Test: Alkanals and Alkanones - JAMB MCQ

Alkanals and alkanones are organic compounds that contain the functional group known as the aldehyde group. Alkanals are aldehydes, while alkanones are ketones.

Alkanals and alkanones generally have higher boiling points compared to other organic compounds due to the presence of polar carbonyl groups. These groups increase intermolecular forces, resulting in higher boiling points.

Butanone is the systematic name for the alkanone with the molecular formula C₃H₆O. It is also known as methyl ethyl ketone (MEK).

Alkanals and alkanones are commonly used as food preservatives to prevent spoilage. They have antimicrobial properties that inhibit the growth of bacteria and fungi in food products.

Fehling's test is commonly used to distinguish between alkanals (aldehydes) and alkanones (ketones). It involves the reaction of the carbonyl group with copper(II) ions, resulting in the formation of a colored precipitate.

Alkanals (aldehydes) would form a silver mirror in the Tollen's test. The aldehyde group reduces silver ions to metallic silver, resulting in the formation of a silver mirror on the inner surface of the test tube.

Fehling's test involves the use of Fehling's solution, which contains copper(II) sulfate. The alkanal or alkanone reacts with the copper(II) ions, leading to the reduction of copper(II) ions to copper(I) oxide, which appears as a colored precipitate.

A positive result in the Fehling's test is the formation of a brick-red precipitate. This indicates the presence of an alkanal (aldehyde) or a reducing sugar, which can react with the copper(II) ions in Fehling's solution.

The reaction of an alkanal or alkanone with 2,4-DNP (2,4-dinitrophenylhydrazine) reagent forms a colored precipitate. This test is known as Schiff's test and is used to identify the presence of aldehydes and ketones.

Butanone would give a positive result in the 2,4-DNP test, forming a colored precipitate. This test is specific for alkanones (ketones) and helps differentiate them from aldehydes.