Chemistry Aldehydes & Ketones MDCAT 2011
PMDC Verified Question 92 of 94
Consider the reaction:

$$ HCHO + HCN \longrightarrow H_2C(OH)CN $$

In the above reaction nucleophile is:
A
\( CN^- \)
B
\( HCl \)
C
\( Cl^- \)
D
\( OH^- \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( CN^- \)
Concept:

The addition of Hydrogen Cyanide (\( HCN \)) to a carbonyl compound is a base-catalyzed nucleophilic addition reaction.

Solution:

  • The base removes a proton from \( HCN \) to generate the active nucleophile, the cyanide ion (\( CN^- \)).


  • The \( CN^- \) ion attacks the electrophilic carbonyl carbon of formaldehyde (\( HCHO \)), breaking the carbon-oxygen \( \pi \) bond to form an intermediate alkoxide.


  • Protonation of the alkoxide yields the final cyanohydrin product.


Why other options are incorrect:

\( HCl \) is an acid, not a nucleophile. \( Cl^- \) and \( OH^- \) are not involved as the attacking species forming the new carbon-carbon bond in this specific reaction.

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