1. Introduction

Alcohols, phenols and ethers are organic compounds containing oxygen.

Compound	Functional Group	General Formula
Alcohol	–OH attached to an aliphatic carbon	R–OH
Phenol	–OH attached directly to a benzene ring	Ar–OH
Ether	Oxygen atom between two carbon groups	R–O–R’

Examples

Methanol → CH₃OH
Ethanol → C₂H₅OH
Phenol → C₆H₅OH
Dimethyl ether → CH₃OCH₃

Remember

Alcohol ≠ Phenol
In alcohols, –OH is attached to an alkyl carbon.
In phenols, –OH is attached directly to a benzene ring.

2. Classification of Alcohols

A. Based on Number of –OH Groups

(i) Monohydric Alcohol

Contains one –OH group.

Example:
CH₃OH

(ii) Dihydric Alcohol

Contains two –OH groups.

Example:
HO–CH₂–CH₂–OH

(Ethane-1,2-diol)

(iii) Trihydric Alcohol

Contains three –OH groups.

Example:
Glycerol

(iv) Polyhydric Alcohol

Contains more than three –OH groups.

B. Based on Carbon Attached to –OH

Primary (1°) Alcohol

–OH is attached to a carbon connected with only one other carbon.

General Formula

R–CH₂OH

Example

CH₃CH₂OH

Secondary (2°) Alcohol

–OH is attached to a carbon connected with two carbons.

General Formula

R₂CHOH

Example

CH₃CHOHCH₃

Tertiary (3°) Alcohol

–OH is attached to a carbon connected with three carbons.

General Formula

R₃COH

Example

(CH₃)₃COH

Special Types

Allylic Alcohol

–OH is attached to the carbon next to a C=C double bond.

Example

CH₂=CH–CH₂OH

Benzylic Alcohol

–OH is attached to the carbon next to a benzene ring.

Example

C₆H₅CH₂OH

3. Classification of Phenols

Monohydric Phenol

One –OH group

Example

Phenol

Dihydric Phenol

Two –OH groups

Examples

Catechol
Resorcinol
Hydroquinone

Trihydric Phenol

Three –OH groups

4. Classification of Ethers

A. Symmetrical (Simple) Ether

Both alkyl/aryl groups are the same.

Example

CH₃OCH₃

Dimethyl ether

B. Unsymmetrical (Mixed) Ether

Two groups are different.

Examples

CH₃OC₂H₅

C₂H₅OC₆H₅

5. Nomenclature

Alcohols (IUPAC Rules)

Rule 1

Choose the longest carbon chain containing –OH.

Rule 2

Number from the end nearest to –OH.

Rule 3

Replace -e of alkane with -ol.

Rule 4

Mention position of –OH.

Examples

Formula	IUPAC Name
CH₃OH	Methanol
CH₃CH₂OH	Ethanol
CH₃CH₂CH₂OH	Propan-1-ol
CH₃CHOHCH₃	Propan-2-ol
HOCH₂CH₂OH	Ethane-1,2-diol
Glycerol	Propane-1,2,3-triol

Shortcut

1 –OH → ol

2 –OH → diol

3 –OH → triol

Phenols

The parent compound is Phenol.

Substituents are numbered from the carbon bearing –OH.

Common names:

ortho (1,2)
meta (1,3)
para (1,4)

Examples

2-Methylphenol (o-Cresol)
3-Methylphenol (m-Cresol)
4-Methylphenol (p-Cresol)

Ethers

Common Name

Write the names of both alkyl groups alphabetically + “ether”.

Example

CH₃OC₂H₅

Ethyl methyl ether

IUPAC Name

Smaller alkyl group → alkoxy

Larger chain → parent alkane

Examples

Compound	IUPAC Name
CH₃OCH₃	Methoxymethane
C₂H₅OC₂H₅	Ethoxyethane
CH₃OC₃H₇	Methoxypropane
C₆H₅OCH₃	Methoxybenzene (Anisole)

6. Structure of Functional Groups

Alcohol

Oxygen is sp³ hybridised.
Carbon attached to –OH is sp³ hybridised.
Bond angle is slightly less than 109.5° because of lone pair repulsion.

Phenol

Carbon attached to –OH is sp² hybridised.
C–O bond is slightly shorter than in alcohol due to resonance.

