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What is the primary purpose of the Molisch test?
What is the primary purpose of the Molisch test?
To identify the presence of carbohydrates in a sample.
What happens to carbohydrates during the Molisch test when concentrated sulfuric acid is added?
What happens to carbohydrates during the Molisch test when concentrated sulfuric acid is added?
Carbohydrates undergo dehydration, forming an aldehyde that condenses with phenol-type molecules.
Describe the appearance of the result when carbohydrates are present in a Molisch test.
Describe the appearance of the result when carbohydrates are present in a Molisch test.
A reddish violet colored ring is observed at the interface of the two liquids.
What role does α-naphthol play in the Molisch test?
What role does α-naphthol play in the Molisch test?
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Why is the Molisch test considered sensitive for detecting carbohydrates?
Why is the Molisch test considered sensitive for detecting carbohydrates?
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Study Notes
Molisch Test for Carbohydrates
- Objective: Identify carbohydrates
- Materials: Test tubes, dropper, test tube holder, concentrated sulfuric acid (H₂SO₄), carbohydrate sample, Molisch reagent
- Principle: Carbohydrates, when treated with concentrated acid, undergo dehydration to form aldehydes. These aldehydes condense with phenol-like molecules (like α-naphthol, resorcinol, or thymol) to create a colored complex.
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Procedure:
- Add 2 mL of the carbohydrate solution to a clean, dry test tube.
- Add 2 drops of Molisch reagent and mix gently.
- Carefully add concentrated sulfuric acid down the side of the test tube, avoiding mixing.
- Observation: A reddish-violet ring forms at the junction of the two liquids (carbohydrate solution/sulfuric acid).
- Result: The presence of a reddish-violet ring confirms the presence of carbohydrates in the sample.
- Mechanism: The test is sensitive because it detects the formation of the colored condensation product. The dehydration of the carbohydrate by sulfuric acid produces an aldehyde, which reacts with the α-naphthol component of the Molisch reagent to create a colored compound.
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Description
This quiz evaluates your understanding of the Molisch test, a vital method for identifying carbohydrates. You'll explore the objective, materials, principles, and procedures involved in this test, as well as interpret the results and observations. Hone your knowledge on how carbohydrates are detected through this biochemical test.
