| time
requ.: |
25 minutes. |
|
objective: |
Test for
aldehyde and ketone groups |
| material: |
- beaker 100ml
- magnetic stirring bar
- magnetic stirrer
- funnel, stand, clamp
- graded cylinder 10ml
|
- fluted filter paper
- test tubes d=18mm
- test tube stand
- stopper
- 2-5 teat pipettes
|
| chemicals: |
- 2,4-dinitrophenylhydrazine,
- hydrochloric acid w=37%,
acetic acid
- actone, ethyl acetate
 
|
- ethanol
- distilled water
|
|
preparation: |
Note: adapt
volume of stock solution to the estimated number of tests you plan. For
about 50 tests: Prepare a
stock solution by dissolving 0,25g dinitrophenylhydrazine (DNPH) in 42ml water and
8ml hydrochloric acid. Stir well for 15 minutes and
then filtrate to get a clear yellow reagent solution. |
|
procedure: |
To 1ml DNPH reagent add 1 drop of the sample and
shake. |
|
observation: |
If it contains
a carbonyl compound, a yellow precipitate or turbid is observed. Run blank
tests with positve reacting compounds (aldehydes, ketones) and with
negative reacting compounds (e.g. hydrocarbons, alcohols, carbonic
acids, esters). Note that ethanol may be contaminated with ketones and
then also gives a positive test. |
|
disposal of: |
Organic
solvents. |
|
source: |
Barke, H.-D. et al.: One Hundred
Chemistry-Experiments to Avoid Chalk and Talk; University of Muenster,
2004. |
