Acetic acid aspirin derived from

Important chemicals derived from phenol are salicylic acid acetylsali-cyclic acid (aspirin) 2,4-dichlorophenoxy acetic acid (2,4-D), and 2,4,5-triphenoxy acetic acid (2,4,5-T), which are selective herbicides and pentachlorophenol, a wood preservative ... 

Carboxylic acids, compounds of the type RCOH, constitute one of the most frequently encountered classes of organic compounds. Countless natural products are carboxylic acids or are derived from them. Some carboxylic acids, such as acetic acid, have been known for centuries. Others, such as the prostaglandins, which are powerful regulators of numerous biological processes, remained unknown until relatively recently. Still others, aspirin for example, are the products of chemical synthesis. The therapeutic effects of aspirin, welcomed long before the discovery of prostaglandins, are now understood to result from aspirin s ability to inhibit the biosynthesis of prostaglandins. 

Salicylic acid is only used externally therefore various derivatives of this acid have been synthesized for systemic use. These comprise two large classes, namely esters of salicylic acid obtained from substitutions within the carboxyl group and salicylate esters of organic acids, in which the carboxyl group is retained and substitution is made in the hydroxyl group. For example, aspirin is an ester of acetic acid. In addition, there are salts of salicylic acid (Figure 26-1). 

For many years, acetylsalicylic acid (ASA) was thought not to fluoresce and was commonly determined by hydrolysis to salicylic acid, followed by fluorometric determination of the salicylic acid. A tedious separation of the salicylic acid from the acetyl derivative was therefore necessary for the determination of both in aspirin tablets. Recently, it was found that ASA does indeed fluoresce in a solvent of 1 % acetic acid in chloroform [14]. ASA is excited at 280 nm and emits at 335 nm. 

Acetic acid, its name derived from the Latin word acetum meaning vinegar, is another acyclic compoimd in widespread use. Its structure is shown in Figure 2.3. It has numerous uses other than as a culinary condiment, which is a solution in water containing between 4 and 8 percent acetic acid. In nature, acetic acid is formed by the action of bacteria on wine or other fermented alcohol but because of its many industrial applications it is manufactured from carbon monoxide and methanol in the presence of a catalyst. Its many uses include the manufacture of the pharmaceutical known as aspirin, photographic films, rayon, various glues and certain types of plastics. 

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