E-CONTENT FOR

COMPLETE COURSE

e-book:
PHARMACEUTICAL
ORGANIC CHEMISTRY-II
(BP301T)
(For B.Pharm 3rd Semester Student)

Editor: Dr.Alok Kumar Dash

Institute Of Pharmacy
V.B.S.P.University,Jaunpur,U.P.
Email:dr.alokdash@gmail.com
 COURSE CONTENT:

General methods of preparation and reactions of compounds superscripted with

asterisk (*) to beexplained To emphasize on definition, types, classification,
principles/mechanisms, applications, examplesand differences
UNIT I
Benzene and its derivatives
A. Analytical, synthetic and other evidences in the derivation of structure
of benzene, Orbital picture, resonance in benzene, aromatic
characters, Huckel’s rule
B. Reactions of benzene - nitration, sulphonation, halogenationreactivity,
Friedelcrafts alkylation- reactivity, limitations,
Friedelcrafts acylation.
C. Substituents, effect of substituents on reactivity and orientation of
mono substituted benzene compounds towards electrophilic
substitution reaction
D. Structure and uses of DDT, Saccharin, BHC and Chloramine
UNIT II
Phenols* - Acidity of phenols, effect of substituents on acidity, qualitative
tests, Structure and uses of phenol, cresols, resorcinol, naphthols
Aromatic Amines* - Basicity of amines, effect of substituents on basicity,
and synthetic uses of aryl diazonium salts
Aromatic Acids* –Acidity, effect of substituents on acidity and
important reactions of benzoic acid.
UNIT
10 Hours
Fats and Oils
a. Fatty acids – reactions.
b. Hydrolysis, Hydrogenation, Saponification and Rancidity of oils, Drying
oils.
c. Analytical constants – Acid value, Saponification value, Ester value,
Iodine value, Acetyl value, Reichert Meissl (RM) value – significance and
principle involved in their determination.
UNIT IV
Polynuclear hydrocarbons:
a. Synthesis, reactions
b. Structure and medicinal uses of Naphthalene, Phenanthrene, Anthracene,
Diphenylmethane, Triphenylmethane and their derivatives
UNIT V
Cyclo alkanes*
Stabilities – Baeyer’s strain theory, limitation of Baeyer’s strain theory,
Coulson and Moffitt’s modification, Sachse Mohr’s theory (Theory of
strainless rings), reactions of cyclopropane and cyclobutane only
CHAPTER-1
TOPIC- Analytical, synthetic and other evidences
in the derivation of structure of benzene, Orbital
picture, resonance in benzene, aromatic characters,
Huckel’s rule

Email: dr.alokdash@gmail.com
Derivation of the Structure of
Benzene and Its Aromatic
Character
1. Introduction
Benzene (C₆H₆) is a fundamental aromatic compound with a unique cyclic planar structure,
exceptional stability, and distinctive reactivity patterns. The structure of benzene was not
obvious from its molecular formula alone, and understanding its true nature involved analytical,
synthetic, spectroscopic, and theoretical studies. Today, benzene is best represented using
concepts from molecular orbital theory, resonance, and Hückel’s rule.

2. Analytical and Synthetic Evidences for the Structure of

Benzene
2.1 Molecular Formula and Degree of Unsaturation

The molecular formula of benzene is C₆H₆, suggesting a high degree of unsaturation (index of
hydrogen deficiency = 4). This could correspond to three double bonds and one ring, but its
reactivity and properties deviate from typical alkenes.

2.2 Lack of Addition Reactions

Unlike alkenes, benzene does not readily undergo addition reactions. For example, it resists
bromination without a catalyst and prefers substitution reactions (e.g., electrophilic aromatic
substitution), indicating exceptional stability and delocalization of π-electrons.

2.3 Equal Bond Lengths (Spectroscopic Evidence)

X-ray diffraction and spectroscopic studies show that all carbon-carbon bond lengths in
benzene are equal: approximately 1.39 Å, intermediate between a typical C–C single bond
(1.54 Å) and a C=C double bond (1.34 Å).

2.4 Heat of Hydrogenation

The heat of hydrogenation of benzene is significantly less exothermic than expected.

Cyclohexene gives −119 kJ/mol. Three such double bonds should release ~−357 kJ/mol.
Benzene, however, gives only −208 kJ/mol, indicating it is 149 kJ/mol more stable than
expected for a cyclic triene—evidence for resonance stabilization.

2.5 Substitution Product Patterns

Benzene undergoes monosubstitution reactions (e.g., nitration, sulfonation) producing a single

isomer, indicating all hydrogens are equivalent, supporting a highly symmetrical structure.

3. Kekulé’s Structure and its Limitations

3.1 Kekulé’s Proposal (1865)

Kekulé proposed a cyclic structure with alternating single and double bonds:

• Two resonance forms exist by interchanging double bonds.

• The actual molecule is a resonance hybrid of both forms.

3.2 Limitations of Kekulé’s Structure

• Predicts alternating bond lengths, not supported by experimental data.

• Does not explain extraordinary thermodynamic stability.
• Fails to fully account for uniform reactivity at all six carbon atoms.

4. Modern Orbital Picture of Benzene

4.1 Hybridization and σ Framework

Each carbon atom in benzene is sp² hybridized:

• Three sp² orbitals form σ bonds: two with adjacent carbon atoms and one with a
hydrogen.
• The six carbon atoms form a planar hexagonal ring.

4.2 Unhybridized p Orbitals and π-System

Each carbon has one unhybridized p orbital perpendicular to the ring plane. These six p orbitals
overlap laterally, forming a delocalized π-electron cloud above and below the ring.

• The π-electrons are not localized between specific carbon atoms.

• Instead, they are delocalized over the entire ring, contributing to benzene’s stability
and aromaticity.

5. Resonance in Benzene
Benzene is best represented as a resonance hybrid of two Kekulé structures:

[C₆H₆]↔[C₆H₆]\text{[C₆H₆]} \leftrightarrow \text{[C₆H₆]}[C₆H₆]↔[C₆H₆]

The actual molecule:

• Has equal bond lengths throughout.

• Is more stable than either resonance contributor.
• Possesses resonance energy of ~149 kJ/mol.

The resonance stabilizes the structure and explains:

• Chemical inertness toward addition

• Preference for substitution reactions
• Equal reactivity of all positions on the ring

6. Aromatic Character and Hückel’s Rule

6.1 Definition of Aromaticity

A molecule is aromatic if it satisfies the following criteria:

• Cyclic
• Planar
• Fully conjugated (every atom in the ring has a p orbital)
• Contains (4n + 2) π-electrons, where n is a non-negative integer (Hückel’s Rule)

6.2 Hückel’s Rule

Derived from quantum mechanical calculations by Erich Hückel, the rule states:

A monocyclic, planar, conjugated system is aromatic if it contains (4n+2) π-electrons.\text{A

monocyclic, planar, conjugated system is aromatic if it contains } (4n + 2) \text{ π-
electrons.}A monocyclic, planar, conjugated system is aromatic if it contains (4n+2) π-electrons.

Where n = 0, 1, 2, 3…

6.3 Application to Benzene

• Benzene has 6 π-electrons

• Plugging into Hückel’s Rule: 4n + 2 = 6 → n = 1
• Therefore, benzene is aromatic

6.4 Consequences of Aromaticity

 • Enhanced thermodynamic stability
• Unique chemical behavior (substitution vs. addition)
• Characteristic diamagnetic ring currents (NMR evidence)
• High symmetry and planarity

7. Summary
Property Benzene’s Behavior
Molecular formula C₆H₆ (high degree of unsaturation)
Reactivity Undergoes substitution, not addition
Bond lengths All C–C bonds are equal (1.39 Å)
Thermodynamic stability High (149 kJ/mol resonance energy)
Resonance Resonance hybrid of two Kekulé structures
Orbital picture Delocalized π-system formed by overlapping p orbitals
Aromaticity Satisfies Hückel’s rule (6 π-electrons, n = 1)

Hückel’s Molecular Orbital (MO) Theory

1. Introduction
Hückel’s Molecular Orbital (HMO) Theory, developed by Erich Hückel in the 1930s, is a
quantum mechanical model used to explain the electronic structure and stability of planar
conjugated π-systems, particularly aromatic compounds.

The theory focuses on π-electrons, ignoring σ-bonding electrons (which are treated as a stable
framework). By solving the Schrödinger equation for π-electrons in conjugated systems,
Hückel's method helps predict:

• Molecular orbitals
• Electron configurations
• Stability (aromaticity) of the system

2. Basic Assumptions of Hückel Theory

Hückel’s MO theory uses the Linear Combination of Atomic Orbitals (LCAO) approximation
and is built on the following key assumptions:

1. Only π-electrons are considered (σ-framework remains unchanged).

2. Each carbon atom contributes one p_z orbital to the π-system.
3. These p_z orbitals interact only with adjacent p_z orbitals.
4. The interaction parameters are:
o α (alpha): Coulomb integral (energy of an electron in an isolated p orbital)
 o β (beta): Resonance integral (stabilization due to overlap between neighboring p
orbitals)
o S = 0: Overlap between atomic orbitals is neglected (simplification)

3. Hückel’s π Molecular Orbital Diagram for Benzene

(C₆H₆)
3.1 Structure of Benzene

• Benzene has 6 carbon atoms arranged in a planar hexagon.

