Aspirin alkaline hydrolysis

Esters are derived from carboxylic acids by reaction with alcohols. They have a wide variety of applications ranging from flavouring agents to solvents and explosives. One of the most used painkillers in medication, aspirin, is an ester, while a major class of polymers are the poly(esters). Fats and vegetable oils are naturally occurring esters and the alkaline hydrolysis of such esters (saponification) is used to produce soaps. 

He also observed that aspirin was easily split in weakly alkaline medium which had consequences for the metabolism (see Section 7). One could say that he established the first profile for the pH dependence of hydrolysis of aspirin. Of course, the definition of pH was unknown at the time. 

Aspirin itself is acidic enough to produce efTervcscence with carbonates and. in the presence of iodides, to cause the slow liberation of iodine. In the presencx of alkaline hydroxides and carbonates, it decomposes, although it does form salts with alkaline metals and alkaline earth metals The presence of salicylic acid, formed on hydrolysis, nia) be confirmed by the formation of a violet color on the addition of ferric chloride solution. 

Pharmaceutical Incompat, (from Remington s Pharmaceutical Sciences) Aspirin forms a damp to pasty mass when triturated with acetanilide, phenacetin, antipyrine, amidopyrine, methenamine, phenol or phenyl salicylate. Powders containing aspirin with an alkali salt such as sodium bicarbonate become gummy on contact with atmospheric moisture. Hydrolysis oecnrs in admixture with salts contg water of crystallization. Solns of the alkaline acetates and citrates, as well as alkalies themselves, dissolve aspirin but the result -ing solns hydrolyze rapidly to form salts of acetic and salicylic acids. Sugar and glycerol have been shown to hinder this decompn. Aspirin very slowly liberates hydriodic acid from potassium or sodium iodide. Subsequent oxidation by air produces free iodine. 

Acetylsalicylic acid, or aspirin, is a white powder that is stable in a dry environment but that is hydrolyzed to salicylic acid and acetic acid under humid or moist conditions. Hydrolysis also can occur when aspirin is combined with alkaline salts or with salts containing water of hydration. Stable aqueous solutions of aspirin are thus unobtainable despite the addition of modifying drugs that tend to decrease hydrolysis. Aspirin is rapidly absorbed largely intact from the stomach and upper small intestine on oral administration but is rapidly hydrolyzed by plasma esterases. 

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