Q8. - Organic Chemistry

Question

Question: As we learned in Chapter 20, organolithium reagents (RLi) are strong bases that readily react with acidic protons. Why aren’t organolithium reagents used to generate enolates?

Step-by-Step Solution

Answer

Answer

Organolithium reagents are nucleophiles with a strong base. By using them in reactions containing carbonyl groups, they can undergo enolizations as well as take part in a nucleophilic attack. Thus, the yield of enolates decreases.

 

So, it preferred to use those reagents that act only as a base, for example, LDA and NaH.

Step 1: Function of organolithium reagents

Organolithium reagents function both as a nucleophile and a base. They function as a nucleophile when there is a possibility of a nucleophilic attack, while they function as a base when strong acidic protons are present. When a carbonyl group is present, they tend to function both as a nucleophile and a base.

Representation of RLi acting both as a nucleophile and a base

Step 2: Preferred reagents for enolate formation

Reagents that function only as a base are found to be more suitable for enolate formation.

Representation of an enolate formation by the addition of a base

Based on the steps mentioned, it is clear that organolithium reagents are nucleophiles with a strong base. By using them in reactions containing carbonyl groups, they can undergo enolizations as well as take part in a nucleophilic attack. Thus, the yield of enolates decreases.

 

So, it preferred to use those reagents that act only as a base, for example, LDA and NaH.