Predict the direction of the following equilibrium and the approximate value of Keq.
R-C≡C⁻ + RCH₂OH $⇌$ R-C≡C-H + RCH₂O⁻ (pKa : alcohol = 16, terminal alkyne = 25)

Question

Predict the direction of the following equilibrium and the approximate value of Keq. R-C≡C⁻ + RCH₂OH ⇌ R-C≡C-H + RCH₂O⁻ (pKa : alcohol = 16, terminal alkyne = 25)

TestHub · Accepted Answer

The acid on the left is the alcohol (pKa 16) and the acid on the right is the terminal alkyne (pKa 25). The alkyne is the much weaker acid, so the equilibrium lies far to the right : an alkoxide is more than strong enough to deprotonate a terminal alkyne. Keq ≈ 10²⁵⁻¹⁶ = 10⁹·

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