CHEMICAL TEST & IMPORTANCE OF CARBOHYDRATES ( Glocose+Fructose)

1. CHEMICAL TEST & IMPORTANCE OF CARBOHYDRATES
1.How can you identify carbohydrate from an unknown source?
ANSWER: The following test are done for identify carbohydrate from
an unknown source:
1.Molisch Test: specific for carbohydrates.
This test is specific for all carbohydrates Monosaccharidegives a rapid positive
test, Disaccharides and polysaccharides reactslower.
Method :
1-Two ml of a sample solution is placed in a test tube.
2-Two drops of the Molisch reagent (which α-naptholin 95% ethanol) is
added.
3-The solution is then poured slowly into a tube containing two ml of
concentrated sulfuric acid so that two layers form, producing violet ring appear
as liaison between the surfaceseparations.

2. FIGURE: MOLISCH TEST
2.Benedict's Test: presence of reducing sugars.
• All monosaccharides arereducing sugars; they all have a free reactive
carbonylgroup.
• Somedisaccharides haveexposed carbonylgroups and are also reducing
sugars. Other disaccharides such as sucrosearenon-reducing sugars and will
not react with Benedict's solution
-Largepolymers of glucose, such as starch, are not reducing sugars, sincethe
concentration of hemiacetal groups is very low

3. Method :
• Oneml of a samplesolution is placed in a test tube.
• Two ml of Benedict’s reagent(complex mixture of sodium carbonate, sodium citrate
and copper(II) sulfate pentahydrate) is added.
• The solution is then heated in a boiling water bath for five minutes.
• A positive test is indicated by: The formation of a reddish precipitate.
FIGURE: Benedict’s test

4. 3.Barfoed's Test: test used for detecting the presence
of monosaccharides.
Method:
• Place one ml of a sample solution in a test tube.
• Add 3 ml of Barfoed's reagent (a solution of cupric acetate and acetic acid).
• Heat the solution in a boiling water bath for 6 minutes(after the 3 min check
the tubes)
•Reducing monosaccharides areoxidized by the copper ion in solution to form
a carboxylic acid and a reddish precipitate of copper (I) oxidewithin three
minute
4. Seliwanoff's Test: distinguish between aldoses and
ketoses.
Used to distinguish between aldoses (like glucose) and ketoses (like fructose).

5. Method:
• Onehalf ml of a samplesolution is placed in a test tube.
• Two ml of Seliwanoff's reagent (a solution of resorcinoland HCl) is added.
• The solution is then heated in a boiling water bath for two minutes.
• A positivetest is indicated by producea cherry red product for ketohexos &
yellow to faint pink for aldohexos.
FIGURE: Seliwanoff's test
2.How will you distinguish between glucose & fructoseby a chemical test?
Write down their pharmaceuticaluses?
ANSWER:
Bromine water oxidizes glucose to gluconic acid when treated with it.

6. Fructose does not react with bromine water .
Bromine water is a mild (very) oxidising agent. It's not strong enough
to oxidise the ketone group Fructose has.This is why they don'treact.
Pharmaceutical importance of glucose:
a.In industry, glucose is used as a precursorto make vitamin C.
b.Glucose in a fluid form is a benefitin the food industry because it is
easy to mix into formulations on a big scale.
c.In jams and jellies, liquid glucose can supply the osmotic pressure
necessaryto prevent bacterial growth and spoilage
d.In the medicine-making process,liquid glucose is useful as a
sweetenerfor syrups and tonics.
e.It is also used to coat tablets and as a granulating agent.
f.Liquid glucose can also be used as a medicationfor diabetic patients.
g. Ingested orallyor through injection, liquid glucose can raise blood
sugar immediately.
Pharmaceutical importance of fructose:
a.High fructose corn syrup is used to sweetenfoods and beverages

7. b.It is used as a food for diabetic people.
c.Infant feeding formula often contain fructose.
d.Itis an ingredient of fructose+NaCl injection.