Question

Complete each proton transfer reaction using curved arrows to show electron movement.  Use pK_avalues (or approximate ones, from notes or textbook) to determine whether the reaction is reactant or product favored. Give an approximate equilibrium constant for the reaction (like 10⁵or 10^-16, etc.).

i.hydroxide ion with phenol.

ii.CH₃OH (methanol) with sulfuric acid

iii.Aniline (PhNH₂) with HCl.

iv.NaNH₂with ethanol.

v.Hydride ion with 1-butyne

vi.Phenol (acid) with water (base)

vii.Phenoxide (PhO^-) ion with water

viii.Acetone with NaOH

Answer 1

1.Reaction will favour product side. Phenoxide ion is much more stable than the hydroxide ion. This makes phenol a much better acid than hydroxide ion. This can also be verified using pka data. The better the acid the lesser is the pka.

2.Sulphuric acid is one of the best acids so the reaction will favour the product side. Only concept I use here is that the acid in the reaction should have lesser pka value to the base.

3.This reaction also favours product side. Due to the very high acidic strength of HCl.

4.This reaction also favours product side. Same logic is used. (pka values)

5.This reaction also favours product side. Same logic.

6.This reaction also favours the product side.

7.This reaction favours the reactant side. This is because phenol is a stronger acid as compared to water. So the opposite reaction is favourable.

8.This reaction with the normal logic should not favour the product side. But, surprisingly it does. This is because after the proton transfer the deprotonated acetone goes through aldol-condensation. As a result the product of our acid-base reaction constantly gets used up so the reaction proceeds moore and more forward.