Interconversion of Alcohols, Phenols, and Ethers

Master the key conversions among alcohols (R–OH), phenols (Ar–OH), and ethers (R–O–R′) with summary tables, notes, and a self-check quiz.

Alcohols

General Formula: R–OH   |   Types: 1° (primary), 2° (secondary), 3° (tertiary)

Phenols

General Formula: Ar–OH (–OH directly on aromatic ring)   |   Example: Phenol (C₆H₅OH)

Ethers

General Formula: R–O–R′ or Ar–O–R′   |   Symmetrical (R = R′) or Unsymmetrical (R ≠ R′)

Interconversion Summary

From	To	Method
Alcohol	Ether	Williamson Ether Synthesis (R–O⁻ + R′–X → R–O–R′ + X⁻)
Alcohol	Phenol	Oxidation of benzylic alcohol / Diazonium route from aniline
Phenol	Ether	Phenoxide (ArO⁻) + R–X → Ar–O–R (Williamson)
Ether	Alcohol	Acidic cleavage with HI/HBr (HI > HBr ≫ HCl)

Alcohol → Ether (Williamson)

Route: R–OH → R–O⁻ (Na/NaH) → R–O–R′ (R′–X, primary)   |   Avoid 2°/3° halides (E2 risk).

Alcohol → Phenol

Via: (i) Oxidation of benzyl alcohol to phenol under specific conditions; (ii) Aniline → Diazonium → Hydrolysis to phenol.

Alcohol → Alkyl Halide

Reagents: HCl/ZnCl₂, SOCl₂, PCl₅, HBr, HI.

Alcohol ↔ Alkene ↔ Alcohol

Dehydration: conc. H₂SO₄ → alkene   |   Hydration: acid-catalyzed addition → alcohol (rearrangements possible).

Phenol → Ether

Method: Phenol + NaOH → ArO⁻; ArO⁻ + R–X → Ar–O–R (e.g., phenol + CH₃I → anisole).

Ether → Alcohol

Cleavage: R–O–R′ + HI/HBr → R–I + R′–OH (or two alkyl halides depending on substrate).

Notes

• Phenol is more acidic than alcohol → forms phenoxide (ArO⁻) readily.
• Phenol does not form aryl halide with HX under normal conditions.
• Ether cleavage ease: HI > HBr >> HCl.
• Use primary halides in Williamson to favor SN2 over E2.

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Related Topics (Internal Links)

• Classification of Ethers
• Ethers – Structure, Properties & Reactions
• Chemical Reactions of Alcohols
• Chemical Reactions of Phenol

External References

• Ethers – Britannica

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MCQs (with Answers)

1. Best method for Alcohol → Ether:
   a) Dehydration then hydration
   b) Williamson ether synthesis ✅
   c) Ozonolysis
   d) Friedel–Crafts acylation
   Answer: b
2. In Williamson synthesis, choose:
   a) 3° alkyl halide for faster SN1
   b) 2° alkyl halide to avoid elimination
   c) 1° alkyl halide for clean SN2 ✅
   d) Vinyl halide for better reactivity
   Answer: c
3. Order for ether cleavage by HX is:
   a) HCl > HBr > HI
   b) HI > HBr >> HCl ✅
   c) HBr > HI > HCl
   d) All equal
   Answer: b
4. Phenol + HX (room temp.) gives:
   a) Aryl halide
   b) Ether
   c) No C–O cleavage to aryl halide ✅
   d) Phenyl cation
   Answer: c
5. Alcohol → Alkyl halide reagent set:
   a) SOCl₂, PCl₅, HBr, HI ✅
   b) KMnO₄ only
   c) PCC only
   d) O₃ only
   Answer: a

True / False (with Answers)

• 1. All ethers are cleaved easily by HCl. — ❌ False (HI > HBr ≫ HCl)
• 2. Primary halides are preferred in Williamson. — ✅ True
• 3. Phenol readily forms aryl halide with HI. — ❌ False
• 4. Alkoxide + primary alkyl halide → ether via SN2. — ✅ True
• 5. Dehydration of alcohol gives alkene; hydration reforms alcohol. — ✅ True