Question

An unknown Aldehyde 'A' on reacting with alkali gives Beta-hydroxy-aldehyde, which loses water to from an unsaturated aldehyde, But-2-enal. Another aldehyde 'B' undergoes disproporational reaction in the presence of con.alkali to form products 'C' and 'D'. C is an aryl alcohol with the formula C7H8O.
i. Write the sequence of the reactions involved.
ii. Name the product, when 'B' reacts with Zinc amalgam and HCl.

Answer 1

When B reacts with Zinc Amalgam and HCl, Toluene (C6H5CH3) is formed

Explanation:

Aldehyde compound A in reacting with alkali gives a β-hydroxy aldehyde which loses water to form unsaturated aldehyde but-2-enal. This is Aldol condensation reaction.

The aldehyde compound B undergo disproportion reaction with concentrated alkali. This is Cannizzaro's reaction.

Product C is an aryl alcohol with formula C7H8O. It must be C6H5CH2OH and formed by the condensation of benzaldehyde.

A is Ethanol - CH3CHO.

B is Benzaldehyde - C6H5CHO

Please refer to the attached picture for the sequence of reactions.

When B reacts with Zinc Amalgam and HCl, Toluene (C6H5CH3) is formed.