Macromolecular antioxidants based on polysaccharides and 2,6-diisobornyl-4-methylphenol derivatives

New macromolecular antioxidants that were conjugates of dextran or hydroxyethylated starch with functionalized derivatives synthesized from 2,6-diisobornyl-4-methylphenol were prepared. Their antiradical activity compared with derivatives of 2,6-di-tert-butyl-4-methylphenol was studied in a model reaction with 2,2-diphenyl-1-picrylhydrazyl. The studied conjugates exhibited greater activity than sterically hindered phenols not bonded to a polymer chain. The synthesized isobornyl derivatives were more active than previously studied tert-butyl analogs.     

Synthesis of unsymmetrical hydroxybenzylphenols containing isobornyl fragments

4-(Bromomethyl)-2,6-diisobornylphenol was synthesized from 2,6-diisobornyl-4-methylphenol through intermediate 4-bromo-2,6-diisobornyl-4-methylcyclohexa-2,5-dien-1-one. Reactions of 4-(bromomethyl)-2,6-diisobornylphenol with 2,6- and 2,4-dialkylphenols gave new 4-(hydroxybenzyl)phenol derivatives containing bulky tert-butyl and isobornyl substituents.     

The production of artifacts during preparation of fatty acid methyl esters from fish oils,food products and pathological samples

Methyl esters were synthesized from lipid extracted by a modified Bligh and Dyer technique. The lipid was saponified and the free fatty acids methylated using boron trifluoride in methanol. Butylated hydroxytoluene (BHT; 2,6-di-tert-butyl-4-methylphenol) was added to the initial sample and to the extracted lipid prior to methyl ester synthesis. Under these conditions, the BHT was derivatized to a range of compounds, some of which can result in misinterpretation of the GC trace. Three components have been characterized by mass spectroscopy. Two of these, which eluted slightly before 16:0 on a polar column, were shown to be 2,6-di-tert-butyl-4-methoxyphenol and 2,6-di-tert-butyl-4-methoxy-methylphenol. The third component, which coeluted with 15:0 on the same column, is 2,6-di-tert-butyl-4-methoxy-5-hydroxyphenol.     

Photolysis of 2,6 di-tert-butyl-4-tert-butylperoxy-4-methyl-2,5-cyclohexadienone

The photolysis of a heptane solution of 2,6-di-tert-butyl-4-tert-butylperoxy-4-methyl- 2,5-cyclohexadienone (1) with light of 360–480 nm in the presence of 2,6-di-tert-butyl-4-methylphenol or 2,4,6-tri-tert-butylphenol gives rise to their corresponding phenoxyls in a reaction with the tert-butoxyl arising in the photolysis. Direct evidence of the formation of t-BuO^. by the photolysis of 1 was provided by the ESR characterization of spin-adducts of this radical with nitrosobenzene and nitrosodurene. Evidence of the photolysis of the peroxide bond in 1 is important for the mechanism of reaction of phenolic chain-breaking antioxidants.     

Synthesis of phosphorus derivatives of 2,6-Di-tert-butyl-4-methylphenol

Convenient procedures for the synthesis of 2,6-di-tert-butyl-4-methylphenol (ionol) mono-, di-and triphosphorus derivatives, starting from the readily accessible 3,5-di-tert-butyl-4-hydroxybenzaldehyde, are proposed, and some properties of the obtained compounds are presented.     

Synthesis of inulin and starch derivatives with a 2,6-diisobornyl-4-methylphenol (dibornol<Superscript>TM</Superscript>) fragment

Water-soluble polysaccharide derivatives containing covalently bound 2,6-diisobornyl-4-methylphenol (dibornol^TM) were synthesized by a Williams reaction of inulin and starch with 2,6-diisobornyl-4-bromomethylphenol. The conversion of 2,6-diisobornyl-4-bromomethylphenol was 85–95%.     

Oxidation of phenols with chlorine dioxide

The oxidation of different phenols, viz., phenol, 3-methylphenol, 4-methylphenol, 4-tert-butylphenol, 2-cyclohexylphenol, 2,6-di-tert-butyl-4-methylphenol, and 2,4-dichlorophenol, with chlorine dioxide in acetonitrile was studied spectrophotometrically. The reaction rate is described by a second-order equation w = k[PhOH]· [ClO₂]. The rate constants were measured and activation parameters of oxidation were determined in a temperature interval of 10–60°C. A dependence of the reaction rate constant on the phenol structure was found. The oxidation products were identified, and their yields were established.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2184–2187, October, 2004.     

