Question

To test the effect of solvent on the rate of SN1 reactivity compare the time needed for a precipitate to appear when 2-chlorobutane is treated with 1% ethanolic silver nitrate solution, and when treated with 1% silver nitrate in a mixture of 50% ethanol and 50% water. Please explain the results (below) for this experiment.

Results

1% ethanolic silver nitrate solution --> formed precipitate after 8:03 minutes

1% silver nitrate (in a mixture of 50% ethanol and 50% H2O) --> formed precipitate after 9:16 minutes

Answer 1

Solution:- When 2-chlorobutane is treated with silver nitrate then product 2-nitrobutane and side product silver chloride are formed. silver chloride comes as the precipitate.This reaction is SN¹ so rate of the reaction is dependent on both the reactant 2-chlorobutane and silver nitrate.

2-chlorobutane is a nonpolar compound which is insoluble in water . so in first case

1) When 1% ethanolic silver nitrate solution was taken all of the reactant was present for the reaction so reaction is comparatively fast then when 1% silver nitrate in a mixture of 50% ethanol and 50% water was taken

2) In second case 1% silver nitrate in a mixture of 50% ethanol and 50% water was taken the portion of silver nitrate which was soluble in water was unavailable for the reaction because 2-chlorobutane is insoluble in water , as the reaction is SN₁ means rate depends on both the reactants, due to water as solvent available concentration of silver nitrate decreased hence the rate also decreased in the second case.