Question

The correct sequence of steps involved in the mechanism of Cannizzaro reaction is:
A. nucleophilic attack, transfer of ${{H}^{-}}$ and transfer of ${{H}^{+}}$
B. transfer of ${{H}^{-}}$, transfer of ${{H}^{+}}$ and nucleophilic attack
C. transfer of ${{H}^{+}}$ nucleophilic attack and transfer of ${{H}^{-}}$
D. electrophilic attack by $O{{H}^{-}}$ transfer of${{H}^{-}}$ and transfer of ${{H}^{-}}$

Answer 1

Hint: Cannizzaro reaction is a reaction in which disproportionation of two molecules of aldehyde takes place to give a primary alcohol and a carboxylic acid, it involves the nucleophilic substitution on aldehydes.

Complete step by step answer:
- We can see from the following mechanism that how Cannizzaro reaction takes place:
- We can see that in step 1, we have, one HCHO and one $O{{H}^{-}}$, which will react together and this will be the fast step of the reaction, we can say that there is nucleophilic attack of $O{{H}^{-}}$ to the carbonyl carbon and we get:

- In step 2, we can see that the transfer of hydride ions from anion to the second molecule of aldehyde takes place. And finally the rapid transfer of protons takes place.

- Hence, we can conclude that the correct sequence of steps involved in the mechanism of Cannizzaro reaction is: nucleophilic attack, transfer of ${{H}^{-}}$ and transfer of ${{H}^{+}}$
So, the correct answer is “Option C”.

Note: - This reaction is always given by aldehydes that doesn’t have an alpha hydrogen atom (it is present on the alpha carbon). For example, acetaldehyde doesn’t undergo a cannizzaro reaction because it has alpha hydrogen.