Ether

Oxygen is sp³ hybridised.
Molecule has a bent shape.
C–O–C bond angle is slightly greater than tetrahedral due to repulsion between alkyl groups.

7. Preparation of Alcohols

1. From Alkenes

(A) Acid-Catalysed Hydration

Reaction

Alkene + H₂O → Alcohol

Catalyst: Dilute H₂SO₄

Important Point

Follows Markovnikov’s rule.
H attaches to the carbon with more H atoms.
–OH attaches to the more substituted carbon.

Example

CH₃CH=CH₂ → CH₃CHOHCH₃ (Propan-2-ol)

Mechanism (Very Important)

Protonation of alkene
Carbocation formation
Water attacks carbocation
Loss of H⁺ gives alcohol

Exam Tip: Learn only the four steps; detailed electron movement is usually not required unless specifically asked.

(B) Hydroboration–Oxidation

Reagents

BH₃ (or diborane)
H₂O₂ / NaOH

Important Features

Gives anti-Markovnikov product.
–OH attaches to the carbon having more hydrogen atoms.
High yield of alcohol.

Remember

Hydration → Markovnikov

Hydroboration → Anti-Markovnikov

2. From Carbonyl Compounds

Reduction of Aldehydes

Aldehyde → Primary alcohol

Reducing agents

H₂/Ni
NaBH₄
LiAlH₄

Reduction of Ketones

Ketone → Secondary alcohol

Same reducing agents as above.

3. Reduction of Carboxylic Acids

Carboxylic acid → Primary alcohol

Reagent

LiAlH₄

Important: LiAlH₄ is a strong but expensive reducing agent, so it is mainly used for laboratory synthesis.

4. From Grignard Reagents (Most Important)

Reaction occurs in two steps:

Grignard reagent reacts with a carbonyl compound.
Hydrolysis gives alcohol.

Products Obtained

Carbonyl Compound	Alcohol Formed
Methanal	Primary alcohol
Other aldehydes	Secondary alcohol
Ketones	Tertiary alcohol

Memory Trick

M-A-K → 1°-2°-3°

Methanal → 1°
Aldehyde → 2°
Ketone → 3°

Quick Revision Box (Part 1)

✔ Alcohol = R–OH

✔ Phenol = Ar–OH

✔ Ether = R–O–R’

✔ Primary, Secondary & Tertiary alcohols depend on the carbon attached to –OH.

✔ Acid hydration → Markovnikov addition

✔ Hydroboration → Anti-Markovnikov addition

✔ Aldehyde → 1° alcohol

✔ Ketone → 2° alcohol

✔ Carboxylic acid → 1° alcohol

✔ Grignard + Methanal → 1°

✔ Grignard + Aldehyde → 2°

✔ Grignard + Ketone → 3°

8. Preparation of Phenols

Phenol (C₆H₅OH) can be prepared by the following methods:

1. From Haloarenes (Dow Process)

Reaction

Chlorobenzene is heated with NaOH at:

Temperature: 623 K
Pressure: 320 atm

Sodium phenoxide is formed, which on acidification gives phenol.

Reaction:

C₆H₅Cl + NaOH → C₆H₅ONa → C₆H₅OH

Important Point

Requires very high temperature and pressure.
Used for industrial preparation of phenol.

2. From Benzenesulphonic Acid

Steps:

Benzene reacts with oleum to form benzene sulphonic acid.
Heating with molten NaOH gives sodium phenoxide.
Acidification produces phenol.

Reaction:

Benzene → Benzene sulphonic acid → Sodium phenoxide → Phenol

3. From Diazonium Salts

Formation of Diazonium Salt

Aniline reacts with nitrous acid at 273–278 K.

Reagents:

NaNO₂ + HCl

Aniline → Benzene diazonium chloride

Hydrolysis

On warming with water:

Benzene diazonium chloride → Phenol

Important Point

Diazonium salts are useful because:

–NH₂ group can be replaced by –OH group.

4. From Cumene (Industrial Method)

Cumene = Isopropylbenzene

Steps:

Cumene is oxidised by air.
Cumene hydroperoxide is formed.
Acid treatment gives:

Phenol
Acetone

Importance

Most industrial phenol is prepared by this method.

