Synthesis of Aspirin

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In this experiment, acetylsalicylic acid was synthesized from the acidification of salicylic acid and acetic anhydride. The objective was to convert a specific amount of salicylic acid into the same amount of aspirin that was high in purity. Furthermore, the other objectives were to enable students to conduct the synthesis of aspirin, reinforce skills or recrystallisation and the technique of melting point determination. The amount of each compound should be the same because there is a 1:1 ratio between them. The purity of the synthesized aspirin was measured by determining its melting point and percent yield. Soluble impurities increase the range over which a compound melts and often decreases its overall melting point temperature1. If the experiment went as expected, a pure sample of aspirin with a high percent yield would have been obtained. The percent yield obtained was 56.1% and the melting point was 134.7- 136.8.

Aspirin (acetylsalicylic acid) is a versatile drug that is consumed in huge quantities worldwide. It is a non-steroidal anti-inflammatory drug (NSAID) with a wide range of physiological effects. The first discovery of aspirin occurred in England, in 1963, believing that the bark of willow trees with a beneficial effect in alleviating distress due to fevers, aches, and pains2. Salicylic acid was later extracted from the willow bark and it proved to be an active ingredient. Salicylic acid was synthesized from basic starting materials by 1860 which was helpful to the medicinal field but there were some problems2. Salicylic acid turned out to be irritating to the membranes of the throat, mouth, and stomach. The product had a high acidity of the compound but fortunately, successful amendments were done, namely, the replacement of the acidic phenolic hydrogen atom with an acetyl group. In 1893, a effective synthesis of acetylsalicylic acid was created, patented in 1899, commercialized under the trade name of ‘aspirin’ by the Bayer Company in Germany3. The name ‘aspirin’ was invented by the chemist, Felix Hoffman, who originally synthesized acetylsalicylic acid for Bayer3. At very low doses, aspirin is used to treat and prevent heart attacks and blood clots. At higher doses, it is used as an analgesic to reduce pain and as an antipyretic to reduce fever. At very high doses, it is an effective anti-inflammatory agent used to treat rheumatic fever, gout and rheumatoid arthritis. It is also an anticoagulant, it dissolves corns and calluses, and it provokes loss of uric acid (a toxin) but promotes retention of fluids in the kidneys. It kills bacteria and induces peptic ulcers. When ingested, acetylsalicylic acid remains intact in the acidic stomach, but in the basic medium of the upper intestinal tract, it hydrolyzes forming the salicylate and acetate ions. When ingested, acetylsalicylic acid remains intact in the acidic stomach, but in the basic medium of the upper intestinal tract, it hydrolyzes forming the salicylate and acetate ions. The exact mechanisms of its pharmacological actions are still under study. In many plants, salicylate can induce flowering. However, aspirin may cause side effects for example, nausea, vomiting, stomach pain and heartburn.

Aspirin is prepared from salicylic acid and acetic anhydride with the help of an acid catalyst. Concentrated sulphuric acid acts as a catalyst. After preparation, the product is purified. This is especially important for chemicals that are used as food additives and pharmaceuticals. The most common method of purifying solid organic compounds is by recrystallization. When an impure solid compound is dissolved in a solvent, it is then allowed to slowly crystallize out as the solution cools. As the compound crystallizes from the solution, the molecules of the other compounds dissolved in solution are excluded from the growing crystal lattice, giving a pure solid.

Crystallization of a solid is different from a precipitation of...
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