Question

What is the product of the reaction of an ester with excess acetylide ion followed by the addition of pyridinium chloride?

Short answer

The product is tertiary alcohol.

Step-by-step solution

Reaction of acetylide ion with ester

When ester is reacted with acetylide ion, it forms a ketone first.This is a type of nucleophilic addition-elimination reaction.

Step 2: Addition of pyridinium chloride

After the nucleophilic addition-elimination reaction, the ketone is then converted to a tertiary alcohol finally. This is a process of nucleophilic addition reaction. The complete reaction is given below:

Addition of pyridinium chloride

Use of pyridinium chloride in nucleophilic addition reaction

Pyridinium chloride helps in protonating the alkoxide ion. HCl or H₃O⁺ is not used instead of pyridinium chloride because they cannot form triple bonds.