• Each carbon is sp²-hybridized and has a perpendicular unhybridized p orbital.
• These 6 p orbitals combine to form 6 π molecular orbitals.

3.2 Energy Levels and Symmetry

Solving the secular determinant for benzene yields 6 π-molecular orbitals with the following
energy levels (in units of β):

MO Energy (α + xβ) Degeneracy Number of Electrons

ψ₁ α + 2β 1 2
ψ₂, ψ₃ α + β 2 (degenerate) 4 (2 each)
ψ₄, ψ₅ α − β 2 (degenerate) 0
ψ₆ α − 2β 1 0

3.3 π-Electron Configuration of Benzene

• Benzene has 6 π-electrons.

• These electrons fill the lowest three bonding MOs (ψ₁, ψ₂, ψ₃).
• Result: Completely filled bonding orbitals and empty antibonding orbitals (ψ₄–ψ₆)

This electronic configuration explains benzene’s:

• Extraordinary thermodynamic stability

• Equal bond lengths (due to electron delocalization)
• Resistance to addition reactions (as breaking aromaticity is unfavorable)

4. Hückel’s (4n + 2) π-Electron Rule

Using the outcomes of his MO theory, Hückel proposed a simple empirical rule:

A monocyclic, planar, fully conjugated system is aromatic if it contains (4n + 2) π-electrons,

where n is an integer (0, 1, 2, ...).
4.1 Examples

Compound π-Electrons n Aromatic?

Benzene (C₆H₆) 6 1 Yes
Cyclopentadienyl anion 6 1 Yes
Cyclobutadiene 4 1 No (Anti-aromatic)
Cycloheptatrienyl cation (tropylium ion) 6 1 Yes
Naphthalene (C₁₀H₈) 10 2 Yes

5. Antiaromaticity and Nonaromaticity

5.1 Antiaromatic Compounds

• Planar, cyclic, fully conjugated, but contain 4n π-electrons

• Example: Cyclobutadiene (4 π-electrons)
• These compounds are highly unstable due to electron pairing in degenerate orbitals

5.2 Non-Aromatic Compounds

• Do not satisfy one or more criteria for aromaticity

• May be acyclic, non-planar, or non-conjugated
• Example: Cyclohexene, cyclopentadiene

6. Significance of Hückel’s MO Theory

Hückel’s theory provides valuable insights into:

• Stability trends in conjugated hydrocarbons

• Prediction of aromaticity
• Orbital symmetry in pericyclic reactions (basis for Woodward-Hoffmann rules)
• Foundation for modern computational chemistry

Despite being semi-empirical and limited to planar π-systems, it successfully explains the
behavior of a vast number of aromatic molecules and heterocycles (e.g., pyrrole, furan,
thiophene).

7. Summary
Concept Description
Hückel Theory MO approach for π-electrons in conjugated, planar cyclic systems
Criteria for Aromaticity Planar, cyclic, conjugated, (4n + 2) π-electrons
Benzene’s π-system 6 p orbitals → 6 π-MOs, 3 bonding and 3 antibonding
 Concept Description
Resulting configuration Filled bonding orbitals → stability and equal bond lengths
Antiaromatic compounds 4n π-electrons → destabilized due to electron pairing
CHAPTER-2
TOPIC- Reactions of benzene- nitration,
sulphonation, halogenation reactivity, Friedelcrafts
alkylation reactivity, limitations, Friedelcrafts acylation.

Email: dr.alokdash@gmail.com
Reactions of Benzene
1. Introduction
Benzene, an aromatic hydrocarbon with a stable π-electron system, predominantly undergoes
electrophilic aromatic substitution (EAS) reactions rather than addition reactions. The
delocalized electrons in benzene confer aromatic stability, which is preserved during
substitution.

The most important EAS reactions of benzene include nitration, sulphonation, halogenation,
Friedel–Crafts alkylation, and acylation.

2. Nitration of Benzene
Reaction:

C₆H₆+HNO₃→H₂SO₄C₆H₅NO₂+H₂O\text{C₆H₆} + \text{HNO₃} \xrightarrow{\text{H₂SO₄}}

\text{C₆H₅NO₂} + \text{H₂O}C₆H₆+HNO₃H₂SO₄C₆H₅NO₂+H₂O

Reagents:

• Concentrated nitric acid and sulfuric acid

Mechanism:

1. Generation of Electrophile (NO₂⁺):

HNO₃+H₂SO₄→NO₂⁺+HSO₄⁻+H₂O\text{HNO₃} + \text{H₂SO₄} \rightarrow \text{NO₂⁺}

+ \text{HSO₄⁻} + \text{H₂O}HNO₃+H₂SO₄→NO₂⁺+HSO₄⁻+H₂O

2. Attack on benzene ring to form the sigma complex.

3. Loss of proton to restore aromaticity.

Use:

• Production of nitrobenzene, precursor to aniline, dyes, and explosives.

3. Sulphonation of Benzene
Reaction:

C₆H₆+SO₃→H₂SO₄C₆H₅SO₃H\text{C₆H₆} + \text{SO₃} \xrightarrow{\text{H₂SO₄}}

\text{C₆H₅SO₃H}C₆H₆+SO₃H₂SO₄C₆H₅SO₃H
Reagents:

• Fuming sulfuric acid (H₂SO₄ + SO₃)

Mechanism:

• Formation of the sulfonium ion (SO₃H⁺) which acts as the electrophile.

• Similar EAS mechanism as nitration.

Reversibility:

• Sulphonation is reversible.
• Desulphonation can occur with dilute acid and heat.

Use:

• Important for directing group manipulation in synthesis.

• Produces detergents and sulfa drugs.

4. Halogenation of Benzene
Reaction:

C₆H₆+Cl₂→FeCl₃C₆H₅Cl+HCl\text{C₆H₆} + \text{Cl₂} \xrightarrow{\text{FeCl₃}}

\text{C₆H₅Cl} + \text{HCl}C₆H₆+Cl₂FeCl₃C₆H₅Cl+HCl

Reagents:

• Halogen (Cl₂ or Br₂)

• Lewis acid catalyst (FeCl₃, FeBr₃, or AlCl₃)

Mechanism:

1. Activation of halogen:

Cl₂+FeCl₃→Cl⁺+FeCl₄⁻\text{Cl₂} + \text{FeCl₃} \rightarrow \text{Cl⁺} +

\text{FeCl₄⁻}Cl₂+FeCl₃→Cl⁺+FeCl₄⁻

2. Electrophilic attack by Cl⁺.

3. Restoration of aromaticity by deprotonation.

Use:

• Produces aryl halides, used in agrochemicals, pharmaceuticals, and dyes.

5. Friedel–Crafts Alkylation
Reaction:

C₆H₆+R–Cl→AlCl₃C₆H₅–R+HCl\text{C₆H₆} + \text{R–Cl} \xrightarrow{\text{AlCl₃}}

\text{C₆H₅–R} + \text{HCl}C₆H₆+R–ClAlCl₃C₆H₅–R+HCl

Reagents:

• Alkyl halide (R–Cl)

• Aluminum chloride (AlCl₃)

Mechanism:

1. Generation of carbocation (R⁺):

R–Cl+AlCl₃→R⁺+AlCl₄⁻\text{R–Cl} + \text{AlCl₃} \rightarrow \text{R⁺} +

\text{AlCl₄⁻}R–Cl+AlCl₃→R⁺+AlCl₄⁻

2. Electrophilic attack by carbocation on benzene.

3. Loss of proton to restore aromaticity.

Reactivity:

• Carbocations can undergo rearrangement, leading to unexpected products.

• E.g., 1° carbocations rearrange to 2° or 3° forms.

Limitations:

• Not effective with:

o Aryl halides or vinyl halides (don’t form stable carbocations)
o Deactivated rings (e.g., nitrobenzene)
• Polyalkylation may occur due to increased activation of the ring post-substitution.

6. Friedel–Crafts Acylation
Reaction:

C₆H₆+RCOCl→AlCl₃C₆H₅–COR+HCl\text{C₆H₆} + \text{RCOCl} \xrightarrow{\text{AlCl₃}}

\text{C₆H₅–COR} + \text{HCl}C₆H₆+RCOClAlCl₃C₆H₅–COR+HCl

Reagents:

• Acid chloride (RCOCl)

 • Aluminum chloride (AlCl₃)

Mechanism:

1. Formation of acylium ion:

RCOCl+AlCl₃→RCO⁺+AlCl₄⁻\text{RCOCl} + \text{AlCl₃} \rightarrow \text{RCO⁺} +

\text{AlCl₄⁻}RCOCl+AlCl₃→RCO⁺+AlCl₄⁻

2. Electrophilic attack on benzene.

3. Deprotonation and restoration of aromaticity.

Advantages over alkylation:

• No rearrangement (acylium ion is resonance-stabilized).

