2.6- Di-/-butyl-4-methylphenol

The reaction is retarded by the addition of the radical chain scavengers 2,6-di-/-butyl-4-methylphenol and hydroquinone. The oxidation rate is not affected by the oxygen pressure (Table 2), indicating that re-oxidation of Ce(III) in 1 is not rate limiting. The oxidation rate is first order in formaldehyde and goes through a maximum with increasing concentration of 1. All these phenomena are consistent with a chain radical mechanism of oxidation (11,12). 

A diastereoselective intramolecular hetero-Diels-Alder reaction of optically active 428 gave unstable 1,3,4,8,9,9a-hexahydropyrido[2,l-f][l,3]oxazin-l-one 429 (X = 0), and l,3,4,8,9,9a-hexahydropyrido[l,2-(z]pyrazin-l-one 429 (X = NTs) (Equation 80) <2003JA4970, 2004T10277>. In the case of pyrido[l,2- ]pyrazine, the reaction was carried out in the presence of 2,6-di- /-butyl-4-methylphenol. 

The general rules that should therefore be observed include the use of a blanket of nitrogen whenever possible and evaporation of solvents at the lowest feasible temperatures, which must not exceed 50°C. The addition of an antioxidant such as butylated hydroxytoluene (2,6-di-/-butyl-4-methylphenol) to the extraction solvents (0.1 g 1 ) might be necessary to prevent deterioration of unsaturated lipids but it is essential for storage of lipid extracts at about 0.1% of the weight of lipid. Inactivation of lipolytic enzymes may usually be achieved by addition of an alcohol such as methanol or, in some cases, isopropanol. The latter is recommended for some more stable enzymes sometimes found in plant tissues. Alternatively the plant may be briefly immersed in boiling water. 

Simple alkyl esters show rather low stereoselectivity. However, highly hindered esters derived from 2,6-dimethylphenol or 2,6-di-/-butyl-4-methylphenol provide the anti stereoisomers. 

The metalloporphyrin-initiated polymerizations are accelerated by the presence of steri-cally hindered Lewis acids [Inoue, 2000 Sugimoto and Inoue, 1999]. The Lewis acid coordinates with the oxygen of monomer to weaken the C— O bond and facilitate nucleophilic attack. The Lewis acid must be sterically hindered to prevent its reaction with the propagating center attached to the prophyrin structure. Thus, aluminm ortho-substituted phenolates such as methylaluminum bis(2,6-di-/-butyl-4-methylphenolate) accelerate the polymerization by factors of 102-103 or higher. Less sterically hindered Lewis acids, including the aluminum phenolates without ortho substituents, are much less effective. 

Di-/ -butyl-4-methylphenol [25377-2/ -i 2,6-Di-/ -butyl-4-methylphenol (di-/ -butyl-/>-cresolDi-/ -butyl- >-cresol or butylated hydroxytoluene (BHT)) is most commonly used as an antioxidant in plastics and mbber. Use in food is decreasing because of legislation and it is being replaced by butylated hydroxy anisole (BHA) (see Antioxidants Food additives). 

A peroxide-free grade of anhydrous tetrahydrofuran (stabilized by 0.025% of 2,6-di-<-butyl-4-methylphenol) in 1-lb. bottles is available currently (1970) from Fisher Scientific Co. This product as obtained from freshly opened bottles has been found to be suitable for reactions, such as the formation of Grignard reagents, in which purity of solvent is critical (Du Pont Company, unpublished observations). It is standard practice in at least one laboratory to use only tetrahydrofuran (Fisher) from freshly opened bottles and to discard whatever material is not used within 2 to 3 days. 

An interesting [4-F2] cycloaddition approach to various indoline systems has been devised, as illustrated by the preparation of the tricyclic molecule 158 (Equation 48). The inclusion of 2,6-di-/-butyl-4-methylphenol (BHT) in the reaction mixture gave somewhat improved yields <2005JA5776>. 

