Course Objectives :
The course aims to provide an in-depth knowledge of various photochemical reactions & their basic principles which enables students to learn a variety of photochemical reactions and their mechanisms. They will also understand the various organic transformation through disconnection approach.
Course Outcomes |
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Assessment Strategies |
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On completion of this course, the students will be able to- CO92- distinguish between thermal and photochemical energies and their effect on the course of chemical reactions. CO93- explain pericyclic reactions i.e. electrocyclic reactions, cycloaddition reactions and sigmatropic reactions. CO94- comprehend the orbital interactions and orbital symmetry correlations of various pericyclic reactions. CO95- use various reagents and organic reactions in a logical manner in organic synthesis. CO96- hypothesize retrosynthetic methods for the logical dissection of complex organic molecules and devise synthetic methods |
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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).
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).
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.
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.
Synthons and synthetic equivalents, Types-d1, d2, d3 and d4 synthons, disconnection approach, 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.
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