Phenolic acetylation

Various ionization methods were used to bombard phenol-formaldehyde oligomers in mass spectroscopic analysis. The molecular weights of resole resins were calculated using field desorption mass spectroscopy of acetyl-derivatized samples.74 Phenol acetylation was used to enable quantitative characterization of all molecular fractions by increasing the molecular weights in increments of 42. 

The level of phenol detected in blood or urine may not accurately reflect actual phenol exposure because phenol may also appear as a metabolite of benzene or other drugs. It has been shown that under certain acidic conditions used for the hydrolysis of conjugated phenols, acetyl salicylic acid (aspirin) may produce phenol (Baldwin et al. 1981) and yield spuriously higher values for phenol in blood and urine. 

Phenols Acetylation Benzoylation Sulfonation Ferric chloride test Solubility in aqueous base ppt of a characteristic melting point ppt of a characteristic melting point ppt of a characteristic melting point Variety of colors characteristic of the individual phenol Most phenols are soluble in dilute sodium hydroxide but insoluble in dilute sodium bicarbonate phenols with strong electron withdrawing groups (e.g., picric acid) are soluble in sodium bicarbonate... 

Fries rearrangement and phenol acetylation The Fries rearrangement is the acid catalysed transformation of aryl esters into hydroxyarylketones. Both this rearrangement and the two-step transformation (esterification, Fries rearrangement) in one-pot operation of phenols with carboxylic acid or anhydrides will be examined hereafter. Most studies in which acid zeolites were used as catalysts (Tables 3.6 and 3.7) deal with the synthesis of o- and p-hydroxyacetophenones (o- and p-HAP) either by the Fries rearrangement of phenyl acetate [Reaction (3.5)] ... 

Table 3.6 Gas phase Fries rearrangement of phenyl acetate and phenol acetylation over zeolite and mesoporous molecular sieves. All the reactions were carried out in fixed bed...

Finally, the amide must be hydrolysed, the amino converted into an OH group by diazotization and hydrolysis, and the new phenol acetylated. 

Chemical methods for analysis of phenolic hydroxyl groups include determination of the increase in methoxyl content resulting from diazomethane methylation (Bjorkman and Person 1957), the increase in phenolic acetyl group content after acetylation (Lenz 1968, Mansson 1983), and low-molecular weight compounds derived from the degradation of phenolic structures (Chap. 5.2). The phenolic acetyl group of acetylated lignin may also be determined by an NMR spectroscopic technique (Lenz 1968, Robert et al. 1986) or by a selective deacetylation in pyrrolidine (aminolysis) (Mansson 1983). 

The phenolic acetyl content (equivalent to the phenolic hydroxyl content) is calculated by extrapolating the linear region of the kinetic curve to zero time as illustrated in Fig. 7.2.1 A... 

Aminolysis is a laborious procedure, e.g., for wood samples, a 6-7-h reaction period may be required for the aminolysis step alone. The accuracy of this method is critically dependent upon both a quantitative acetylation of phenolic hydroxyl groups and a selective deacetylation of phenolic acetyl groups. Although these requirements may not represent a serious concern in the analysis of soluble or reagent-accessible lignin preparations, they could present a problem in the case of lignocellulosic materials. 

Acetylation of 179, followed by partial hydrolysis (phenolic acetyl group) and etherification (CH2N2), gave derivative 180. By hydrogenolysis, the C-16—C-17 bond in 180 was opened after etherification the resulting phenol was transformed to 181 (see Scheme 33). Under modified hydrogenation conditions that N-10—C-l 1 bond can be hydrogenolyzed as well. 

Figure 1.6 Phenol acetylation and related Condensed Graph of Reaction. Dynamical bonds marked with green and red correspond, respectively, to formation and breaking a single bond.

Poly(formaldehyde-co-phenol) (acetylated) 2200 ethyl acetate 298.15 4.0 1992KI1... 

Acenaphthene 2-Acety lam i no-4-methy I phenol Acetyl chloride Aluminum chloride anhydrous o-Aminoacetanilide p-Aminobenzoic acid 2-Aminobiphenyl 4-Ami nobiphenyl 1-Ami no-2,4-dibromoanthraquinone 2-Amino-6-ethoxybenzothiazole... 

Constitaeint of leaves of Loranthva europeeue, Linn. Cryst. from EtOH. M.p. 71-2°. S[Pg.515]

The products of phenol acetylation, 2-hydroxyacetophenone and 4-hydroxyacetophe-none, were also converted to phenol and acetic add when high-temperature water was used as the solvent. 

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