2- -2-methylphenol

IMINES, CYCLIC] (Vol 14) 2,2y-Thiobis(6-tert-butyl-4-methylphenol) [90-66-4]... 

Commercial appHcation of this type of reaction is used to produce 2,2 -methylenebis(6-/ f2 -butyl-4-methylphenol) (R = tert — butyl = methyl R = H) and 2,2 -ethylidenebis(4,6-di-/ /f-butylphenol) R = R = tert — butyl R = CH ). 

Methylphenol. y -Cresol is produced synthetically from toluene. Toluene is chlorinated and the resulting chlorotoluene is hydrolyzed to a mixture of methylphenols. Purification by distillation gives a mixture of 3-methylphenol and 4-methylphenol since they have nearly identical boiling points. Reaction of this mixture with isobutylene under acid catalysis forms 2,6-di-/ f2 -butyl-4-methylphenol and 2,4-di-/ f2 -butyl-5-methylphenol, which can then be separated by fractional distillation and debutylated to give the corresponding 3- and 4-methylphenols. A mixture of 3- and 4-methylphenols is also derived from petroleum cmde and coal tars. 

Methylphenol. T -Cresol is produced synthetically from toluene. Toluene is sulfonated to yield T i ra-toluenesulfonic acid, which is then converted to 4-methylphenol via the caustic fusion route. A minor amount of 4-methylphenol is also derived from petroleum cmde and coal tars. 4-Methylphenol [106-44-5] is available in 55-gal dmms (208-L) and in bulk quantities as a molten material. 

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-/ f2 -butyl-4-methylphenol [2409-55-4] and 2,6-di-/ f2 -butyl-4-methylphenol [128-37-0]. The former condenses with formaldehyde under acid catalysis to yield 2,2 -methylene bis(6-/ f2 -butyl-4-methylphenol) [119-47-1], which is widely used in the stabilization of natural and synthetic mbber (43). The reaction of 2-/ l -butyl-4-methylphenol with sulfur dichloride yields 2,2 -thiobis(6-/ l -butyl-4-methylphenol) [90-66-4]. 

Di-/ f2 -butyl-4-methylphenol, which is commonly known as BHT (butylated hydroxy toluene), is a widely used phenoHc antioxidant in the stabilization of oils, mbber, and polyolefins (44). BHT is also one of the few phenolic antioxidants approved by the FDA as a direct food additive where it is used to retard the oxidation of naturally occurring oils in food. 

Other uses of 4-methylphenol include its conversion to a benzotriazole uv stabilizer, 2-(2 -hydroxy-5 -methylphenyl)benzotriazole [2440-22-4] (45). The benzotriazole-based uv stabilizer makes possible the extended use of thermoplastics in outdoor appHcations. Other minor appHcations for 4-methylphenol include its use in the production of novolak or resole phenoHc resins. It is also used in the production of certain dyes and fragrances (Table 3). 

Di-/ l -butyl-4-methylphenol /2j5 i77-2/-i72,6-Di-/ l -butyl-4-methylphenol (di-/ l -butyl-/)-cresolDi-/ l -butyl-j )-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 Eood additives). 

Di-tert-butyl-p-cresol (2,6-di-tert-butyl-4-methylphenol, butylatedhydroxytoluene, BHT) [128-37-0] M 230.4, m 71.5 , pK 12.23. Dissolved in n-hexane at room temperature, then cooled with rapid stirring, to -60°. The ppte was separated, redissolved in hexane, and the process was repeated until the mother liquor was no longer coloured. The final product was stored under N2 at 0° [Blanchard J Am Chem Soc 82 2014 7960]. Also crystd from EtOH, MeOH, benzene, n-hexane, methylcyclohexane or pet ether (b 60-80°), and dried under vacuum. 

Figure 10.9 Cliromatogi ams of foitified coconut oil obtained by using (a) normal-phase HPLC and (b) GPC/noimal-phase HPLC. Peak identification is as follows 1 (a,b), DL-a-toco-pheryl acetate, 2 (b), 2,6-di-tert-butyl-4-methylphenol 2 (a) and 3 (b), retinyl acetate 3 (a) and 4 (b), tocol 4 (a) and 5 (b), ergocalciferol. Reprinted from Analytical Chemistry, 60, J. M. Brown-Thomas et al., Determination of fat-soluble vitamins in oil matrices by multidimensional liigh-peiformance liquid cliromatography , pp. 1929-1933, copyright 1988, with permission from the American Chemical Society.

If t he directing effects of the two groups oppose each other, the more powerful activating group has the dominant influence, but mixtures of products often result. For example, bromination of p-methylphenol yields primarily 2-bromo-4-methylphenol because —OH is a more powerful activator than -CH3. 

Furthermore, the reaction of several hindered phenols, such as 2,6-di-t-butyl-4-methylphenol, 3,5-di-t-butyl-4-hydroxybenzyl alcohol, and 2,6-di-t-butylphenol, with BTMA Br3 were carried out in dichloromethane in the presence of water, t-butyl alcohol, or aq. sodium hydroxide at room temperature. Sequential reaction processes were provided by the obtained products. As an example, we show the reaction of 2,6-di-t-butyl-4-methylphenol with BTMA Br3 in Fig. 26 (ref. 34). 

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