Download Analysing Alcohols

Analysing Alcohols(12/03/2016)
Aim: To outline an experiment to determine whether an unknown liquid is a
primary secondary or tertiary alcohol.
Equations
Primary alcohol+excess oxygen
CH3CH2OH+[O]
Aldehyde
CH3COH +H2O
Secondary alcohol+excess oxygen
CH3CHOHCH3+[O]
keytone
CH3COCH3+H2O
Aldehyde
carboxylic acid
CH3COH +[O]
CH3COOH
Equipment





250cm beaker
Bunsen burner
Tri-pod
Gauze
4xtestubes
Method
1. Half fill a 250cm beaker with water
2. Heat it over a Bunsen burner.
3. Put 10cm of the alcohol in a test tube and add 1cm3 of potassium
dichromate then add 5cm of sulphuric acid.
4. Label the test tubes and place them in the water bath
5. Check for colour changes and if the colour of the unknown liquid goes green
then it is a secondary or primary alcohol. However if the colour remains orange
it is a tertiary alcohol
If it is primary or secondary alcohol
6. You then put another fresh 10cm of the unknown alcohol in a new test tube
and add Tollens’ reagent to it
7. put the test tube in the water bath and wait for 5mins
8.keytones(originating from a secondary alcohol) will have no colour change
while aldeyhdes (originating from a primary alcohol) will produce a grey
precipitate
Risk Assessment
Sources
http://www.chemguide.co.uk/organicprops/carbonyls/oxidation.html12/03/2016