Gas-phase thermochemical properties of some tri-substituted phenols: A density functional theory study

The study of the energetics of phenolic compounds has a considerable practical interest since this family of compounds includes numerous synthetic and naturally occurring antioxidants. In this work, density functional theory (DFT) has been used to investigate gas-phase thermochemical properties of the following tri-substituted phenols: 2,4,6-trimethylphenol, 2,6-dimethyl-4-tert-butylphenol, 2,6-dimethyl-4-methoxyphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-methoxyphenol, 2,4,6-trimethoxyphenol, 2,6-dimethoxy-4-methylphenol and 2,6-dimethoxy-4-tert-butylphenol. Molecular structures were computed with the B3LYP and the ωB97X-D functionals and the 6-31G(d) basis set. More accurate energies were obtained from single-point energy calculations with both functionals and the 6-311++G(2df,2pd) basis set. Standard enthalpies of formation of the phenolic molecules and phenoxyl radicals were derived using an appropriate homodesmotic reaction. The OH homolytic bond dissociation enthalpies, gas-phase acidities and adiabatic ionization enthalpies were also calculated. The general good agreement found between the calculated and the few existent experimental gas-phase thermochemical parameters gives confidence to the estimates concerning the phenolic compounds which were not yet experimentally studied.     

Synthesis of 3,3′,5,5′-Tetra-<Emphasis Type="Italic">tert</Emphasis>-butyl-4,4′-stilbenequinone and Its Catalytic Activity in the Liquid-Phase Oxidation of Inorganic Sulfides

The oxidation of 2,6-di-tert-butyl-4-methylphenol with hydrogen peroxide in the presence of potassium iodide gave 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone which catalyzed liquid-phase oxidation of sodium sulfide with oxygen more efficiently than did 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone.     

Radical Processes in the Low-Temperature Radiolysis of Liposome Dispersions

Processes occurring with the participation of radiolytic radicals in the low-temperature radiolysis of aqueous liposome dispersions were studied. The initial radiation-chemical yields of the resulting radicals were determined, and the transformations of these radicals upon freezing-out the systems were examined. It was found that ionol (2,6-di-tert-butyl-4-methylphenol) introduced into the lipid bilayer of liposomes is an effective scavenger of radiolytic species formed in a frozen (77 K) dispersion upon irradiation.     

Synthesis of new ordered aromatic polyester copolymers

Aromatic polyesters of 3,5-di-tert-butyl-4-hydroxybenzoic acid and 3,5-diisopropyl-4-hydroxybenzoic acid were prepared. The polymers were found to be high-melting but largely insoluble in organic solvents. The polymer based on 3,5-di-tert-butyl-4-hydroxy-benzoic acid was not degraded to monomer by sulfuric acid. A number of new aromatic polyesters were also prepared. Several new monomers for aromatic polyesters were synthesized, including bis(2,5-di-tert-butyl-4-carbophenoxyphenyl)terephthalate, m- and p-phenylene bis(3,5-di-tert-butyl-4-hydroxybenzoate), bis(2,6-di-tert-butyl-4-chlorocarboxyphenyl)terephthalate, and m-phenylene bis(3,5-diisopropyl-4-hydroxybenzoate). An aromatic polyester prepared from bis(2,6-di-tert-butyl-4-chlorocarboxyphenyl) terephthalate and resorcinol had a η_inh (trichloroethylene) of 1.05 (0.5%, 30°C) and a possible melting point of 330°C (DSC). Tough, creasable films could be cast from trichloroethylene solution of this polymer. Attempts to observe or to trap the keto-ketene that might result when 3,5-di-tert-butyl-4-hydroxybenzoyl chloride is treated with base were unsuccessful.     

Solvolysis of 3,5-Di-tert-butyl-4-hydroxybenzyl Acetate in Alcohol Solutions

Solvolysis of 3,5-di-tert-butyl-4-hydroxybenzyl acetate in alcohol solutions involves intermediate formation of 2,6-di-tert-butyl-4-methylene-1-benzoquinone that further takes up a molecule of the alcohol.     

