4 credits – 60 theoretical hours
OBJECTIVES:
Give the student an understanding of the study of the interactions of atoms and small molecules with light (or electromagnetic radiation)
SUMMARY:
1. Atomic orbitals and molecular orbitals
2. Classification of photochemical addition and substitution reactions
3. Cycloaddition reactions
4. Isomerization and Rearrangements
5. Photochemical fragmentation reactions
6. Oxidation reactions via singlet oxygen
7. Synthetic applications of photochemical reactions
PROGRAM CONTENT:
1. Atomic orbitals and molecular orbitals. Electronic configuration. Electronic States. Singlet and triplet states. Transition between states. Franck-Condon principles and radioactive and non-radiotive transitions. The absorption and emission of light. absorption and emission spectra: Fluorescence and phosphorescence. Jablonskii diagram. Quantum yield: definition and measurement method. Actinometry. Energy transfer. Sensitivity and depression.
2. Classification of photochemical addition and substitution reactions. Photoreduction of carbonyl compounds. Photoreduction of ethylenic compounds. Synthetic applications of photochemical hydrogen abstraction reactions. Mechanistic analysis of ketone photoreduction. Quantitative analysis of photoreduction efficiency. Competition between hydrogen abstraction and electron transfer. Intramolecular hydrogen abstraction: Norrish type II reactions. Electron transfer and hydrogen abstraction in carbonyl derivatives and unsaturated nitrogenous compounds. Ethylene addition reactions. Radiation-induced aromatic substitution in ultraviolet.
3. Cycloacidation reactions. Classification. Photocycloadditions via intermediates: diradicals, zwitterions and exciplexes. 2+2 photocycloaddition of carbonyl compounds. Benzene photocycloadditions. Photocycloaddition reactions of conjugated enones. Photocycloaddition of unsaturated nitrogenous compounds. Photochemistry of thioketones.
4. Isomerizations and Rearrangements. Classification. Cis-trans isomerization of unsaturated compounds.
Positional and carbon skeleton photoisomerizations: Sigmatropic rearrangements. Electrocyclic reactions. Intramolecular cycloadditions of conjugated hydrocarbons. Electrocyclic reactions in heteroatomic conjugated systems. Electrocyclic isomerizations of beta, gamma-unsaturated enones.
5. Photochemical fragmentation reactions. Photofragmentations and photoeliminations. Alpha cleavage in ketones.: Norrish type I reactions. Sigmatropic rearrangements of beta, gamma unsaturated ketones initiated by alpha cleavage. Photoelimination reactions of azo compounds. Photochemical cleavage into 3- and 4-membered rings.
6. Oxidation reactions via singlet oxygen. Chemiluminescence reactions. Chemilunescence of dioxanes and endoperoxides. Applications of chemiluminescence to photochemical problems.
7. Synthetic applications of photochemical reactions. Photochemistry of heterocyclics. Photochemistry of alkaloids. Protection/deprotection of functional groups via photochemical reactions. Photochemistry of natural products. Photochemistry of selenium and tellurium compounds.
METHODOLOGY:
Expository classes, with various teaching resources (blackboard/chalk, data show, multimedia and computers). Students will be assessed with individual seminars and individual or group work. Individual tests may be applied.
BIBLIOGRAPHY:
1. N. J. Turro, “Modern Molecular Photochemistry”, Benjamin Cummings Publishing Co., Inc. California, 1978.
2. J. M. Coxon and B. Halton, “Organic Photochemistry”, Cambridge University Press, London, 1974.
3. R. P. Wayne, “Principles and Applications of Photochemistry”, Oxford University Press, London, 1988.
4. A. Gilbert and J. Baggott, “Essentials of Molecular Photochemistry,” Blackwell Scientific
Publications, London, 1991.
5. C.E. Wayne; R.P. Wayne, Photochemistry, Oxford Chemistry Primers, NY, 92pp., 2001.
6. Wayne, C.E. and Wayne, R.P. Photochemistry, Oxford Chemistry Primers, Oxford Science Publication, 1999.
7. R. V. Bensasson, E. J. Land and T. G. Truscott, “Flash Photolysis and Pulse Radiolysis”, Pergamon Press, London, 1st Ed., 1983.
8. M. Jones, Jr and R. A. Moss, Editors, “Reactive Intermediates”, Volume 1, John Wiley and Sons, NY, 1978.
9. M. Jones, Jr and R. A. Moss, Editors, “Reactive Intermediates”, Volume 2, John Wiley and Sons, NY, 1981.
10. M. Jones, Jr and R. A. Moss, Editors, “Reactive Intermediates”, Volume 3, John Wiley and Sons, NY, 1985.
J. B. Birks, “Photophysics of Aromatics Molecules”, Wiley-Interscience, Chichester, 1970.
11. J. Rabek, “Experimental Methods in Photochemistry and Photophysics”, Part 1 and Part 2, John Wiley, Chichester, 1982.
12. J. C. Scaiano, Editor, “CRC Handbook of Organic Photochemistry”, Vol 1, Boca Raton, Florida, CRC Press, 1989.
13. J. C. Scaiano, Editor, “CRC Handbook of Organic Photochemistry”, Vol 2, Boca Raton, Florida, CRC Press, 1989.
14. M. A. Fox and M. Chanon, “Photoinduced Electron Transfer”, Parts A – D, Elsevier 1988.
SERIES THAT SHOULD BE USED FOR SYSTEMATIC CONSULTATIONS:
1. “Organic Photochemistry”, Volume 1 – 11, Albert Padwa, Editor, Marcel Dekker, Inc., New York.
2. “Advances in Photochemistry”, Vol 1 – 16, Various Publishers, J.Wiley and Sons, Inc., New York
3. “Photochemistry”, Vol.1 – 22, Specialist Periodical Report, Senior Reporter: D. Bryce-Smith, Royal
Society of Chemistry, London.
MAGAZINES IN SPECIALIZED PERIODICALS SUCH AS:
– Journal of Photochemistry and Photobiology A: Chemistry, Photochemistry and Photobiology, Journal of the American Chemical Society, Journal of Organic Chemistry, Journal of Physical Chemistry, Photochemistry and Photobiology Science, Organic Letters.
