About Pharmaceutical Organic Chemistry II
Subject Code
BP301T
Semester
Semester 3
Credits
4 Credits
Pharmaceutical Organic Chemistry II (BP301T) builds upon POC-I to cover aromatic organic chemistry. It focuses on Benzene and its derivatives, the chemistry of Phenols and Aromatic Amines, the biochemistry of Fats and Oils (very important in formulation), and Polynuclear Hydrocarbons. Understanding aromaticity and electrophilic substitution reactions is critical for Medicinal Chemistry.
Key Learning Objectives
- Understand Aromaticity: Apply Huckel’s rule to determine whether a compound is aromatic.
- Explain Electrophilic Substitution: Write mechanisms for Nitration, Sulphonation, and Halogenation of benzene.
- Predict Substitution Orientation: Use the concept of electron-donating and withdrawing groups to predict ortho/para vs meta products.
- Analyze Fats & Oils: Calculate Iodine Value, Saponification Value, and other analytical constants.
- Recognize Polycyclic Compounds: Draw structures of Naphthalene, Anthracene, and Phenanthrene.
Syllabus & Topics Covered
Unit 1: Benzene and its Derivatives
- Analytical, synthetic, and other evidences for the structure of Benzene; Orbital picture, resonance, aromatic character.
- Huckel’s rule (4n+2 π electrons), criteria for aromaticity.
- Reactions of Benzene: Nitration, Sulphonation, Halogenation – mechanism (Electrophilic Aromatic Substitution).
- Friedel-Crafts Alkylation: Mechanism, reactivity, and limitations (polyalkylation, rearrangement).
- Friedel-Crafts Acylation: Mechanism and advantages over alkylation.
- Effect of substituents on reactivity and orientation (Activating: o/p directors; Deactivating: m directors).
- Structure and uses of DDT, Saccharin, BHC, and Chloramine.
Unit 2: Phenols, Aromatic Amines & Acids
- Phenols: Acidity, effect of substituents on acidity, qualitative tests.
- Structure and uses of Phenol, Cresols, Resorcinol, and Naphthols.
- Aromatic Amines: Basicity of amines, effect of substituents on basicity.
- Synthetic uses of Aryl Diazonium Salts (Sandmeyer reaction, coupling).
- Aromatic Acids (Benzoic acid): Acidity, effect of substituents on acidity, important reactions.
Unit 3: Fats and Oils
- Fatty acids: Reactions (hydrogenation, halogenation, oxidation).
- Hydrolysis of fats, Hydrogenation (vanaspati ghee), Saponification, and Rancidity of oils.
- Drying oils: Mechanism of drying.
- Analytical Constants: Acid Value, Saponification Value, Ester Value.
- Iodine Value, Acetyl Value, Reichert Meissl (RM) Value – significance and determination.
Unit 4: Polynuclear Hydrocarbons
- Polynuclear hydrocarbons: Synthesis and reactions.
- Structure and medicinal uses of Naphthalene.
- Structure and medicinal uses of Phenanthrene and Anthracene.
- Structure and medicinal uses of Diphenylmethane and Triphenylmethane and their derivatives.
Unit 5: Cycloalkanes
- Cycloalkanes: Stabilities.
- Baeyer’s Strain Theory and its limitations.
- Coulson and Moffitt’s modification.
- Sachse-Mohr’s Theory (Theory of Strainless Rings).
How to Score High in Pharmaceutical Organic Chemistry II
- 1
Memorize EAS Mechanism: The Electrophilic Aromatic Substitution (EAS) mechanism (σ-complex/Wheland intermediate) applies to Nitration, Halogenation, FC-Alkylation/Acylation – learn it once.
- 2
Director Groups Table: Make a table of Activating (o/p directors) vs Deactivating (m directors) substituents. This is exam gold.
- 3
Analytical Constants: Memorize the formulas and significance of all 6 analytical constants for fats – they are straightforward marks.
- 4
Diazonium Salt Reactions (Sandmeyer): Practice converting aniline to various products via diazonium salts (Cl, Br, CN, OH, N=N-Ar).
- 5
Huckel’s Rule: Any organic molecule with 4n+2 π electrons (n=0,1,2…) in a planar cyclic system is aromatic.
Why it Matters for Career
Aromatic chemistry is the foundation of Medicinal Chemistry, which begins in Semester 4. Most drug molecules have aromatic rings. Understanding EAS, directing effects, and phenol/amine chemistry is essential for modifying drug molecules (SAR). Fats & Oils knowledge is critical for lipid-based formulations.
Exam Weightage
Unit 1 (Benzene/EAS Mechanisms) and Unit 2 (Phenols + Diazonium salts) are the highest-weightage units. Unit 3 (Fats & Oils analytical constants) is a sure-shot scoring unit. Unit 4 and 5 are shorter.
Frequently Asked Questions (FAQs)
What is Huckel’s Rule?
A molecule is aromatic if it is cyclic, planar, fully conjugated, and has (4n+2) π electrons (n = 0, 1, 2…). Benzene has 6 π electrons (n=1), so it is aromatic.
What are the limitations of Friedel-Crafts Alkylation?
1. Polyalkylation (product is more reactive than starting material). 2. Carbocation rearrangement (gives unexpected product). 3. Does not work with deactivated rings (e.g., nitrobenzene). Acylation avoids these issues.
How is Iodine Value determined and what does it indicate?
Iodine Value = grams of Iodine absorbed by 100g of fat/oil. It measures the degree of unsaturation. Higher Iodine Value = more double bonds = more unsaturated fat (e.g., Linseed oil has high IV).
What is the Sandmeyer Reaction?
A reaction where an aryl diazonium salt is converted to aryl chloride or bromide using CuCl or CuBr catalyst (Cuprous salts).
Why is Phenol more acidic than Cyclohexanol?
In phenol, the negative charge on the phenoxide ion is delocalized into the benzene ring by resonance, stabilizing the conjugate base. No such stabilization exists in cyclohexanol, making phenol ~10^6 times more acidic.