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					Chemical identification of
carbohydrates


           Charbohydrates




       By: TA/ Jawaher Al-Qahtani
                        Charbohydrates

Charbohydrates

The CHO indicates that these compounds are hydrates of Carbon, CHO
contain Carbon, Hydrogen and Oxygen.

Classification:




                                 1
                           Charbohydrates

                            A-General tests

1-Molish`s test:
                       +Ve with all CHO.



                                                           Shake
   Sol. of sample + 4 drops of 15% alc. a naphthol

   Conc H2So4                    Purple ring between the 2 layers.




2-Reduction of Fehling solution:


       +Ve with monosacch and reducing disacc.

Sol. of sample + Fehling sol.(W.B 15-60 sec)              change in
colour. (red,yellow or green).




3-Reduction of Barfoed`s sol.:


            +Ve with monosaccharides(G,F)
            (within 5 min.).


Sol. of sample + Barfoeds sol.(W.B 5 min.)            Reddish ppt.




                                    2
                           Charbohydrates

4-Osazone test :


                   +ve with(monosacch.)
                   Glucose and fructose.



 Add 1 part of suger+3 parts of phenyl hydrazine HCl+4 parts of Na
acetate+ 5 ml water(in w.b 30 min)         white ppt.




                                     3
                            Charbohydrates



                            B-Specific tests:
1- Specific test for Sucrose

Cobalt nitrate test:

In test tube, add sol. of sucrose+cobalt nitrate+exss NaOH
Violet colour.



2- Specific test for fructose:

Rapid furfural test:

In test tube, add sol. of fructose+few drops of Conc Hcl+Resorcinol
crystals(W.B 2min. )            Red colour.



3- Specific test for Glucose:

I-In test tube add glucose sol.+NaOH sol. (W.B)          Yellow change
to brown.

II- In test tube add glucose sol.+lead subacetate + conc ammonia (W.B)
pink to orange.



4-Specific for arabinose:

Bials test

In test tube add arabinose sol.+Bial's reagent (W.B)         Green colour.




                                    4
                                            Charbohydrates




            Scheme for identification of Carbohydrates



                                                 Fehling test



                       +ve
                      G,F,M,L                                          _ve
                                                                    Sucrose


                Barfoeds test &
                                                                Cobalt nitrat test
                 Osazone test
                                                                  +ve Sucrose




 +ve Barfoed(5min.)                       - ve
+ve osazone (30 min)                Maltose,lactose
Glucose or Fructose




Rabid furfural test




  +ve                             - ve
Fructose                        Glucose




                               Specific
                       tests of Glucose




                                                      5

				
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posted:9/15/2012
language:English
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