Q.An aromatic organic compound 'A' with molecular formula $C_8H_8O$ gives positive DNP and iodoform tests. It neither reduces Tollens' reagent nor does it decolourise bromine water. Write the structure of 'A'.

Haloform (Iodoform) Reaction

The haloform reaction is a characteristic reaction of methyl ketones (compounds containing the $CH_3\text{-}CO\text{-}$ group) and of ethanal and ethanol (which carry the $CH_3\text{-}CH(OH)\text{-}$ unit). When such a compound is treated with a halogen ($X_2$) in the presence of a base (NaOH), the three hydrogens of the methyl group are successively replaced by halogen, and the resulting trihalomethyl carbonyl compound is then cleaved by hydroxide.

The overall result is that the $CH_3\text{-}CO\text{-}$ fragment is lost as a haloform ($CHX_3$), while the rest of the molecule is converted into a carboxylate ion (and, on acidification, a carboxylic acid). For example, with iodine and NaOH a methyl ketone $R\text{-}CO\text{-}CH_3$ gives $R\text{-}COO^-Na^+$ and a yellow precipitate of iodoform, $CHI_3$:

$R\text{-}CO\text{-}CH_3 + 3I_2 + 4NaOH \rightarrow R\text{-}COONa + CHI_3\downarrow + 3NaI + 3H_2O$ …