Hydrolysis Hydroxybenzoic acid

The selective alkylation of a chemically distinct phenohc site on a perfluorinated aromatic has been achieved following a polymer assisted solution phase protection of an alternative o-hydroxybenzoic acid unit as the dioxin-4-one (19) (Scheme 2.45) [66]. A diverse set of 22 different alkyl and benzyl bromides were then attached to the free phenol using cesium fluoride as the base, followed by treatment with Amberlyst 15 and Amberlyst A-21 as the work-up. Subsequent hydrolysis of the dioxin-4-one group with NaOH proceeded smoothly and was quenched... 

Soil. In soils, Klebsiella pneu/nonrae metabolized bromoxynil to 3,5-dibromo-4-hydroxybenzoic acid and ammonia (McBride et al., 1986). In soil, bromoxynil undergoes nitrile and then amide hydrolysis yielding 3,5-dibromo-4-hydroxybenzoic acid and 3,5-dibromo-4-hydroxybenzamide (Smith, 1988). Degradation was rapid in a heavy clay soil, sandy loam, and clay loam. After 1 wk, only 10% of the applied dosage was recovered. 

A sample of aspirin of accurately known mass is reacted with a known excess amount of sodium hydroxide solution. The alkali first catalyses the hydrolysis of aspirin to ethanoic acid and salicylic acid (2-hydroxybenzoic acid) and then neutralises these acids. The overall balanced equation for the reaction is ... 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

Liquid dosage forms which are disperse systems (colloidal, i.e., microspheres, nanoparticles, and micelles suspensions and emulsions) often contain preservatives which are methyl, ethyl, propyl, and butyl esters of para-hydroxybenzoic acid in various combinations. A typical example is the antacid suspensions which have high pH values which make the esters of the preservatives susceptible to hydrolysis. One way to circumvent this problem is to use several preservatives in combination with the hope that some quantities of the preservatives will remain to prevent the suspension from microbial attack. A report showing the assay of the four esters and the parent acid (one of the decomposition products) in drug products in which all the preservatives were used has been given [13]. 

Alkaline hydrolysis of pentafluorobenzoic acid gives a high yield of perfluoro-4-hydroxybenzoic acid (4),35 -37... 

Enantioselective Birch reduction-alkylation The chiral benzoic acid derivative 1, prepared by condensation of o-hydroxybenzoic acid with L-prolinol followed by cyclization (Mitsunobu reaction), undergoes Birch reduction (K, NH3, THF, t-butyl alcohol) followed by alkylation with C2H5I to give essentially only 2. Acid hydrolysis returns the chiral auxiliary and provides the 2-alkylated cyclo-hexenone 3. 

Transgenic plants containing a nitrilase specific for the herbicide bromoxynil (= 3,5-dibromo-4-hydroxybenzonitrile)have also been developed [93] the Cal-gene company transformed tobacco plants with the bacterial Klebsiella ozaenae gene encoding nitrilase [94] that detoxifies the herbicide by hydrolysis (conversion of bromoxynil to 3,5-dibromo-4-hydroxybenzoic acid), resulting in the establishment of the herbicide-resistant transgenic plants. 

Hydrolysis experiments with the second siderophore, parabactin, gave four products 2,3-dihydroxybenzoic acid, 2-hydroxybenzoic acid, l-threonine, and spermidine, in a ratio of 2 1 1 1. It was shown that parabactin is enzymatically built up from 34, L-threonine, and 2-hydroxy-benzoic acid. Furthermore, it was shown that the threonine amino group is... 

The hydrolysis product p-hydroxybenzoic acid has practically no antimicrobial activity. 

Main components During fermentation, vanillin (up to app. 2.5%) is formed from the odourless glucovanillin by enzymatic hydrolysis. Its aroma is rounded-off and modified by p-hydroxybenzoic acid, p-hydroxybenzaldehyde, p-hydroxybenzyl methyl ether, vanillyl alcohol, vanillic acid, cinnamic acid ester and various other trace constituents [291, 292], Also the resins, gums, amino acids and other organic acids contribute to the typical flavour of the cured beans [293[. For further constituents and characterisations of fruits from different growing areas see [294[. 

The hydrolysis of alkyl salicylates often a prolonged process under alkaline conditions can be effected in quantitative yield with trifluoroacetic ackJ. Thus methyl 2-hydroxybenzoate in trifluoroacetic acid (10 moles) sealed in a thick glass tube, after heating at 100°C for 13 hours, gave 2-hydroxybenzoic acid in 100% yield (ref.91). 

When carbon tetrachloride is used instead of chloroform a similar condensation takes place the compound formed in this way is a derivative of benzotrichloride and on hydrolysis yields a mixture of ortho- and para-hydroxybenzoic acid. 

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. 

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