Phenols 0-methylation

Ciesol and xylenol can be prepared by the methylation of phenol with methanol over both acid and base catalysts. It is postulated that phenol methylation on acid catalysts proceeds through the initial formation of anisole (methoxybenzene [100-66-3]) followed by intramolecular rearrangement of... 

Me2BBr, CICH2CH2CI, 0°-rt, 70-93% yield.This reagent also cleaves phenolic methyl ethers. Tertiary ethers give the bromide rather than the alcohol. 

Mel, K2CO3, acetone, reflux, 6 h. This is a veiy common and often veiy efficient method for the preparation of phenolic methyl ethers it is also applicable to the. formation of phenolic benzyl ethers. 

BCI3, 0°, 5-6 h, 90% yield. In this example a phenolic methyl group, normally cleaved with boron trichloride, was not affected. 

ISiCl3, rt, 20-30 min, 74-95% yield. Esters and phenolic methyl ethers are reported to survive, whereas with the related TMSI they are cleaved. 

One major problem of the industrial process of phenol methylation is the low yield with respect to methanol, due to its decomposition consequently, a large excess of methanol is usually fed in order to reach an acceptable per-pass conversion of phenol. This aspect, however, is often forgotten in scientific literature, and only... 

Figures 44.1 and 44.2 report the performance in the gas-phase phenol methylation of the H-mordenite and of the Mg/Fe/O catalyst, respectively. The differences between the two catalysts concerned both the transformations occurring on methanol and the type of phenolic products obtained. The H-mordenite was very active at 350°C the conversion of phenol was 80%. A further increase of temperature led to a decrease of conversion. This can be attributed to a progressive deactivation of the catalyst, due to...

The results obtained indicate that in the reaction between phenol and methanol, formaldehyde is the trae methylating agent when basic catalysts are used. This indicates that the type of transformation occurring with methanol is the factor that mainly differentiates performances in phenol methylation when catalyzed by either basic or acid catalysts. The catalyst plays its role in the generation of the methylating species the nature of the latter then determines the type of phenolic products obtained. 

High boiling polar compounds, diols, phenols, methyl esters of. dicarboxylic acids, amines, diamines, ethanolamines, amides, aldehydes and ketones. 

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... 

Methylphenol, see Phenol Methyl phenyl sulfone, see Fonofos Methyl phosphate, Trichlorfon IV-Methylphosphinic acid, see Glvphosate 2-Methylpropanal, see 2-Methylpropene, 2,2,4-... 

Phenol methylation to 2,6-xylenol has been widely studied for the past few deeades owing to the room for improvisation from the viewpoint of product selectivity. Generally during phenol methylation to 2,6-xylenol, occurs via sequential methylation of phenol to o-cresol to 2,6-xylenol, various reaction parameters mediate the selectivity between the two. For instance, when the reaetants stoichiometry of methanol to phenol molar ratio > 2, and significant residence time of o-cresol may favor 2,6-xylenol selectivity. However, excess methanol is often used, sinee some amount of methanol tend to undergo oxidation into various reformate produets [71] under vapor phase condition. Similarly, reaction temperature, catalyst acid-base property, and space velocity of the reaetant are the parameters that govern the selectivity to 2,6-xylenol. 

Cu-Mn mixed-oxide binary spinel catalysts (CuxMn3 x04, where x = 0, 0.25, 0.5, 0.75 and 1) prepared through co-precipitation method exhibit phenol methylation activity imder vapor phase conditions [75]. All of the catalysts, irrespective of the compositions, produced only C-methylated phenols. However, a total ortho selectivity of 100% with 2,6-xylenol selectivity of 74% was observed over x = 0.25 compositions at 400°C. This composition was found to be relatively stable under reaction conditions compared with the other compositions studied. The catalysts with high copper content suffered severe reduction under methylation conditions whereas, catalysts with low copper content had a hausmannite phase (Mu304) that sustained... 

Figure 7. Effect of synergism on phenol conversion over three selected compositions of Cul-xCoxFe204, x = 0.0, 0.50 and 1.0. Phenol methylation was carried out with phenohmethanohwater composition of 1 5 2 at 3500C and at WFISV of 0.869 h-1. 2,6-xylenol selectivity was maintamedat 75 mol% throughout the 50 h period.

Kotanigawa and co-workers [7-9] studied the adsorption behavior of phenol and methanol on a Zn0-Fe203 system and highlighted the importance of acid-base sites for the selective ortho methylation. However, detailed studies of the adsorption behavior of possible products and reactants of phenol methylation on catalytic systems and their interaction among them are not available widely. 

The mechanism of phenol methylation on Cul-xCoxFe204 and the participation of Lewis acid-base pair site in the methylation step were recently demonstrated in detail [79]. 

The interaction of adsorbed reactants (phenol and methanol adsorbed separately and coadsorbed) and possible reaction products of phenol methylation with the Cul-xCoxFe204 system has been studied at temperatures between lOOoC and 350oC and probed by in situ FTIR spectroscopy. The spectra of adsorbed methanol, phenol and methylated products on catalyst surface, at lOOoC, did not possess much changes compared to the spectra of pure components that indicated the molecular adsorption of species on catalyst surface. The remarkable changes in the spectra occur, above 100°C due to the chemisorption of substrates, were observed and correlated with the observed reaction trend. 

In contrast to phenol methylation, other alkyaltions are hard to carry out on spinel systems, as it is suggestive from very few available reports in the literature. Further, the ease of formation of the side products (alkyl phenols with small alkyl group) increases as the size... 

Studies on phytotoxicity of bibenzyl derivatives were extended to duckweed axenic cultures. Bibenzyls 19 and 20 as well as the synthetic analogs 23—28 were tested by triplicate in cultures of the small aquatic plant. Analogs 23—28 were synthesized to investigate the effect on phytotoxicity of oxygenated substituents (phenolic vs. phenolic methyl ether) and their location on the bibenzyl core structure. All synthesized analogs but... 

Alkyl- benzene Methyl- benzene Methyl- phenol Methyl- naphthalene aiSc... 

Synonyms 2-Methyl phenol 4-Methyl phenol 3-Methyl phenol Methyl phenol SANSS 1989 ... 

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