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Osazonetest 110715202533-phpapp02


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Osazonetest 110715202533-phpapp02

  1. 1. Introduction The technique was developed by Emil Fischer, , a German chemist.
  2. 2. Introduction Phenylhydrazine is the chemical compound with the formula C6H5NHNH2.
  3. 3. Introduction Osazones are formed when the sugars react with acompound known as phenylhydrazine at boiling point. General Reaction:
  4. 4. Introduction These sugars are reducing ones which have either a free aldehyde or a ketone group to react with the phenylhydrazine.
  5. 5. Procedures 1. Pipette 1 ml of the phenylhydrazine mixture to a test tube.
  6. 6. Procedures 2. Add 5 ml of the test solution
  7. 7. Procedures 3. shake vigorously to insure complete solution
  8. 8. Procedures 4. Stopper the mouth of the tube loosely with cotton
  9. 9. Procedures 5. Place the tube immediately in a boiling water bath
  10. 10. Procedures 6. Record the time
  11. 11. Procedures 7. Observe the tube
  12. 12. Procedures 8. If a precipitate is formed, record the time and remove the tube from the bath
  13. 13. Procedures 9. Cool off the tube
  14. 14. Procedures 10. Examine the crystals under low power objective
  15. 15. Results and Discussions The reaction is stepwise;
  16. 16.  Osazone formation involves hydrazone formation at C-1 of an aldose (or C-2 of a ketose) and oxidation of C-2 (or C-1) of an alcohol group to a ketone (or an aldehyde). The new carbonyl group is also converted to a hydrazone. Fructose Mannose Glucose
  17. 17.  Osazone crystals have a characteristic shape under the light microscope and help in the identification of the sugar type. Disaccharides - like Lactose - like tight balls Monosaccharides - like sunflowers of needles needle-shaped or broomstick
  18. 18.  Making Osazone Crystals The difference in the structure of the monosaccharides is caused by the diverse groups attached to the first and second carbons of the sugar molecules. Their needle-shaped crystals show that the position of the first and second carbons do not matter in the crystal formation.
  19. 19.  Viewed under the microscope: Glucosazone
  20. 20.  Viewed under the microscope: Fructosazone
  21. 21.  Viewed under the microscope: Galactosazone
  22. 22.  Viewed under the microscope: Maltosazone
  23. 23.  Viewed under the microscope: Xylosazone
  24. 24.  Viewed under the microscope: Sucrose
  25. 25.  Time to Form The time needed to create osazone crystals varies among the various sugars involved, but helps to identify the sugars being tested. For an osazone crystal to be presented from a hot solution will take as long as follows:  fructose, two minutes;  Actual Time:  glucose, four to five minutes;  Xylose – 20 mins  xylose, seven minutes;  Galactose – 25 mins  galactose, 15-19 minutes;  Glucose – 30 mins  maltose, osazone soluble in hot  Sucrose – 47 mins water  Fructose – 57 mins  Maltose – 59 mins
  26. 26. Application For identifying sugars esp. Reducing sugars. Osazones are used as dyes
  27. 27. References osazone-crystals.html#ixzz1Rx9lFGBJ %20Courses/Freshmen/Spring/BCM101/Practical/Wee k%202%20practical%20_Chemistry%20of%20carbohy drates_.pdf 6/qualanal/tests/osazone.html