Solvent Stabilization of Ions

Solvation is a hard-hard interaction, and therefore the smaller and harder the ion, the more energy is released when it is solvated. The more energy released, the more stabilized and tightly solvated the ion is. Tightly solvated ions will be less useful in reactions because to react they must break out of this stabilizing solvation. The tightness of solvation will have a major effect in determining reactivity. The importance of solvation is often underestimated in chemical reactions. 

Solvent polarity can restrict the possibilities for reaction paths. Whenever charged species are present in a reaction, the reaction barrier is highly dependent on the polarity of the solvent (Fig. 2.27). Solvent stabilization of the reactants more than the products decreases reactivity. Solvent stabilization of the products more than the reactants increases reactivity. In addition to stabilizing ions, polar protic solvents can also allow proton transfer and equilibration between the various ionic species in solution. 

Which of the following solvents, ethanol, hexane, diethyl ether, would dissolve the most KOH The least  

Answer KOH is a salt and therefore very polar. It will dissolve the most in a polar solvent, the least in a nonpolar. The most polar solvent of the three is ethanol. Hexane is nonpolar diethyl ether is slightly polar. 

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