Exp. 12.3a The reactions of the phenolic functional group.

1. Solubility in H₂O

Pipette         test-tube                       small beakers    full range indicator         Bunsen burner

(ethanol water + ethanoic acid water in 2 beakers)

1.     cm³ water into a test-tube

2.     Add small amount of methyl 4-hydroxybenzoate (solid)

3.     with pipette observe if dissolves  (should dissolve)

4.     Test for pH (bit less than 7) (also for the pH of ethanol(7) and acid(lower that phenol)) expl. delocalised system is formed in phenolic, which is less stable than acid (no sys. in alcohol).

2a. Phenolic compounds as acids. Action of sodium

DRY test-tube          Bunsen             phenolic            2.5 mm cube sodium

1.     Heat until phenolic melts and stop heating

2.     Add sodium and observe carefully (hydrogen should be given off, can collect under water)

3.     Before pouring down the sink add ethanol to the cool test-tube

4.     ? In ethanol O-H bond breaks, here should too

2b. Action of NaOH

test-tube       5 cm³ NaOH 2M           2 cm³ dilute HCl

1.     add phenol to alkali

2.     warm and observe for solubility (should be better than in water)

3.     add acid (neutralises NaOH)

2c. Action of Na₂CO₃

5 cm³ carbonate + phenolic (no reaction - weak acid)

3. Formation of an ester

0.5g phenol   4 cm³ 2M NaOH           1 cm³ ethanoic anhydride           cork      ice-bath

1.     add alkali to phenol

2.     add anhydride to mixture

3.     cork tube and shake for few minutes

4.     anhydride is used instead of acid and alkaline conditions

4.a. Properties of the benzene ring

combustion spoon     Bunsen

Set phenolic to fire and observe flame

4.b. Iron (III) chloride

1.     dissolve some crystals of FeCl₃ in 5 cm³ H₂O and add 1 cm³ phenolic in H₂O. Note colour

2.     Do the same with alcohol

4.c. Bromine

1.     shake phenolic with H₂O

2.     Add bromine (reaction occurs readily, because of O delocalising electrons)