JEE Main · 2021 · 26 Aug 2021 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

Acetophenone carries a methyl ketone group, and bromine in alkaline solution replaces all three hydrogens of that methyl group to give ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COCB}{\mathrm{r}}_3$, each substitution being easier than the one before because the electron-withdrawing bromines acidify the remaining hydrogens. Hydroxide then attacks the carbonyl carbon and expels the tribromomethyl anion, which the three bromine atoms stabilise well enough to make it a leaving group, so the carbon-carbon bond breaks. This is the haloform reaction, and in excess alkali the acid formed is isolated as its potassium salt. The products are potassium benzoate, ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOK}$, and bromoform, $\mathrm{CHB}{\mathrm{r}}_3$.