• Product is less reactive than benzene, preventing polyacylation.

Use:

• Introduction of ketone functionality into aromatic rings.

• Intermediate for pharmaceuticals, perfumes, and dyes.

7. Comparative Reactivity and Summary

Reaction Electrophile Catalyst Rearrangement Poly-substitution
Nitration NO₂⁺ H₂SO₄ No Minimal
Sulphonation SO₃ or SO₃H⁺ H₂SO₄ No Reversible
Halogenation Cl⁺/Br⁺ FeCl₃, AlCl₃ No Some
Friedel–Crafts Alkylation R⁺ AlCl₃ Yes Yes
Friedel–Crafts Acylation RCO⁺ AlCl₃ No No

8. Conclusion
Benzene and its derivatives primarily undergo electrophilic aromatic substitution due to the
stability of their aromatic system. The nature of the electrophile, type of catalyst, and
electronic effects of substituents greatly influence the rate and orientation of substitution.
While reactions like nitration, sulphonation, and halogenation are widely used, Friedel–
Crafts reactions provide powerful tools for building complex aromatic compounds—though
their limitations must be carefully managed.
CHAPTER-3
TOPIC- Substituents, effect of substituents on
reactivity and orientation of mono substituted benzene
compounds towards electrophilic substitution reaction

Email: dr.alokdash@gmail.com
Substituents: Their Effects on Reactivity and
Orientation in Electrophilic Aromatic
Substitution (EAS)
1. Introduction
Electrophilic aromatic substitution (EAS) reactions involve the replacement of a hydrogen atom
on the benzene ring with an electrophile, while retaining the aromaticity. When benzene is
monosubstituted, the nature of the substituent already attached to the ring plays a crucial role in
determining:

• The rate (reactivity) of substitution.

• The position (orientation) where the new group enters: ortho (o-), meta (m-), or para
(p-).

These effects are governed by electronic properties of the substituent, which may activate or
deactivate the ring, and influence the electron density at specific positions.

2. Classification of Substituents Based on Reactivity

2.1 Activating Groups

These increase the electron density in the benzene ring, making it more reactive toward
electrophiles. They usually:

• Donate electrons via resonance or inductive effects.

• Direct new substituents to ortho and para positions.

Examples: –OH, –NH₂, –OCH₃, –CH₃, –C₂H₅

2.2 Deactivating Groups

These withdraw electron density from the benzene ring, making it less reactive toward
electrophiles. They usually:

• Pull electrons via –I (inductive) or –R (resonance) effects.

• Direct incoming groups to the meta position (with exceptions).

Examples: –NO₂, –COOH, –SO₃H, –CN, –CHO, –COOH, –COOR

3. Orientation Effects (Ortho/Meta/Para Directing)

3.1 Ortho and Para Directing Groups

These groups increase the electron density at the ortho and para positions through lone pair
resonance donation or hyperconjugation.

Mechanism Example: Anisole (methoxybenzene)

• The –OCH₃ group donates electrons via resonance:

o The oxygen’s lone pair interacts with the π system of the ring.
o This increases electron density at ortho and para positions.
• Thus, electrophiles preferentially attack those positions.

Examples:

Group Type of Effect Directing

–OH, –NH₂ +R (strong resonance) Ortho/Para
–OCH₃, –CH₃ +R or +H (hyperconjugation) Ortho/Para

3.2 Meta Directing Groups

These groups withdraw electrons from the ring via –I and/or –R effects, reducing electron
density particularly at ortho and para positions, making the meta position relatively more
reactive.

Mechanism Example: Nitrobenzene

• The –NO₂ group is strongly electron-withdrawing.

• Through resonance, it removes electron density from ortho and para positions.
• Meta position is least deactivated → E⁺ attacks there.

Examples:

Group Type of Effect Directing

–NO₂, –CN –R and –I Meta
–SO₃H, –COOH –R and –I Meta
–CHO, –COOR –R (moderate) Meta

4. Halogens – Special Case

Halogens (–Cl, –Br, –I) are deactivating due to strong –I effects, but are ortho/para directing
due to their ability to donate electrons by resonance.

This dual behavior makes them electron-withdrawing overall, yet they still guide substitution
to ortho and para positions.
5. Resonance and Inductive Effects Summary
Effect Description Examples
Delocalization of lone pair into ring →
+R (resonance donation) –OH, –NH₂, –OR
activates ring
+H (hyperconjugation) Donation of electrons from alkyl groups –CH₃, –C₂H₅
–NO₂, –CN, –Cl, –
–I (inductive withdrawal) Electron withdrawal via σ-bond
COOH
–R (resonance –NO₂, –COOH, –
Withdrawal via π-system → deactivates ring
withdrawal) SO₃H

6. Summary Table: Substituent Effects on Benzene

Substituent Reactivity Directing Effect Type of Group
–OH Activating Ortho/Para Strong +R
–NH₂ Activating Ortho/Para Strong +R
–OCH₃ Activating Ortho/Para Moderate +R
–CH₃ Activating Ortho/Para Hyperconjugation (+H)
–Cl, –Br Deactivating Ortho/Para –I, weak +R
–NO₂ Deactivating Meta Strong –R and –I
–CHO Deactivating Meta –R and –I
–COOH Deactivating Meta –R and –I
–SO₃H Deactivating Meta –R and –I

7. Practical Implications in Synthesis

• The choice of starting material and knowledge of substituent effects allows for
regioselective synthesis.
• For example:
o Toluene (–CH₃) reacts with nitric acid to give ortho and para nitrotoluene.
o Nitrobenzene reacts with sulfuric acid to give meta-nitrobenzenesulfonic acid.
• Strategic use of sulfonation as a temporary blocking group helps control orientation in
multi-step syntheses.

8. Conclusion
Substituents on a benzene ring significantly influence the reactivity and orientation of further
electrophilic substitution. Activating groups accelerate the reaction and direct new substituents to
ortho and para positions, while deactivating groups slow down the reaction and often direct to
the meta position. Understanding the electronic nature of substituents (via resonance and
inductive effects) is critical in designing efficient synthetic pathways in aromatic chemistry.
Substituent Effects in Electrophilic Aromatic Substitution
(EAS)
1. Substituent Classification by Reactivity

Activating Groups:

• Increase electron density on the benzene ring.

• Make the ring more reactive toward electrophiles.
• Direct new groups to ortho and para positions.
Examples: –OH, –NH₂, –OCH₃, –CH₃

Deactivating Groups:

• Withdraw electron density from the ring.

• Decrease reactivity toward electrophiles.
• Usually direct substitution to the meta position.
Examples: –NO₂, –COOH, –SO₃H, –CHO

2. Direction of Substitution

Ortho/Para Directors (Activating or Resonance Donors):

–OH, –NH₂, –OCH₃, –CH₃, –Cl*, –Br*
(*Halogens are deactivating by induction but direct ortho/para by resonance.)

Meta Directors (Strong Electron Withdrawers):

–NO₂, –COOH, –CHO, –SO₃H, –CN, –COOR

3. Resonance Effects

Activating Example: –OH

• Donates lone pair via resonance

• Increases electron density at ortho/para positions

Deactivating Example: –NO₂

• Withdraws electron density via –R and –I effects

• Depletes ortho/para electron density → meta substitution is favored

4. Summary Table

Substituent Reactivity Directing Mechanism

–OH, –NH₂ Activating Ortho/Para +R (resonance donation)
 Substituent Reactivity Directing Mechanism
–CH₃ Activating Ortho/Para +H (hyperconjugation)
–OCH₃ Activating Ortho/Para +R
–Cl, –Br Deactivating Ortho/Para –I (inductive), weak +R
–NO₂ Deactivating Meta –R and –I (strong withdrawal)
–COOH, –CHO Deactivating Meta –R and –I
CHAPTER-4
TOPIC- Structure and Uses of DDT,
Saccharin, BHC, and Chloramine
Email: dr.alokdash@gmail.com
Structure and Uses of DDT,
Saccharin, BHC, and
Chloramine
1. DDT (Dichlorodiphenyltrichloroethane)

IUPAC Name: 1,1,1-Trichloro-2,2-bis(4-chlorophenyl)ethane

Molecular Formula: C₁₄H₉Cl₅

Uses:

• Insecticide used historically for controlling malaria and typhus.

• Effective against mosquitoes, lice, and agricultural pests.
• Banned or restricted due to bioaccumulation and ecotoxicity.

2. Saccharin

IUPAC Name: 1,2-Benzisothiazol-3(2H)-one 1,1-dioxide

Molecular Formula: C₇H₅NO₃S

Uses:

• Artificial sweetener (300–500 times sweeter than sugar).

• Used in diabetic products, soft drinks, toothpaste, and food.
• Non-nutritive and approved for safe use globally.

3. BHC (Benzene Hexachloride)

IUPAC Name: 1,2,3,4,5,6-Hexachlorocyclohexane

Molecular Formula: C₆H₆Cl₆

Uses:

• Used as a pesticide in agriculture.

