Wednesday, March 21, 2012

Jones (Chromic Acid) Oxidation Test for Aldehydes

Cyclohexanone and Benzaldehyde

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 5 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.


Aldehydes are better characterized in other ways. The color usually develops in 5-15 seconds.
Cleaning up
Place the test solution in the appropriate waste container.


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