Acids salicylic acid

Many pharmaceutical compounds contain chromophores that make them suitable for analysis by UV/Vis absorption. Products that have been analyzed in this fashion include antibiotics, hormones, vitamins, and analgesics. One example of the use of UV absorption is in determining the purity of aspirin tablets, for which the active ingredient is acetylsalicylic acid. Salicylic acid, which is produced by the hydrolysis of acetylsalicylic acid, is an undesirable impurity in aspirin tablets, and should not be present at more than 0.01% w/w. Samples can be screened for unacceptable levels of salicylic acid by monitoring the absorbance at a wavelength of... 

The most common NSAID is aspirin, or acctylsalicvlic acid, whose use goes back to the late 1800s. It had been known from before the time of Hippocrates in 400 bc that fevers could be lowered by chewing the bark of willow trees. The active agent in willow bark was found in 1827 to be an aromatic compound called salicin, which could be converted by reaction with water into sal- icy I alcohol and then oxidized to give salicylic acid. Salicylic acid... 

Conversion of Acid Anhydrides into Esters Acetic anhydride is often used to prepare acetate esters from alcohols. For example, aspirin (acetylsalicylic acid) is prepared commercially by the acetylation of o-hydroxybenzoic acid (salicylic acid) with acetic anhydride. 

The iodometric method has the advantage over the permanganate method (Section 10.95) that it is less affected by stabilisers which are sometimes added to commercial hydrogen peroxide solutions. These preservatives are often boric acid, salicylic acid, and glycerol, and render the results obtained by the permanganate procedure less accurate. 

Gompper et al. (1968) determined the ratio of the two final products obtained from 2-diazoniobenzenecarboxylate in the presence of furan, namely the cycloaddition product 8.31 and 2-hydroxybenzoic acid (salicylic acid). This ratio depends on the water concentration but is independent of the concentration of added furan. This observation is consistent with the stepwise formation of benzyne (route A) involving... 

As the solvent mixture also contained 225 mg of tetramethyl ammonium hydroxide pentahydrate per liter at a high water content (75%), the surface of the reverse phase would have been largely covered with the tetramethyl ammonium hydroxide pentahydrate. This would have acted as an adsorbed ion exchange stationary phase. It is clear that the free acids, salicylic acid, acetylsalicylic acid (aspirin) and benzoic acid were retained largely by ionic interactions with adsorbed basic ion exchanger and partly by dispersive interactions with the exposed reversed phase. The acetaminophen and the caffeine, on the other hand, being unionized substances, were retained only by dispersive interactions with the exposed reversed phase. 

Bromomethyl-3-methylquinoxaline (273) and m-hydroxybenzoic acid (274) gave either 2-(m-hydroxybenzoyloxymethyl)-3-methylquinoxaline (275) [KOH (1 mol), EtOH, reflux, 2h 69%] or 2-(m-carboxyphenoxymethyl)-3-methylquinoxaline (276) [KOH (2 mol), EtOH, 50°C—>reflux, 1 h 44%] p-hydroxybenzoic acid reacted similarly but o-hydroxybenzoic acid (salicylic acid) gave only the isomer of product (275) even in the presence of KOH (2 mol). It would seem that the substrate (275) preferred to react at the phenolic anion rather than at the carboxylate anion when both were present... 

The complexes of aromatic hydroxy carboxylic acids (salicylic acid and its isomers) with [Bu2Sn(IV)] and [Ph3Sn(IV)] were obtained. The FT-IR and Raman spectra clearly demonstrated that the organotin(IV) moieties react with the O, O) atoms of the ligands. It was found that in most cases the -COO group chelated to the central atoms, but monodentate coordination was also observed. The complexes probably have polymeric structures. 

Table 6.1 Formulations of salicylic acid salicylic acid ointment...

Alteration of Membrane Permeability. The ability of allelochemicals to alter membrane permeability and thus inhibit mineral absorption has been investigated in detail with only phenolic acids. Salicylic acid induced the efflux of PO5 (28) and 1C" (42) from barley roots, but -hydroxybenzoic acid did not cause the efflux of K+... 

EL Parrott, M Simpson, DR Flanagan. Dissolution kinetics of a three-component solid II Bezoic acid, salicylic acid, and salicylamide. J Pharm Sci 72 765-768, 1983. 

Recently, Prasad et al. cloned a mammalian Na+-dependent multivitamin transporter (SMVT) from rat placenta [305], This transporter is very highly expressed in intestine and transports pantothenate, biotin, and lipoate [305, 306]. Additionally, it has been suggested that there are other specific transport systems for more water-soluble vitamins. Takanaga et al. [307] demonstrated that nicotinic acid is absorbed by two independent active transport mechanisms from small intestine one is a proton cotransporter and the other an anion antiporter. These nicotinic acid related transporters are capable of taking up monocarboxylic acid-like drugs such as valproic acid, salicylic acid, and penicillins [5], Also, more water-soluble transporters were discovered as Huang and Swann [308] reported the possible occurrence of high-affinity riboflavin transporter(s) on the microvillous membrane. 