• γ-isomer (Lindane) used to treat lice and scabies.
• Restricted use due to toxicity and environmental concerns.

4. Chloramine

Common Form: Monochloramine (NH₂Cl)

Uses:

• Water disinfectant in municipal water treatment.

• Medical antiseptic (e.g., Chloramine-T).
• Preferred over chlorine in some systems due to stability and reduced by-products.

Summary Table

Compound IUPAC Name Main Use Key Note

1,1,1-Trichloro-2,2-bis(4- Insecticide (banned in
DDT Persistent pollutant
chlorophenyl)ethane many regions)
1,2-Benzisothiazol-3(2H)-one 1,1- Non-caloric, FDA-
Saccharin Artificial sweetener
dioxide approved
Insecticide, lice treatment Multiple isomers; γ
BHC 1,2,3,4,5,6-Hexachlorocyclohexane
(γ-isomer) is active
Water and surface More stable than
Chloramine Monochloramine (NH₂Cl)
disinfectant chlorine
CHAPTER-5
TOPIC- Phenols*
Email: dr.alokdash@gmail.com
Phenols
1. Introduction
Phenols are a class of aromatic organic compounds that consist of a hydroxyl group (-OH)
directly bonded to an aromatic benzene ring. They differ from alcohols, where the -OH group
is attached to a saturated carbon atom. The unique structure of phenols gives them distinctive
physical, chemical, and pharmacological properties, making them important in both
industrial and pharmaceutical fields.

2. General Formula
Ar–OH\text{Ar–OH}Ar–OH

Where Ar = aromatic ring (usually benzene).

Example:

Phenol (C₆H₅OH) is the simplest member of the phenol family.

3. Classification of Phenols
Based on the number of –OH groups:

Type Examples
Monohydric Phenol, cresol
Dihydric Catechol, resorcinol, hydroquinone
Trihydric Pyrogallol, phloroglucinol

Based on substitution on the ring:

• Simple phenols: phenol, cresol

• Substituted phenols: thymol, eugenol
• Polyphenols: have more than one –OH group (e.g., catechol)

4. Physical Properties
• State: Colorless to pale pink crystalline solids (may darken due to oxidation)
• Solubility: Slightly soluble in water; readily soluble in alcohol, ether
• Odor: Characteristic medicinal, tar-like odor
• Melting point: 40–43°C
 • Boiling point: 181°C (phenol)

5. Acidic Nature of Phenols

Phenols are more acidic than alcohols, but less acidic than carboxylic acids.

Reason:

• The phenoxide ion formed after deprotonation is stabilized by resonance over the
aromatic ring.

C₆H₅OH⇌C₆H₅O⁻+H⁺\text{C₆H₅OH} \rightleftharpoons \text{C₆H₅O⁻} +

\text{H⁺}C₆H₅OH⇌C₆H₅O⁻+H⁺

Resonance in phenoxide ion distributes the negative charge, stabilizing it, thus making phenols
weak acids (pKa ≈ 10).

6. Chemical Reactions of Phenols

6.1. Reactions due to –OH group:

a. Formation of salts (acid-base reaction):

C₆H₅OH+NaOH→C₆H₅O⁻Na⁺+H₂O\text{C₆H₅OH} + \text{NaOH} \rightarrow

\text{C₆H₅O⁻Na⁺} + \text{H₂O}C₆H₅OH+NaOH→C₆H₅O⁻Na⁺+H₂O

b. Esterification:

C₆H₅OH+RCOCl→C₆H₅OCOR+HCl\text{C₆H₅OH} + \text{RCOCl} \rightarrow

\text{C₆H₅OCOR} + \text{HCl}C₆H₅OH+RCOCl→C₆H₅OCOR+HCl

c. Ether formation (Williamson synthesis):

C₆H₅O⁻Na⁺+R–X→C₆H₅–OR+NaX\text{C₆H₅O⁻Na⁺} + \text{R–X} \rightarrow \text{C₆H₅–OR}

+ \text{NaX}C₆H₅O⁻Na⁺+R–X→C₆H₅–OR+NaX

6.2. Electrophilic Aromatic Substitution Reactions

Phenol activates the benzene ring towards electrophilic substitution, favoring ortho and para
positions due to electron-donating –OH group.

a. Nitration:
C₆H₅OH+HNO₃→dil. H₂SO₄o-/p-nitrophenol\text{C₆H₅OH} + \text{HNO₃}
\xrightarrow{\text{dil. H₂SO₄}} \text{o-/p-nitrophenol}C₆H₅OH+HNO₃dil. H₂SO₄o-/p-
nitrophenol

b. Bromination:

C₆H₅OH+Br₂→2,4,6-tribromophenol\text{C₆H₅OH} + \text{Br₂} \rightarrow \text{2,4,6-

tribromophenol}C₆H₅OH+Br₂→2,4,6-tribromophenol

c. Sulphonation, Friedel–Crafts reactions also occur more readily than in benzene.

7. Tests for Phenols

1. Ferric Chloride Test:

• Purple, blue, or green coloration indicates presence of phenolic –OH group.

2. Liebermann’s Test:

• Reaction with NaNO₂ and H₂SO₄ gives red, blue, or green coloration.

8. Industrial and Pharmaceutical Uses

Industrial Uses:

• Production of plastics (e.g., Bakelite)

• Synthesis of dyes, explosives (e.g., picric acid)
• Antioxidants, UV stabilizers

Pharmaceutical Uses:

• Antiseptics and disinfectants (phenol, cresol, thymol)

• Ingredient in mouthwashes, lozenges, ointments
• Used in synthesis of aspirin, paracetamol, and salicylic acid

9. Toxicity and Handling

• Phenol is toxic, corrosive, and can be absorbed through the skin.
• Causes burns, CNS depression, and renal toxicity in large doses.
• Handle with gloves, goggles, and under fume hood if in lab setting.

10. Examples of Medicinal Phenols

 Name Structure Feature Use
Thymol Phenol with isopropyl group Antiseptic, mouthwash
Eugenol Methoxy-phenol from clove oil Dental analgesic
Salicylic acid o-Hydroxybenzoic acid Acne treatment, keratolytic
Paracetamol Acetylated p-aminophenol Antipyretic, analgesic

Summary
• Phenols are aromatic compounds with hydroxyl groups directly attached to the benzene
ring.
• They show acidic character, undergo electrophilic substitution at ortho/para positions,
and have diverse applications.
• Widely used in medicine, disinfection, and industry, but require careful handling due to
toxicity.
CHAPTER-6
TOPIC- Aromatic Amines
Email: dr.alokdash@gmail.com
Aromatic Amines
1. Introduction
Aromatic amines are organic compounds that contain an amino group (–NH₂, –NHR, or –
NR₂) directly attached to an aromatic ring such as benzene or naphthalene. These compounds
are important intermediates in dyes, drugs, agrochemicals, and polymers, and exhibit distinct
chemical behavior due to the influence of the aromatic system on the lone pair of nitrogen.

2. General Structure
Ar–NH₂, Ar–NHR, or Ar–NR₂\text{Ar–NH₂, Ar–NHR, or Ar–NR₂}Ar–NH₂, Ar–NHR, or Ar–
NR₂

Where Ar = Aromatic ring (e.g., benzene), and R = Hydrogen or alkyl group.

Example:

Aniline (C₆H₅NH₂) is the simplest aromatic amine.

3. Classification of Aromatic Amines

Based on substitution on the nitrogen:

Type Example
Primary (–NH₂) Aniline
Secondary (–NHR) N-Methylaniline
Tertiary (–NR₂) N,N-Dimethylaniline

Based on the number of amino groups:

Name Structure
Aniline C₆H₅–NH₂
o-Phenylenediamine C₆H₄(NH₂)₂ (1,2-)
m-Phenylenediamine C₆H₄(NH₂)₂ (1,3-)
p-Phenylenediamine C₆H₄(NH₂)₂ (1,4-)

4. Physical Properties
• State: Generally colorless to pale yellow liquids or low-melting solids
 • Odor: Characteristic fishy or ammonia-like odor
• Solubility: Slightly soluble in water; soluble in organic solvents
• Boiling Point: Aniline boils at ~184°C

5. Basicity of Aromatic Amines

Aromatic amines are less basic than aliphatic amines due to resonance delocalization of the
nitrogen lone pair into the aromatic ring:

C₆H₅NH₂⇌C₆H₅–N⁺H₂ ↔ Resonance forms\text{C₆H₅NH₂} \rightleftharpoons \text{C₆H₅–N⁺H₂

↔ Resonance forms}C₆H₅NH₂⇌C₆H₅–N⁺H₂ ↔ Resonance forms

This delocalization reduces the availability of the lone pair to accept protons, thus lowering
basicity.

6. Chemical Reactions of Aromatic Amines

6.1. Reaction with Acids (Salt Formation)

Ar–NH₂+HCl→Ar–NH₃⁺Cl⁻\text{Ar–NH₂} + \text{HCl} → \text{Ar–NH₃⁺Cl⁻}Ar–

NH₂+HCl→Ar–NH₃⁺Cl⁻

Forms soluble salts, useful in separation techniques.

