T Butylphenols, oxidation

Oxidative attack at random along the chain leading to chain scission and subsequent depolymerisation. Initial chain scission is reduced by the use of antioxidants (see Chapter 7) and in recent formulations hindered phenols seemed to be preferred. It is reported that 2,2 -methylenebis-(4-methyl-6-t-butylphenol) is present in Celcon and 4,4 -butylidene bis-(3-methyl-6-t-butylphenol) in Derlin. The copolymerisation helps to reduce the rate of depolymerisation where initiation of depolymerisation is not completely prevented. 

The electrostatic effect of the poly(4-vinylpyridine)-Cu(II) catalyst was also reported by Dadze et al. 115). Oxidation of ascorbic acid, salicylic acid, and tri-t-butylphenol was accelerated and that of p-phenylenediamine retarded by the poly(4-vinylpyridine) ligand at lower pH. As described in Section IIIA, a polymer-metal complex behaves as a polycation in aqueous solution, and the reaction is sensitive to the charge of low-molecular-weight species. The electrostatic effect due to the polycationic domain of a polymermetal catalyst is also predominant in the oxidation of charged substrates. 

For the oxidation of 2,6-di-t-butylphenol (42) to diphenoquinone (45) nickel peroxide has proved to be the most suitable reagent At the nickel hydroxide electrode 42 can be oxidized in 92 % yield to 45 (Eq. (8)). For this conversion a temperature of 50-70 °C is necessary, at 25 C the oxidation is very slow. 

The oxidative coupling of 2-halo-4,6-di-t-butylphenols with potassium hexacyanofer-rate(III) in benzene was investigated the 2-bromophenol (227) yielded l,4-dihydro-4-bromo-2,4,6,8-tetra-t-butyl-l-oxodibenzofuran (228 81%) and 2,4,6,8-tetra-t-butyldiben-zofuran (229) (81JOC3784). 

It has been shown that mononuclear cobalt superoxo complexes react with 2,4,6-tri-t-butyl-phenol. The anion [Co(CN)5(02)]3 acts as a base in the oxidation of the phenol. The neutral complex Co(salptr)(Oz) forms a peroxy adduct with 2,4,6-tri-t-butylphenol. An X-ray study on this adduct has revealed the structure shown in (10).m... 

The reagents which have been used here to illustrate these interesting reactions are periodic acid for the oxidation of 2,6-di-t-butylphenol,56 and a Celite-supported silver carbonate reagent for the oxidation of 2,6-dimethyl phenol, and 2,4,6-trimethylphenol57 (Expt 6.129). 

RjCHNHi — R2C=0. Although this conversion was originally reported in 1969, it has not been used widely. A recent overview reports yields of 83-93% from both acyclic and cyclic amines. A further advantage is that the by-product, 2-amino-4,6-di-t-butylphenol, can be converted to the benzoquinone by electrochemical or dichromate oxidation in 55-65% yield. 

The compounding ingredients for preparation of adhesion test specimens, magnesia (MgO), zinc oxide, Zalba Special (hindered phenol antioxidant from E. I. duPont de Nemours and Co.), and Bakelite-brand t-butylphenolic resin CK-1634 (Union Carbide Corp.) were used as... 

SbClj has been claimed to act as an electron-transfer oxidant toward a number of reagents, such as N,N,N, N -tetramethylphenylenediamine, triphenylamine, 2,4,6-tri-t-butylphenolate ion, ferrocene, and N-vinylcarbazole. Among these, triphenylamine is the most difficult to oxidize, and was therefore chosen as a model compound in entry no. 18. By matching the lowest possible experimental rate constant, 103 s , with rate constants calculated as a function of E° for the SbClj/SbCl - couple, the latter was estimated to be 0.54 V. This is an entirely reasonable value (see Cowell et al., 1970). 

Other careful electrochemical measurements of the oxidation potentials of 2,4,6-tri-t-butylphenol and 2,6-di-t-butyl-4-methylphenol in acetate buffered ethanol or acetonitrile have been measured by Mauser et al.184). They determined the static potentials using a boron carbide indicator and a mercury/mercury-acetate reference-electrode. Since in this case the oxidation of the phenols and not the phenolates to the phenoxyls has been determined the oxidation potentials cannot be compared with those in Table 12. For other electrochemical oxidations of phenols in buffered aqueous solutions using a graphite electrode see Ref. 185 186>. 

Oxidation of 2-amino-3,6-di-t-butylphenol with the reagent at pH 7.2 affords 3,6-di-r-butylbenzoquinone-l,2 as a dark-blue crystallizate, m.p. 204°, characterized by UV and IR data.1... 

Lead dioxide will oxidise 4,4 -(trimethylene)bis(2,6-di-t-butylphenol) leading to formation of a dispiro-compound by intramolecular cyclisation at the 4,4 -positions, and irradiation of this compound in a methylcyclohexane matrix at — 150°C gives 4,4 -(trimethylene)bis(2,6-di-t-butylphenoxy) diradical as a stable triplet species. Rose Bengal photooxidation of 2,3-dihydroxy-naphthalene and 2,7-dihydroxynaphthalene in basic aqueous solution gives the l,r-dimeric products by coupling of the radicals formed by electron transfer either to the excited sensitizer or to 02( Ag). ° The dimer which originates from 2,7-dihydroxynaphthalene is subject to further oxidation to 6,7-dihydroxyperylene-l,12-quinone. Irradiation of the dimethoxyphenol (82) under constant current electrolysis leads via (83) to formation of the substituted tricyclo[5.4.0.0 ]undec-8-ene (84) which can be converted into ( )-isoitalicene (85 R = Me, R = H). ... 

Titanosilicates have been synthesized which have the large pore structure of UTD-1. These molecular sieves were prepared using the metal complex Cp 2Co (bis(pentamethylcyclo-pentadienyl)cobalt(III) ion) as the template. Ti-UTD-1 has been found to be an effective catalyst for the oxidation of alkanes, alkenes and phenols using hydrogen peroxide as well as the larger oxidant t-butylhydroperoxide. The channel structure defined by 14 membered rings in Ti-UTD-1 also allows the conversion of larger substrates such as 2,6-di-t-butylphenol. 

Di-t-butylphenol reacts with terminal epoxides via 0- or C-alkylation at the least substituted epoxide carbon atom to give (151 R = H, Me, Et, n-octyl, Ph, or CHaPh) and (152 same The ratio of C- to 0-alkylation increases with the complexity of the group R (cyclohexene oxide gives entirely C-alkylation) and is also increased with the alkali-metal catalyst that is used, in the order K < Na < li. 

Ethylidene bis(4,6-di-t-butylphenol), 2,2 -Ethylidenebis(4,6-di-t-butylphenol)i EINECS 252-816-3 Phenol, 2,2 -ethylidenebis(4,6-bis(1,1-dimethyl-ethyl)- Vanox 1290, Antioxidant oxidative inhibitor for polymers process stabilizer for polyolefins stabilizer for PU and PS, Crystals mp 162-164°, Vanderbilt R.T. Co. Inc. 

Oxidation of 2j6-di-t-butylphenol (3, 245). 4-Hydroxysalcominc (1), orange solid, slightly soluble in water, readily soluble in 1 N Na2C03, is a more effective... 

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