PHOTOCHEMISTRY, PERICYCLIC REACTIONS AND DISCONNECTION APPROACH

Paper Code: 
CHY 321
Credits: 
4
Contact Hours: 
60.00
Max. Marks: 
100.00
Objective: 

Course Objective(s) :
This course will enable the students to –
acquire in-depth knowledge of various photochemical reactions and their basic principles which enables students to learn a variety of photochemical reactions, their mechanisms and understand the various organic transformation through disconnection approach.

Course Outcomes (COs):

Course Outcomes

Teaching  Learning Strategies

Assessment Strategies

On completion of this course, the students will be able to-

CO78:distinguish between thermal and photochemical energies and their effect on the course of chemical  reactions.

CO79:explain pericyclic reactions i.e. electrocyclic reactions, cycloaddition reactions and sigmatropic reactions.

CO80:comprehend the orbital interactions and orbital symmetry correlations of various pericyclic reactions.

CO81:use various reagents and organic reactions in a logical manner in organic synthesis.

CO82:hypothesize retrosynthetic methods for the logical dissection of complex organic molecules and devise synthetic methods
  • Interactive lectures
  • Tutorials
  • Group discussions
  • Use of models
  • Digital learning
  • Problem solving sessions
  • Assertion and Reasoning

 
  • Oral and written examinations
  • Assignments
  • Quiz

 

 
 


 

 

12.00
Unit I: 
Basics of Photochemistry and Photochemical Reactions of Carbonyl Compounds

Laws of photochemistry. Fate of excited molecules: Jablonskii diagram, intersystem crossing, energy transfer, photosensitization, quenching, quantum yield, Stern-Volmer equation. 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).

10.00
Unit II: 
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 III: 
Pericyclic Reactions -I

General characteristics, classification, molecular orbital symmetry.
Electrocyclic reactions: Theories of explanation (FMO, Woodward-Hoffmann and PMO approach), frontier orbitals, electrocyclisation and reterocyclisation of 1,3 butadiene, cyclobutadiene and ,hexatriene derivatives, allylic cations(1,5 diphenylpentadienyl cation) and allylic anions (1,5 diphenylpentadienyl anion), ring opening in bicyclo [4.1.0] heptane derivatives, valence tautomerism.

 

10.00
Unit IV: 
Pericyclic Reactions–II

Cycloaddition 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.

18.00
Unit V: 
Disconnection Approach in Organic Synthesis

Disconnection approach, Synthons and synthetic equivalents, d1, d2, d3 and d4 synthons, , functional group inter-conversions, the importance of the order of events in organic synthesis, one group C-X and two group C-X disconnections, chemoselectivity, reversal of polarity, cyclisation reactions, amine synthesis, principle of protection of alcohol, amine, carbonyl and carboxyl groups.
One and Two Group C-C Disconnections
Alcohols and carbonyl compounds, regioselectivity, alkene synthesis, uses of alkynes and aliphatic nitro compounds in organic synthesis, Diels- Alder reaction, 1,3-difunctionalised compounds, α, β-unsaturated carbonyl compounds, control in carbonyl condensations, 1,5- difunctionalised compounds, Michael addition and Robinson annelation.

Essential Readings: 
  • Fundamentals of Photochemistry, Third Edition; K.K. Rohatagi and Mukherjee; New Age International Publishers Pvt. Ltd., New Delhi, 2007.
  • Reaction Mechanism in Organic Chemistry, Third Edition; S.M. Mukherjee and S.P. Singh; Macmillan, India Ltd., New Delhi, 2003.
  • Modern Methods of Organic Synthesis, Fourth Edition; W. Carruthers; Cambridge Univ. Press, UK, 2005.

 

References: 

SUGGESTED READINGS:

  • CRC Handbook of Organic Photochemistry and Photobiology, Second Edition; W. Horspool and F. Lenci; CRC Press LLC, US, 2004.
  • Molecular Reactions and Photochemistry, First Edition, C. H. Depuy and L. Orville Chapman; Prentice-Hall of India Pvt. Ltd, New Delhi, 1988.
  • Advanced Organic Chemistry Part A & B, Fifth Edition; F. A. Carey and R. J. Sundberg; Springer, US, 2007.
  • Designing Organic Synthesis: A Programmed Introduction to the Sython Approach, First Edition; S. Warren; John Wiley and Sons, Great Britain, 2010.
  • Organic Synthesis- Concepts, Methods and Starting Materials, J. Fuhrhop and G.Penzillin; Second Edition; Wiley-VCH, New York: 2003.

E-RESOURCES:

 

Academic Year: 
2023-2024
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