Names and Properties of Phenols

Phenolic resin is one of the common synthetic resins that have been used in a wide range of applications such as paints, adhesives, and composites. Phenolic resin is one of the thermoset class of polymers which has two types, namely resole type and novolac type, the formation of which depends on the synthetic method and catalyst used. Many attempts have been made to enhance the toughness and thermal properties of phenolic resin. By the fundamental concept of hybrid materials preparation, the sol-gel method can be utilized to incorporate inorganic components into the phenolic resin and improve its properties. These systems have been studied by Haraguchi et al. and Lin et al. ... 

A widespread method for determining the induction period for autoxidation of oils and fats consists of passing a continuous stream of air through the heated sample and collecting the volatile acids evolved in a water trap, where they are determined on a real time basis. The time plot usually presents a flat appearance for a certain period and then takes off in an accelerated manner. This test is the basis of several national and international standards (e.g. AOCS Cd 12b-92—oil stability index" ISO 6886—accelerated oxidation test for oxidative stability of fats and oils ) and the design of the Rancimat equipment, where the end determination is based on conductivity measurements . In addition to oxidation stability as determined by the Rancimat method and POV, which negatively affects virgin olive oil stability, other nonstandard properties were proposed for better assessment of the quality of this oil, namely LC determination of Vitamin E (21), colorimetric determination of total polar phenols and UVD of total chlorophyll. ... 

In this chapter we will try to revise what is known about relationships between phenolic composition and sensory properties of red wine, namely color and astringency, although it is quite possible that in the end more questions than answers will be found. 

Thus, two types of active esters are of interest those formed from an acid and a substituted phenol (12-15) and those formed from an acid and a substituted hydroxylamine (16-19). Both types are reactive by virtue of the electron-withdrawing properties of the OR moiety in 2. The level of activation of the substituted phenyl esters varies directly with the electronic effect going from 4-nitrophenyl to 2,4,5-trichlorophenyl, pentachlorophenyl, and pentafluorophenyl, which corresponds with the increasing acidity of the phenols. A diminution in the rate of aminolysis is caused by the presence of a substituent in the ortho position of the ring.f l An additional phenomenon contributes to the reactivity of the esters formed from substituted hydroxylamines, namely anchimeric assistance. Since the anoinolysis of active esters is a bimolecular reaction, it is dependent on concentration and can be forced to completion by an excess of one of the reactants. Aminolysis is also characterized by a pronounced dependence on the polarity of the solvent in particular for the esters formed from substituted phenols, the half-life of a 2,4,5-trichlorophenyl ester in the presence of benzylamine being one hundred times less in dimethylformamide than in benzene. Furthermore, aminolysis is catalyzed by mild acid such as acetic acid. The rate of anoinolysis is slowed if the side chain of the active ester contains a P-methyl substituent. 

Phenols.—The ring hydroxyl compounds take the class name of phenols from the simplest member, hydroxy benzene or phenol. These are true aromatic compounds and in methods of formation, reactions and properties are distinctly different from aliphatic hydroxyl compounds or alcohols. Their outstanding distinction is their marked acid character, the alcohols being neutral (p. 103). This is attributed to the influence of the phenyl radical (CeHs—). The same influence is present in the amino derivatives, for the ring amines, CeHs— NH2, /CH3... 

Some of the factors identified in determining the final properties of these resins are the phenol-formaldehyde ratio, pH, temperature and the type of catalyst (acid or alkaline) used in the preparation of the resin. The phenol-formaldehyde ratio (P/F) (or formaldehyde to phenol ratio, F/P) is a most important factor as it leads to two different classes of synthetic polymers, namely Novolacs and resoles. The first class of resins, Novolacs, is produced by the reaction of phenol with formaldehyde with a P/F > 1 usually under acidic conditions (Scheme 2a). Resoles are produced by the reaction of phenol and formaldehyde with a P/F <1 usually under basic conditions (Scheme 2b). 

Traditionally, phenol is produced from benzene, cresols from toluene and xylenols from xylenes. There are three isomers of xylenes, namely, / -xylene, o-xylene, and m-xylenes. Accordingly, there are six isomers of xylenols which have been mentioned earher vide 1.1. Some of the properties of various xylenols have also been mentioned. Commercially, xylenols have assumed great significance. In some cases, xylenols can be used as substitutes of cresols. However, some of the individual xylenol isomers have importance in organic chemical synthesis. 

The development of ACF and AC cloths is closely related to that of carbon fibers (CFs). This makes that the raw materials used for the preparation of ACFs be, chronologically, the same as for CFs. Thus, in 1966, viscose and acetate cloths were, like for CFs, the first materials used to obtain ACFs [4, 5]. The low yield of the ACFs, and CFs, obtained from the above precursors, oriented the research towards the seek of other raw materials for the preparation of cheaper CFs and ACFs with a higher yield. In this way, ACFs were prepared from 1970 using lignin (with the brand of Kayacarbon ALF), polyvinylchloride [6] (i.e., Saran polymer, already used to obtain ACs) and phenolic precursors [7]. The high yield and the good mechanical properties of the ACFs obtained make these precursors very useful for this application. In fact. Economy and Lin [8] developed ACFs from a phenol formaldehyde precursor, which are commercialized since 1976 under the name of Novolak. In 1980, Kuray Chemical Co. Ltd commercialized ACFs from phenolic resin under the name of Kynol. ... 

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