Pharmaceutical Organic Chemistry 3 Important Questions are most helpful for the B.Pharm 4th semester examination. You can also download the suggestions PDF.
Stereoisomerism
- What are diastereomers? Explain with a suitable example.
- What is a conformational isomer? Explain with a suitable example.
- Assign the R/S configuration for the following:
(a) Br–H–CH₃CH₂–H–C=
(b) Br–H–Br–CH₃–NO₂–HC–CH₃–Br
(c) COOH–O₂N–H–H–COOH–H–OCH₃
(d) COOH
(e) [Additional structures as shown] - Explain the resolution of a racemic mixture.
- Comment on the resolution of racemic modification.
- Assign R and S configuration. [Structure diagrams included]
- Define enantiomer and meso compound with structures.
- Define chirality and optical isomerism.
- Explain the significance of stereochemistry in biological activity.
- What is resolution? Briefly describe any two methods.
- Differentiate between enantiomers and diastereomers.
- Write a short note on the methods of resolution of a racemic mixture.
- Draw and specify R or S configuration.
- Give the advantage of Z/E nomenclature over cis-trans with examples.
- Assign R and S nomenclature for the following.
- Explain staggered and eclipsed conformations with examples.
- Assign R and S nomenclature for the following:
(i) 3-Chloro-2,2,5-trimethylhexane
(ii) 3-Bromohexane
(iii) 1,3-Dichloropentane - Differentiate between:
(a) Enantiomers and diastereomers
(b) Meso form and racemic mixture - Write the rules for R and S configuration.
- Explain optical isomerism with examples.
- Explain various ways to represent a chiral centre with examples.
- Assign R and S configuration:
(i) H₃C–CN–NH₂–H–COOH
(ii) H–C–COOH–CH₃
(iii) H₃C–CN–NH₂–H–COOH
(iv) H–CH₂–NH₂–CH₂OH - What is racemic resolution? Explain with suitable examples and methods used.
- Write a detailed note on chirality.
- Why do meso compounds not exhibit optical isomerism?
- Define racemic mixture and give examples.
- What is a dihedral angle in stereoisomerism?
- Differentiate and explain geometrical and optical isomerism.
Geometrical Isomerism
- What is a conformational isomer? Explain with a suitable example.
- Explain conformational isomerism in ethane.
- Draw the Fischer projection for 2-chlorobutane.
- Explain the conformation of n-butane.
- Why is the chair conformation more stable than the boat conformation? Explain.
- Assign Z and E forms.
- Define and classify stereoisomerism. Explain different types of structural representation.
- Explain the stability of chair conformation over boat conformation using cyclohexane as an example.
- Why is trans-decalin more stable than cis-decalin? Explain with structures.
- Explain any two stereospecific reactions and any two stereoselective reactions.
- Explain the stereochemistry of monosubstituted cyclohexane.
- What is atropisomerism? Explain with respect to biphenyls.
- Draw sawhorse projections for the following:
(a) Meso-2,3-dibromobutane
(b) 2-Chlorobutane
(c) (R)-2-Butanol
(d) 2R,3S-2-Chlorobutanol - What type of isomerism is involved in allenes?
- Why is trans-1,2-dimethylcyclohexane more stable than its cis isomer?
- Discuss chair, boat, and twist-boat conformations of cyclohexane.
- Assign E and Z nomenclature for the following:
(i) C₆H₅–H₃C–CH₃–CH₃–CH₃–H
(ii) NH₂–COOH–OH–OMe–COOH
(iii) C₆H₅–H₃C–HO–H–CHO–CH₃SH–CH₂OH–CHO–Br–CH₃ - Give configurations of the following isomers: [Structures provided]
- Define stereoisomer. Explain how to calculate the number of stereoisomers using one example.
- Explain the conformations of decalin.
- Explain conformational isomerism of dialkylcyclohexane.
- Describe conformational isomerism of n-butane with an energy profile diagram.
- Explain the terms “enantiomers” and discuss Newman and sawhorse representations of ethane.
- What is meant by geometric isomerism? What conditions must a compound fulfill to exhibit it?
Heterocyclic Compounds
- Discuss Knorr pyrrole synthesis with its reaction mechanism.
- Write two drugs derived from furan.
- Write the method of preparation and reactions of furan.
- Write methods of preparation and reactions of pyrrole.
- Give resonance structures of furan and one of its reactions.
- Write any three reactions of pyrrole.
- Write a short note on pyrrole.
- Write a note on furan.