Halogenation of n-substituted p -quinone monoimines and p -quinone monooxime esters: VIII. Halogenation of N -aroyl(arylsulfonyl)-2,6-di- tert -butyl-1,4-benzoquinone monoimines and their reduced forms

Chlorination of N-aroyl(arylsulfonyl)-2,6-di-tert-butyl-1,4-benzoquinone imines gave Z and E isomers of 4-arylsulfonylimino-2,6-di-tert-butyl-5,6-dichlorocyclohex-2-en-1-ones and Z isomers of 4-aroyl-(arylsulfonyl)imino-2,6-di-tert-butyl-5,5,6-trichlorocyclohex-2-en-1-ones, in which the tert-butyl group on the sp ³-hybridized carbon atom occupies exclusively the axial position. The formation of Z/E-isomeric structures is related to configurational stability of the chlorination products. The chlorination of 4-aroylamino-2,6-di-tertbutylphenols was found to be accompanied by replacement of one tert-butyl group by chlorine atom with formation of 4-aroylimino-6-tert-butyl-2,3,5,6-tetrachlorocyclohex-2-en-1-ones. Original Russian Text ? A.P. Avdeenko, V.V. Pirozhenko, O.V. Shishkin, G.V. Palamarchuk, R.I. Zubatyuk, S.A. Konovalova, O.N. Ludchenko, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 6, pp. 818–824. For communication VII, see [1].     

Control of composition in ethylene copolymerizations using magnesium chloride supported Ziegler–Natta catalysts

Incorporation of a sterically hindered phenol (2,6-di-tert-butyl-4-methylphenol) during the preparation of MgCl₂-supported titanium catalysts coupled with the use of an aluminum alkyl activator modified with the same phenol and an electron donor such as ethyl benzoate allows the systematic modification of the reactivity ratios of ethylene and 1-olefin copolymerizations. The polymers obtained tend to be largely random with a tendency toward alternating at high comonomer incorporation. Very low density LLDPE copolymers have been prepared in stable slurry polymerizations. The same catalysts allow the preparation of copolymers with dienes.     

Effect of the nature of the cation in 2,6-di-tert-pentylphenolates on the kinetics and mechanism of the reaction of 2,6-di-tert-pentylphenol with methyl acrylate

The nature of the cation (K or Na) in 2,6-di-tert-pentylphenolates (ArOK or ArONa) affects the kinetics of the reaction of 2,6-di-tert-pentylphenol (ArOH) with methyl acrylate. This is associated with the ability of ArONa to replace the cation with a proton during interaction with methyl 3-(4-hydroxy-3,5-di-tert-pentylphenyl)propionate (HOArAlkOMe) to form a more efficient catalyst, sodium 4-(2-methoxycarbonylethyl)-2,6-di-tert-pentylphenolate (NaOArAlkOMe). Two different kinetic schemes, which describe the kinetics of the consumption of ArOH in the presence of ArOK and ArONa, are proposed. The elemental-stage rate constants are calculated by mathematical simulation of the reaction kinetics with consideration of the features of catalysis in the presence of ArOK and ArONa.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 827–830, May, 1994.     

Synthesis and study of electrochemical properties of the sterically hindered phenol derivatives and the corresponding radicals

1-(3,5-Di-tert-butyl-4-hydroxyphenyl)-2-arylbenzimidazoles were synthesized by the condensation of 2,6-di-tert-butyl-p-benzoquinone imine with aromatic aldehydes. 2-(3,5-Di-tert-butyl-4-hydroxybenzylidene) benzimidazoles were synthesized by the reaction of 2-aminobenzimidazole with 2,6-di-tert-butyl-4-hydroxybenzaldehyde. The substances were characterized by elemental analysis, IR and NMR spectra. The electrochemical reduction and oxidation of these compounds and phenoxy radicals derived from them was studied by cyclic voltammetry. The stability of the studied phenoxy radicals was confirmed by the electron spin resonance method.     

Dissociation energies of O–H bonds in alkylseleno- and alkyltelluro-substituted phenols

