The following two compounds I and II are distinguished by using which of the reagent:

(i)

                     (ii)   

Reagents:

(P) aq. ${\mathrm{NaHCO}}_3$     (Q) Neutral ${\mathrm{FeCl}}_{3 }$  (R) Blue litmus solution   (S) Na metal       (T) $\mathrm{HCl}/{\mathrm{ZnCl}}_2$ anhydrous

Neutral ${\mathrm{FeCl}}_{3 }$used to detect the presence of a phenol functional group in a given sample. This test is based on the fact that the phenols give a colored complex with neutral ferric chloride solution. Phenol group reacts with the ferric ion of ferric chloride and forms a colored complex.

HCl/ZnCl₂ is known as Lucas reagent. This reagent is used to test the presence of alcohol whether it is primary, secondary, or tertiary.