Question

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

(c)

Short answer

n- BuLi$\left({\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Li}\right)$ will deprotonate 1- butyne.

Step-by-step solution

n-Butyllithium

This is also an organometallic compound in which there is a bond between carbon atom and lithium group. It is also written as n-BuLi and its chemical formula is${\mathrm{C}}_4{\mathrm{H}}_9\mathrm{Li}$. It is most commonly used in polymerization reaction. It is a colorless compound and is highly unstable.

Structure and Applications

It exists as a cluster. When n- BuLi is placed in ether solution it exist as a tetrameric cluster and when it is placed in cyclohexane solution it exist as a hexameric cluster. When substituted alkyl groups are attached with the n- BuLi then it will form distorted cluster.

Its main application is it acts as an initiator for the polymerization of alkenes.

Explanation

Conjugate acid of n- BuLi is butane and its pK_avalue is approximately 60 and that of 1- butyne is 25. Among these pK_a value of conjugate acid of base (n- BuLi) is higher and as we know that higher the pK_a value, weaker will be that acid. Hence, conjugate acid of given base is weak acid and as we are aware that if conjugate acid will be weak base will be able to easily deprotonate other acid.

Hence, n- BuLi will deprotonate 1- butyne.