Para-methylphenol

This enzyme accepts a broad range of substrates para-methylphenols are preferably oxidized to the corresponding aldehydes, whereas the oxidation of para-alkylphe-nols results in the formation of significant amounts of (S)-alcohols (Table 16.3-11) l59 63i. 

Figure 7.4. Kinetic curves of the ethylbenzene hydroperoxide accumulation for ethylbenzene oxidation initiated by AIBN without (1) and with (2) 6 -10" M para-methylphenol (3) at simultaneous presence of 610 M ora-methylphenol and 0.03 M ethylbenzene hydroperoxide, [AIBN o=410 M, T=60°C (points - experimental tines - calculation).

Figure 7.7. Reduced value contributions of individual steps (N denotes step number) over the induction period for liquid-phase inhibited oxidation of ethylbenzene at different reaction times at 60 "C. Contributions less than 0.01 are ignored. Initial concentration of the para-methylphenol was 10" M (a)...

Scheme 8.25. A path for hydrogenolysis of a phenol to an aromatic hydrocarbon. The para-methylphenol first reacts (via addition-elimination) with l-phenyl-5-chlorotetrazole to produce a dehydrohalogenated adduct. Catalytic reduction with hydrogen (H2) and palladinm on carbon powder (Pd-C) as the catalyst then produces methylbenzene (toluene) and hydroxytetrazole (which can be recycled to chlorotetrazole by treatment with phosphoryl chloride or thionyl chloride) (see Musliner.W. J. Gates, J.W. Jr. Org. Chem. Bm//., 1967,59,1).

Draw all four resonance structures of the conjugate base of para-methylphenol. Circle the least important (least favorable) resonance structure, and explain your reasoning. 

The hydrolysis of p bromotoluene with aqueous sodium hydroxide at 300°C yields m methylphenol and p methylphenol in a 5 4 ratio What is the meta—para ratio for the same reac tion carried out on p chlorotoluene" ... 

The literature on basic- and acid-catalyzed alkylation of phenol and of its derivatives is wide [1,2], since this class of reactions finds industrial application for the synthesis of several intermediates 2-methylphenol as a monomer for the synthesis of epoxy cresol novolac resin 2,5-dimethylphenol as an intermediate for the synthesis of antiseptics, dyes and antioxidants 2,6-dimethylphenol used for the manufacture of polyphenylenoxide resins, and 2,3,6-trimethylphenol as a starting material for the synthesis of vitamin E. The nature of the products obtained in phenol methylation is affected by the surface characteristics of the catalyst, since catalysts having acid features address the electrophilic substitution in the ortho and para positions with respect to the hydroxy group (steric effects in confined environments may however affect the ortho/para-C-alkylation ratio), while with basic catalysts the ortho positions become the... 

BHT (2,6-di-tert-butyl-4-methylphenol), a phenolic antioxidant, on reaction with NO under neutral conditions, results in scavenging of the potentially harmful NO via radical reactions [143]. Sodium phenolate under basic conditions undergoes a Traube-type reaction at the ortho-position to produce a cupferron derivative [144]. When the ortho-positions are sterically blocked and the para-position does not bear a proton, cyclohexadienone diazeniumdiolates may be formed (Scheme 3.12) [145]. 

This does not occur in the case of catalyst and reactants here described. With Bronsted-type catalysis, the reaction between the benzoyl cation, Ph-C" =0, and the hydroxy group in phenol is quicker than the electrophilic substitution in the ring. This hypothesis has been also confirmed by running the reaction between anisole and benzoic acid in this case the prevailing products were (4-methoxy)phenylmethanone (the product of para-C-benzoylation) and methylbenzoate (obtained by esterification between anisole and benzoic acid, with the co-production of phenol), with minor amounts of phenylbenzoate, phenol, 2-methylphenol and 4-methylphenol. Therefore, when the 0 atom is not available for the esterification due to the presence of the substituent, the direct C-acylation becomes the more favored reaction. 

The aryne intermediate from p-iodotoluene can undergo addition of hydroxide ion at the position meta to the methyl group or para to it. The two isomeric phenols are m- and p-methylphenol. 

All UV spectral data were obtained by measurement using a conventional UV / vis spectrometer (HP8458) with either aqueous or acetonitrile solutions of the benchmark chemicals. The spectrum of DBP was assumed to be the same as the spectrum of 2,6-di-t-butyl-4-methylphenol. Since DBP differs from this compound by only a para methyl group, the assumption of identical spectra is a good approximation and the absence of absorbance above 300 nm quite certain. Values of were calculated from the absorption at the wavelength centers X (shown in Table 15.1, and the concentration using Equation (2). 

The p-cyclodextrin-catalyzed reaction of phenols and carbon tetrachloride in an alkaline medium in the presence of copper powder also results in almost exclusive attack at the para-position to give 4-hydroxybenzoic acids. 2-Methylphenol also undergoes almost exclusive para-carboxylation. P-Cyclodextrin has only a negligible effect on the carbox-ylation of 3-methylphenol.-... 

Coupling in para or ortho positions is easily accomplished with phenols 912,1037,1095] and aromatic amines [915]. -Naphthol, on refluxing with anhydrous ferric chloride in ether, is converted in 60% yield into a,a -bi-p-naphthol [9i2], and 2,4-bis(rert-butyl)-5-methylphenol, on heating with chromic acid, yields the corresponding dimer [1095] (equation 44). 

Synonyms p-cresylic acid 4-hydroxytoluene 4-methylphenol para-cteso. ... 

Phenols are highly reactive toward the Friedel-Crafts alkylation reactions involving tertiary alkyl halides. Phenol, 2-methylphenol and 2,6-dimethylphenol react with tertiary alkyl halides such as 1-bromoadamantane in the absence of any external catalyst to give exclusively the para-(l-adamantyl)phenols (equation 1). These compounds have found... 

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