1. Chapter 11 Phenols

2. 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
Chapter 21

3. Nomenclature of Phenols
Phenol is the parent name for the family of hydroxybenzenes
Methylphenols are called cresols
Chapter 21

4. Synthesis of Phenols Laboratory Synthesis
Phenols can be made by hydrolysis of arenediazonium salts
Chapter 21

5. 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 (Section 21.11B)
2. Alkali Fusion of Sodium Benzenesulfonate
Sodium benzenesulfonate is melted with sodium hydroxide
Chapter 21

6. Reactions of Phenols as Acids
Strength of Phenols as Acids
Phenols are much stronger acids than alcohols
Chapter 21

7. 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
Chapter 21

8. 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
Chapter 21

9. Other Reactions of the O-H Group of Phenols
Phenols can be acylated with acid chlorides and anhydrides
Chapter 21

10. Phenols in the Williamson Ether Synthesis
Phenoxides (phenol anions) react with primary alkyl halides to form ethers by an SN2 mechanism
Chapter 21

11. 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
Chapter 21

12. 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
Chapter 21

13. Sulfonation
Sulfonation gives mainly the the ortho (kinetic) product at low temperature and the para (thermodynamic) product at high temperature
Chapter 21

14. 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)
Chapter 21