NSAIDs) has been reported [36]. As shown in Table 8.3, the hydrolysis of the methyl esters in human plasma proceeds far too slowly to be of therapeutic interest, with tm values ranging from ca. 5 to 150 h. In contrast, the carbamoylmethyl benzoates are hydrolyzed very rapidly (perhaps too rapidly ) with tm values in the order of minutes. But Table 8.3 also illustrates another important point, namely the marked influence of the acyl moiety on the rate of hydrolysis, with a more than 500-fold difference between the smallest and the largest acid (salicylic acid and sulindac, respectively). 

A review by Galli et al. describes several buffer-absorbing chromophores as co-ions. These include phthalate, PDG (2,6-pyridinedicarboxylic acid), PMA (1,2,4,5-benzenetetra-carboxylic acid or pyromellitic acid), TMA (trimellitic acid), MES, 2,4-dihydrobenzoic acid with s-aminocaproic acid, p-hydroxybenzoate, p-anisate, 3,5-dinitrobenzoic acid, salicylic acid with TRIS, benzoic acid with tris (hydroxymethyl)aminomethane (TRIS), and many others. On the other hand, some inorganic chromophores such as chromate (Figure 9) or molybdate may be added to a buffer. A BGE-containing chromate should have a pH above 8, because it precipitates below this value. The advantage of a TRIS buffer or buffers at around pH 6 is that carbonate will not interfere with the separation because it is not soluble in TRIS or at lower pHs. 

In pond water, carbaryl degraded very rapidly to 1-naphthol. The latter degraded, presumably by Flavobacterium sp., into hydroxycinnamic acid, salicylic acid, and an unidentified compound (HSDB, 1989). Four d after carbaryl (30 mg/L and 300 ng/L) was added to Fall Creek water, >60% was mineralized to carbon dioxide. At pH 3, however, <10% was converted to carbon dioxide (Boethling and Alexander, 1979). Under these conditions, hydrolysis of carbaryl to 1-naphthol was rapid. The authors could not determine how much carbon dioxide was attributed to biodegradation of carbaryl and how much was due to the biodegradation of 1-naphthol (Boethling and Alexander, 1979). Hydrolysis half-lives of carbaryl in filtered and sterilized Hickory Hills (pH 6.7) and U.S. Department of Agriculture Number 1 pond water (pH 7.2) were 30 and 12 d, respectively (Wolfe et al., 1978). 

Uses Antiseptic and disinfectant pharmaceuticals dyes indicators slimicide phenolic resins epoxy resins (bisphenol-A) nylon-6 (caprolactum) 2,4-D solvent for refining lubricating oils preparation of adipic acid, salicylic acid, phenolphthalein, pentachlorophenol, acetophenetidin, picric acid, anisole, phenoxyacetic acid, phenyl benzoate, 2-phenolsulfonic acid, 4-phenolsulfonic acid, 2-nitrophenol, 4-nitrophenol, 2,4,6-tribromophenol, 4-bromophenol, 4-/ert-butylphenol, salicylaldehyde, and many other organic compounds germicidal paints laboratory reagent. 

Take aspirin, for example. It has its origins in salicin, the active ingredient in willow bark. When salicin is hydrolysed it produces glucose and salicyl alcohol the latter can be oxidised to salicylic acid. Salicylic acid was also used as a medicine, but it caused irritation and bleeding in the stomach and intestines. However, when salicylic acid is treated with ethanoic anhydride, acetylsalicylic acid (aspirin) is produced. 

Topical preparations for the treatment of acne include the use of azelaic acid, salicylic acid, benzoyl peroxide and triclosan. Clindamycin is an antibacterial preparation available for use in the treatment of acne both topically and systemically. 

The relatively high acidity of orf/zo-hydroxyben-zoic acid (salicylic acid), compared with the other derivatives just considered, is ascribed to intramolecular hydrogen bonding, which is not possible in the other compounds, even with ortho-methoxybenzoic acid. 

The Levitan and Barker series has also been examined by Hansch (18), who reported that the benzoic acids, salicylic acids and four miscellaneous acids could all be correlated using log Pi, Equation 17. The difference is in the calculation of log Pi values which were obtained by subtracting constants from the log P values, 3.69 for salicylic acids and 4.36 for benzoic acids. 

Fig. 4 Elution profiles for (A) propranolol (a), promethazine (b), and chlorprom-azine (c) applied separately on a 5-mm ILC column containing cytoskeleton-depleted red blood cell membrane vesicles entrapped in dextran-grafted agarose gel beads (1.4 /amol phospholipid, 0.5 mL/min) and (B), from left to right, acetylsalicylic acid, salicylic acid, warfarin, and pindolol on a capillary continuous bed containing liposomes immobilized by use of C4 ligands (1.0 /xmol phospholipid, 10 /xl./min). The elution volumes in the absence of lipid are shown (a0, b0, and c0, and the arrow, respectively). (Part A is reprinted with permission, with slight modification, from Ref. 26. Copyright 1999 Elsevier Science. Part B is reprinted with permission from Ref. 23. Copyright 1996 Elsevier Science.)...

In model studies with a hydroxycarboxylic acid (salicylic acid), a coordination complex has been isolated from the reaction with the C3A hydrates [45], as shown in Fig. 1.20. 

Acetylsalicylic Acid Salicylic Acid Paracetamol Naproxen Ibuprofen Diclofenac... 

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