- Write a note on nitrogen-containing heterocycles.
- Discuss why imidazole is more acidic than pyrrole.
- Differentiate between the reactivity of pyrrole and pyridine towards electrophilic and nucleophilic reagents.
- Compare furan, pyrrole, and thiophene in terms of reactivity.
- Write a note on the synthesis of furan.
- Give the numbering and IUPAC nomenclature of the following. [Structures provided]
- Explain the electrophilic substitution of pyrrole.
- Write any two reactions of thiophene.
- Write a note on Feist-Benary synthesis of furan.
- Give reasons: Electrophilic substitution occurs in the pyrrole ring, whereas nucleophilic substitution occurs in the benzene ring of indole. Explain with examples.
- Give a detailed account of the synthesis and reactions of thiophene.
- Give structures and numbering of the following heterocycles with one drug example each:
(i) Cinnoline
(ii) Benzoxazole
(iii) Benzimidazole
(iv) Xanthine
(v) Pyrrole - Write notes on Diels–Alder and Gomberg reactions.
- Give reasons: Pyridine is a much stronger base than pyrrole. Draw its resonance structures.
Synthesis, Reactions, and Medicinal Uses of Heterocycles
- Discuss Skraup synthesis of quinoline with mechanism.
- Write any four chemical properties of indole with reactions.
- Give any two methods of preparation and two chemical reactions of pyridine.
- Give any two methods of preparation and chemical reactions of imidazole.
- Draw the structures of imidazole and indole.
- Write any three reactions of indole.
- Why is pyridine more reactive towards nucleophiles than benzene?
- Draw the structures of imidazole, 1,3-oxazole, and isoquinoline with numbering.
- Write examples of pharmaceutical drugs containing a pyridine skeleton.
- Explain Fischer indole synthesis.
- Give the structure, numbering, and corresponding drug of five-membered heterocycles containing two heteroatoms.
- Explain the synthesis and reactions of quinoline.
- Write pharmaceutical applications of isoquinoline.
- Write short notes on:
(a) Pyridine
(b) Indole
(c) Quinoline
(d) Thiazole - Give structures and numbering of:
(i) 2-Benzylthiazole
(ii) 6-Aminoquinoline - Why does nucleophilic substitution in pyridine occur at the β-position?
- Give structures of drugs containing the following heterocycles:
(i) Imidazole
(ii) Quinoline - Discuss the chemistry of pyridine. Explain its hybridization and resonance forms.
- Give any two methods of synthesis and four reactions of isoquinoline.
- Give any two methods of synthesis and four reactions of indole.
- Give any two methods of synthesis and four reactions of imidazole.
- Write any four reactions of thiazoles.
- Give the structure and name of medicinal drugs containing an isoquinoline ring.
- Predict the products of the following: [Reaction schemes given]
- Explain the acidic and basic character of imidazole.
- Why is pyridine basic in nature?
- Explain why quinoline undergoes electrophilic substitution at C-5 and C-8.
- Draw resonance structures of:
(a) Imidazole
(b) Pyridine - Explain electrophilic substitution reactions of quinoline.
- Explain methods of synthesis of indole.
- Write the following reactions of pyridine:
(i) Raney/Nickel, H₂/Pt
(ii) NaBH₃CN, Et₃NBH₄
(iii) Conc. H₂SO₄
(iv) Oleum, 300°C
(v) Nitration
(vi) Sulfonation - Why does nucleophilic substitution in pyridine occur preferably at the 2-position rather than the 4-position?
- Define heterocyclic chemistry. Write any three synthetic methods and any three chemical reactions of pyridine or indole.
- Write a note on Paal–Knorr synthesis and Skraup quinoline synthesis.
Reactions of Synthetic Importance
- How does the Beckmann rearrangement help distinguish between syn- and anti-isomerism in oximes?
- Write synthetic reactions for:
(a) Synthesis of aniline using the Hoffmann rearrangement.
(b) Synthesis of anthranilic acid using Baeyer–Villiger oxidation. Write the mechanisms. - Explain rearrangement reactions that proceed through an isocyanate intermediate and mention their side products.
- Give the mechanism of the Schmidt rearrangement.
- Explain Birch reduction and Wolff–Kishner reduction with mechanisms.
- Identify the rearrangement and predict the products and mechanism:
(i) CH₃–H₃C–CH₃–CHO–OH–OCH₃ → 200°C, H₂O → ?
(ii) OH–CH=CH–CH₃–HCl → 200°C → ? - Write a short note on Oppenauer oxidation.