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Tests for Alcohols
Jones Oxidation for Primary and Secondary Alcohols
Lucas Test for Secondary and Tertiary Alcohols
Jones Oxidation for Primary and Secondary Alcohols
Alcohol
Standards
1-Butanol, 2-Butanol, t-Butyl alcohol
Procedure
Dissolve 10 mg or 2 drops of the unknown in 1 mL of pure acetone
in a test tube and add to the solution 1 small drop of Jones reagent
(chronic acid in sulfuric acid). A positive test is marked by the formation
of a green color within 15 seconds upon addition of the orange-yellow
reagent to a primary or secondary alcohol. Aldehydes also give a positive
test, but tertiary alcohols do not.
The Jones reagent will already be prepared for you.
Positive Test
A positive test for aldehydes and primary or secondary
alcohols consists in the production of an opaque suspension with a green
to blue color. Tertiary alcohols give no visible reaction within 2 seconds,
the solution remaining orange in color. Disregard any changes after 15
seconds.
Complications
- Enols may give a positive test.
- Phenols give a dark colored solution which is not blue-green like a positive test.
Cleaning up
Place all solutions in the appropriate waste container.
Lucas Test for Secondary and Tertiary Alcohols
Alcohols
Standards
1-Butanol, 2-Butanol, t-Butyl alcohol.
Procedures
To 0.2 mL or 0.2 g of the unknown in a test tube add 2 mL of
the Lucas reagent at room temperature. Stopper the tube and shake vigorously,
then allow the mixture to stand. Note the time required for the formation
of the alkyl chloride, which appears as an insoluble layer or emulsion.
The Lucas reagent is already prepared for you.
Positive test
Appearance of a cloudy second layer or emulsion
- 3o alcohols: immediate to 2-3 minutes
- 2o alcohols: 5 -10 minutes
- 1o alcohols: no reaction
Complications
The test applies only to those alcohols soluble in the reagent
(monofunctional alcohols lower than hexyl and some polyfunctional alcohols.)
This often means that alcohols with more than six carbon atoms cannot
be tested.
Cleaning Up
Place all solutions in the appropriate waste container.