In the case of the rhenium-catalyzed oxidation of methoxy- and hydroxy-substituted substrates, there is some complementary work concerning the general mechanism of the arene oxidation [10b, 11]. Since the major products in the oxidation of such arenes or phenols are the quinones, the formation of intermediary epoxides seems to be a predominant reaction step. When p-substituted phenols such as 2,6-di( -butyl)-4-methylphenol are treated with the MTO/H2O2 oxidant and acetic acid as solvent, the formation of hydroxydienones is observed. This is also reported for the oxidation using dimethyldioxirane as oxidant [20]. Since an arene oxide intermediate was postulated for the dioxirane oxidation, a similar mechanism is plausible here [11], e. g., for the oxidation of l,2,3-trimethoxy-5-methylbenzene (Scheme 3) or 2,6-di(f-butyl)-4-methyl-phenol. 

Terbutol is prepared from 2,6-di-/-butyl-4-methylphenol and methyl isocyanate in an apolar solvent in the presence of a tertiary amine as catalyst (Haubein, 1972). 

The bulk of 4-methylphenol is used in the production of phenoHc antioxidants. The alkylation of 4-methylphenol with isobutylene under acid catalysis yields 2-/ y-butyl-4-methylphenol [2409-55-4] and 2,6-di-/ -butyl-4-methylphenol [128-57-0]. The former condenses with formaldehyde under acid catalysis to yield 2,2 -methylene bis(6-/ y-butyl-4-methylphenol) [119-47-17, which is widely used in the stabilization of natural and synthetic mbber (43). The reaction of2-/ f-butyl-4-methylphenolwith sulfur dichloride yields 2,2 -thiobis(6-/ f-butyl-4-methylphenol) [90-66-4]. 

Although the preferred route of polymerization is anionic, free-radical polymerization is also possible, particularly at higher temperatures. Thus, low levels of suitable inhibitors, e.g., hydroquinone, p-methox-yphenol, 2,6-di- -butyl-4-methylphenol, etc., may also be incorporated in the adhesive formulation. The type and concentration of such stabilizers may be determined by RPLC with UV detection. 

Thus a separation by distillation of the 2,6-di- butyl-4-methylphenol from its dimer deactivation product at 100 C was successful and provided evidence for the isomerisation of the phenoxy radicals formed primarily to oxybenzyl radicals and their recombination to dioxydiphenylethane ... 

On the other hand the high volatility of additives occurring in the classic method of re-concentrating polymer extracts by distillation - even by evaporation of the solutions will result in considerable loss of substance as was found by Schrdder [38] in the case of 2,6-di- -butyl-4-methylphenol. He found an evaporation loss of 0.75% after 24 hours when storing lonol with a large surface in stagnant air. This loss increased to 63% when the chloroform solution was evaporated in a fmne cupboard. 

Irganox 1010 2,6-di-/-butyl-4-methylphenol Wtahydro phenanthroline " propyl-fluoroanthene. 

The phenoxy radical, derived from an H-abstraction reaction by NO, couples with another -NO molecule to give 4-nitrocyclohexa-2,5-dienone, which readily rearranges, after a keto-enol tautomerism to 2,6-di- -butyl-4-nitrophenol. 2,4-di-t-butylphenol and 4-r-butylphenol react in the same way, whereas the presence of three substituents on the aromatic ring of 2,4,6-tri-r-butylphenol and 2,6-di- butyl-4-methylphenol does not allow keto-enol tautomerism in these cases 2,4,6-tri- -butyl-4-nitrocyclohexa-2,5-dienone and 2,6-di-r-butyl-4-methylnitrocyclohexa-2,5-dienone were the sole nitro compounds obtained. The reaction between NO and 2,6-di-t-butylphenol or 2,4-di- -butylphenol in methanol resulted in phenoxyl radical dimerisation together with nitration. As shown in (Scheme 5.100), phenoxyl radical dimerises to give an... 

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