Amongst the following compounds, the one that will not respond to Cannizzaro reaction upon treatment with…

Amongst the following compounds, the one that will not respond to Cannizzaro reaction upon treatment with alkali is
  1. $\mathrm{Cl}_{3} \mathrm{CCHO}$
  2. $\mathrm{Me}_{3} \mathrm{CCHO}$
  3. $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CHO}$
  4. HCHO

Solution

For a carbonyl group to give Cannizaro reaction, it should not have an $\alpha$ -hydrogen atom. Among the given compound $\mathrm{Ne}_{3} \mathrm{CCHO}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CHO}$ and HCHO respond
to Cannizaro reaction but $\mathrm{Cl}_{3} \mathrm{CCHO}$ do not due to the following reason.


When hydroxyl group attacks the carbonyl group a tetrahedral intermediate forms. This tetrahedral intermediate will revert to a carbonyl compound by
expelling the best leaving group. The CCl $_{3}$ carbonium is resonance stabilised therefore it is better leaving group than OH. These initial products exchange a proton to give ion of carboxylic acid and trichloromethane ($CHCl_{3}$). ^

Asked in: JEE-TOPICTESTS-CHEMISTRY

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