Molisch reagent is used to identify following compound:

Sulphuric acid causes carbohydrates to dehydrate, producing aldehyde as a byproduct. Aldehyde then proceeds through condensation in the presence of Molisch reagent (napthanol dissolved in ethanol), producing a purple chemical. The Molisch test to find carbs is based on this. The Molisch reagent can be used to distinguish between the carbohydrates glucose, raffinose, and deoxyribose.