Question

Product of this Cannizzaro reaction is:
(A) $\text{D}-\text{CO}_{_{2}}^{-}+\text{C}{{\text{H}}_{2}}\text{DOD}$
(B) $\text{H}-\text{CO}_{_{\text{2}}}^{-}+\text{D}-\text{C}{{\text{O}}_{2}}$
(C) $\text{D}-\text{CO}_{_{2}}^{-}+\text{C}{{\text{H}}_{\text{2}}}\text{DOH}$
(D) \[\text{D}-\text{CO}_{_{\text{2}}}^{-}+\text{CH}{{\text{D}}_{\text{2}}}\text{OH}\]

Answer 1

Hint: The products that form during the Cannizzaro reaction are usually primary alcohols and carboxylic acid or carboxylate ions sometimes. It is a disproportionation reaction of an aldehyde with no alpha hydrogens.

Complete step by step solution: The Cannizzaro reaction is a disproportionation reaction of two molecules of aldehyde that does not contain any alpha hydrogens in the presence of a base. The products obtained from this reaction are a primary alcoholic compound and a carboxylic acid.
The reaction proceeds through a mechanism of nucleophilic acyl substitution on an aldehyde where a nucleophile is a hydroxyl group that comes from a base and produces a dianion.

The dianion intermediate then acts as a reducing agent and releases hydride ion which further attacks another aldehyde molecule. The products formed at this step are a carboxylate ion and an alkoxide ion.

In the last step, an alkoxide ion takes up a proton from the solvent (water) and forms alcohol.

The carboxylate remains as it is because it is less basic than water and thus it cannot acquire a proton from water to form a carboxylic acid. So, the products formed are – carboxylate ions and primary alcohol.
The overall reaction can be represented as follows:

Hence, the answer is (C) $\text{D}-\text{CO}_{_{2}}^{-}+\text{C}{{\text{H}}_{\text{2}}}\text{DOH}$.

Note: Aldehydes having alpha hydrogen undergo crossed Cannizzaro reaction in which both the aldehydes get used up to form an alcohol and a carboxylic acid and thus this reaction is generally used to get a better yield of products without wastage of reactants.