9. Physical Properties of Alcohols and Phenols

The properties mainly depend on:

Hydroxyl group (–OH)
Size of alkyl/aryl group

A. Boiling Point

Reasons for High Boiling Point:

Alcohols and phenols have:

Strong intermolecular hydrogen bonding
Greater attraction between molecules

Therefore:

Alcohols have higher boiling points than:

Hydrocarbons
Ethers
Haloalkanes

of similar molecular mass.

Effect of Carbon Chain

Boiling point:

Increases with increase in carbon atoms

because van der Waals forces increase.

Effect of Branching

Boiling point:

Decreases with branching

because surface area decreases.

Example:

Straight chain alcohol > Branched alcohol

B. Solubility in Water

Alcohols and phenols dissolve in water because:

They form hydrogen bonds with water molecules.

Trend:

Solubility decreases as alkyl group size increases.

Reason:

Large hydrocarbon part is hydrophobic.

Examples:

Methanol and ethanol are highly soluble.
Higher alcohols are less soluble.

10. Chemical Reactions of Alcohols

Alcohols react mainly by:

Breaking O–H bond
Breaking C–O bond

A. Reactions Involving O–H Bond Cleavage

1. Reaction with Metals

Alcohols react with active metals like:

Sodium
Potassium
Aluminium

to form alkoxides and hydrogen gas.

General Reaction:

2ROH + 2Na → 2RONa + H₂

Example:

Ethanol + Sodium → Sodium ethoxide + Hydrogen

Reaction of Phenol with Sodium Hydroxide

Phenol reacts with NaOH to form sodium phenoxide.

C₆H₅OH + NaOH → C₆H₅ONa + H₂O

Conclusion:

Alcohols and phenols show acidic character.

Acidity of Alcohols

Alcohols are weak acids.

Reason:

The O–H bond is polar due to oxygen’s electronegativity.

Effect of Alkyl Groups

Electron releasing groups like:

CH₃
C₂H₅

increase electron density on oxygen.

This decreases O–H bond polarity.

Therefore acidity decreases.

Acid Strength Order:

Primary alcohol > Secondary alcohol > Tertiary alcohol

(For simple alcohols)

Acidity of Phenols

Phenols are more acidic than alcohols.

Reasons:

1. Electron Withdrawal

The benzene ring attracts electrons from oxygen.

This increases O–H bond polarity.

2. Stability of Phenoxide Ion

When phenol loses H⁺:

Phenol → Phenoxide ion

The negative charge is spread over the benzene ring by resonance.

Therefore phenoxide ion is more stable.

More stable conjugate base = stronger acid.

Comparison of Acidity

Strength increases:

Alcohol < Phenol < Nitro substituted phenol

Effect of Substituents

Electron withdrawing groups

Examples:

–NO₂

Increase acidity.

Reason:

They stabilise phenoxide ion.

Electron donating groups

Examples:

–CH₃

Decrease acidity.

Reason:

They destabilise phenoxide ion.

2. Esterification Reaction

Alcohols and phenols react with:

Carboxylic acids
Acid chlorides
Acid anhydrides

to form esters.

General Reaction:

Alcohol + Acid → Ester + Water

Catalyst:

Concentrated H₂SO₄

Example:

Ethanol + Ethanoic acid

→ Ethyl ethanoate + Water

Acetylation

Introduction of acetyl group (CH₃CO–) into alcohols or phenols is called acetylation.

Example:

Salicylic acid → Aspirin

11. Reactions Involving C–O Bond Cleavage

1. Reaction with Hydrogen Halides

Alcohols react with HX to form alkyl halides.

General Reaction:

ROH + HX → RX + H₂O

Reactivity:

Tertiary alcohol > Secondary alcohol > Primary alcohol

Lucas Test

Used to distinguish different classes of alcohols.

Lucas reagent:

Concentrated HCl
ZnCl₂

Observation:

Alcohol Type	Turbidity
Tertiary	Immediate
Secondary	After some time
Primary	No turbidity at room temperature

2. Dehydration of Alcohols

Removal of water molecule from alcohol gives alkene.

Reagents:

Concentrated H₂SO₄
H₃PO₄
Al₂O₃

Example:

Ethanol → Ethene + Water

Temperature:

443 K

Ease of Dehydration

Tertiary alcohol > Secondary alcohol > Primary alcohol

Reason:

Formation of stable carbocation.

