Polyhydroxy phenol

The other class of primary antioxidants are the phenols (hindered phenols, hindered bisphenols, hindered thiobisphenols, polyhydroxy phenols) (Fig. 34). Phenolic antioxidants are generally used when the discolouration of the amine antioxidants cannot be tolerated. Phenols may produce coloured reaction products (yellow, tan or pink) but the discolouration is significantly less than produced with amines. 

The lower members of the homologous series of 1. Alcohols 2. Aldehydes 3. Ketones 4. Acids 5. Esters 6. Phenols 7. Anhydrides 8. Amines 9. Nitriles 10. Polyhydroxy phenols 1. Polybasic acids and hydro-oxy acids. 2. Glycols, poly-hydric alcohols, polyhydroxy aldehydes and ketones (sugars) 3. Some amides, ammo acids, di-and polyamino compounds, amino alcohols 4. Sulphonic acids 5. Sulphinic acids 6. Salts 1. Acids 2. Phenols 3. Imides 4. Some primary and secondary nitro compounds oximes 5. Mercaptans and thiophenols 6. Sulphonic acids, sulphinic acids, sulphuric acids, and sul-phonamides 7. Some diketones and (3-keto esters 1. Primary amines 2. Secondary aliphatic and aryl-alkyl amines 3. Aliphatic and some aryl-alkyl tertiary amines 4. Hydrazines 1. Unsaturated hydrocarbons 2. Some poly-alkylated aromatic hydrocarbons 3. Alcohols 4. Aldehydes 5. Ketones 6. Esters 7. Anhydrides 8. Ethers and acetals 9. Lactones 10. Acyl halides 1. Saturated aliphatic hydrocarbons Cyclic paraffin hydrocarbons 3. Aromatic hydrocarbons 4. Halogen derivatives of 1, 2 and 3 5. Diaryl ethers 1. Nitro compounds (tertiary) 2. Amides and derivatives of aldehydes and ketones 3. Nitriles 4. Negatively substituted amines 5. Nitroso, azo, hy-drazo, and other intermediate reduction products of nitro com-pounds 6. Sulphones, sul-phonamides of secondary amines, sulphides, sulphates and other Sulphur compounds... 

Polyhydroxy- phenols. amino acids, di- and polyamino compounds, amino alcohols. Sulphonic acids. Sulphinic acids. Salts. sulphinic acids, aminosulphonic acids and sulphonamides. Some diketones and /3-keto esters. Ethers and acetals. Lactones. Acyl halides. Diaryl ethers. intermediate reduction products of nitro compounds. Sulphones, sulphonamides of secondary amines, sulphides, sulphates and other sulphur compounds. 

Bromo derivatives are often difficult to prepare, particularly in the case of polyhydroxy phenols which oxidise easily. 

This suggests that the bark extract responds as a highly reactive polyhydroxy phenolic compound comparable to resorcinol since gelation time for each is immediate in the presence of formaldehyde hydrochloric acid at room temperature (14) ... 

Tannin is a commercially important substance that can be extracted from the wood, bark, or leaves of certain trees and other plants. Tannins are complex dark-colored polyhydroxy phenolic compounds, related to catechol or pyrogallol, and vary in composition from species to species. They have the important property of combining with the proteins of animal skins to produce leather. 

Formaldehyde and polyhydroxy phenols, or their oligomeric derivatives, " may also lead to erosslinking by reaetion with amino groups located in the macromolecular chain, thus producing derivatives with structure 432. 

Lignin is a major component of plants where it serves as a binding agent for cellulose and other materials, and the kraft process of paper production, heating with alkali and sulfide, produces polyhydroxy phenolic, carboxylic acid, and sulfide functional groups in a soluble black liquor mixture [5]. Acidification precipitates this modified lignin as a powder, hereafter referred to as limin, a 20630% by product in the manufacture of paper. 

Most of the primary antioxidants that act as chain breakers or free radical interceptors are mono- or polyhydroxy phenols with various ring substitutions. 

The Kolbe-Schmitt reactions of polyhydroxy phenols such as resorcinol, pyrogallol and phloroglucinol are exceptionally carried out in aqueous solution.[6] Any explanation has not yet been given to the reason of the exception. Kinetic studies on the carboxylation of resorcinol (ROH) with hydrogencarbonate (KHCO-O were carried out in aqueous solutions. 

Finally, there still remains the problem of the degradation products of the estrogens. The crucial question here is whether the degradation products are mainly oxygenated nonsteroidal compounds or polyhydroxy phenolic steroids. A complete picture of the metabolism of estrogens will be obtained only after this problem has been solved. 

Polyhydroxy phenols. Representative chemical structures of the various phenolic antioxidants are shown in Figure 2. 

Novalac resins can be produced from alkyl phenols, aryl phenols and polyhydroxy phenols to obtain special properties and Table 13.5 lists resins derived from o-cresolformaldehyde and ECH. 

Several artificial smoke flavors or liquid smokes are available on the market. These differ in their method of manufacture and in the quality and intensity of the smoke flavor, although all are derived from thermal decomposition of hardwood. The effect of several of these preparations on fat oxidation has been tested (Watts and Faulkner, 1954) and found to vary from no protection or even a slight pro-oxidant effect at one extreme to a strong antioxidant effect in concentrations of a few hundredths per cent of the commercial preparation at the other. The antioxidant activity of the latter preparation thus approaches that of the pure phenolic inhibitors. Discolorations with iron salts, such as occur with gallates and other polyhydroxy phenols, do not take place with these liquid smokes. 

Murugananthan, M., G. Bhaskar Raju, and S. Prabhakar. 2005. Removal of tannins and polyhydroxy phenols by electro-chemical techniques. J. Chem. Technol. Biotechnol. 80 1188-1197. 

Each major manufacturer (e.g. Ciba Geigy, Dow, Shell, Du Pont) of epoxy resins has an extensive range of products based on the glycidation of epichlorohydrin (EPC) and polyhydroxy phenols (or polybasic acids). The most signiricant series of resins for the can coatings industry is based on the condensation reaction of EPC and diphenylolpropane (4,4-isopropylidenediphenol, Bisphenol A) as illustrated in Figure 2-18. 

Pclyhydric Phenols, Methylol derivatives of di- or polyhydroxy phenols aie not readily isolated since they react with considerable rapidity to... 

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