bio chem
TRANSCRIPT
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Phenylhydrazine Reaction
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Phenylhydrazine Reaction
• This is a test for reducing carbohydrate, reducing disaccharides and many monosaccharides to be identified with the formation of osazone crystals
• Used to differentiate simple sugars by their varied forms of osazones and their rates of osazone formation
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Procedure
• Fill round bottoms of 6 test tubes with phenyhydrazine mixture.
• Add 5 ml of the different sugars to each corresponding test tube.
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Procedure
• Shake vigorously to insure complete solution• Loosely place a cotton stopper• Place immediately in a boiling water bath• Record time
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Procedure
• Observe tube carefully for a distinct precipitate to form. Record time
• Remove tube from the water bath• *If no precipitate forms after 40 minutes of
heating, remove tube and add 4ml distilled water. (causes immediate precipitation of osazones)
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Procedure
• Tube then returned to boiling water bath for few minutes until osazones redissolves.
• Allow water bath and test tubes to cool slowly to room temperature.
• Examine crystals under the microscope
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Sample pictures showing crystals
After 3 minutes After 8 minutes
http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA5/MAIN/1ORGANIC/ORG18/TRAM18/C/PICTURE.HTM?5
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Mullikin’s Figures
Sugar Time (minutes)
Glucose 4-5
Fructose 2
Sucrose 30-35 (after hydrolysis)
Maltose Osazone soluble in hot water
Lactose Osazone soluble in hot water
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Principle
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Principle1. Free C=O groups of sugars react with
phenylhydrazine to form phenylhydrazones.
fructose
+
phenylhydrazone
phenylhydrazine
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Principle1. Free C=O groups of sugars react with
phenylhydrazine to form phenylhydrazones.
2. With excess phenylhydrazine, the C adjacent to C=O reacts with phenylhydrazine to form yellow compounds called OSAZONES.
phenylhydrazone
+
osazone
phenylhydrazine
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Results
Glucose Fructose
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MaltoseLactose
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Galactose Sucrose
No crystallization will be observed until hydrolysis of the sucrose occurs, which will yield both fructosazones and glucosazones
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