Osazone test

OSAZONE TEST

Introduction

The technique was developed by Emil Fischer, , a German chemist.

IntroductionPhenylhydrazine is the chemical compound

with the formula C6H5NHNH2.

IntroductionOsazones are formed when the sugars react

with a compound known as phenylhydrazine at boiling

point.General Reaction:

Introduction

These sugars are reducing ones which have either a free aldehyde or a ketone group to react with the phenylhydrazine.

Procedures

1. Pipette 1 ml of the phenylhydrazine mixture to a test tube.

Procedures

2. Add 5 ml of the test solution

Procedures

3. shake vigorously to insure complete solution

Procedures

4. Stopper the mouth of the tube loosely with cotton

Procedures

5. Place the tube immediately in a boiling water bath

Procedures

6. Record the time

Procedures

7. Observe the tube

Procedures

8. If a precipitate is formed, record the time and remove the tube from the bath

Procedures

9. Cool off the tube

Procedures

10. Examine the crystals under low power objective

Results and DiscussionsThe reaction is stepwise;

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

Osazone crystals have a characteristic shape under the light microscope and help in the identification of the sugar type.

Disaccharides - like sunflowers

Lactose - like tight balls of needles

Monosaccharides - like needle-shaped or broomstick

Making Osazone CrystalsThe 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.

Viewed under the microscope: Glucosazone

Viewed under the microscope: Fructosazone

Viewed under the microscope: Galactosazone

Viewed under the microscope: Maltosazone

Viewed under the microscope: Xylosazone

Viewed under the microscope: Sucrose

Time to FormThe 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; glucose, four to five minutes; xylose, seven minutes; galactose, 15-19 minutes; maltose, osazone soluble in

hot water

Actual Time:Xylose – 20 minsGalactose – 25 minsGlucose – 30 minsSucrose – 47 minsFructose – 57 minsMaltose – 59 mins

ApplicationFor identifying sugars esp. Reducing sugars.Osazones are used as dyes

Referenceshttp://www.ehow.com/info_8392949_different-

osazone-crystals.html#ixzz1Rx9lFGBJhttp://www.pua.edu.eg/Version2/Courses2/

Dentistry%20Courses/Freshmen/Spring/BCM101/Practical/Week%202%20practical%20_Chemistry%20of%20carbohydrates_.pdf

http://www.chemistry.ccsu.edu/glagovich/teaching/316/qualanal/tests/osazone.html