Chemistry · Alcohols, Phenols and Ether

Substrates that successfully undergo the haloform reaction are methyl ketones and secondary alcohols oxidizable to methyl ketones, such as isopropanol. The only primary alcohol and aldehyde to undergo this reaction are ethanol and acetaldehyde, respectively.

Formaldehyde does not have the necessary structure to undergo the haloform reaction, which requires a methyl ketone or an alcohol that can be oxidized to one.

Acetaldehyde gives the haloform test because it contains the necessary -CHO group adjacent to a methyl group.

Acetone is a methyl ketone, and it can undergo the haloform reaction to form a haloform like iodoform.

Alpha-phenylethyl alcohol can be oxidized to a methyl ketone, making it capable of giving a positive haloform test.

Options B, C, and D all give a positive haloform test due to their structures.