Carbohydrates

-glucose exists in two optically active forms known as glucose and -glucose. The two isomers are interconvertible in aqueous solution.

Carbon- in both configurations I and II is called an anomeric carbon atom.

Step 1: Molisch Test
Molisch's test is a general test for the presence of carbohydrates.
In this test, a few drops of Molisch's reagent (alpha-naphthol solution) are added to the sample followed by concentrated sulfuric acid.
A purple or violet ring at the interface indicates the presence of carbohydrates.
Step 2: Explanation of Other Options
Option (a) fats are not detected by Molisch’s test.

Option (c) alkyl halides are not detected by Molisch’s test.
Option (d) alkaloids are not detected by Molisch’s test.

Step 3: Conclusion
Thus, Molisch's test is used for the detection of carbohydrates.