What is Molisch’s test?

Molisch’s test is a general test for carbohydrates.

Principle of the test

In this test, carbohydrates are dehydrated by concentrated $\mathrm{H_2SO_4}$ to form compounds like furfural or hydroxymethylfurfural, which then react with Molisch reagent ($\alpha$-naphthol) to give a violet/purple ring.

Evaluate each option

• A: Nitro compounds

  Nitro compounds do not give Molisch’s test.

• B: Sugars

  Sugars are carbohydrates, so they do give Molisch’s test.

• C: Amines

  Amines do not respond to Molisch’s test.

• D: Primary alcohols

  Primary alcohols generally do not give Molisch’s test.

Conclusion

Since Molisch’s test is used to detect carbohydrates, the correct option is:

$\boxed{\text{B: Sugars}}$