6.2. Acylation

Reaction with acid chlorides or anhydrides gives amides.

Ar–NH₂+RCOCl→Ar–NHCO–R+HCl\text{Ar–NH₂} + \text{RCOCl} → \text{Ar–NHCO–R}

+ \text{HCl}Ar–NH₂+RCOCl→Ar–NHCO–R+HCl

6.3. Alkylation

Aromatic amines react with alkyl halides to form secondary and tertiary amines.

6.4. Electrophilic Aromatic Substitution

Due to the +R effect of the –NH₂ group, aromatic amines are highly reactive towards
electrophilic substitution at ortho and para positions.

Examples:

• Nitration (requires protection due to oxidation risk)

• Sulphonation
• Halogenation: Often leads to poly-substitution unless controlled
6.5. Diazotization (Important Reaction)

Primary aromatic amines react with nitrous acid (NaNO₂ + HCl) at 0–5°C to form diazonium
salts:

Ar–NH₂+HNO₂+HCl→Ar–N₂⁺Cl⁻+2H2O\text{Ar–NH₂} + \text{HNO₂} + \text{HCl} →

\text{Ar–N₂⁺Cl⁻} + 2H₂OAr–NH₂+HNO₂+HCl→Ar–N₂⁺Cl⁻+2H2O

6.6. Coupling Reactions

Diazonium salts can react with phenols or aromatic amines to form azo dyes:

Ar–N₂⁺Cl⁻+Ar’–OH/NH₂→Ar–N=N–Ar’+HCl\text{Ar–N₂⁺Cl⁻} + \text{Ar'–OH/NH₂} →
\text{Ar–N=N–Ar'} + HClAr–N₂⁺Cl⁻+Ar’–OH/NH₂→Ar–N=N–Ar’+HCl

7. Tests for Aromatic Amines

a) Carbylamine Test:

• Aromatic primary amines give foul-smelling isocyanides with chloroform and KOH.

b) Diazotization and Coupling:

• Red/orange azo dye formation confirms the presence of a primary aromatic amine.

8. Uses of Aromatic Amines

Compound Uses
Aniline Dye intermediate, rubber accelerator, paracetamol base
p-Phenylenediamine Hair dyes, polymers (e.g., Kevlar)
N,N-Dimethylaniline Methyl orange synthesis
Benzidine Azo dye precursor (limited due to carcinogenicity)

9. Toxicity and Safety

• Many aromatic amines are toxic and carcinogenic.
• Example: Aniline can cause methemoglobinemia.
• Benzidine and β-naphthylamine are strong bladder carcinogens.
• Use with gloves, fume hood, and proper disposal protocols.

Summary
• Aromatic amines are compounds with –NH₂ or substituted amino groups directly attached
to an aromatic ring.
• They are less basic than aliphatic amines due to resonance.
• Undergo acylation, alkylation, electrophilic substitution, diazotization, and coupling.
• Widely used in dyes, drugs, and polymers, but many are toxic or carcinogenic.
CHAPTER-7
TOPIC- Aromatic Acids*
Email: dr.alokdash@gmail.com
Aromatic Acids
1. Introduction
Aromatic acids are organic compounds that contain a carboxylic acid group (–COOH) directly
or indirectly attached to an aromatic ring (such as benzene, naphthalene, etc.). These
compounds exhibit the combined properties of aromatic rings and carboxylic acids and are
important in the synthesis of drugs, dyes, perfumes, and food preservatives.

2. General Structure
Ar–COOH\text{Ar–COOH}Ar–COOH

Where Ar = aromatic group (e.g., phenyl ring)

Examples:

• Benzoic acid (C₆H₅–COOH) – simplest aromatic acid

• Salicylic acid (2-hydroxybenzoic acid) – used in acne creams and aspirin synthesis

3. Classification of Aromatic Acids

Based on the position of the –COOH group:

1. Directly attached to the aromatic ring:

o Benzoic acid
o Toluic acids (o-, m-, p-)
2. Substituted aromatic acids:
o Salicylic acid (–OH group on the ring)
o Anthranilic acid (–NH₂ group on the ring)
3. Polycarboxylic acids:
o Phthalic acid (1,2-benzenedicarboxylic acid)
o Terephthalic acid (1,4-benzenedicarboxylic acid)

4. Physical Properties
• Appearance: Crystalline solids
• Solubility: Sparingly soluble in water; more soluble in hot water, alcohol
• Melting point: Benzoic acid ~122°C
• Odor: Benzoic acid has a faint pleasant smell

5. Acidic Nature
 • The carboxyl group (–COOH) is the source of acidity.
• Aromatic acids are weak acids and ionize in water:

Ar–COOH⇌Ar–COO⁻+H⁺\text{Ar–COOH} ⇌ \text{Ar–COO⁻} + \text{H⁺}Ar–

COOH⇌Ar–COO⁻+H⁺

• Acidity is influenced by substituents on the ring:

o Electron-withdrawing groups (–NO₂, –Cl) → Increase acidity
o Electron-donating groups (–OH, –CH₃) → Decrease acidity

6. Chemical Reactions
6.1 Reactions of the –COOH Group

a. Salt formation:

Ar–COOH+NaOH→Ar–COO⁻Na⁺+H₂O\text{Ar–COOH} + \text{NaOH} → \text{Ar–

COO⁻Na⁺} + \text{H₂O}Ar–COOH+NaOH→Ar–COO⁻Na⁺+H₂O

b. Esterification:

Ar–COOH+ROH→H⁺Ar–COOR+H₂O\text{Ar–COOH} + \text{ROH} \xrightarrow{\text{H⁺}}

\text{Ar–COOR} + \text{H₂O}Ar–COOH+ROHH⁺Ar–COOR+H₂O

c. Decarboxylation:

Ar–COOH→ΔAr–H+CO₂\text{Ar–COOH} \xrightarrow{\Delta} \text{Ar–H} + \text{CO₂}Ar–

COOHΔAr–H+CO₂

(E.g., heating benzoic acid with soda lime)

6.2 Reactions of the Aromatic Ring

a. Electrophilic substitution (less reactive than benzene due to –COOH being deactivating):

• Nitration:

Ar–COOH+HNO₃→H2SO4Nitro-aromatic acid\text{Ar–COOH} + \text{HNO₃}

\xrightarrow{H₂SO₄} \text{Nitro-aromatic acid}Ar–COOH+HNO₃H2SO4Nitro-
aromatic acid

• Halogenation:
 Ar–COOH+Br₂→FeBr3Bromo-aromatic acid\text{Ar–COOH} + \text{Br₂}
\xrightarrow{FeBr₃} \text{Bromo-aromatic acid}Ar–COOH+Br₂FeBr3Bromo-
aromatic acid

• Substitution occurs mainly at meta position (–COOH is a meta-directing group)

7. Important Aromatic Acids and Their Uses

Aromatic Acid Structure Feature Uses
Benzoic acid C₆H₅–COOH Preservative (E210), antiseptic, plasticizer
Salicylic acid o-Hydroxybenzoic acid Used in acne creams, precursor to aspirin
Anthranilic acid o-Aminobenzoic acid Intermediate for dyes and perfumes
Phthalic acid 1,2-benzenedicarboxylic acid Synthesis of plasticizers (e.g., phthalates)
Terephthalic acid 1,4-benzenedicarboxylic acid Manufacture of polyesters (e.g., PET bottles)
Cinnamic acid Phenylprop-2-enoic acid Flavoring agent, fragrance intermediate

8. Tests for Aromatic Acids

1. Sodium bicarbonate test:

• Effervescence due to CO₂ confirms the presence of –COOH group.

2. Ester test:

• Aromatic acids form esters with alcohols and acid catalyst → fruity smell.

9. Industrial and Pharmaceutical Importance

• Used as intermediates in the manufacture of dyes, perfumes, polymers, and
pharmaceuticals.
• Benzoic acid is widely used as a food preservative.
• Salicylic acid is key to the synthesis of aspirin and other non-steroidal anti-
inflammatory drugs (NSAIDs).
• Terephthalic acid is used in making polyethylene terephthalate (PET) for bottles and
fibers.
Summary
• Aromatic acids have a –COOH group attached to an aromatic ring.
• They are weakly acidic, and show meta-directing effects in substitution.
• React chemically like carboxylic acids and participate in esterification,
decarboxylation, and salt formation.
• Widely used in food, pharmaceuticals, polymers, and dyes.
CHAPTER-8
TOPIC- Fatty acids– reactions.
Email: dr.alokdash@gmail.com
Fatty Acids – Reactions
1. Introduction
Fatty acids are long-chain aliphatic carboxylic acids, typically containing 12 to 24 carbon
atoms, and are major components of lipids in living organisms. They may be saturated (no
double bonds) or unsaturated (one or more double bonds).

Fatty acids play a vital role in energy storage, membrane structure, and metabolic pathways.
Their carboxyl group (–COOH) and hydrocarbon chain allow them to undergo a variety of
chemical and biochemical reactions.

