Study-Unit Description

Study-Unit Description


CODE CHE3091

 
TITLE Organic Photochemistry

 
UM LEVEL 03 - Years 2, 3, 4 in Modular Undergraduate Course

 
MQF LEVEL 6

 
ECTS CREDITS 2

 
DEPARTMENT Chemistry

 
DESCRIPTION Photochemistry of organic compounds

1. The interaction of light with matter. Quantum theory for the absorption of electromagnetic radiation. Electronic transitions. Spin multiplicity of excited states. State (Jablonski) diagrams.
2. UV Absorption spectra: fine structure, solvent shifts, positions and intensity of bands. Selection rules. The Franck-Condon principle.
3. Emission spectra. Fluorescence and phosphorescence. Relationship to absorption spectra. Experimental measurement techniques: the spectrofluorimeter and spectrophosphorimeter.
4. Deactivation of excited states. Radiative and radiationless transitions. Internal conversion and inter-system crossing. Types and mechanisms of electronic energy transfer.
5. Kinetics of photochemical processes. Rate constants. Quantum yields and actinometry. Excited state lifetimes and their measurements. Flash photolysis. Quenching processes: the Stern-Volmer equation. Rates of energy transfer: the diffusion-controlled limit and the Debye equation.
6. Fundamental photochemical reaction types. Photo-reductions, -dimerisation, -additions, -oxidations, -rearrangements, -dissociation, -elimination, and -isomerisations. Use of sensitisers. Norrish type I and II processes. Comparison of S1 and T1 biradicals. Photofragmentation reactions: the Barton reaction.

Study-unit Aims:

The aims of this study-unit is to give students an understanding of how the interaction of light with matter can give rise to electronic transitions in molecules and how these are reflected spectroscopically as well as how they can lead to the formation of reactive intermediates and chemical reactions.

Learning Outcomes:

1. Knowledge & Understanding:

By the end of the study-unit the student will be able to:
1. Describe the possible electronic transitions that can occur in the interaction of light with matter.
2. Explain the types and mechanisms of electronic transitions taking place when electronically excited molecules are deactivated.
3. Interpret absorption and emission spectra in terms of electronic transitions possible within a molecule and interactions of molecules with solvent.
4. Describe the instrumentation required to measure emission spectra, and the lifetimes of excited states.
5. Derive kinetic and quantum yield information of photochemical processes from photochemical data, including quenching processes.
6. Describe the mechanism and application of photosensitisers.
7. Describe the mechanisms of fundamental photochemical reaction types of simple organic molecules.

2. Skills:

By the end of the study-unit the student will be able to:
1. Summarise information to give concise explanations.
2. Organise data and plan solutions to problems.
3. Derive information through calculations.

Main Text/s and any supplementary readings:
(availability at the Library or otherwise is indicated against each entry)

- Gilbert A. & Baggot J., Essentials of Molecular Photochemistry, (1991) (available)

 
ADDITIONAL NOTES Pre-requisite Study-units: CHE1360, CHE2362, CHE2364

 
STUDY-UNIT TYPE Lecture and Tutorial

 
METHOD OF ASSESSMENT
Assessment Component/s Assessment Due Sept. Asst Session Weighting
Assignment SEM1 Yes 15%
Examination (1 Hour and 30 Minutes) SEM1 Yes 85%

 
LECTURER/S Emmanuel Sinagra

 

 
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It should be noted that all the information in the description above applies to study-units available during the academic year 2024/5. It may be subject to change in subsequent years.

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