Phenolic compounds solid forms

Phenolic compounds that form intermolecular hydrogen bonds are typically solid at room temperature. 

Bisphenol A is a solid material in the form of white flakes, insoluble in water but soluble in alcohols. As a phenolic compound, it reacts with strong alkaline solutions. Bisphenol A is an important monomer for producing epoxy resins, polycarbonates, and polysulfones. It is produced by the condensation reaction of acetone and phenol in the presence of HCI. (See Chapter 10, p. 273)... 

In some instances, combinations of Cig and silica columns are also used for better purification of the crude extracts (431, 445). A combination of Cg, silica, and amino solid-phase extraction columns has been successfully employed to fractionate anabolic and catabolic steroid hormone residues from meat in polar and nonpolar neutral and phenolic compounds, and to purify further each fraction effectively (452). Another combination of two solid-phase extraction columns, one using a graphitized carbon black sorbent and the other Amberlite resin in the hydroxyl form, allowed neutral anabolics to be isolated and separated from acidic anabolics and their metabolites (453). A combination of basic alumina column placed in tandem with an ion-exchange column has also been applied for the purification of the crude extracts in the determination of diethylstilbestrol and zeranol (427), and estradiol and zeranol in tissues (450). 

It is well known that the oxidation of phenolic compounds at solid electrodes produces phenoxy radicals, which couple to form a passivating polymeric film on the electrode surfaces [20,21]. The anodic reaction proceeds through an initial one-electron step to form phenoxy radicals, which subsequently can undergo either polymerization or further oxidation with the transfer of oxygen from hydroxyl radicals at the electrode... 

An HPLC-DAD method was developed for the separation and the determination of flavonoid and phenolic antioxidants in commercial and freshly prepared cranberry juice.Two sample preparation procedures were used with and without hydrolysis of the glycoside forms of flavonoids carried out by the addition of HCl in the step prior to solid-phase extraction (SPE). The flavonoid and phenolic compounds were then fractionated into neutral and acidic groups via a solid-phase extraction method (Sep-Pak Cig), followed by a RP HPLC separation with gradient elution with water-methanol-acetic acid and a detection at 280 and 360 nm. A comparison of the chromatograms obtained for extracts prepared with and without hydrolysis showed that flavonoids and phenolic acids exist predominantly in combined forms such as glycosides and esters. In a freshly squeezed cranberry juice, for instance, 400 mg of total flavonoids and phenolics per liter of sample was found, 56% of which were flavonoids. Quercetin was the main flavonoid in the hydrolyzed products, where it accounted for about 75% of the total flavonoids, while it was absent in the unhydrolyzed products. 

Phenolic compounds in aqueous and solid samples may be estimated as total phenols by colorimetric analysis. The method involves the reactions of phenols with 4-aminoantipyrine in the presence of potassium ferricyanide at pH 8 to form a yellow antipyrine dye (soluble in chloroform), the absorbance of which is measured by a spectrophotometer at 500 nm. 

Phenols are so reactive toward electrophilic aromatic substitution that all unsubstituted positions ortho and para to the hydroxy group are brominated. The brominated compounds so formed are often solids and may be used as derivatives (Sec. 25.12E). Aniline and substituted anilines are also very reactive toward bromine and react analogously however, solubility tests are normally used to distinguish between anilines and phenols. 

Phenolic resins, which are formed as condensation products of formaldehyde and different phenols, form the basis of a unique class of rigid, cross-linked polymers. From a structural point of view, these resins are categorized into two types, one-step (resole) resins and two-step (Novolac) resins. One-step (resole) phenolic resins are formed from phenol and an excess of formaldehyde, in an aqueous catalytic medium. The reaction is terminated before the completion to produce a resin material that may be cross-linked in its final application. Both liquid and solid forms of these resins are available, and are formed by removing water or retaining water from the reaction. Phenolic resole resins are a mixture of the following compounds ... 

For all processes that involve the adsorption step, such as physical processes of separation or catalytic transformations, the usage of solid materials with optimised activity as adsorbents and catalysts is necessary. Various solids, such as porous materials (zeolites—molecular sieves with hierarchical porosities and natural clays), activated carbons, mesoporous silica-based materials, pillared clays and metal oxides, have shown the ability to act as adsorbents or as catalysts for the conversions of previously mentioned atmospheric pollutants. Solid materials are also used for the removal of pollutants that can be found in wastewaters. The possibilities to remove polyaromatic hydrocarbons (PAHs) and heavy metal particles using the adsorptive characteristics of activated carbon and porous materials from wastewaters have been proven [15-17]. The same classes of solids are used for the elimination of organic pollutants form wastewaters by heterogeneous catalytic oxidation processes one of the most important tasks is to eliminate phenolic compounds [13]. 

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