Question

Identify the final product formed during the course of the given reactions.
% Reaction given Pentan-2-one $\xrightarrow{\text{NaCN/HCl}} [X] \xrightarrow{\Delta, 95% H_2SO_4} [Y]$

• A. \text{CH}_3-\text{C}=\text{CH}-\text{CH}_2\text{CH}_3
  \text{CH}_2\text{NH}_2
• B. \text{CH}_2=\text{C}-\text{CH}_2\text{-CH}_2\text{-CH}_3
  \text{CN}
• C. \text{CH}_2=\text{C}-\text{CH}_2\text{-CH}_2\text{-CH}_3
  \text{COOH}
• D. \text{CH}_3-\text{C}=\text{CH}-\text{CH}_2\text{CH}_3 \text{CN}

Hint:

In reactions involving carbonyl compounds, nucleophilic substitution of the carbonyl group with a cyanide ion can form an intermediate nitrile, which, under dehydration conditions, can lead to the formation of an $\alpha$,$\beta$-unsaturated compoun(D)

Answer 1

The Correct Option is D

The given reaction involves pentan-2-one, which is a $\alpha$-keto compoun(D) The first reaction involves the nucleophilic substitution of a cyanide ion (from NaCN/HCl) with the carbonyl carbon of pentan-2-one. This leads to the formation of an intermediate product (X) with a nitrile group (-CN) attached to the alpha carbon. In the second step, heating with concentrated H\(_2SO_4\) induces a dehydration reaction. The result of this dehydration is the formation of an $\alpha$,$\beta$-unsaturated nitrile compound (Y), which is a conjugated system between the carbon-carbon double bond and the nitrile group. Thus, the final product formed is: \[ \text{CH}_3-\text{C}=\text{CH}-\text{CH}_2\text{CH}_3 \text{CN} \] This is option (D).