MCQ Detailed View

Dimethyl ketones, also known as acetone and its derivatives, are important members of the ketone family. To identify and characterize them, specific chemical tests are used. One of the most important tests for dimethyl ketones is the Iodoform test. This test detects the presence of a methyl ketone group (–COCH₃) or alcohols that can be oxidized to a methyl ketone.

In the Iodoform test, the compound is treated with iodine and a base such as sodium hydroxide. If a methyl ketone group is present, a yellow precipitate of iodoform (CHI₃) is formed, which has a distinct antiseptic smell. This yellow solid is an unmistakable confirmation of the methyl ketone functional group. Acetone, being the simplest dimethyl ketone, gives a strong positive result in this test.

The other reagents listed are used for different purposes. Tollen’s reagent is a solution of silver nitrate in ammonia, which is commonly used to detect aldehydes. Aldehydes reduce Tollen’s reagent to form a silver mirror, but ketones generally do not respond to this test. Schiff’s test is also specific for aldehydes, where the reagent turns pink or magenta in their presence. Benedict’s reagent is mainly used to identify reducing sugars and aldehydes, not ketones.

Therefore, among the options provided, only the Iodoform test is specific for dimethyl ketones. This test is widely discussed in organic chemistry laboratories as a classical method for identifying methyl ketones. It is an important reaction because it not only helps in qualitative analysis but also demonstrates how functional groups determine the behavior of organic compounds.

By focusing on the reaction pathway and characteristic yellow precipitate, students can easily remember that the iodoform test is the standard method of characterizing dimethyl ketones.