Mais conteúdo relacionado


Synthesis of Aspirin.pptx

  1. Synthesis of Aspirin Prepared by Bahman Mhamad Ali Ahmad mhamad mustafa Shalaw Wahid Supervisor by Muslih
  2. Introduction : • Salicylic acid which is a constituent of certain plant is itself an analgesic & was originally administered as sodium salicylate, since salicylic acid has an irritating effect on the stomach, chemists thought of a modification which would retain its properties while decreasing the adverse side effects. • Conversion to the ester satisfied this requirement& aspirin proved to be as effective as sodium salicylate without the irritation of phenolic compound. • Aspirin however hydrolyzed to salicylic acid in the alkaline media of the intestine by esterase enzyme.
  3. history The aspirin we know came into being in the late 1890s in the form of acetylsalicylic acid when chemist Felix Hoffmann at Bayer in Germany used it to alleviate his father's rheumatism, a timeline from Bayer says. Beginning in 1899, Bayer distributed a powder with this ingredient to physicians to give to patients.The drug became a hit and, in 1915, it was sold as over-the-counter tablets.
  4. An ester is a chemical compound derived from an acid (organic or inorganic) in which at least one –OH hydroxyl group is replaced by an –O– alkyl (alkoxy) group, as in the substitution reaction of a carboxylic acid and an alcohol. Salicylic acid contains a phenol group, and phenols are known to be irritating. because replaced the phenol group with an ester group. When phenol group replace to ester group, that salicylic acid change to acetylsalicylic acid, was much less irritating than salicylic acid. Unfortunately, it is still irritating to the stomach and can cause hemorrhaging of the stomach walls. ESTRER AND EFFECT IN SYNTHESIS OF ASPIRIN
  5. Esterification nucleophilic acyl substitution)
  6. Synthesis of aspirin • Aspirin is prepared in our lab by acetylating of salicylic acid with acetic anhydride in the presence of H2SO4 as catalyst.
  7. • Because of its low solubility in H2O it is isolated from the reaction mixture by precipitation with H2O, we pour cold water to hydrolyze acetic anhydride & complete the ppt of aspirin. • Heat is produced in this reaction (exothermic reaction) • Aspirin recrystallized from benzene, even though aspirin is insoluble in cold water & soluble in hot water but it is not a suitable recrystallizing solvent for Aspirin because aspirin undergoes partial hydrolysis to salicylic acid & acetic acid in hot water.
  8. Procedure: 1-Place 3 gm of salicylic acid in 100 ml E.f. and add with constant stirring 6 ml of acetic anhydride followed by 1 ml of conc. H2SO 2- Stir the mixture gently observing the rise in temp. to 70-80 oC. While the salicylic acid dissolves, after 15 minutes the solution cools by it self and a solid mass of aspirin forms 3-Pour 35 ml of ice-cold water over the contents of the flask to hydrolyze excess acetic anhydride and to complete the ppt of aspirin 4- Collect the crude aspirin using a Buchner funnel and wash with ice-cold water, air-dry the product and calculate the yield 5- Perform FeCl3 test on produced aspirin
  9. Identification test of aspirin: • Ferric chloride test; • The presence of phenolic group in a compound is indicated by the formation of violet iron complex when treated with ferric chloride solution • Aspirin ------------► give –ve result with FeCl3 due to absence of phenolic group • Salicylic acid--------► + ve result
  10. Identification of aspirin
  11. Think • What is le chatelier’s principle? • Mention methods in formulation or synthesis to overcome the problem of irritability of salicylic acid to stomach? • Why cold water is used in Aspirin washing? • What are the methods which are used to assesse aspirin purity? • List the steps used for recrystallization. • What is the difference between vacuum filtration & gravity filtration?