MCQ Detailed View

Dimethyl ketone, also known as acetone, is the simplest ketone with the formula CH₃COCH₃. It contains a methyl group directly attached to the carbonyl carbon, classifying it as a methyl ketone. Methyl ketones are uniquely identified using the iodoform test.

The iodoform test uses iodine (I₂) in the presence of a base like sodium hydroxide (NaOH). In this reaction, the methyl group adjacent to the carbonyl in a methyl ketone undergoes halogenation and subsequent cleavage to form a yellow precipitate of iodoform (CHI₃), which has a distinct antiseptic smell. The formation of this yellow solid confirms the presence of a methyl ketone group.

The test is specific to compounds that have the CH₃–CO– structure. Acetone, being a dimethyl ketone, gives a strong positive iodoform test. Other compounds like ethanol (which can oxidize to acetaldehyde) also yield a positive result, but the test is most commonly associated with methyl ketones.

Tollen’s reagent is used to identify aldehydes, not ketones. Schiff’s test is also specific to aldehydes and gives a purple color upon reaction. Benedict’s reagent is mainly used to detect reducing sugars and aldehydes with free carbonyl groups, not ketones.

The iodoform test remains an important qualitative method in organic chemistry labs to identify methyl ketones like acetone. It helps in distinguishing between aldehydes, non-methyl ketones, and methyl ketones based on their reaction behavior with halogens under alkaline conditions.