3. Oxidation of Alcohols

Primary Alcohol

Primary alcohol → Aldehyde → Carboxylic acid

Example:

CH₃CH₂OH

↓

CH₃CHO

↓

CH₃COOH

Secondary Alcohol

Secondary alcohol → Ketone

Example:

CH₃CHOHCH₃ → CH₃COCH₃

Tertiary Alcohol

Do not undergo oxidation easily.

Important Revision Points (Part 2)

✔ Phenol preparation:

Haloarenes
Benzenesulphonic acid
Diazonium salts
Cumene

✔ Alcohols have high boiling points due to hydrogen bonding.

✔ Solubility decreases with increasing carbon chain.

✔ Phenol is more acidic than alcohol because phenoxide ion is resonance stabilised.

✔ Nitro groups increase phenol acidity.

✔ Alkyl groups decrease phenol acidity.

✔ Lucas test differentiates 1°, 2°, 3° alcohols.

✔ Oxidation:

1° alcohol → aldehyde → acid
2° alcohol → ketone
3° alcohol → resistant

12. Chemical Reactions of Phenols

Phenols show reactions mainly because of:

–OH group attached to benzene ring
Resonance effect of oxygen lone pair

The –OH group:

Activates the benzene ring.
Directs incoming groups mainly to ortho and para positions.

A. Electrophilic Substitution Reactions

1. Nitration of Phenol

(i) Dilute Nitric Acid

Phenol reacts with dilute HNO₃ at low temperature to give:

o-Nitrophenol
p-Nitrophenol

Important Point:

o-Nitrophenol is steam volatile because of intramolecular hydrogen bonding.

p-Nitrophenol has intermolecular hydrogen bonding, so it has higher boiling point and is less volatile.

(ii) Concentrated Nitric Acid

Phenol reacts with concentrated HNO₃ to form:

2,4,6-Trinitrophenol (Picric acid)

Picric acid is strongly acidic because three –NO₂ groups withdraw electrons and stabilise the phenoxide ion.

2. Halogenation of Phenol

Phenol reacts with bromine differently depending on conditions.

(A) Bromination in Non-polar Solvent

Solvents:

CHCl₃
CS₂

Product:

Monobromophenols

(B) Bromination with Bromine Water

Phenol gives:

2,4,6-Tribromophenol

Appearance:

White precipitate

Reaction does not require Lewis acid catalyst because –OH strongly activates the ring.

3. Kolbe’s Reaction (Kolbe-Schmitt Reaction)

Reaction:

Phenol + NaOH → Sodium phenoxide

Sodium phenoxide reacts with CO₂ under pressure.

Product:

o-Hydroxybenzoic acid (Salicylic acid)

Important Points:

Phenoxide ion is more reactive than phenol.
CO₂ acts as electrophile.
Substitution occurs mainly at ortho position.

4. Reimer–Tiemann Reaction

Phenol reacts with:

Chloroform (CHCl₃)
NaOH

to introduce –CHO group at the ortho position.

Product:

Salicylaldehyde (o-hydroxybenzaldehyde)

Important:

This reaction is used for preparation of aldehydes from phenols.

5. Reaction with Zinc Dust

Phenol on heating with zinc dust gives:

Phenol → Benzene

Reaction:

C₆H₅OH + Zn → C₆H₆ + ZnO

6. Oxidation of Phenol

Phenol is oxidised to:

p-Benzoquinone

Strong oxidising agents like chromic acid are used.

In presence of air, phenol slowly forms coloured quinones.

13. Commercially Important Alcohols

1. Methanol (CH₃OH)

Common name:

Wood spirit

Preparation:

Produced by catalytic hydrogenation of carbon monoxide.

Conditions:

High pressure
High temperature
ZnO–Cr₂O₃ catalyst

Reaction:

CO + 2H₂ → CH₃OH

Properties:

Colourless liquid
Boiling point: 337 K
Highly poisonous

Uses:

Solvent in paints and varnishes
Used for manufacturing formaldehyde

Toxicity:

Methanol oxidation produces:

Methanal → Methanoic acid

which can cause blindness and may be fatal.

2. Ethanol (C₂H₅OH)

Preparation:

Mainly prepared by fermentation of sugars.

