Thermal and Photochemical Reactions

Paper Code: 
CHY - 321
Credits: 
4
Contact Hours: 
60.00
Max. Marks: 
100.00
Objective: 
To learn about the importance of light in organic reactions.
 
12.00
Unit I: 
Basics of Photochemistry
Electromagnetic radiation, photochemical excitation – interaction of electromagnetic radiation with organic molecules, types of excitations (π → π*, n → π* etc.) fate of excited molecules - Jablonskii diagram, intersystem crossing, energy transfer, photosensitization, quenching, quantum yield, Frank-condon principle Stern-Volmer equation. 
 
12.00
Unit II: 
Photochemical Reactions of Carbonyl Compounds
Photochemical reactions of ketones – alpha cleavage or Norrish type I cleavage, gamma hydrogen transfer or Norrish type II cleavage; photo reductions; Paterno-Buchi reactions; photochemistry of α,β-unsaturated ketones, β,γ-unsaturated ketones, cyclohexadienones (cross conjugated and conjugated).
 
14.00
Unit III: 
Photochemistry of Alkenes and Aromatic Compounds
Photochemistry of alkenes: intramolecular reactions of the olefinic bond – cis-trans  isomerisation (stilbene), cyclization reactions, rearrangement of 1, 4 and 1, 5-dienes, di-π methane rearrangement.
Photochemistry of aromatic compounds: photochemical rearrangement, photostationary state, 1, 3, 5 – trimethyl benzene to 1, 2, 4-trimethyl benzene. 
Miscellaneous Photochemical Reactions: Barton reaction, photo Fries rearrangement of ethers and anilides, singlet oxygen reactions (photo oxygenation).
 
10.00
Unit IV: 
Pericyclic Reactions -I
General characteristics, classification, molecular orbital symmetry. 
Electrocyclic reactions: theories of explanation (FMO, Woodword-Hoffmann and PMO approach), frontier orbitals of ethylene, 1, 3-butadiene, 1, 3, 5-hexatriene and allyl systems, valence tautomerism.
 
12.00
Unit V: 
Pericyclic Reactions –II
Cycloaddtion Reactions: 2+2, 4+2 cycloaddition, 1, 3-dipolar cycloaddition and cheletropic reactions; stereoselectivity (endo, exo), stereospecific and regioselective hydrogen reactions, Lewis-acid catalysis in Diels’ Alder reaction. 
Sigmatropic rearrangements: suprafacial and antarafacial shifts of H, sigmatropic shifts involving carbon moieties, 3, 3- and 5, 5-sigmatropic rearrangements; Claisen, Cope and Aza-Cope rearrangements; isomerization of divinyl cyclopropane; fluxional tautomerism (bullvalene); ene reaction. 
 
References: 
  1. Photochemistry; Horsepool;
  2. Fundamentals of Photochemistry; First Edition; K.K. Rohatagi – Mukherjee; New Age International Publishers Pvt. Ltd., New Delhi, 2005.
  3. Molecular Reactions and Photochemistry; First Edition; Charles H. Depuy and Orville L. Chapman; Prentice-Hall of India Pvt. Ltd, New Delhi, 1988.
  4. Reaction Mechanism in Organic Chemistry; Third Edition; S.M. Mukherjee and S.P. Singh; Macmillan, India Ltd., New Delhi, 1999.
  5. Advanced Organic Chemistry Part A & B; Fourth Edition; Francis A. Carey and Richard J. Sundberg; Kluwer Academic/Plenum Publishers, New York, 2000.
 
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