Preferred direction of proton transfer
Acid-base reactions involve proton (H+) transfer from the reactant acid to the reactant base.
This proton transfer is reversible as the products of the reaction are also an acid and a base.
If the reactant acid is weaker than the product acid, the forward reaction is
Reactions are product-favoured in one direction and reactant-favoured in the opposite direction.
Thus it is true that if the
This proton transfer is reversible as the products of the reaction are also an acid and a base.
| HA | + | B |  | BH+ | + | A– |
| acid | base | conjugate acid | conjugate base |
Proton transfer reactions are fast, and equilibrium is reached on mixing.
If the reactant acid is stronger than the product acid, the forward reaction is
product-favoured (products predominate in the reaction mixture).
If the reactant acid is weaker than the product acid, the forward reaction is
reactant-favoured (reactants predominate in the reaction mixture).
Reactions are product-favoured in one direction and reactant-favoured in the opposite direction.
Thus it is true that if the
preferred direction of proton transfer is known, the relative strengths of the acid reactant and the acid product can be deduced.
pKa of both the reactant and product acids are known, the preferred direction of proton transfer can be predicted.
pKa of both the reactant and product acids are known, the preferred direction of proton transfer can be predicted.