BAYER’S TEST (Unsaturation)

Question

1. To a clean test tube, add 1 -2 ml of the unknown organic solution
2. Measure 2ml of distilled water and add to the test tube containing the unknown solution and shake
well
3. Add 2-3 drops of the KMnO4 solution to it.
4 Observe the changes and the reaction carefully. Take note of the changes.
What are the possible results

Answer 1

Bayer's test, also known as the Baeyer test, is used to detect the presence of unsaturation, particularly alkenes and alkynes, in organic compounds. The test utilizes potassium permanganate (KMnO4), which is a strong oxidizing agent that reacts with unsaturated compounds to form diols and gets reduced in the process.

Here are the possible results of the test:

1. Positive Result (Unsaturation Present):

   • If the unknown organic solution contains alkenes or alkynes, the purple color of the potassium permanganate solution will disappear, and the solution may turn brown due to the formation of manganese oxide (MnO2) precipitate.
   • This indicates that unsaturation (C=C or C≡C) is present in the compound.

2. Negative Result (No Unsaturation Present):

   • If there is no unsaturation (e.g., the compound is an alkane or a saturated alcohol), the purple color of the KMnO4 solution will persist, and there will be no significant color change.
   • This indicates that the unknown compound does not possess any double or triple bonds.

3. Intermediate Result:

   • In some cases, if the compound is a partially unsaturated or conjugated compound, there may be a slow fading of the purple color, but it may not disappear completely. Observations of the reaction conditions and timing are crucial for interpretation in these instances.

In conclusion, a disappearance of the purple color indicates the presence of unsaturation, while retention of the color suggests saturation in the unknown organic compound.