2. General Structure
CH₃–(CH₂)ₙ–COOH\text{CH₃–(CH₂)ₙ–COOH}CH₃–(CH₂)ₙ–COOH

• Saturated fatty acid: e.g., palmitic acid (C₁₆H₃₂O₂)

• Unsaturated fatty acid: e.g., oleic acid (C₁₈H₃₄O₂) with a C=C bond

3. Classification
• Saturated fatty acids: No double bonds (e.g., stearic acid)
• Monounsaturated fatty acids (MUFA): One double bond (e.g., oleic acid)
• Polyunsaturated fatty acids (PUFA): Two or more double bonds (e.g., linoleic acid)

4. Chemical Reactions of Fatty Acids

Fatty acids undergo various chemical reactions primarily due to the presence of:

1. Carboxylic acid group (–COOH)

2. Unsaturated bonds (C=C) in the hydrocarbon chain (if present)

4.1. Reactions of the Carboxylic Group

a) Formation of Salts (Neutralization)

Fatty acids react with bases to form soaps (alkali metal salts):

R–COOH+NaOH→R–COONa+H₂O\text{R–COOH} + \text{NaOH} → \text{R–COONa} +

\text{H₂O}R–COOH+NaOH→R–COONa+H₂O

• This is the basis of saponification.

b) Esterification

Fatty acids react with alcohols (especially glycerol) in the presence of acid catalysts to form
esters (fats and oils):

R–COOH+ROH→H+R–COOR+H₂O\text{R–COOH} + \text{ROH} \xrightarrow{H⁺} \text{R–

COOR} + \text{H₂O}R–COOH+ROHH+R–COOR+H₂O

• Reaction with glycerol forms triglycerides (triacylglycerols).

c) Amide Formation

With amines, fatty acids form amides:

R–COOH+R’NH₂→R–CONHR’+H₂O\text{R–COOH} + \text{R'NH₂} → \text{R–CONHR'} +

\text{H₂O}R–COOH+R’NH₂→R–CONHR’+H₂O

• Fatty acid amides are found in pharmaceuticals and surfactants.

d) Reduction

Fatty acids can be reduced to alcohols using strong reducing agents like LiAlH₄:

R–COOH→LiAlH4R–CH₂OH\text{R–COOH} \xrightarrow{LiAlH₄} \text{R–CH₂OH}R–

COOHLiAlH4R–CH₂OH

e) Decarboxylation

Upon heating, especially with soda lime, fatty acids undergo decarboxylation to form
hydrocarbons:

R–COOH→NaOH/heatR–H+CO₂\text{R–COOH} \xrightarrow{NaOH/\text{heat}} \text{R–H}

+ \text{CO₂}R–COOHNaOH/heatR–H+CO₂

4.2. Reactions of Unsaturated Fatty Acids

These reactions involve the double bonds (C=C) present in unsaturated fatty acids.

a) Hydrogenation

Addition of H₂ in the presence of Ni or Pt catalyst converts unsaturated fatty acids into

saturated ones:

R–CH=CH–R’+H₂→R–CH₂–CH₂–R’\text{R–CH=CH–R'} + \text{H₂} → \text{R–CH₂–CH₂–

R'}R–CH=CH–R’+H₂→R–CH₂–CH₂–R’
 • Used in manufacturing margarine and solid fats from vegetable oils.

b) Halogenation

Halogens (Br₂ or Cl₂) add across the double bond:

R–CH=CH–R’+Br₂→R–CHBr–CHBr–R’\text{R–CH=CH–R'} + \text{Br₂} → \text{R–CHBr–

CHBr–R'}R–CH=CH–R’+Br₂→R–CHBr–CHBr–R’

• Used to test for unsaturation (bromine test).

c) Oxidation

• Unsaturated fatty acids undergo auto-oxidation in the presence of air and light → leads
to rancidity.
• Controlled oxidation produces aldehydes and ketones.

R–CH=CH–R’+[O]→aldehydes + acids\text{R–CH=CH–R'} + [O] → \text{aldehydes +

acids}R–CH=CH–R’+[O]→aldehydes + acids

d) Polymerization (in drying oils)

Unsaturated fatty acids in linseed oil can polymerize on exposure to air → used in paints and
varnishes.

5. Biochemical Reactions (in vivo)

a) β-Oxidation:

• Catabolism of fatty acids to generate acetyl-CoA, which enters the Krebs cycle for ATP
production.

b) Esterification with Glycerol:

• Formation of triglycerides in adipose tissues for energy storage.

c) Prostaglandin Synthesis:

• Certain fatty acids like arachidonic acid are precursors to eicosanoids (prostaglandins,
thromboxanes, leukotrienes).
6. Applications
Field Application
Pharmaceuticals Drug carriers, emulsifiers, skin formulations
Food Cooking oils, preservatives, margarine
Industry Soaps, detergents, cosmetics, lubricants
Medicine Omega-3 fatty acids → cardiovascular health

Summary
• Fatty acids are carboxylic acids with long aliphatic chains (saturated or unsaturated).
• Undergo reactions at –COOH group (salt formation, esterification, reduction,
decarboxylation).
• Unsaturated fatty acids undergo addition, oxidation, and polymerization.
• Play critical roles in energy metabolism, lipid synthesis, and inflammation regulation.
CHAPTER-9
TOPIC- Hydrolysis, Hydrogenation,
Saponification and Rancidity of oils,
Drying oils.
Email: dr.alokdash@gmail.com
Hydrolysis, Hydrogenation,
Saponification, Rancidity of
Oils, and Drying Oils
1. Hydrolysis of Oils
Hydrolysis refers to the chemical breakdown of a compound due to reaction with water. In the
context of fats and oils (which are triglycerides), hydrolysis cleaves the ester bonds, producing
glycerol and free fatty acids.

Reaction:

Triglyceride+3H₂O→acid/base/enzymeGlycerol+3Fatty Acids\text{Triglyceride} + 3
\text{H₂O} \xrightarrow{acid/base/enzyme} \text{Glycerol} + 3 \text{Fatty
Acids}Triglyceride+3H₂Oacid/base/enzymeGlycerol+3Fatty Acids

Types of Hydrolysis:

• Acidic Hydrolysis: Carried out in presence of dilute HCl or H₂SO₄

• Alkaline Hydrolysis: Basis of saponification (produces soaps)
• Enzymatic Hydrolysis: Catalyzed by lipase enzymes in biological systems

Applications:

• Industrial production of fatty acids and glycerol

• Biological lipid digestion in the intestines

2. Hydrogenation of Oils
Hydrogenation is the process of adding hydrogen atoms across double bonds in unsaturated
fatty acids, converting them to saturated fatty acids. This process increases the melting point
and turns oils into semi-solid fats.

Reaction:

R–CH=CH–R’+H₂→Ni/Pt,heatR–CH₂–CH₂–R’\text{R–CH=CH–R'} + \text{H₂}
\xrightarrow{Ni/Pt, heat} \text{R–CH₂–CH₂–R'}R–CH=CH–R’+H₂Ni/Pt,heatR–CH₂–CH₂–R’
Catalysts: Nickel (Ni), Platinum (Pt), or Palladium (Pd)

Partial Hydrogenation:

• May lead to formation of trans fats, which are unhealthy and associated with
cardiovascular disease.

Uses:

• Conversion of vegetable oils to margarine

• Improving shelf life and texture of processed foods

3. Saponification
Saponification is the alkaline hydrolysis of fats and oils, leading to the formation of glycerol
and soap (alkali salts of fatty acids).

Reaction:

Fat/Oil+NaOH/KOH→Glycerol+Soap (R–COONa)\text{Fat/Oil} + \text{NaOH/KOH} →

\text{Glycerol} + \text{Soap (R–COONa)}Fat/Oil+NaOH/KOH→Glycerol+Soap (R–COONa)

Soap: Sodium or potassium salt of long-chain fatty acids

Applications:

• Soap and detergent industry

• Analytical chemistry: saponification number measures the average molecular weight of
fatty acids in fats

4. Rancidity of Oils
Rancidity is the chemical spoilage of fats and oils due to oxidation or hydrolysis, leading to
unpleasant odor, taste, and color.

Types of Rancidity:

a) Hydrolytic Rancidity:

• Caused by the action of lipase enzymes or moisture

 • Releases free fatty acids, especially short-chain volatile acids (e.g., butyric acid)

b) Oxidative Rancidity:

• Occurs in unsaturated fats

• Involves auto-oxidation at the double bonds, forming peroxides, aldehydes, and
ketones

Prevention:

• Use of antioxidants: BHA, BHT, vitamin E

• Proper storage: Cool, dark, airtight conditions

Health Effects:

• Oxidized fats may generate free radicals, contributing to inflammation and chronic
diseases

5. Drying Oils
Drying oils are unsaturated oils that undergo oxidative polymerization when exposed to air,
forming a solid film. This property makes them useful in paints, varnishes, and inks.

