According do J.D. Lee's Concise Inorganic Chemistry, LiCl is soluble in alcohols because it has some covalent nature, althought it is mainly polar.

Why would LiCl have covalent character? Why doesn't this happen to NaCl?

Also, is this explanation true? A friend of mine said this solubility was because of the polar nature of small alcohols. Which of them is right?

  • 3
    $\begingroup$ en.m.wikipedia.org/wiki/Fajans'_rules is a good place to start $\endgroup$ Apr 12 '19 at 14:26
  • $\begingroup$ Small sized cations have high electronegativity due to strong electrostatic attraction between the cation to the valence electron orbital. Cl and Li have quite similar electronegativities, so a (largely) covalent bond results. Sodium has a much larger size than Li, thus has low electronegativity. The solubility of LiCl in alcohols is due to covalent nature of bonding in both of them (like-dissolves-like). The polarity of alcohols is less than that of water; you'd expect LiCl to be more soluble in water than alcohols then. $\endgroup$
    – Kartik
    Apr 13 '19 at 16:36
  • $\begingroup$ Related: chemistry.stackexchange.com/questions/115112/…. $\endgroup$ Mar 13 '20 at 10:21

The covalent character of any compound can be predicted on the basis of Fajans' Rule.

Fajans' Rule, simply stated, says that a smaller cation can polarize a given anion better than a larger cation and that larger anions are more polarizable than smaller anions.

$\ce{Li+}$ being a small cation polarizes $\ce{Cl-}$ to a good extent and since any amount of polarization increases the covalent character of a compound, $\ce{LiCl}$ can be said to have some covalent nature.

$\ce{LiCl}$ being somewhat covalent dissolves in organic solvents(Remember, Like dissolves Like) such as ethanol, acetone, ethyl acetate and pyridine.

Further, since $\ce{Na+}$ is unable to polarize $\ce{Cl-}$ to a good degree it is regarded mainly as an ionic compound.


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