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Experimental Reports - PowerPoint PPT Presentation

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Experimental Reports
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  1. Experimental Reports • Next week is the final week of practicals • Make sure you are up to date with your reports by next week – all reports • Final reports must be handed up no later than one week after completion of final practical – otherwise marks will be forfeited

  2. Experiment 17 Reactions of Alcohols and Carboxylic Acids

  3. Introduction • Given samples of various alcohols and carboxylic acids • Establish some of their physical and chemical properties & perform various reactions

  4. Introduction • You will perform solubility and acidity tests on all the compounds provided • Ester formation from an alcohol and carboxylic acid • Oxidation of an alcohol to a carboxylic acid using permanganate solution

  5. Solubility Tests • To 1ml of water in three test tubes, add each of the alcohols dropwise until they cease to dissolve or until 10 drops have been added • Record your observations • Repeat with the two carboxylic acids • Comment on your conclusions regarding the solubilities in water

  6. Acidity Tests • Use the aqueous solutions of ethanol and ethanoic acid from the solubility tests • Test both with blue litmus paper • Add 1ml of 10% NaHCO3 to each • Record your observations in each case

  7. Acidity Tests • Dissolve 0.5g of sodium acetate in 5ml water – note if there is any odour • Add 1ml dilute H2SO4 and again note if there is any odour • Record your observations in each test and explain any reactions observed

  8. Ester Formation • Already encountered in Experiment 14 • Heat 2ml of ethanol, 1ml ethanoic acid and a few drops of conc H2SO4 for 5 mins • Note any changes you observe – odour?

  9. Ester Formation - Mechanism Include mechanism for ester formation in your report

  10. Oxidation of Phenylmethanol • Phenylmethanol (benzyl alcohol) can be oxidized to give benzoic acid • To 1ml of phenylmethanol in a conical flask add 25ml of KMnO4 solution and 0.5g of sodium carbonate • Heat on the water bath for 20 mins • Cool & acidify with conc HCl

  11. Oxidation of Phenylmethanol • Add sodium sulphite solution until the brown maganese dioxide dissolves • Cool to room temperature – white precipitate of benzoic acid settles out

  12. Oxidation of Phenylmethanol • Isolate crystals on the Hirsch funnel, wash with water & dry • Get melting point when dry • Calculate % yield from number of moles of phenylmethanol you began with

  13. Calculations • Density of phenylmethanol = 1.05 gml-1 • Use the density & volume to calculate the mass of phenylmethanol used

  14. Calculations • Use the mass of phenylmethanol to calculate the number of moles • When dry, weigh the benzoic acid product and thus calculate the number of moles of product • % yield = moles benzoic acid/moles phenylmethanol

  15. Report • Introduction • All observations from the solubility and acidity tests & reactions • Mechanism for ester formation • Weight and melting point • % yield of benzoic acid • Discussion & conclusions