Examples:

• Linseed oil
• Tung oil
• Poppy seed oil

Mechanism:

• Presence of polyunsaturated fatty acids (linoleic and linolenic acids)

• Absorb oxygen from the air
• Undergo free-radical polymerization, forming a cross-linked network

Applications:

• Paint and coating industry

• Printing inks
• Wood finishes
Summary Table
Process Definition Products Use/Application
Splitting of triglycerides using Fatty acids + Digestion, industrial fatty
Hydrolysis
water Glycerol acid production
Addition of H₂ to unsaturated
Hydrogenation Saturated fats Margarine, shelf-stable fats
bonds
Alkaline hydrolysis of
Saponification Soap + Glycerol Soap manufacturing
triglycerides
Spoilage due to oxidation or Free fatty acids,
Rancidity Degrades food quality
hydrolysis aldehydes
Oxidative polymerization Crosslinked
Drying Oils Paints, varnishes, inks
forming solid films polymers
CHAPTER-9
TOPIC- Analytical constants– Acid value,
Saponification value, Ester value, Iodine value, Acetyl
value, Reichert Meissl (RM) value– significance and
principle involved in their determination.

Email: dr.alokdash@gmail.com
Analytical Constants of Fats
and Oils
Analytical constants are standardized values used to characterize, identify, and assess the
quality and purity of fats and oils. These constants help in detecting adulteration,
degradation, and evaluating their chemical composition. Below are the most commonly
determined constants:

1. Acid Value
Definition:

The number of milligrams of potassium hydroxide (KOH) required to neutralize the free fatty
acids present in 1 gram of fat or oil.

Principle:

Free fatty acids in the fat are titrated with standard alcoholic KOH using phenolphthalein as an
indicator.

Formula:

Acid Value=Volume of KOH (ml)×Normality of KOH×56.1Weight of sample (g)\text{Acid

Value} = \frac{\text{Volume of KOH (ml)} \times \text{Normality of KOH} \times
56.1}{\text{Weight of sample
(g)}}Acid Value=Weight of sample (g)Volume of KOH (ml)×Normality of KOH×56.1

Significance:

• Indicates hydrolytic rancidity.

• Higher acid value = poor quality or degraded oil.
• Important in food, cosmetics, and pharmaceuticals.

2. Saponification Value
Definition:

The number of milligrams of KOH required to saponify 1 gram of fat or oil.

Principle:
Fat is boiled with excess alcoholic KOH, and the remaining unreacted KOH is titrated with
standard HCl.

Formula:

Saponification Value=(B−S)×N×56.1Weight of sample (g)\text{Saponification Value} =

\frac{(B - S) \times N \times 56.1}{\text{Weight of sample
(g)}}Saponification Value=Weight of sample (g)(B−S)×N×56.1

Where:

• B = Volume of HCl for blank

• S = Volume of HCl for sample
• N = Normality of HCl

Significance:

• Inversely related to average molecular weight of fatty acids.

• High saponification value = short-chain fatty acids.
• Helps in detecting adulteration and identifying type of oil.

3. Ester Value
Definition:

The difference between the saponification value and the acid value.

Ester Value=Saponification Value−Acid Value\text{Ester Value} = \text{Saponification Value}

- \text{Acid Value}Ester Value=Saponification Value−Acid Value

Significance:

• Represents the amount of esterified (combined) fatty acids.

• Helps differentiate free and bound fatty acids.
• Important in perfumes, cosmetics, and flavor industries.

4. Iodine Value
Definition:

The number of grams of iodine absorbed by 100 grams of fat or oil.

Principle:

Iodine reacts with double bonds (C=C) in unsaturated fatty acids. Unreacted iodine is titrated
with sodium thiosulfate.

Method Used:

• Wijs method or Hanus method

Formula:

Iodine Value=(B−S)×N×12.69Weight of sample (g)\text{Iodine Value} = \frac{(B - S) \times N

\times 12.69}{\text{Weight of sample (g)}}Iodine Value=Weight of sample (g)(B−S)×N×12.69

Significance:

• Indicates degree of unsaturation.

• Higher iodine value = more unsaturation = less stability.
• Used in soap, paint, and food industries.

5. Acetyl Value
Definition:

The number of milligrams of KOH required to neutralize the acetic acid liberated from 1 gram
of acetylated fat or oil.

Principle:

Hydroxyl-containing oils are acetylated using acetic anhydride, then hydrolyzed to release
acetic acid, which is titrated.

Significance:

• Measures the hydroxyl group content in the fat.

• Helps in identifying castor oil, ricinoleic acid derivatives.
• Important in industrial and medicinal oil characterization.

6. Reichert–Meissl (RM) Value

Definition:

The number of milliliters of 0.1 N KOH required to neutralize the volatile water-soluble fatty
acids distilled from 5 grams of fat.
Principle:

Fat is saponified, acidified, and the volatile fatty acids (like butyric and caproic acid) are
distilled off, and titrated.

Significance:

• Indicates the presence of short-chain fatty acids.

• Used to detect adulteration in butter, ghee, and milk fats.
• Butter has a high RM value (~28), whereas vegetable oils have low or zero.

Summary Table
Constant Definition Significance
Indicates free fatty acids; used to
Acid Value mg KOH to neutralize FFA in 1 g fat
detect rancidity
Saponification Inverse of average fatty acid chain
mg KOH to saponify 1 g fat
Value length
Represents combined (esterified)
Ester Value SV – AV
fatty acids
Iodine Value g I₂ absorbed by 100 g fat Measures degree of unsaturation
mg KOH to neutralize acetic acid from
Acetyl Value Indicates hydroxyl group content
1 g acetylated fat
ml of 0.1 N KOH for volatile fatty Identifies milk fats and detects
RM Value
acids from 5 g fat adulteration in butter

Conclusion
Analytical constants are essential quality control parameters for oils and fats. They provide
information about:

• The type and purity of the oil

• Its chemical stability and suitability for consumption or industrial use
• Its functional groups, chain lengths, and degree of saturation

They are critical in pharmaceutical formulations, food quality standards, cosmetics, and
forensic analysis of adulteration.
CHAPTER-11
TOPIC- Polynuclear hydrocarbons:
Synthesis, reactions

Email: dr.alokdash@gmail.com
Polynuclear Hydrocarbons:
Synthesis and Reactions
1. Introduction
Polynuclear hydrocarbons (also known as polycyclic aromatic hydrocarbons or PAHs) are
organic compounds consisting of two or more fused aromatic rings. These compounds are
found in coal tar, tobacco smoke, grilled foods, and are also formed during incomplete
combustion of organic matter.

Examples:

• Naphthalene (2 rings)
• Anthracene (3 linear rings)
• Phenanthrene (3 angular rings)
• Chrysene, Benzo[a]pyrene, Pyrene (4 or more rings)

2. Classification
Type Structure Example Formula
Bicyclic Aromatic Naphthalene C₁₀H₈
Tricyclic Aromatic Anthracene, Phenanthrene C₁₄H₁₀
Tetracyclic and Higher Benzo[a]pyrene C₂₀H₁₂

3. General Properties
• Planar, conjugated π-systems
• Highly stable due to resonance
• Hydrophobic and often volatile
• Most are toxic and carcinogenic (especially benzo[a]pyrene)

4. Synthesis of Polynuclear Hydrocarbons

4.1 Naphthalene Synthesis

a) From Coal Tar:

• Naphthalene is naturally present in the light oil fraction of coal tar (~10%).
b) Haworth Synthesis:

Used for synthesizing substituted naphthalenes.

4.2 Anthracene and Phenanthrene

a) From Coal Tar:

• Obtained by fractional crystallization from the green oil fraction of coal tar.

b) Haworth Synthesis (for Phenanthrene):

A multi-step synthetic method involving Friedel–Crafts acylation, cyclization, and reduction.

4.3 Benzo[a]pyrene and Higher PAHs

• Synthesized via multiple Friedel–Crafts reactions or cyclodehydrogenation methods.

5. Reactions of Polynuclear Hydrocarbons

Most reactions involve electrophilic substitution and oxidation, reflecting their aromatic
character.

5.1 Electrophilic Substitution Reactions (EAS)

Like benzene, PAHs undergo:

• Nitration
• Sulphonation
• Halogenation
• Friedel–Crafts reactions

Example: Nitration of Naphthalene

C₁₀H₈+HNO₃→H2SO4α-nitronaphthalene\text{C₁₀H₈} + \text{HNO₃} \xrightarrow{H₂SO₄}

\text{α-nitronaphthalene}C₁₀H₈+HNO₃H2SO4α-nitronaphthalene

• Alpha (1-) position is more reactive than beta (2-) in naphthalene.

• Substitution occurs preferentially at the most electron-rich ring in phenanthrene or
anthracene.

5.2 Oxidation Reactions

a) Mild Oxidation:
 • Oxidation of side chains or certain rings.
• E.g., anthracene → anthraquinone (important dye intermediate)

b) Severe Oxidation:

• Complete breakdown to phthalic acid, CO₂, and water

5.3 Reduction Reactions

a) Catalytic Hydrogenation:

• Converts PAHs to tetralin (naphthalene → decalin)

• Industrial use in lubricants and fuels

b) Chemical Reduction:

• Lithium or sodium in alcohol can partially reduce PAHs (e.g., naphthalene → 1,4-
dihydronaphthalene)

5.4 Addition Reactions

At high temperatures and pressures:

• Unsaturated systems can undergo hydrogenation or Diels-Alder additions with

dienophiles.

