Alcohols, Phenols and Ethers are important organic compounds containing oxygen functional groups. These compounds are widely used in industry, medicine, and daily life products like disinfectants, fuels, and solvents.
👉 Core Idea: The presence and position of the –OH group (hydroxyl group) determine the properties and reactions of these compounds.
1. Alcohols
Definition
Alcohols are organic compounds in which one or more hydrogen atoms of alkanes are replaced by –OH (hydroxyl group).
General Formula
R–OH
Structure
R — OH
Classification of Alcohols
(A) Primary Alcohol (1°)
OH group attached to carbon connected to one carbon.
Example:
CH₃CH₂OH
(B) Secondary Alcohol (2°)
OH group attached to carbon connected to two carbons.
Example:
CH₃CHOHCH₃
(C) Tertiary Alcohol (3°)
OH group attached to carbon connected to three carbons.
Example:
(CH₃)₃COH
Nomenclature
Replace “e” of alkane with “ol”
Example:
Ethane → Ethanol
2. Preparation of Alcohols
(A) From Alkenes (Hydration)
R–CH=CH₂ → R–CH(OH)–CH₃
(B) From Alkyl Halides
R–X → R–OH
(C) Reduction of Carbonyl Compounds
- Aldehydes → Primary alcohol
- Ketones → Secondary alcohol
3. Physical Properties of Alcohols
- High boiling point (due to hydrogen bonding)
- Soluble in water (lower members)
Concept Clarity
👉 WHY alcohols have high boiling point?
Because of strong intermolecular hydrogen bonding.
4. Chemical Reactions of Alcohols
(A) Oxidation
- 1° alcohol → aldehyde → acid
- 2° alcohol → ketone
- 3° alcohol → resistant
(B) Dehydration
Alcohol → alkene
(C) Esterification
R–OH + R′–COOH → Ester
5. Phenols
Definition
Phenols are compounds where –OH group is directly attached to benzene ring.
General Formula
Ar–OH
Structure
OH
|
C6H5 —
Example
Phenol (C₆H₅OH)
Preparation of Phenol
- From chlorobenzene
- From benzene sulfonic acid
Physical Properties
- Slightly soluble in water
- Higher boiling point than alcohols
Chemical Properties
(A) Acidic Nature
Phenol is more acidic than alcohol
(B) Electrophilic Substitution
Occurs at ortho and para positions
(C) Reaction with NaOH
Forms sodium phenoxide
Concept Clarity
👉 WHY phenol is acidic?
Because phenoxide ion is stabilized by resonance.
6. Ethers
Definition
Ethers are compounds in which oxygen is bonded to two alkyl or aryl groups.
General Formula
R–O–R′
Structure
R — O — R'
Example
CH₃–O–CH₃ (Dimethyl ether)
Preparation of Ethers
Williamson Ether Synthesis
R–X + R′–ONa → R–O–R′
Physical Properties
- Low boiling point
- Less soluble in water
Chemical Properties
(A) Cleavage with HX
R–O–R′ + HI → alcohol + alkyl iodide
(B) Inert Nature
Ethers are less reactive
Concept Clarity
👉 WHY ethers are less reactive?
Because they lack reactive functional groups like –OH or C=O.
7. Important Differences
Alcohol vs Phenol
| Alcohol | Phenol |
|---|---|
| –OH attached to alkyl | –OH attached to benzene |
| Less acidic | More acidic |
Alcohol vs Ether
| Alcohol | Ether |
|---|---|
| Contains –OH | Contains –O– |
| Hydrogen bonding | No H-bonding |
8. Important Reactions Summary
- Oxidation of alcohols
- Esterification
- Williamson synthesis
- Phenol substitution reactions
9. Important Named Reactions
- Williamson Ether Synthesis
- Kolbe’s reaction (phenol)
- Reimer-Tiemann reaction
10. Concept Clarity Section (Very Important)
👉 WHY phenol is more acidic than alcohol?
Because of resonance stabilization.
👉 WHY tertiary alcohol does not oxidize easily?
Because no hydrogen on carbon bearing OH.
👉 WHY ethers have low boiling point?
Because no hydrogen bonding.
11. Common Mistakes
- Confusing alcohol and phenol
- Ignoring oxidation rules
- Mixing ether reactions
Conclusion
Alcohols, Phenols and Ethers are fundamental organic compounds with wide applications in chemistry and industry.
👉 Focus on functional groups + reactions + concept clarity for best results.