1. Phenols

2. Classification of Phenols
Phenols classified according to the number of hydroxyl groups attached directly to the benzene ring
1- Monohydroxy phenol

3. Classification of Phenols
2- Dihydroxy phenol

4. Classification of Phenols
1- Trihydroxy phenol

5. Structure and Nomenclature of Phenols
Phenols have hydroxyl groups bonded directly to a benzene ring
Naphthols and phenanthrols have a hydroxyl group bonded to a polycyclic benzenoid ring

6. Nomenclature of Phenols
Phenol is the parent name for the family of hydroxybenzenes
Methylphenols are called cresols

7. Synthesis of Phenols Laboratory Synthesis
Phenols can be made by hydrolysis of arenediazonium salts

8. Industrial Syntheses 1. Hydrolysis of Chlorobenzene (Dow Process)
Chlorobenzene is heated with sodium hydroxide under high pressure
The reaction probably proceeds through a benzyne intermediate
2. Alkali Fusion of Sodium Benzenesulfonate
Sodium benzenesulfonate is melted with sodium hydroxide

9. Reactions of Phenols as Acids
Strength of Phenols as Acids
Phenols are much stronger acids than alcohols

10. Phenol is much more acidic than cyclohexanol
Experimental results show that the oxygen of a phenol is more positive and this makes the attached hydrogen more acidic
The oxygen of phenol is more positive because it is attached to an electronegative sp2 carbon of the benzene ring
Resonance contributors to the phenol molecule also make the oxygen more positive

11. Distinguishing and Separating Phenols from Alcohols and Carboxylic Acids
Phenols are soluble in aqueous sodium hydroxide because of their relatively high acidity
Most alcohols are not soluble in aqueous sodium hydroxide
A water-insoluble alcohol can be separated from a phenol by extracting the phenol into aqueous sodium hydroxide
Phenols are not acidic enough to be soluble in aqueous sodium bicarbonate (NaHCO3)
Carboxylic acids are soluble in aqueous sodium bicarbonate
Carboxylic acids can be separated from phenols by extracting the carboxylic acid into aqueous sodium bicarbonate

12. Other Reactions of the O-H Group of Phenols
Phenols can be acylated with acylation agents (acid chlorides and anhydrides )

13. Phenols in the Williamson Ether Synthesis
Phenoxides (phenol anions) react with primary alkyl halides to form ethers by an SN2 mechanism

14. Cleavage of Alkyl Aryl Ethers
Reaction of alkyl aryl ethers with HI or HBr leads to an alkyl halide and a phenol
Recall that when a dialkyl ether is reacted, two alkyl halides are produced

15. Reaction of the Benzene Ring of Phenols
Bromination
The hydroxyl group is a powerful ortho, meta director and usually the tribromide is obtained
Monobromination can be achieved in the presence of carbon disulfide at low temperature
Nitration
Nitration produces o- and p-nitrophenol
Low yields occur because of competing oxidation of the ring

16. Sulfonation
Sulfonation gives mainly the the ortho (kinetic) product at low temperature and the para (thermodynamic) product at high temperature

17. The Kolbe Reaction
Carbon dioxide is the electrophile for an electrophilic aromatic substitution with phenoxide anion
The phenoxide anion reacts as an enolate
The initial keto intermediate undergoes tautomerization to the phenol product
Kolbe reaction of sodium phenoxide results in salicyclic acid, a synthetic precursor to acetylsalicylic acid (aspirin)