6. Applications
Polynuclear Hydrocarbon Application
Naphthalene Mothballs, synthetic dyes, phthalic anhydride
Anthracene Dyes (alizarin), UV detector coatings
Phenanthrene Intermediate for hormones, alkaloids
Benzo[a]pyrene Studied as a potent carcinogen in environmental toxicology

7. Toxicity and Health Hazards

Many PAHs are:

• Mutagenic
• Carcinogenic
• Bioaccumulative
Source of Exposure:

• Grilled meat, vehicle exhaust, cigarette smoke, coal tar

Example: Benzo[a]pyrene

• Activated by liver enzymes → epoxides → bind to DNA → mutations → cancer

Summary
Property Polynuclear Hydrocarbons
Structure 2+ fused aromatic rings
Stability High, due to extended conjugation
Reactions Electrophilic substitution, oxidation, reduction
Sources Coal tar, combustion processes
Uses Dyes, pesticides, pharmaceuticals
Hazards Carcinogenic, environmental pollutants
CHAPTER-12
TOPIC- Structure and medicinal uses of
Naphthalene, Phenanthrene, Anthracene,
Diphenylmethane, Triphenylmethane and
their derivatives

Email: dr.alokdash@gmail.com
Structure and Medicinal Uses of
Naphthalene, Phenanthrene,
Anthracene, Diphenylmethane, and
Triphenylmethane
1. Naphthalene
Structure:

• Consists of two fused benzene rings in a linear arrangement.

• Molecular formula: C₁₀H₈

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Medicinal and Other Uses:

• Antiseptic: Used in older antiseptic powders and dusting agents.

• Moth repellent: Active ingredient in mothballs.
• Precursor for phthalic anhydride, which is used in drug and dye synthesis.
• Derivatives such as naphthoquinones have antimicrobial and anticancer potential.

2. Phenanthrene
Structure:

• Consists of three fused benzene rings arranged in an angular (non-linear) fashion.

• Molecular formula: C₁₄H₁₀

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Medicinal and Biological Uses:

 • Phenanthrene is a core nucleus in steroids and bile acids.
• Used in synthesis of estrogenic compounds, hormones, and alkaloids.
• Derivatives are explored in anti-inflammatory, antioxidant, and anticancer drug
development.
• Also used in the development of analgesics and antipyretics.

3. Anthracene
Structure:

• Composed of three linearly fused benzene rings.

• Molecular formula: C₁₄H₁₀

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Medicinal and Industrial Uses:

• Used as a precursor to anthraquinone, an intermediate in the manufacture of laxatives

(e.g., danthron, aloin, emodin).
• Basis for anti-parasitic and antimicrobial agents.
• Employed in photovoltaic and fluorescent materials for medical imaging.

4. Diphenylmethane
Structure:

• Consists of two benzene rings linked by a methylene (-CH₂-) bridge.

• Molecular formula: C₁₃H₁₂

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Ph–CH₂–Ph

Where Ph = Phenyl group (C₆H₅)

Medicinal Uses:

• Structural core in first-generation antihistamines like diphenhydramine (Benadryl).

• Found in antitussives, sedatives, and antiemetics.
• Used in drugs that act on the CNS, especially anticholinergic agents.
• Derivatives include:
 o Diphenhydramine: Antihistamine with sedative effect
o Orphenadrine: Used for muscle spasms and Parkinsonism

5. Triphenylmethane
Structure:

• Consists of a central methane carbon bonded to three phenyl groups.

• Molecular formula: C₁₉H₁₆

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Ph
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Ph–C–Ph

Medicinal and Industrial Uses:

• Parent structure of triphenylmethane dyes: brilliant green, malachite green, crystal

violet.
• Some dyes have antibacterial and antifungal properties and are used in:
o Antiseptic preparations
o Wound disinfectants
• Used to develop agents with DNA-intercalating properties (potential anticancer agents).
• Structural basis for histological staining in pathology labs.

Important Derivatives and Their Applications

Core Compound Derivative Use/Activity
Naphthalene Naphthoquinone Anticancer, antimalarial (e.g., atovaquone)
Phenanthrene Estrone, Estradiol Estrogenic hormones
Anthracene Danthron, Aloin Laxatives, anti-constipation agents
Diphenylmethane Diphenhydramine Antihistamine, sedative
Triphenylmethane Crystal violet, Malachite green Antiseptic dyes, DNA stains

Summary Table
Compound Structure Major Uses
Naphthalene Two fused benzene rings Mothballs, antiseptics, dye intermediates
Hormone synthesis, anti-inflammatory drug
Phenanthrene Angular tricyclic aromatic
base
Anthracene Linear tricyclic aromatic Laxatives, dye synthesis, photoconductors
Diphenylmethane Two phenyl groups linked by CNS drugs, antihistamines, antispasmodics
 Compound Structure Major Uses
CH₂
Triphenylmethane Three phenyls on one central C Antiseptics, dyes, potential anticancer agents

Conclusion
The hydrocarbon scaffolds of naphthalene, phenanthrene, anthracene, diphenylmethane, and
triphenylmethane serve as important chemical backbones in the development of numerous
therapeutic agents and industrial dyes. Their derivatives are widely used in antihistamines,
hormone therapies, laxatives, and antiseptic preparations.
CHAPTER-13
TOPIC- Cyclo alkanes*
Email: dr.alokdash@gmail.com
Cycloalkanes
1. Introduction
Cycloalkanes are a class of saturated hydrocarbons where the carbon atoms are arranged in a
closed ring. They contain only single bonds (σ bonds) between carbon atoms and follow the
general molecular formula:

CₙH₂ₙ\text{CₙH₂ₙ}CₙH₂ₙ

They are also known as naphthenes (especially in petroleum chemistry) and are considered
alicyclic compounds because they exhibit properties of both alkanes and cyclic structures.

2. General Formula and Examples

Cycloalkane Formula Structure
Cyclopropane C₃H₆ Triangle ring
Cyclobutane C₄H₈ Square ring
Cyclopentane C₅H₁₀ Pentagon ring
Cyclohexane C₆H₁₂ Hexagonal ring

3. Nomenclature
Cycloalkanes are named by:

1. Adding the prefix “cyclo” to the name of the corresponding alkane.

2. Substituents are named and numbered to give the lowest possible numbers.

Examples:

• Methylcyclopentane (a methyl group on a cyclopentane ring)

• 1,2-Dimethylcyclobutane

4. Structure and Bond Angles

Cycloalkanes differ in ring size, which affects their bond angles and stability:

Ring Ideal Angle (sp³) Actual Bond Angle Strain

Cyclopropane 109.5° ~60° High (angle strain)
Cyclobutane 109.5° ~90° Moderate strain
 Ring Ideal Angle (sp³) Actual Bond Angle Strain
Cyclopentane 109.5° ~108° Low strain
Cyclohexane 109.5° ~109.5° (chair form) Minimal strain

Types of Strain:

• Angle strain: Deviation from ideal tetrahedral angle

• Torsional strain: Due to eclipsing interactions
• Steric strain: Due to repulsion between bulky groups

5. Conformations of Cycloalkanes
Cyclohexane:

• Exists in chair, boat, and twist-boat conformations.

• Chair conformation is the most stable, minimizing angle and torsional strain.

Cyclopentane:

• Adopts an envelope conformation to reduce torsional strain.

6. Chemical Properties
Cycloalkanes are relatively less reactive than alkenes and alkynes but undergo:

a) Combustion:

CₙH₂ₙ+O2→CO2+H2O\text{CₙH₂ₙ} + O₂ → CO₂ + H₂OCₙH₂ₙ+O2→CO2+H2O

• Used in energy generation from petroleum.

b) Substitution Reactions:

• Undergo halogenation in the presence of UV light (like alkanes).

c) Ring-opening Reactions:

• Small rings (cyclopropane, cyclobutane) are reactive due to strain and can undergo
ring-opening reactions with nucleophiles.

7. Laboratory and Industrial Importance

• Cycloalkanes are major components of petroleum and natural gas.
 • Used as intermediates in chemical synthesis.
• Cyclohexane is used in the production of nylon (via adipic acid and caprolactam).
• Cyclopropane has historical use as a gaseous anesthetic.

8. Comparison with Alkanes and Alkenes

Property Cycloalkanes Alkanes Alkenes
Formula CₙH₂ₙ CₙH₂ₙ₊₂ CₙH₂ₙ
Reactivity Low Low High
Type of Bond Single (ring) Single Double
Isomerism Geometrical possible Not possible Geometrical

Summary
• Cycloalkanes are saturated cyclic hydrocarbons with formula CₙH₂ₙ.
• Stability depends on ring size and conformation.
• Undergo combustion, substitution, and ring-opening reactions.
• Widely used in industrial chemistry, petrochemicals, and organic synthesis.