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Experiment Identify ketones using 2, 4-dinitrophenyl
hydrazine test.
11.2
Date ________________

2, 4-Dinitrophenylhydrazine is often abbreviated as 2, 4-DNP or

Background 2, 4-DNPH. This reagent is prepared by dissolving 2, 4-dinitrophenylhydrazine
Information
in ethanol. Then a few cm3 of concentrated sulphuric acid are added slowly. The

mixture becomes warm and the solid dissolves completely. Fructose is a
O
carbohydrate which has a ketonic group ( R C R ) present in it.

Materials APPARATUS: Test tubes, test tube holder, burner, water bath, match box, dropper,
Required safety goggles,

CHEMICALS: Fructose solution, distilled water , 2,4-DNPH, ethanol, concentrated
sulphuric acid.

DO YOU KNOW?

Å’ Suspend 0.25g of 2,4 1. 2, 4-Dinitrophenylhydrazine is a
dinitrophenylhy drazine in 5 cm3 red, crystalline powder with a
Procedure ethanol and add 8 to 10 drops of melting point of approximately
concentrated sulphuric acid 200°C. It is soluble in dilute
 cautiously. Use this solution to rest inorganic acids and is used as a
any ketone. reagent for the identification of
1. Do ketones give positive aldehydes and ketones. The
In a test tube, take 2cm3 of 95% aldehyde or ketone is converted
tests with Fehling's and ethanol and add a few crystals of to its hydrazone by reaction with
fructose. Shake it to dissolve 2, 4-dinitrophenylhydrazine.
Tollen's reagents? Ž fructose.
2. Can you use 2, 4 DNPH 2. Acetone (CH3 CO CH3) is a
Add 3cm3 of 2,4-dinitrophenyl commercially important ketone.
reagent to test sugar in the hydrazine reagent in the above It is a solvent used in
mixture. Shake vigorously and if manufacturing other organic
urine of a diabetic patient? no precipitate appears immediately chemicals, drugs and explosives.
allow the solution to stand for a It is also used as a nail polish
few minutes. If no precipitate remover.
appears dilute the solution

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