Other Common Phenols

Chromium is highly acid-resistant and is only attacked by hydrochloric, hydrofluoric, and sulfuric acids. It is also resistant to other common corroding agents including acetone, alcohols, ammonia, carbon dioxide, carbon disulfide, foodstuffs, petroleum products, phenols, sodium hydroxide, and sulfur dioxide. 

Phenol, the simplest and industrially more important phenolic compound, is a multifunctional monomer when considered as a substrate for oxidative polymerizations, and hence conventional polymerization catalysts afford insoluble macromolecular products with non-controlled structure. Phenol was subjected to oxidative polymerization using HRP or soybean peroxidase (SBP) as catalyst in an aqueous-dioxane mixture, yielding a polymer consisting of phenylene and oxyphenylene units (Scheme 19). The polymer showed low solubility it was partly soluble in DMF and dimethyl sulfoxide (DMSO) and insoluble in other common organic solvents. 

As seen in the retro-synthetic Scheme 5.3, intermediate 15 is useful for both routes. The choice of benzyl protection group was made based on the robust stability of benzyl phenol ethers toward most reactions and several possible avenues to remove it, although it was reported from Medicinal Chemistry that benzyl group removal via hydrogenolysis posed challenges in this compound. The choice of iodide substitution was born out of the known high reactivity of iodides in the Ullmann-type coupling reaction with alcohols and the robust stability of aryl iodides in many other common reactions. 

Carboxylic acids are soluble in either aqueous NaOH or NaHCOj. The other common group of organic acids, phenols, are weaker than the carboxylic acids. Phenols are only soluble in aqueous NaOH. Di- and trinitrophenols are stronger acids than most other phenols, so they are also soluble in aqueous NaHCOj. 

Many different solvent developers have been used in the separation of sugars and related compounds. Three of these, phenol-water, collidine-water, and 1-butanol-acetic acid-water,27 also commonly employed in the resolution of amino acid mixtures, are widely used. Other commonly used solvent developers are 1-butanol-ammonia-water, 1-butanol-ethanol-water,27 1-butanol-pyridine-water,61 ethyl acetate-acetic acid-water, and ethyl acetate-pyridine-water.26... 

A hindered phenol commonly used as an antioxidant is 2,6-di-terf-butyl-4-meth-ylphenol (also known as butylated hydroxy toluene or "BHT"). Structures of BHT and other hindered phenol antioxidants are shown in Figure 8.3. Many of these complex structures have lengthy lUPAC names and are frequently called by trade names assigned by manufacturers, e.g., Irganox 1135 from Ciba (now BASF). 

Further cleavage of the chain with double bonds formed after the alcohol elimination explains the formation of some aromatic compounds such as benzene, toluene, styrene, benzaldehyde, etc. Two other common small molecules in the pyrolysate are phenol and the corresponding acid of the side chain substituent. 

Phenol, the simplest and most important phenolic compound in industrial fields, is a multifunctional monomer for oxidative polymerization, and hence, conventional polymerization catalysts afford an insoluble product with uncontrolled structure. On the other hand, the peroxidase catalysis induced the polymerization in aqueous organic solvent to give a powdery polymer consisting of phenylene and ox-yphenylene units showing relatively high thermal stability (Scheme 2).5,6 In the HRP and soybean peroxidase (SBP)-catalyzed polymerization in the aqueous 1,4-dioxane, the resulting polymer showed low solubility the polymer was partly soluble in N,N-dimethylformamide (DMF) and dimethyl sulfoxide and insoluble in other common organic solvents.5 On the other hand, the aqueous methanol solvent af-... 

The range of applications is somewhat restricted, since the cost of most polymeric adsorbents is typically about ten times more than that of other common adsorbents. In some instances, polymeric materials are the only choice. In other cases, they compensate for the cost differential by yielding much better performance, especially for high value-added uses. Current applications include recovery and purification of antibiotics and vitamins, decolorization, decaffeination, hemop-erfusion, separation of halogenated light orgaifics from water, and treatment of certain industrial wastes such as aqueous phenolics and VOC recovery from off-gases. 

By choosing an eluent that does not dissociate strongly it is possible to eliminate the suppressor column. Such compounds as phenol, pK, = 1.3 x 10 , or phthalic acid, K, = 1.3 x 10 K,2 = 3.9 x 10, are examples. When compounds of this type are used the system is called single column ion chromatography (SCIC). Table 24-2 lists some of the other common eluents for anions. 

The degradation of lignin and other plant polyphenols releases relatively large quantities of free phenolic acids to the soil. These compounds are potentially important because of their pronounced antifungal and phytotoxic activity. The five most common phenolic acids, all related to the lignins of grasses, conifers and deciduous trees, are / -hydroxybenzoic acid, vanillic acid (26), ferulic acid (27), syringic acid (28), and p-coumaric acid (29). Quantitative studies are rare, but the most abundant... 

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