Chemistry - GOC Question with Solution | TestHub

A base deprotonates water ($\mathrm{p}{K}_{\mathrm{a}}$ 15.7) only if its own conjugate acid is weaker than water, i.e. has a higher $\mathrm{p}{K}_{\mathrm{a}}$. (a) isopropoxide : iPrOH $\mathrm{p}{K}_{\mathrm{a}}$ ≈ 17 - yes. (b) phenoxide : phenol $\mathrm{p}{K}_{\mathrm{a}}$ ≈ 10 - no. (c) $\mathrm{N}{\mathrm{H}}_2^{-}$ : $\mathrm{N}{\mathrm{H}}_3$ $\mathrm{p}{K}_{\mathrm{a}}$ 38 - yes. (d) ${\mathrm{F}}^{-}$ : $\mathrm{HF}$ $\mathrm{p}{K}_{\mathrm{a}}$ 3.2 - no. (e) ketone enolate : α C-H $\mathrm{p}{K}_{\mathrm{a}}$ ≈ 20 - yes. (f) acetate : AcOH $\mathrm{p}{K}_{\mathrm{a}}$ 4.8 - no. So the bases are a, c and e.