)
Prompted by the observation that the regioselectivities of phenolate reactions (C versus O attack) are opposite to the predictions by the principle of hard and soft acids and bases, we performed a comprehensive experimental and computational investigation of phenolate reactivities. Rate and equilibrium constants for the reactions of various phenolate ions with benzhydrylium ions (Aryl2CH+) and structurally related quinone methides have been determined photometrically in polar aprotic solvents. Quantum chemical calculations at the SMD(MeCN)/M06-2X/6-31+G(d,p) level confirmed that O attack is generally favored under kinetically controlled conditions, whereas C attack is favored under thermodynamically controlled conditions. Exceptions are diffusion-limited reactions with strong electrophiles, which give mixtures of products arising from O and C attack, as well as reactions with metal alkoxides in nonpolar solvents, where oxygen attack is blocked by strong ion pairing. The Lewis basicity (LB) and nucleophilicity (N, sN) parameters of phenolates determined in this work can be used to predict whether their reactions with electrophiles are kinetically or thermodynamically controlled and whether the rates are activation- or diffusion-limited. Comparison of the measured rate constants for the reactions of phenolates with carbocations with the Gibbs energies for single-electron transfer manifests that these reactions proceed via polar mechanisms.