Hydroxybenzoic acid and derivs

Salicylic Acid and Derivatives. See under Hydroxybenzoic Acid and Derivatives in Vol 7, H236-L to H238-L. Addns to this entry are ... 

Amino-2-hydroxybenZOiC acid. This derivative (18) more commonly known as 4-aminosa1icy1ic acid, forms white crystals from ethanol, melts with effervescence and darkens on exposure to light and air. A reddish-brown crystalline powder is obtained on recrystallization from ethanol —diethyl ether. The compound is soluble ia dilute solutioas of nitric acid and sodium hydroxide, ethanol, and acetone slightly soluble in water and diethyl ether and virtually insoluble in benzene, chloroform or carbon tetrachloride. It is unstable in aqueous solution and decarboxylates to form 3-amiaophenol. Because of the instabihty of the free acid, it is usually prepared as the hydrochloride salt, mp 224 °C (dec), dissociation constant p 3.25. 

Glucose (65) kits Commercial kits are based on the enzymatic process shown in equation 16, followed by a chromogenic oxidation process catalyzed by peroxidase, similar to equation 27, involving 4- aminoantipyrine (81) and a phenol or aniUne derivative, leading to a quinoneimine dye. Among the latter aromatic substrates in use are A -ethyl-Al-(2-hydroxy-3-sulfopropyl)-3, 5- dimethoxyaniline (92) , phenol , p-hydroxybenzoic acid and p-hydroxybenzenesidfonate other chromogenic reactions are peroxidase-catalyzed oxidation of iV,iV,iV, iV -tetramethyl-p-phenylenediamine (89) and D-ditoluidine (93) . d... 

TABLE 3. Thermal properties of copolyesters derived from 4-hydroxybenzoic acid and 6-(4 -acetoxyphenyl)-2-naphthoic acid. 

Among the derivates of HBAs, further compounds have been identified. GUntert et al. (1986) identified ethyl esters of vanillic acid and p-hydroxybenzoic acid, and methyl esters of vanillic acid and protocatechuic acid. Ethyl esters of protocatechuic acid and vanillic acid, as well as the glucose ester of vanillic acid, were isolated from a German Riesling wine (Baderschneider and Winterhalter 2001). Analytically, HBA are mostly determined as trimethylsilane derivatives by using... 

As apparent from their stmctures, many benzoic acid derivatives are directly formed from shikimic acid by dehydration, dehydrogenation, and enolization reactions. Gallic acid is a component of gallotannins common in some plants that are used in the tanning of animal hides to make leather. Astringency of some foods and beverages, especially coffee, tea, and wines, is because of their constituent tamuns. Other benzoic acid derivatives that occur in plants include protocatechuic acid, 4-hydroxybenzoic acid, and salicylic acid. 

Fig. 7.10. Structures of PAR (2-pyridylazo) and PAR derivative (2-pyridylazo) (3-hydroxy-5-phenoxy)ethylpentanoic acid—PAGPA), QABA 4-(3-quinolinoazo)-3-hydroxybenzoic acid) and QABA protein labeled cbelator (QABA-AP).

A whole series of high-performance polyester LCPs was introduced in 1985. They were assembled from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. Polyarylates (PARs) - amorphous phenolic esters derived from aromatic dicarboxylic acids (mixtures of terephthalic acid and isophthalic acid) and biphenols such as bisphenol A - are produced by Amoco (Ardel ), Celanese (Durel ) and DuPont (Arylon ) at a volume of approx. 2000 t/a. 

Phenol acids are phenols in which there is also a carboxylic acid group attached to the benzene ring. They include salicylic acid (ortho-hydroxybenzoic acid) and para-hydroxy-benzoic acid (Figure 25.8). Acetylsalicylic acid (aspirin) and sodium salicylate are derivatives of salicylic acid. Like phenol, they have antipyretic and analgesic properties. The methyl, ethyl and propyl esters of para-hydroxybenzoic acid (parabens) are used as preservatives in pharmaceuticals, cosmetics and foodstuffs. 

Bourbonniere and Meyers (unpublished) hydrolyzed humic substances from Lake Huron sediments with 5N NaOH at 170°C for 12 hours under a nitrogen atmosphere and found the following organic acids -Ci6 and n-Cig monocarboxylic acids lactic acid, 2-hydroxybutanoic acid, 3,4-dihydroxy-butanoic acid, oxalic acid, and succinic acid. It was proposed that the smaller organic acids were derived from cellulose-related materials. 2-Hy-droxybenzoic acid, 4-hydroxybenzoic acid, 2,5-dihydroxy-3-pentenoic acid, and vanillic acid were also observed. It was believed that 4-hydroxybenzoic acid and vanillic acid originated from lignin and that the ratio of 3,4-dihy-droxybutanoic acid to vanillic acid indicates the proportion of cellulose to lignin. The proportion was in the order of fulvic acid > humic acid > humin. 