Steps:

Sugar → Glucose + Fructose

(using invertase enzyme)

Glucose/fructose → Ethanol + CO₂

(using zymase enzyme)

Conditions:

Absence of air (anaerobic)
Yeast is used

Properties:

Colourless liquid
Boiling point: 351 K

Uses:

Solvent in paint industry
Preparation of organic compounds

Denaturation of Alcohol

Commercial ethanol is made unfit for drinking by adding:

Copper sulphate (colour)
Pyridine (bad smell)

This process is called denaturation of alcohol.

14. Ethers

Preparation of Ethers

Two important methods:

Dehydration of alcohols
Williamson synthesis

1. Dehydration of Alcohols

Alcohols form ethers in presence of:

Concentrated H₂SO₄
Controlled temperature

Example:

2C₂H₅OH → C₂H₅–O–C₂H₅ + H₂O

Temperature:

413 K

Important Conditions

Suitable mainly for primary alcohols.
Lower temperature favours ether formation.
Higher temperature favours alkene formation.

Example:

At 443 K:

Ethanol → Ethene

At 413 K:

Ethanol → Diethyl ether

2. Williamson Ether Synthesis

Most important laboratory method.

General Reaction:

R–X + R′ONa → R–O–R′ + NaX

(Alkyl halide + Sodium alkoxide → Ether)

Mechanism

Follows SN2 reaction.
Best with primary alkyl halides.

Limitations

Secondary and tertiary alkyl halides mainly undergo elimination instead of ether formation.

Reason:

Alkoxides are:

Strong nucleophiles
Strong bases

Preparation of Phenyl Ethers

Phenols react with sodium hydroxide to form phenoxide ions.

Phenoxide + Alkyl halide → Ether

Example:

Phenoxide + CH₃Br → Anisole

15. Physical Properties of Ethers

Boiling Point

Ethers have:

Lower boiling points than alcohols.
Boiling points similar to alkanes of comparable mass.

Reason:

Ethers cannot form intermolecular hydrogen bonds with themselves.

Solubility

Ethers are slightly soluble in water.

Reason:

Oxygen atom of ether forms hydrogen bonds with water.

Their solubility is similar to alcohols of comparable molecular mass.

16. Chemical Reactions of Ethers

Ethers are comparatively less reactive compounds.

Main reactions:

Cleavage of C–O bond
Electrophilic substitution

A. Cleavage of C–O Bond

Ethers react with strong hydrogen halides:

Most commonly:

Order of reactivity:

HI > HBr > HCl

Reaction:

Ether + HI → Alkyl iodide + Alcohol

Important Points:

Reaction requires concentrated HI.
High temperature is used.
Alkyl-oxygen bond breaks.

Cleavage of Anisole

In anisole:

C₆H₅–O–CH₃

The weaker bond breaks:

O–CH₃

Products:

Phenol
Methyl iodide

Reason:

Phenyl–oxygen bond has partial double bond character and is stronger.

B. Electrophilic Substitution of Ethers

The alkoxy group (–OR):

Activates benzene ring.
Directs substitution to ortho and para positions.

1. Halogenation

Example:

Anisole + Br₂

Product:

p-Bromoanisole (major product)

Reason:

–OCH₃ group activates ring.

2. Friedel-Crafts Reaction

Anisole reacts with:

Alkyl halides
Acyl halides

in presence of:

AlCl₃ catalyst

Products:

Alkyl anisoles
Acyl anisoles

3. Nitration

Anisole + HNO₃/H₂SO₄

gives:

o-Nitroanisole
p-Nitroanisole

Complete Chapter Quick Revision

Alcohols

Prepared by hydration of alkenes, reduction of carbonyl compounds, Grignard reaction.
Show acidity, dehydration and oxidation reactions.
Oxidation:
- 1° → Aldehyde → Acid
- 2° → Ketone
- 3° → Resistant

Phenols

More acidic than alcohols.
Undergo electrophilic substitution.
Important reactions:
- Kolbe reaction → Salicylic acid
- Reimer–Tiemann → Salicylaldehyde
- Bromination → Tribromophenol

Ethers

Prepared by Williamson synthesis.
Lower boiling point than alcohols.
Cleaved by HI/HBr.
Alkoxy group is ortho-para directing.