Would adding a water soluble salt (e.g. NaCl) affect a water sensitive reaction?

Question

Let's take for example a reaction that would benefit from having less water in it, ester formation from alcohol and acid. We know that the equilibrium can be shifted to the right (ester formation) if water is constantly removed through distillation. My question is: would adding an excess of NaCl affect the reaction and push the reaction to the right?

The water would solvate the NaCl and theoretically be "preoccupied." I would like to think that water adding back to the ester to form an alcohol and acid would be more energetically favourable, but I don't really have enough knowledge to answer that on my own. Any thoughts?

Answer 1

Esterification

$\ce{R_1-COOH + HO-R_2 <=> R1-COO-R2 + H2O}$

has the equilibrium constant, expressed in compound activities:

$$K = \frac{a_\mathrm{ester} \cdot a_\mathrm{\ce{H2O}} }{ a_\mathrm{acid} \cdot a_\mathrm{alkohol}}$$

The water activity is decreased by dissolved salts by 2 ways:

1. decreasing the molar fraction of water by dissolved salt
2. decreasing its activity coefficient by bounding it by ion hydration.

As the result, dissolved salts decrease the numerator of the equilibrium expression and shift the equilibrium toward production of ester.

Present dissolved salts will partially affect activities of the acid and the alcohol as well, but in lesser extend.