Molisch's test is a general chemical test used to detect the presence of carbohydrates, specifically sugars. It is named after the Austrian botanist Hans Molisch who developed it.

Principle: The test is based on the dehydration of carbohydrates by concentrated sulfuric acid to form furfural or hydroxymethylfurfural derivatives. These compounds then react with α-naphthol (present in Molisch's reagent) to form a purple or violet-colored complex.

Reagents Used: Molisch's reagent is a solution of α-naphthol in ethanol. Concentrated sulfuric acid is added carefully along the side of the test tube.

Procedure:

1. Take the sample solution in a test tube.
2. Add a few drops of Molisch's reagent (α-naphthol in alcohol).
3. Carefully add concentrated sulfuric acid along the side of the test tube to form a layer beneath the aqueous solution without mixing.
4. Observe the formation of a purple or violet ring at the junction of the two layers, which indicates a positive test for carbohydrates.

Specificity: While Molisch's test is highly sensitive for carbohydrates (both monosaccharides and disaccharides), it can also give a positive result for other compounds that can be dehydrated to furfural derivatives, such as glycoproteins and nucleic acids. However, it is primarily known for detecting sugars.

Answering the Question: Among the given options:

• Amines: Not detected by Molisch's test.
• Sugars: Detected by Molisch's test (correct answer).
• Primary alcohols: Not detected by Molisch's test.
• Nitro compounds: Not detected by Molisch's test.

Related Topics

Carbohydrates: Organic compounds consisting of carbon, hydrogen, and oxygen, with a general formula often written as C_x(H₂O)_y. They include sugars, starches, and cellulose, and serve as energy sources and structural components in living organisms.

Qualitative Tests for Carbohydrates: Besides Molisch's test, other specific tests include:

• Benedict's test: For reducing sugars (e.g., glucose).
• Iodine test: For starch (blue-black color).
• Fehling's test: For reducing sugars.
• Barfoed's test: To distinguish between monosaccharides and disaccharides.

Important Formulae

While Molisch's test is qualitative and doesn't involve mathematical formulae, the dehydration reaction for a pentose sugar (like xylose) to furfural can be represented as:

(Furfural formation from a pentose)

For hexoses (like glucose), hydroxymethylfurfural is formed:

(Hydroxymethylfurfural formation from a hexose)

The subsequent reaction with α-naphthol forms a colored complex, but the exact structure is complex and not typically represented with a simple formula.