9-9-56 E-d - Organic Chemistry (Mcmurry)

Question

Which of the following bases could be used to deprotonate 1-butyne?

d)

Step-by-Step Solution

Answer

Acetone enolate will not deprotonate 1- butyne.

Enolate

Enolates are referred to as those species which are having negative charge on the oxygen atom due to the formation of anions whenever alpha- hydrogen atoms are deprotonated. Alpha- hydrogen atoms are those hydrogen atoms which are attached to the carbon atoms which are lying next to the carbonyl group. Ketons and aldehyde groups both are carbonyl compounds and enolates are conjugate base of both the keto and enol forms.

Explanation

This is an enolate of keto form and also known as acetone enolate this is a base and its conjugate acid is acetone whose pK_a value is 19 which is stronger acid than 1- butyne which have pK_a  value equals to 25. As we know that if conjugate acid of a base is a stronger acid then that base will not be able to deprotonate other acid.

Hence, acetone enolate will not deprotonate 1- butyne.