ALDEHYDE AND KETONE

OBJECTIVE

To identify carbonyl compounds as aldehyde and ketone using qualitative analysis

APPARATUS

Stopper, test tubes, water bath, thermometer

CHEMICAL REAGENTS

Iodine solution or potassium iodide, Tollens’ reagent, Schiff reagent, Fehling’s solution,

NaOH 10% solution, Dioxane or its equivalent, 2,4-Dinitrophenylhydrazine, ethanal,

benzaldehyde, propanone, an unknown carbonyl compound (X compound), ammonia 5%

solution.

METHOD

A. Fehlings’ Test1. 2 ml of Fehlings’ solution was placed in each test tube. 1-2 drops of the

compound was added to be tested.

2. Tubes were shaked gently.

3. The mixture was heated in boiling water for 15-20 minutes and was determined

whether any precipitate has been formed.

B. Tollens’ Test1. 1 ml Tollens’ reagent was added to each test tube contains the compound to be

tested and tubes were shaked gently

2. The mixtures allowed to stand for 3 minutes and then the formation of any silver

formation was noted.

3. When there is no change, the mixture was warmed in a water bath at 65°C-75°C

for 3 minutes.

4. Observation was recorded.

C. Schiff’s Test1. One drop of ethanal, benzaldehyde, propanone and an unknown carbonyl

compound was placed into 4 different test tubes respectively.

2. 1 ml of Schiff’s reagent was added into each of test tube.

3. They were shaked slowly and noted whether there is any change in color.

4. When the compounds do not dissolve, the test tube was stopper and was shaked

vigorously until an emulsion is formed.

5. Observation was recorded.

D. Iodoform Test1. 5 drops of ethanal, benzaldehyde, propanone and an unknown compound was

placed into 4 different test tubes respectively.

2. 5 ml dioxane was added in each tube and shake to dissolve the compounds.

3. 1 ml 10% NaOH solution was added.

4. While shaking, iodine or potassium iodide solution was added one drop at a time

until the iodine color is retained.

5. The test tube was warmed in a water bath at 65°C-75°C for a minute. When

iodine color disappears, more iodine or potassium iodide solution was added.

The formation of precipitate was noted. Observation was recorded. The functional

group of the unknown carbonyl was suggested .

CONCLUSION

Hypothesis accepted. Fehling’s n Tollen’s is used to test for aldehyde. Schiff’s test used to

test aldehyde except benzenealdehyde and it will be negative result for ketone except

propanone. Iodoform test is used to test ethanal.