Question

In reaction
\[C{H_3}CN + 2H \overset{HCl,ether}{\rightarrow} X \to Y\] the term Y is?
A. Acetaldehyde
B. Ethylamine
C. Acetone
D. Dimethylamine

Answer 1

Hint: Alkyl cyanide or acetonitrile has a cyanide functional group which have triple bonds and a basic character. In the acidic condition, it would get protonated and on further steps, there is a chance of oxidation.

Complete Step by Step Solution:
In this reaction acetonitrile reacts with hydrogen in the presence of \[HCl\] and ether to give ethanimine with an imide functional group. Here, the triple bond of cyanide is converted into double bonds because of the addition of hydrogen to carbon and nitrogen. This is a reduction process and product X is ethanimine. Then X, on boiling with water gives acetaldehyde. Their oxidation reaction takes place. In this step, \[N{H_4}Cl\]i.e., ammonium chloride as a by-product forms and double bond of carbon attached to the oxygen of water.
This is Stephan’s reaction where alkyl cyanides are used to synthesize aldehyde.

Image:Steps in the reaction of alkyl cyanide to form acetaldehyde

So, option A is correct.

Additional Information:Ethers are very good solvents for organic reaction.\[HCl\] and ether reacts with each other to form etherate. \[HCl\] dissolves in ether and the \[C - O\]bond of ether get broken. The carbon of ether protonates and becomes a good leaving group. Here in this reaction, they work together as a solvent and help in the reduction of alkyl cyanides in presence of two hydrogens.

Note: Ethanimine are the organic compounds having imine functional group i.e.,\[ - C = N - \]. This reacts with water and forms a compound containing a carbonyl functional group such as ketone or aldehyde. In this question acetonitrile is given so it forms acetaldehyde. Here, the overall number of carbons remains the same.