Which of the following bases cannot deprotonate acetylene? You are given the pK_a values of the conjugate acids in parentheses. $\mathrm { CH } _ { 3 } \mathrm { NH } ^ { - } \left( \mathrm { p } K _ { a } = 40 \right) \quad \mathrm { CO } _ { 3 } ^ { 2 - } \left( \mathrm { p } K _ { a } = 10.2 \right) \quad \mathrm { CH } _ { 2 } = \mathrm { CH } ^ { - } \left( \mathrm { p } K _ { a } = 44 \right) \quad \left( \mathrm { CH } _ { 3 } \right) _ { 3 } \mathrm { CO } ^ { - } \left( \mathrm { p } K _ { a } = 18 \right)$
I $\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad$ II $\quad\quad\quad\quad\quad\quad\quad\quad\quad$ III $\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad$ IV

Question

Which of the following bases cannot deprotonate acetylene? You are given the pK_a values of the conjugate acids in parentheses.

\mathrm { CH } _ { 3 } \mathrm { NH } ^ { - } \left( \mathrm { p } K _ { a } = 40 \right) \quad \mathrm { CO } _ { 3 } ^ { 2 - } \left( \mathrm { p } K _ { a } = 10.2 \right) \quad \mathrm { CH } _ { 2 } = \mathrm { CH } ^ { - } \left( \mathrm { p } K _ { a } = 44 \right) \quad \left( \mathrm { CH } _ { 3 } \right) _ { 3 } \mathrm { CO } ^ { - } \left( \mathrm { p } K _ { a } = 18 \right)

I

\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad

II

\quad\quad\quad\quad\quad\quad\quad\quad\quad

III

\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad

IV

Quizplus · Accepted Answer

A base can deprotonate acetylene if its conjugate acid has a higher pKa than acetylene (pKa ~ 25). CO3^2- (pKa = 10.2) and (CH3)3CO^- (pKa = 18) have conjugate acids with lower pKa values than acetylene, so they cannot deprotonate it.

Which of the Following Bases Cannot Deprotonate Acetylene? You Are