Products of aniline (0.2

Oxidation of Phenols

Organic Chemistry 4e Carey
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Chapter 24: Phenols

Summary | Phenols | Preparation of Phenols | | Reactions of Aryl Ethers | Spectroscopic Analysis | Self Assessment | Quiz |

Reactions of Phenol

Chapter 24: Phenols

Electrophilic Aromatic Substitution

Reaction type: Electrophilic Aromatic Substitution

Summary

  • Phenols are potentially very reactive towards electrophilic aromatic substitution.
  • This is because the hydroxy group, -OH, is a strongly activating, ortho- / para- directing substituent (review)
  • Substitution typically occurs para to the hydroxyl group unless the para position is blocked, then ortho substitution occurs.
  • The strong activation often means that milder reaction conditions than those used for benzene itself can be used (see table below for a comparison)
Reaction Phenol
Nitration dil. HNO3 in H2O or CH3CO2H HNO3 / H2SO4
Sulfonation conc. H2SO4 H2SO4 or SO3 / H2SO4
Halogenation X2 X2 / Fe or FeX3
Alkylation ROH / H+ or RCl / AlCl3 RCl / AlCl3
Acylation RCOCl / AlCl3
Nitrosation aq. NaNO2 / H+
Related reactions

Study Tip:
Consider the phenolate to be an enolate, hence reactions at the a-C are typically favored.

MECHANISM FOR CARBOXYLATION OF PHENOLS
Step 1:
The nucleophilic phenolate (reacting like an enolate) reacts with the electrophilic carbon of carbon dioxide in the ortho position (compare this with an Aldol reaction)
Step 2:
The non-aromatic cyclohexadienonecarboxylate intermediate tautomerises to the more stable aromatic enol which is further stabilized by an intramolecular hydrogen bond. An acidic work-up will generate the carboxylic acid.
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