4-Methyl-phenol determination

Varma [106] determined iodide in seawater in amounts down to 2 mg/1 by a method based on pre-column derivatisation of the iodide into 4-iodo-2,6-di-methyl phenol. An ultraviolet detector was employed. 

Methylated phenols very often form part of the molecule of natural products, in particular, of alkaloids. In the elucidation of their constitution the quantitative determination of the methoxyl groups is of great importance. This determination is carried out by the excellent method of Zeisel, in which the methyl group is removed as methyl iodide by the action of concentrated hydriodic acid. This method (directions, p. 80) should be practised with the anisole already prepared. 

Potentiometric Determination of Lead (II) Ion using 2-[(4-Chloro-Phenylimino)-Methyl]-Phenol as an electroactive Material... 

Laszlo A. Heredy There is NMR spectroscopic evidence for the presence of both a- and /3-CHa groups in coal, based on depolymerization work with phenol-BF.3 reagent. For example, isopropyl groups were shown to be present in a high volatile bituminous coal. Is there a distinct difference in the behavior of these two types of CHs groups with respect to the reagent used in wet analytical methyl group determination ... 

To determine how a strong insolubility promoter like cadmium stearate, and a strong insolubility retarder like 2,6-di-ferf-butyl-4-methyl-phenol affects the resin when both are present, a series of one-hour oven-aging tests were run. The results are given in Table IV. Even at very low cadmium concentration the insolubilization effect is great and is only slightly altered by adding the hindered phenol. 

In a study of 92 Finnish edible and nonedible plant materials, a total of 15 berry samples were screened for antioxidant activity (Kahkonen et al., 1999). The activity was compared with the total phenolic content of the samples. Inhibition of methyl linoleate oxidation was used as a measure of antioxidant activity of berry acetone extracts and total phenolics determined by the Folin-Ciocalteau method as GAE/g dry matter of extracts. Berry extracts were high in antioxidant activity among the... 

A very sensitive method for determination of phenol, methylated phenols and resorcinol is based on bromination in acidic solution, LLE with benzene and GC-ECD, with or without previous silylation. For phenol-cresol mixtures, RSD was 4.9-8.5%, using 10 mL of 0.1 p.M aqueous solution and 2 mL benzene for extraction. The method was applied for determination of phenols in cigarette smoke and human urine" . Conditions were investigated for precolumn quantitative bromination of phenols in water solution for subsequent determination by GC-ECD. Analytical errors of 5 to 25% were found for concentrations in the 0.5 to 100 xgL range". ... 

The American Water Work Association (AWWA) and US ERA developed a number of methods for phenol determination . ERA Method 528 is dedicated to the determination of phenols in drinking water by solid-phase extraction and GC/MS analysis and is developed for 12 phenols, mainly chlorophenols, nitro- and methyl-substituted phenols . Unfortunately, users have to take into account that the recommended internal standard tetrachlorophenol can also be found in water samples and has to be used with precaution or, better, substituted with another compound. The same problem applies in the case of the recommended surrogate 2,4,6-tribromophenol, which cannot be used in the analysis of water in areas with high bromine ion content. (Some examples of tribromophenol formation by humic or fulvic acid chlorination was mentioned by Richardson °°.)... 

Dobies [35] has described detailed procedures for determining various antioxidants in PE and PP films. A feature of this method is that it requires only a small polymer sample (5 g) for the determination of down to 0.02% antioxidant compared to sample sizes of up to 1 kg in previously reported procedures. They describe the extraction procedure used for isolating the antioxidants from the polyolefins, the TLC separation of various antioxidants used industrially, and a quantitative determination of the antioxidant to detect 0.02-0.20% of an antioxidant by the use of the double beam scanning densitometer. The six antioxidants he studied were 4,4 -butylidene (2-tert-butyl-5-methyl)phenol 4,4-thiobis(6-tcft-butyl-m-cresol) pentaerythritol tetrakis(3,5-di- er -butyl-4-hydroxyhydrocinnamate) 2,2 -methylenebis(4-methyl-6-tcft-butylphenol) octadecyl (3,5-di-tert-butyl-4-hydroxyphenyl) acetate and 2,6-di-tert-butyl-p-cresol. 

The principle of the 4-substituted 2,6-xylenol method is as follows. First, the phenolic component without steric hindrance is determined by means of second derivative - difference spectroscopy of the bathochromically shifted, basified extract using the non-basified extract as a reference. The second derivative spectral amplitudes of a non-basified extract are additive for both antioxidants. The contribution of 4-substituted 2,6-xylenol to the total second derivative amplitude is then subtracted and the residual corrected amplitude corresponds to the 2,6-di rerr-butyl-4-methyl phenol content. 

As might be expected, the type of feedstock chemical and industrial process play a key role in determining the presence of phenols in wastewater. For example, the nitration of benzene and toluene to produce nitrobenzene and dinitrotoluene also leads to the incidental formation of nitrophenol, dinitrophenol, and dinitro-o-cresol. Similarly, alkylphenols and methyl-phenols may be produced during alkylation and solvent extraction of toluene, xylene, and Cg-Q alkylphenols. Wise and Fahrenthold (1981) suggested that most industrial processes were not sources of priority pollutants because the processes do not involve critical precursor/process combinations. In addition, synthetic production methods generally lead to an increase in complexity of priority pollutant molecules. These in turn exhibit variable toxicity and persistance, which may be comparable to related priority pollutants. 

