Question

How many of the following regents can distinguish between phenol and cyclohexanol? (1) Na (2) anh. $ZnCl_2$ + conc. HCl (3) $NaNH_2$ (4) $Na_2Cr_2O_7$ (5) Neutral $FeCl_3$ (6) $(NH_4)_2[Ce(NO_3)_6]$ (7) $Br_2/H_2O$

Answer 1

5

Answer 2

• Reagent 2 (Lucas Reagent): Cyclohexanol (2° alcohol) reacts to form turbidity; phenol does not react.
• Reagent 4 ($Na_2Cr_2O_7$/Acid): Cyclohexanol is oxidized (color change from orange to green); phenol is resistant to oxidation.
• Reagent 5 (Neutral $FeCl_3$): Phenol gives a characteristic color; cyclohexanol does not.
• Reagent 6 (CAN): Phenol gives a color; cyclohexanol does not.
• Reagent 7 ($Br_2/H_2O$): Phenol forms a white precipitate and decolorizes $Br_2$; cyclohexanol does not.
• Reagents 1 (Na) and 3 ($NaNH_2$) react with both compounds, producing similar observable gas evolution ($H_2$ and $NH_3$ respectively), hence they are not distinguishing.