P-Methoxyphenol

Fig. 1. A single step perturbation fails for the mutation of p-methylphenol to p-methoxyphenol because no configuration with a cavity large enough to accommodate the methoxy group is sampled in a simulation of p-methylphenol in water.

Aq methacrylic acid (90%) was satd with NaCl (to remove the bulk of the water), then the organic phase was dried with CaCl2 and distd under vacuum. Polymerisation inhibitors include 0.25% p-methoxyphenol, 0.1% hydroquinone, or 0.05% A/,A/ -diphenyl-p-phenylenediamine. 

The handling of the monomer presents a number of problems. The monomer will polymerise on storage even under an inert gas. Polymer deposition may be observed after standing for less than a day. Exposure to air, to water or to light will accelerate polymerisation. A number of phenolic materials are effective inhibitors, a typical example being 0.02% p-methoxyphenol. Exposure to light, air and water must, however, still be avoided. The monomer has an anaesthetic action and chronic toxic properties and care must therefore be taken in its handling. 

Acryloyl chloride (0.2 mol) in dry benzene (60 ml) was added over 0.5 hour with mechanical stirring to pentane-1,5-diol (0.1 mol), triethylamine (0.2 mol) and pyrogallol (0.1 g) in dry benzene (100 ml). Further dry benzene (ca 100 ml) was added followed by triethylamine (10 ml), and the mixture stirred at 50°C for 0.5 hour. The triethylamine hydrochloride was fii-tered off and the solvent removed In vacuo to leave a yellow oil which was distilled in the presence of a trace of p-methoxyphenol, excluding light, to give 1,5-pen tarn ethylene diacrylate (12.9g 61% BP90°to95°C/0,01 mm Hg),... 

The effect of hydroquinone and p-methoxyphenol is remarkable, but this seems beyond argument at present because considerable parts of them can not be recovered after reaction, suggesting that very complex side reactions are taking place. 

Trimethyl phenol 1-Naphthol p-Phenylphenol p-Methoxyphenol Hydroquinone... 

A combination of a Pd-catalyzed nucleophilic substitution by a phenol and a ring expansion was described by Ihara and coworkers [127] using cis- or trans-substituted propynylcyclobutanols 6/l-262a or 6/l-262b. The product ratio depends on the stereochemistry of the cyclobutanols and the acidity of the phenol 6/1-263. Thus, reaction of 6/l-262b with p-methoxyphenol 6/1-263 (X = pOMe) led exclu-... 

The palladium-catalyzed substitution of the less reactive racemic ethyl 3-cyclohexe-nyl carbonate could, in a similar fashion, be completed with dimethyl malonate, p-methoxyphenol, or phthalimide as nucleophiles, with satisfactory ee (Eq. 11.38) [55]. These reactions, when irradiated for 1 min with temperatures up to 100 °C, delivered yields (91-96%) and ee values (94—95%) identical with those performed in... 

The introduction of 0.5 mol L 1 pyridine into 1,1-dimethylethanol containing phenol and hydroperoxide increases the rate constant kn from 10-4 to 1.2 x 10 L mol-1 s 1 (353 K) [121]. At concentrations lower than 0.1 mol L 1, pyridine enhances the rate of the reaction of p-methoxyphenol with hydroperoxide in benzene at 353 K from almost zero to v = 3.7 x 10 2[ArOH][ROOH][C5H5N] [121]. The addition of pyridine to tert-butanol with p-methoxyphenol increases both the reaction rate and the electroconductivity of an ArOH solution. All these results are in agreement with the following reaction mechanism ... 

In aqueous solutions, ROOH can react with p-methoxyphenol at pH > 8 however, at pH >10 the reaction slows down due to ROOH dissociation and a weak oxidative ability of the ROz anion. 

Enthalpies, Activation Energies, and Rate Constants of Reactions of Nitroxyl Radicals (>NO ) with O—H Bond of p-methoxyphenol, lonol, and 4,4-dimethoxydiphenylamine Calculated by IPM Method for Equations See Chapter 6 and for the Values of a, bre, and A, See Table 18.5... 

Instead of 3-amlno-l-group would be on the xyethvl)acrylamide, t -15 C Instead of -5 to erature (9 ) to obtain a action, the mixture was iltered. The filtered Ide salt was washed several lie. The filtrates were nitrile was removed by amounts of p-methoxyphenol... 

An early investigation concerned the photoreactions of p-nitroanisole. Letsinger and Steller (1969) elegantly demonstrated not only that its photosubstitution by hydroxide ion and by pyridine could be sensitized (by benzophenone), but also that the product distribution of the photohydrolysis (/ -nitrophenol/p-methoxyphenol 1 4) was the same whether it was the result of direct irradiation or of a sensitized reaction. 

Sopchak D, Miller B, Avygal Y, Kalish R (2002) Rotating ring-disk electrode studies of the oxidation of p-methoxyphenol and hydroquinone at boron-doped diamond electrodes. J. Electroanal Chem 538 39-45. 

Borras, C, Rodriguez P, Laredo T, Mostany J, Scharifker BR (2004) Electrooxidation of aqueous p-methoxyphenol on lead oxide electrodes. J Appl Electrochem 34 583-589. 

As normally supplied, acrylic esters are inhibited to enhance the shelf life. Aside from dissolved oxygen, inhibitors that are deliberately added include phenolic compounds such as hydroquinone (HQ) and p-methoxyphenol (MEHQ, i.e., methyl ether of hydroquinone ). These inhibitors are usually present in concentrations of 50 to 100 parts per million (ppm) by weight. Oxidation products of the phenolic inhibitors may also be present. 

Problem 14.23 Give the main products of (a) mononitration of p-methylphenetole, (b) monobromination of p-methoxyphenol. ... 

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