In the studies of Land and Porter (1963) flash photolysis was carried out on 18 different alkyl-radical-substituted phenols with R = CH3, C2H5, tert-C4H9, and/or CeHs in various nonpolar and polar solvents, and the absorption spectra of the corresponding phenoxy radical was observed in all cases. Grabner et al. (1990) made an extensive study of the photochemistry of the methylated phenols in hydrocarbon solvents at 293 K and with A,exdt = 275 nm they determined the quantum yields of fluorescence, triplet molecule formation, and photodecomposition. The quantum yields of photodecomposition of phenol and its 2-methyl-, 3-methyl-, 4-methyl-, 2,6-dimethyl-, 3,5-dimethyl-, 2,4,6-trimethyl-, and 2,3,5-trimethyl-derivatives, as measured through the absorption of the phenoxy radicals formed were 0.13, 0.18, 0.14, 0.08, 0.21, 0.14, 0.20, and 0.18, respectively. Evidence suggested that this photodecomposition occmred from a vibrationally excited triplet state. 

The values of the 1-hydroxy moiety of (5)-(- -)-iVb-acetyl- 1-hydroxytrypto-phan methyl ester (32), methyl l-hydroxyindole-3-butylate (33), iVb-methoxy-carbonyl-l-hydroxytryptamine (34), 1-hydroxymelatonm (19), l-hydroxy-6-nitroindole (35), and l-hydroxy-5-nitroindole (36) are determined to be 9.8, 8.4, 8.2, 8.1, 6.9, and 6.8, respectively (Fig. 2) (2000H1881). Thus, 1-hydroxyindoles are weak acids, stronger than phenol and weaker than succinimide. Therefore,... 

Tables XXVIII and XXIX, respectively. Excellent correlations were obtained for all three sets. The stereochemistry of the sy -methyl ketoximes is discussed by Charton and Charton (73). The values of pj obtained for the trans-heterovinylene sets are not in good agreement with each other. Two sets gave values of 54 and 55, respectively, and the third set gave a value of 35. The difference in pj values cannot be accounted for. A value of 54 to 55 for pj suggests the possibility of some exaltation between substituent and reaction site such as that which occurs in para-substituted phenols and anilines. To demonstrate this with certainty requires that the value of pj be determined for a set of imines bearing a reaction site on the nitrogen which will not interact strongly with substituents. No such set of data is extant in the literature at the present time.

The reaction products from 2,4-dichlorophenol were tetrachloro-phenoxyphenols and tetrachlorodihydroxybiphenyls (Figure 5), as determined from their mass spectra and those of their methyl ethers. 4,6-Dichloro-2-(2, 4 -dichlorophenoxy)phenol (V) was the major phenoxy-phenol the mass spectral fragmentation pattern of o-hydroxyphenol ethers is quite characteristic since a hydrogen transfer occurs during the fragmentation (Figure 6). A trace of a trichlorophenoxyphenol also was detected and was formed presumably by the unsensitized reductive loss of chlorine, discussed previously. 

Probucol, another di-r-butyl phenol, is an anti-atherosclerotic agent that can suppress the oxidation of low-density lipoprotein (LDL) in addition to lowering cholesterol levels. The antioxidant activity of probucol was measured, using EPR, with oxidation of methyl linoleate that was encapsulated in liposomal membranes or dissolved in hexane. Probucol suppressed ffee-radical-mediated oxidation. Its antioxidant activity was 17-fold less than that of tocopherol. This difference was less in liposomes than in hexane solution. Probucol suppressed the oxidation of LDL as efficiently as tocopherol. This work implies that physical factors as well as chemical reactivity are important in determining overall lipid peroxidation inhibition activity (Gotoh et al., 1992). 

Compounds with cis double bonds in the side chain were in general found to be more potent and efficacious than their triple-bond congeners, both in in vivo and in in vitro functional assays [98, 106, 107]. QSAR models have been generated for the compounds with unsaturated [108] and l, l -dimethyl [96] side chains to determine more precisely the pharmacophoric requirements of the receptor. It is postulated that for optimum potency, the side chain must be of a suitable length and flexibility to have the ability to loop back so that its terminus is in proximity to the phenolic ring. The widely used, potency enhancing 1 - and 2 -methyl substituents would be expected to increase the tendency of the side chain to adopt a looped back, rather than an extended conformation. 

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. 

Substituents on the 2- and 6-positions of phenol rings greatly influence QM reactivity. Reaction rates for QMs derived from several of the phenols, shown in Fig. 10.1, were determined in methanolic or aqueous solutions and are listed in Table 10.1. Replacing a tert-butyl substituent of BHT by a methyl group (i.e., BDMP-QM) increased the rate of hydration by 60-70-fold at pH 7.4 and this... 

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