Write a mechanism for the reaction of ethanal and HCN to form 2-hydroxypropanenitrile, and name the type of…

Question

Write a mechanism for the reaction of ethanal and HCN to form 2-hydroxypropanenitrile, and name the type of reaction.

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Here are the solutions to the questions:

5. (b)

(iv) The compound P can be obtained from the reaction of ethanal and HCN. Write a mechanism for the Reaction. Compound P is 2-hydroxypropanenitrile ( $\text{CH}_3\text{CH(OH)CN}$ ). This is formed by the nucleophilic addition of cyanide to ethanal ( $\text{CH}_3\text{CHO}$ ). The reaction is typically catalyzed by a base (e.g., $\text{CN}^-$ from $\text{KCN}$ ) to generate the nucleophilic cyanide ion.

Mechanism:

Nucleophilic attack by the cyanide ion on the carbonyl carbon of ethanal.
The $\pi$ -electrons of the C=O bond shift to the oxygen atom, forming an alkoxide intermediate. $\text{CH}_3\text{CHO} + \text{CN}^- \longrightarrow \text{CH}_3\text{CH}(\text{O}^-)\text{CN}$
Protonation of the alkoxide ion by HCN (or water) to form the cyanohydrin and regenerate the cyanide ion.
$$ \text{CH}_3\text{CH}(\text{O}^-)\text{CN} + \text{HCN} \longrightarrow \text{CH}_3\text{CH}(\text{OH})\text{CN} + \text{CN}^- $$ Overall reaction: $$ \boxed{\text{CH}_3\text{CHO} + \text{HCN} \xrightarrow{\text{CN}^-} \text{CH}_3\text{CH}(\text{OH})\text{CN}} $$
- (v) What name is given to the type of reaction between this reaction ethanal and HCN? The type of reaction is $\boxed{\text{Nucleophilic addition}}$ .

Write a mechanism for the reaction of ethanal and HCN to form 2-hydroxypropanenitrile, and name the type of reaction.