Question

The mechanism of Cannizzaro's reaction of benzaldehyde is

Which of the following reactants can undergo Cannizzaro's reaction?
A.

B. $R_{3}CCHO$
C.

D. All of these

Answer 1

Hint: Cannizzaro reaction is a disproportionation reaction that means the reaction involves the self oxidation and reduction reaction. As a result of the reaction, one molecule of the reactant was reduced to alcohol and the other oxidized to the carboxylic acid.

Complete step by step answer:
As we know that the aldehyde which does not contain α hydrogen undergoes the Cannizzaro reaction. If we talk about option A i.e. formaldehyde or methanal, there is no $\alpha$ hydrogen thus it undergoes the Cannizzaro reaction.
If we talk about the in option B, there is a presence of α hydrogen thus it does not undergo a Cannizzaro reaction.
If we talk about option C, there is also no α hydrogen thus it undergoes the Cannizzaro reaction.

So, the correct answer is Option A,C .

Additional information:
If two different aldehydes are present as a reactant then the reaction carried out is known as the cross Cannizzaro reaction. If one of the reactants is formaldehyde then the cross Cannizzaro reaction is of a great synthetic utility and it gives sodium formate and alcohol corresponding to the other aldehyde.

Note: It may be noted that the Cannizzaro reaction is the characteristic of aldehydes having no α hydrogen, but it is not confirmed to them. Certain aliphatic monoalkylated aldehydes undergo disproportionation reactions when heated with aq. NaOH. This exceptional behavior is probably due to the +I effect of two alkyl groups. In this aldehydes prefer to undergo a nucleophilic attack by $O{H}^{-}$ ion at the aldehyde group giving intermediate which acts as a hydride donor to the second molecule of aldehyde to give disproportionation reaction.