Which one of the following does not give Cannizzaro reaction?

Concept:

Cannizzaro’s reaction-

• Aldehydes that do not have alpha hydrogen, undergo Cannizaro reaction.
• Self oxidation and reduction take place here in presence of a concentrated aqueous or alcoholic solution of potassium hydroxide.
• Products formed are - an alcohol and a salt of carboxylic acid are produced. 

 Basically,

• Compounds having alpha hydrogen will not give Cannizzaro's reaction
• Compounds not having alpha hydrogen will give Cannizzaro's reaction.

Mechanism:

Explanation:

Let us examine the above structures to check for alpha hydrogens.

1.Formaldehyde has no alpha hydrogen.

Hence, this will show Cannizzaro’s reaction.

2.

Hence, acetaldehyde will not show Cannizzaros Reaction.

3. Benzaldehyde will show Cannizzaro reaction as it has no alpha hydrogen atoms giving products benzyl alcohol and benzoic acid.

4. Formaldehyde will also show Cannizzaro reaction due to the presence of alpha Hydrogen.

Hence, acetaldehyde does not give Cannizzaro reaction.

Additional Information

• All aldehydes can be made to undergo the Cannizaro reaction in the presence of the base Aluminium Ethoxide.
• Under these conditions, the acid and the base combine to form Ester and the reaction is known as Tischenko reaction.