Phenolic acids classification

Phenol sulfonic acid liquid Sulfocarbolic acid Classification Aromatic organic compd. 

A straightforward classification attempts to divide the broad category of phenolics into simple phenols and polyphenols, based exclusively on the number of phenol subunits present, but many plant phenolic compounds are polymerized into larger molecules. Thus, the term plant phenolics encompasses simple phenols, phenolic acids, coumarins, flavonoids, stilbenes, hydrolyzable and condensed tannins, lignans, and hgnins [4]. 

There is considerable overlap between work on phenolic acids and that on aromatic carboxylic acids. Relatively few aromatic acids other than benzoic acid and the isomeric dicarboxylic acids have major industrial significance. Hydroxybenzoic acids, as either salicylic, 4-hydroxybenzoic or gallic acid (3,4,S-trihydroxybenzoic acid), tend to appear under both phenolic and aromatic acid classifications. In this section as with the previous one on phenols, a summary of the systems which have been used and the applications of TLC in the analysis of derivatives of aromatic acids is given. 

Phenols are considered important bioactive compounds isolated from plants because of their potential role in human health management. Phenolic structure consists of an aromatic ring with attached hydroxyl groups. Based on structural differences, phenols can be classified into groups and components. The broad classifications include phenolic acids, stilbenes, lignans, and fiavonoids [4]. 

The imides, primaiy and secondary nitro compounds, oximes and sulphon amides of Solubility Group III are weakly acidic nitrogen compounds they cannot be titrated satisfactorily with a standard alkaU nor do they exhibit the reactions characteristic of phenols. The neutral nitrogen compounds of Solubility Group VII include tertiary nitro compounds amides (simple and substituted) derivatives of aldehydes and ketones (hydrazones, semlcarb-azones, ete.) nitriles nitroso, azo, hydrazo and other Intermediate reduction products of aromatic nitro compounds. All the above nitrogen compounds, and also the sulphonamides of Solubility Group VII, respond, with few exceptions, to the same classification reactions (reduction and hydrolysis) and hence will be considered together. 

The most characteristic reaction of butadiene catalyzed by palladium catalysts is the dimerization with incorporation of various nucleophiles [Eq. (11)]. The main product of this telomerization reaction is the 8-substituted 1,6-octadiene, 17. Also, 3-substituted 1,7-octadiene, 18, is formed as a minor product. So far, the following nucleophiles are known to react with butadiene to form corresponding telomers water, carboxylic acids, primary and secondary alcohols, phenols, ammonia, primary and secondary amines, enamines, active methylene compounds activated by two electron-attracting groups, and nitroalkanes. Some of these nucleophiles are known to react oxidatively with simple olefins in the presence of Pd2+ salts. Carbon monoxide and hydrosilanes also take part in the telomerization. The telomerization reactions are surveyed based on the classification by the nucleophiles. 

Proanthocyanidins and Procyanidins - In a classical study Bate-Smith ( ) used the patterns of distribution of the three principal classes of phenolic metabolites, which are found in the leaves of plants, as a basis for classification. The biosynthesis of these phenols - (i) proanthocyanidins (ii) glycosylated flavonols and (iii) hydroxycinnamoyl esters - is believed to be associated with the development in plants of the capacity to synthesise the structural polymer lignin by the diversion from protein synthesis of the amino-acids L-phenylalanine and L-tyro-sine. Vascular plants thus employ one or more of the p-hydroxy-cinnarayl alcohols (2,3, and 4), which are derived by enzymic reduction (NADH) of the coenzyme A esters of the corresponding hydroxycinnamic acids, as precursors to lignin. The same coenzyme A esters also form the points of biosynthetic departure for the three groups of phenolic metabolites (i, ii, iii), Figure 1. 

For phenolics in fruit by-products such as apple seed, peel, cortex, and pomace, an HPLC method was also utilized. Apple waste is considered a potential source of specialty chemicals (58,62), and its quantitative polyphenol profile may be useful in apple cultivars for classification and identification. Chlorogenic acid and coumaroylquinic acids and phloridzin are known to be major phenolics in apple juice (53). However, in contrast to apple polyphenolics, HPLC with a 70% aqueous acetone extract of apple seeds showed that phloridzin alone accounts for ca. 75% of the total apple seed polyphenolics (62). Besides phloridzin, 13 other phenolics were identified by gradient HPLC/PDA on LiChrospher 100 RP-18 from apple seed (62). The HPLC technique was also able to provide polyphenol profiles in the peel and cortex of the apple to be used to characterize apple cultivars by multivariate statistical techniques (63). Phenolic compounds in the epidermis zone, parenchyma zone, core zone, and seeds of French cider apple varieties are also determined by HPLC (56). Three successive solvent extractions (hexane, methanol, aqueous acetone), binary HPLC gradient using (a) aqueous acetic acid, 2.5%, v/v, and (b) acetonitrile fol-... 

A non-parametric classification technique was recently proposed by Schatzki and Vandercook (172) to evaluate orange juice. The system considers the total sugars, reactive phenols, total amino acids, arginine and y -aminobutyric acid. With the para-... 

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ACGIH TLV TWA 2 mg(Al)/m3 DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Moderately toxic by ingestion. Experimental teratogenic and reproductive effects. Mutation data reported. The dust is an irritant by ingestion, inhalation, and skin contact. Highly exothermic polymerization reactions with alkenes. Incompatible with nitrobenzenes or nitrobenzene + phenol. Highly exothermic reaction with water or steam produces toxic ftimes of HCl. See also ALUMINUM COMPOUNDS, CHLORIDES, and HYDROCHLORIC ACID. 

Classification. Phenolic foam is divided broadly into two categories. One is the novolac type and the other is the resol type (see Figure 55). In the novolac type, phenol and formaldehyde react in the presence of an acid catalyst and link the linear condensation product by a methylene bond. The basic curable crosslinking agent, such as hexamethylene tetramine and blowing agent are added to the linear condensation product and the resultant product is molded at elevated temperatures and high pressure. 

If the classification of lipides were to be examined, some points would have to be made clear. In the first place, a definition of lipides should be made that excludes esters of mineral acids such as orthophosphoric acid. The phosphoric esters of alcohols and phenols are alkalino-stable—excluding those possessing a free carbonyl group moreover, they are not very soluble in organic solvents. The definition of lipides should therefore take into account the hydrolysis of ester linkage by heating with alkalies and the solubility of lipides in some organic solvents. 

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