Oxidation of organic compounds with chromic acid
acetone F R 11 S (2)-9-16-23-33
ethanol F R 11 S (2)-7-16
or denatured alcohol
propanal F Xi R 11-36/37/38 S (2)-9-16-29
sulphuric acid potassium dichromate solution T+ C N R 21-25-26-35-37/38-41-43-46-49-50/53 S (1/2)-26-45-53-60-61
Other alcohols, aldehyes and ketones can be used. Diluted chromosulphuric acid can also be used.
3 test tubes
test tube rack
burner (if possible alcohol-)
- Safety goggles. Due to offensive smells, perhaps ventilation.
- Respectively add a couple of drops of alcohol, propanal or acetone into the test tubes.
- Add 1 ml of water to each.
- Add 2-3 drops of sulphuric acid potassium dichromate solution to each. The solutions all become yellow.
- Heat each with the burner until a noticeable vaporization occurs (in the case of acetone and propanal clearly before the boiling point!).
- The alcohol- and the aldehyde solutions have become green, the acetone solution remains yellow.
All solutions are disposed of as heavy metal waste.
The yellow/orange Cr(VI) is in a acidic solution (in the form of chromic acid), especially when warm, a strong oxidant and is reduced to a green Cr(III). Similiarly alcohol and aldehyde are oxidized to carboxylic acid respectively. In the case of aceton a comparable transformation is not possible.
Ethanol (left) und propanal (middle) reduced Cr(VI), acetone (right) not.
Own procedure modelled after a school experiment.