The O?H bond dissociation energy (D _O?H) has been determined for eight alkylseleno-substituted phenols, one alkyltelluro-substituted phenol, and one alkyltelluro-substituted pyridinol. D _O?H has been estimated by the intersecting-parabolas method from kinetic data using five reference compounds: α-tocopherol (D _O?H = 330.0 kJ/mol), 3,5-di-tert-butyl-4-methoxyphenol (D _O?H = 347.6 kJ/mol), 4-methylphenol (D _O?H = 361.6 kJ/mol), 2,6-di-tert-butyl-4-methylthiophenol (D _O?H = 336.3 kJ/mol), and 2,6-di-ter-tbutyl-4-methylphenol (D _O?H = 338.0 kJ/mol). The following D _O?H values (kJ/mol) have been obtained: 335.9 for 2,5,7,8-tetramethyl-2-phytyl-6-hydroxy-3,4-dihydro-2H-1-benzoselenopyran, 342.6 for 2-methyl-5-hydroxy-2,3-dihydrobenzoselenophene, 333.5 for 2,4,6,7-tetramethyl-5-hydroxy-2,3-dihydrobenzoselenophene, 339.4 for 2-tert-butyl-4-methoxy-6-octylselenophenol, 357.9 for dodecyl 3-(4-hydroxyphenyl) propyl selenide, 348.5 for dodecyl 3-(3,5-dimethyl-4-hydroxyphenyl)propyl selenide, 350.9 for dodecyl 3-(3-tert-butyl-4-hydroxyphenyl)propyl selenide, 338.0 for dodecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propyl selenide, 343.0 for 2,6-di-tert-butyl-4-(tellurobutyl-4′-phenoxy)phenol, and 338.8 for 6-octyltelluro-3-pyridinol. The stabilization energies of phenoxyl radicals containing R substituents (X = O, S, Se, Te) have been compared.     

N-amination of 2,6-di-tert-butylpyridine

Summary Despite its low nucleophilicity 2,6-di-tert-butylpyridine (DTBP) easily undergoes N-amination. Other hidered pyridines react similarly. Comparison of the NMR carbon chemical shifts of 2,6-disubstituted 1-aminopyridinium perchlorates and those of the respective 1-methylpyridinium salts shows that the changes are parallel. 1-Amino-2,6-di-tert-butylpyridinium perchlorate does not react withp-dimethylaminobenzaldehyde. However, other hindered 1-(4-dimethylaminobenzylideneamino)pyridinium salts were obtained by a standard procedure.

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N-Aminierung von 2,6-di-tert-Butylpyridin

Zusammenfassung Trotz seiner geringen Nucleophilie ist an 2,6-Di-tert-butylpyridin (DTBP) leicht eine N-Aminierung durchzuführen. Andere gehinderte Pyridine reagieren ähnlich. Ein Vergleich der NMR-Kohlenstoffverschiebungen von 2,6-disubstituiertem 1-Aminopyridiniumperchlorat mit denjenigen der entsprechenden 1-Methylpyridiniumsalze zeigt, daß die Änderungen parallel verlaufen. 1-Amino-2,6-di-tert-butylpyridiniumperchlorat reagiert nicht mitp-Dimethylaminobenzaldehyd, hingegen wurden andere gehinderte 1-(4-Dimethlylaminobenzylidenamino)pyridiniumsalze über Standardmethoden erhalten.

     

Vapour pressure of binary,three-phase (S-L-V) systems and solubility

Solubilities and vapour pressures along the solid-liquid equilibrium line for systems 2-t-butyl-4-methylphenol+benzene, 2-t-butyl-4-methylphenol+cyclohexane, 2,6-di-t-butyl-4-methylphenol+benzene, 2,6-di-t-butyl-4-methylphenol+cyclohexane and enthalpies of fusion for six phenols have been measured.The effect of specific interactions, leading to association, on solubilities and vapour pressures of 13 binary three-phase systems (S—L—V) has been discussed. Results of solubility prediction from vapour pressure measurements and vice versa are presented.     

Potassium and sodium 2,6-di-tert-butylphenoxides and their properties

The crucial factor of the reaction of 2,6-di-tert-butylphenol with alkali hydroxides is temperature, depending on which two types of potassium or sodium 2,6-di-tert-butylphenoxides are formed. These types exhibit different catalytic activity in the alkylation of 2,6-di-tert-butylphenol with methyl acrylate. More active forms of 2,6-Bu^t ₂C₆H₃OK or 2,6-Bu^t ₂C₆H₃ONa are synthesized at temperatures higher than 160 °C and are predominantly the monomers, which dimerize on cooling. The data of ¹H NMR, electronic, and IR spectra for the corresponding forms of 2,6-Bu^t ₂C₆H₃OK and 2,6-Bu^t ₂C₆H₃ONa isolated in the individual state are in agreement with cyclohexadienone structure. In DMSO or DMF, the dimeric forms of 2,6-di-tert-butylphenoxides react with methyl acrylate to form methyl 3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate in 64–92% yield. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2138–2143, December, 2006.