Q17-76E - Organic Chemistry (Mcmurry)

Question

The reduction of carbonyl compounds by reaction with hydride reagents $\left(H{:}^{-}\right)$ and the Grignard addition by reaction with organomagnesium halides $\left(R{:}^{-}{}^{+}\mathrm{MgBr}\right)$ are examples of nucleophilic carbonyl addition reactions. What analogous product do you think might result from reaction of cyanide ion with a ketone?

Step-by-Step Solution

Answer

The resulting molecule will have CN and OH group on same carbon, which was earlier carbonyl carbon.

Step 1: Nucleophile

Nucleophiles are electron rich species which attack electron deficient species. Arrows in a nucleophilic reaction are shown toward electron deficient species.

Step 2: Electrophile

Electrophiles are electron deficient species which are attacked by electron rich species known as nucleophiles.

Step 3: Nucleophile attacking electrophile

In carbonyl group carbon is acting as electrophile as it is electron deficient as oxygen is withdrawing electron from it. Cyanide ion is an electron rich species as it is an anion. 

So cyanide ion will attack the carbon of carbonyl group resulting in attachment of CN and oxygen become negatively charged. This reaction is occuring in presence of hydronium ion so the protonation of oxygen resulted in OH formation. 

The resulting molecule will have CN and OH group on earlier carbonyl carbon.