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Preparation of aspirin - The chemical background This is the overall reaction that is going to be done to synthesise aspirin

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The Commercial Importance of Aspirin Introduction In 1899 Aspirin was first synthesised, and also known as acetylsalicylic acid which is the salicylate ester of ethnic acid. Salicylate origins lie in the naturally occurring compound salicin. It was discovered by the Greeks, around the fifth century B.C, that a substance in the bark of the willow tree, (we now know as salicin) could relieve pain. How does Aspirin work in the body? Aspirin is able to block the production of a substance called prostaglandins. These prostaglandins are produced by the body whenever a cell in the body is injured. Production and release of these prostaglandins leads to swelling, pain and fever which are commonly associated with injuries or disease. Medical uses of Aspirin There are so many medical uses of Aspirin, like: * It is known that aspirin reduces the risk of strokes in patients with early warning signs of Transient Ichaemic attacks. * It is now accepted as an important weapon in the prevention of Coronary Heart disease. * Diabetic patients can now benefit taking one aspirin a day. * Another popular use of aspirin is to treat various forms of Arthritis (Rheumatoid Arthritis and Osteoarthritis). * Evidence is mounting that regular usage of aspirin may reduce the risk of many today's commonest cancer. Although aspirin seems to treat every part of the body apart from the stomach which still remains a mystery. Like many other drugs aspirin also has side effects : * Gastritis * Internal bleeding * Bleeding in the brain (Haemorrhagic) * Reye's syndrome Similar drugs : * Ibuprofen * Acetaminophen Risk Assessment Chemicals Hazard Precautions Hydrochloric acid (concentrated) ...read more.


Wash the product with a little ice cold water and transfer it to a weighed watch glass. Allow to dry overnight. Step 2: The preparation of aspirin is an esterification reaction Stage 1- first weigh how much 2-hydroxybenzoic acid is produced. Then weigh accurately 1g of your sample of 2-hydroxybenzoic acid. Transfer the weighed 2-hydroxybenzoic acid into a pear shape flask and add 2cm3 of Ethanoic anhydride followed by 8 drops of phosphoric acid. Put a condenser on the flask. In a fume cupboard, warm the mixture in a hot water bath, swirling, until all the solid has dissolved and then warm for another 5 minutes. Stage 2- add carefully 5cm3 of cold water to the solution. Fill the beaker with ice and a bit of water and stand the flask in the beaker and stir vigorously using a glass rod until precipitation appears to be complete. Filter off the product using a Buchner funnel and suction apparatus. Wash the product with a little cold water. Then transfer the filtered product on to a weighed watch glass and leave to dry overnight. Finally weigh product (crude aspirin) when dry. Chemical test for purity- the addition of a chemical reagent to identify substances is a common procedure in chemical analysis. The reagent iron (lll) chloride that will be added often forms a coloured compound with the substance under investigation. * Add 5cm3 of water to each of five test tubes and label A, B, C, D and E. * Dissolve a few crystals using a spatula to the following substances in water in test tubes: A=Phenol, B= 2-hydroxybenzoic acid, C= Crude aspirin, D= Re-crystallised aspirin and E= Pure aspirin. ...read more.


Re-crystallised aspirin = 46mm Rf = 46 = 0.82 56 Aspirin Rf value Pure aspirin 0.89 Crude aspirin 0.84 + 0.45 Recrystallised aspirin 0.82 Aspirin linking shape and function The synthesis of prostaglandins and the way in which aspirin interrupts the process. Oxygen molecule Fatty acid molecule Prostaglandins molecule Aspirin molecule Enzyme molecule 1. Prostaglandins are synthesised in the body from fatty acids and oxygen. 2. Some of the prostaglandins in the blood trigger a series of events that cause platelets to change shape, release granules and aggregate this then causes the platelets to clump together and form blood clots. The effectiveness of aspirin is due to its ability to inhibit cyclooxygenase. Aspirin molecule irreversibly blocks the enzyme cyclooxygenase (prostaglandin synthesis), which catalyses the conversion of fatty acid to endoperoxide compounds. The drug decreases the formation of both the prostaglandins and thromboxane A2. Aspirin is absorbed mainly from the intestine but also from the stomach because it provides the quickest route into the bloodstream. To get into the bloodstream the drug must cross cell membranes which are made up of lipids and proteins. Ionic compounds are soluble in polar solvents such as water but insoluble in non-polar solvents (such as hexane and other organic liquids). The lipid layer in a membrane can be thought of as having the properties of a non-polar solvent; drugs which are soluble in this type of solvent cross membranes easily while water-soluble drugs cannot be absorbed so easily. Fat soluble molecules can pass through the lipid layer, the proteins can act as carriers transporting selected molecules and ions across the lipid bilayer which is not permeable to water soluble compounds. Reference : * Work sheet from Aspirin-SATIS 16-19 unit 7 * ?? ?? ?? ?? ...read more.

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