Could you explain why we would want to attempt to remove an impurity of a water insoluble thiol from a water insoluble alcohol by washing with aqueous NaOH? (Thiols are more acidic than alcohols, so can be significantly deprotonated in an aqueous solution at pKa 14 or less. - GS).

^^^So would the same answer apply if the question was to attempt to remove an impurity of a water insoluble alcohol from a water insoluble ester? (No. pKa of alcohols are about 15. - GS).