Benzo[c] cinnoline aldehydes are as yet unknown. The 2- and 3-acetyl derivatives have been prepared, but the majority of known compounds relevant to this section are mono- and dicarboxylic acid derivatives. These include the 2-, - - 3-, ° and 4. - o2.J55,i57 monoacids and esters, the lactone of 10-hydroxybenzo[c]cinnoline-l-carboxylic acid, some halogeno- and methyl-substituted 2- and 4. carboxylic acids, and the 2,9-, 3,8-, - - and 4,7- dicarboxylic acids and derivatives. These compounds have been obtained by ring synthesis, or, in the case of 2-methylbenzo[c]dnnoline-9-carboxylic acid, by side-chain oxidation, " rather than by the introduction of substituents into benzo[c] cinnoline. Benzo[c]cinnoline-l-carbonitrile has been prepared, albeit in low... 

Hydroxybenzophenones have been derived by various intermolecular acylations. Thus 4-hydroxybenzoic acid and phenol with a catalytic amount of 98% methanesulphonic acid afforded, after 4.5 hours at SOX, 4,4 -dihydroxybenzophenone in 51% yield (ref.20). 

Salicylic Acid, HO.C6H4.COOH(l, 2), is the most important hydroxybenzoic acid. It derives its name from salicin, a glucoside obtained from the bark of the willow salix) which yields glucose and o-hydroxybenzyl alcohol on hydrolysis. 

Protocatechuic acid is the main benzoic acid derivative in onions although jD-hydroxybenzoic acid and vanillic acid may also be observed [64]. In the outer dry coloured skins protocatechuic acid may represent up to 2% of plant material. The internal pulpy tissues show lower concentrations (ca 20 mg/kg f.w.). Unlike the bulbs, the green leaves of onions contain almost exclusively ferulic acid and jD-coumaric acid derivatives. 

FIGURE Al.l Simple separation of four small molecules for calculations of practical use. Separation of mesityl oxide [an EOF (neutral) marker], p-hydroxyphenylacetic acid, p-hydroxybenzoic acid, and benzoic acid [in borate buffer, pH 8.3 3-s pressure ( 0.5 psi) injection]. Analysis was carried out on a Beckman P/ACE System 2050. Separation conditions capillary, 50 /rm x 40 cm (effective length), 47 cm total length bare fused silica T, 28°C voltage, 25 kV buffer, 100 mM borate, pH 8.3 detection, 200 nm. Inset data derived from System Gold (vs7.1) data management software. 

The Kolbe-Schmitt reaction has been applied to the preparation of other o-hydroxybenzoic acids. Alkyl derivatives of phenol behave very much like phenol itself. Phenols that bear strongly electron-withdrawing substituents usually give low yields of carboxylated products their derived phenoxide anions are less basic, and the equilibrium constants for their carboxylation are smaller. 

The m-CyN unit is derived from the shikimate pathway and possesses a Cj group and an amino group meta-disposed on a benzene ring. For example, some of the alkaloids described in this chapter are established to be derived from 3-amino-5-hydroxybenzoic acid, and other isomers are also involved in the biosynthesis of various alkaloids. 

Figure 2 Structure of phenolic compounds. (A) Phenolic acids (i) derivatives of o- and p-hydroxybenzoic acid, (ii) derivatives of cinnamic acid (B) flavonoids (C) anthocyanins and (D) Tannins.

Distribution of Hydroxybenzoic Acids and Their Derivatives Biological Activity Allelopathy References... 

Ghlorobenzoic acid is a degradation product of some RGBs. It is now known that certain bacteria are able to dehalogenate 4-chlorobenzoic acid by an enzymatic nucleophilic aromatic substitution reaction. The product is 4-hydroxybenzoic acid, and a mechanism for this enzyme-catalyzed process is shown here. The sequence begins with the thioester of 4-chlorobenzoic acid derived from coenzyme A (GoA) ... 

Stockman, H., Schwarz, K. and Huyn-Ba, T. The influence of various emulsifiers on the partitioning and antioxidant activity of hydroxybenzoic acids and their derivatives in oil-in-water emulsions. J. Am. Oil Chem. Soc. 77, 535-542 (2000). 

Hydroxybenzoic Acids, Hydroxycinnamic Acids, and Derived Compounds. 2346... 

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