Course

Unit I

Nucleophilic Substitution: SN1, SN2, and Borderline (ion pair), SNi, SET mechanisms, Neighboring group participation, substitution at allylic carbons, substitution at aliphatic trigonal carbon, substitution atvinylic carbon. Effect of substrate structure, nucleophile, leaving group and medium on reactivity. Ambident nucleophiles and substrates. Aromatic nucleophilic substitution: SNAr, SN1, benzyne and SRN1 mechanisms. Effect of substrate structure, leaving group and attacking nucleophile on reactivity.

Unit II

Electrophilic substitution: SE2 and SEi, SE1, substitution accompanied by double bond shift. Effect of substrate, leaving group, and solvent on reactivity. Aromatic electrophilic substitution: arenium mechanism, structure reactivity relationship, substituent effect, o/p ratio, ipso substitution, orientation and reactivity, quantitative treatment. Free radical reactions: radical addition. Effect of substrate (aliphatic, aromatic, bridgehead), nature of the radical and solvent on reactivity.

Unit III

Addition reactions: mechanism of electrophilic, nucleophilic and radical addition. Addition to conjugated systems. Orientation and reactivity. Addition of hydrogen halides, oxymercuration, halogenation, sulphenylation, selenylation, addition involving epoxides, addition via organoborane. Addition of water, alcohol, sulphides, to aldehydes, ketones, imines, isothiocyanates, nitro compounds, nitriles. Mannich reaction, elimination reactions: mechanism of elimination reactions E2, E1, E1CB, steric effect. Effect of substrate structure, base, leaving group and medium on reactivity. Mechanism of pyrolytic elimination.

Unit IV

Rearrangement reaction: mechanism of nucleophilic, electrophilic and radical rearrangements. Nature of migration, migratory aptitudes, memory effects. Wagner-Meerwein, Pinacol, Demyanov, dienone-phenol, benzil-benzilic acid, Favorskii, Wolff, Neber, Hofmann, Curtius, Lossen, Schmidt, Beckmann, Baeyer-Villiger, Stevens, benzidine, Hofmann-Loffler and Chapman rearrangements and their mechanisms.

Unit V

Photochemistry and pericyclic reactions: general principles–fate of excited state–Jablonski diagram-chemical process – photochemistry of alkenes, dienes and polyenes, carbonyl compounds, Norrish type 1 and type2, Patterno –Buchi reaction.
Pericyclic reactions: cyclo addition – Diels-Alder reaction, substituent effect on reactivity, regioselectivity and stereochemistry, catalysis of Lewis acids, synthetic applications, enantio-selective Diels-Alder reactions, Intramolecular Diels-Alder reactions. 1,3 dipolar cycloaddition – reactivity, regio and stereoselectivity, applications. [2+2] cycloaddition – ketenes and alkenes – photochemical electrocyclic reactions, orbital symmetry, charged species. Sigmatropic rearrangements – [1,3], [1,5], and [1,7] sigmatropic shifts – [3,3] sigmatropic rearrangements – Cope, Oxy-Cope and Claisen rearrangement. [2,3] rearrangements – oxides and ylides–Wittig and aza –Wittig rearrangements, cheletropic reactions.

• CO01: Elucidate organic reaction mechanisms including nucleophilic and electrophilic substitutions (aliphatic & aromatic) such as SN1, SN2, SNi, SNAr, benzyne, SRN1 and related pathways.
• CO02: Analyze and predict reaction outcomes (rate, stereochemistry, regioselectivity and product distribution) for substitution, addition, elimination and radical reactions by applying the effects of substrate structure, nucleophile/base, leaving group and solvent/medium
• CO03: Apply mechanistic principles to complex transformations including rearrangements, photochemical reactions and pericyclic reactions.

Textbooks

1. Michael B Smith,“March’s Advanced Organic Chemistry: Reactions, Mechanisms and Structure”, 7^th edition, Wiley (2015).
2. Francis A. Carey and Richard J. Sundberg, “Advanced Organic Chemistry-Part A: Structure and Mechanisms”,5^th Edition, Springer, 2008
3. Francis A.Carey and Richard J. Sundberg, “Advanced Organic Chemistry-Part B: Reactions and Synthesis”,5^th Edition, Springer, 2008.
4. Singh S Pand S M Mukherji,“Reaction Mechanism in Organic Chemistry”,2014

References

1. Reinhard Bruckner, Advanced Organic Chemistry, Reaction Mechanisms, Elsevier, 2002
2. O. C. Norman and J. M. Coxon,“Principles of organic synthesis”, C R C press, 2014
3. Ian Fleming, Frontier Orbitals and Organic Chemical Reactions 1^st Edition, Wiley, 1991.