Elements of Organic Photochemistry

1 Basic Photophysical and Photochemical Concepts.- 1.1. Introduction.- 1.2. Energy Distribution in the Excited Molecule.- 1.2a. Light Absorption.- 1.2b. Internal Conversion and Intersystem Crossing.- 1.2c. Fluorescence and Phosphorescence.- 1.3. Photochemical Kinetics: Concentrations, Rates, Yields, and Quantum Yields.- 1.4. Classification of Molecular Electronic Transitions and Excited States.- 1.4a. ? ? ?* Transitions.- 1.4b. n ? ?* and l? a? Transitions.- 1.4c. Intramolecular Charge-Transfer Transitions (CT).- Problems.- 2 Photochemical Techniques and the Photodimerization of Anthracene and Related Compounds.- 2.1. Absorption and Emission Spectra.- 2.1a. Transition Probability.- 2.1b. Polarization Spectra.- 2.1c. The Measurement of Fluorescence Spectra and Fluorescence Quantum Yields.- 2.1d. The Measurement of Fluorescence Lifetimes.- 2.2. The Photodimerization of Anthracene and Related Compounds.- 2.2a. Structural Aspects: The Effect of Substituents on the Photodimerization.- 2.2b. Preparative Photochemical Techniques.- 2.2c. Kinetic and Mechanistic Aspects of the Anthracene Photodimerization.- 2.3. The Anthracene Triplet State.- Problem.- References.- 3 Photochemical Techniques and the Photochemistry of Ketones.- 3.1. The Photoreduction of Aryl Ketones: Nature of the Excited State.- 3.2. Flash Photolysis.- 3.3. The Photoreduction of Aryl Ketones: Structural Aspects.- 3.4. The Photoreduction of Aryl Ketones: Secondary Reactions.- 3.5. The Photoreduction of Aryl Ketones: Synthetic Applications.- 3.6. The Photoreduction of Alkanones.- 3.7. Intramolecular Hydrogen Abstraction by Ketones (Type II Cleavage).- 3.7a. The Multiplicity of the Excited State.- 3.7b. Stereoelectronic Effects.- 3.7c. Substituent Effects.- 3.7d. Synthetic Applications.- 3.8. Hydrogen Abstraction by Groups Other Than the Carbonyl.- Problems.- References.- 4 The Photochemistry of Simple Carbonyl Compounds: Type I Cleavage and Oxetane Formation.- 4.1. Type I Cleavage.- 4.1a. The Nature of the Excited State: Part I.- 4.1b. Some Examples and Synthetic Applications of Type I Cleavage Reactions.- 4.1c. Type I Cleavage Reactions Resulting in Loss of Carbon Monoxide.- 4.1d. ?-Cleavage of Cyclopropyl Ketones.- 4.1e. The Nature of the Excited State: Part II.- 4.2. The Formation of Oxetanes from Carbonyls and Olefins.- 4.2a. Oxetane Formation from Olefins and Aryl Ketones and Aldehydes.- 4.2b. Synthetic Applications of Oxetane Formation.- 4.2c. Oxetane Formation from Olefins and Aliphatic Aldehydes and Ketones.- 4.2d. Perturbational Molecular Orbital Theory (PMO) Applied to Oxetane Formation.- Problems.- References.- 5 The Triplet State.- 5.1. Introduction.- 5.1a. The Identity of the Phosphorescent State as a Triplet.- 5.1b. The Definition and Properties of a Triplet State.- 5.2. Determination of Triplet Energy Levels.- 5.2a. Phosphorescence Spectroscopy.- 5.2b. Singlet ? Triplet Absorption Spectra.- 5.2c. Phosphorescence Excitation Spectroscopy.- 5.2d. Flash Photolysis.- 5.2e. Electron Excitation.- 5.2f. The Lowest Triplet Levels of Organic Molecules.- 5.3. Determination of the Efficiency of Intersystem Crossing.- 5.3a. Flash Photolysis.- 5.3b. Triplet-Sensitized Isomerization.- 5.3c. Photooxidation.- 5.3d. Delayed Fluorescence.- 5.3e. Electron Spin Resonance Spectroscopy.- 5.3f. Intersystem Crossing Quantum Yields of Organic Molecules.- 5.4. Determination of Triplet Lifetimes.- 5.4a. Flash Photolysis.- 5.4b. Luminescence Decay.- 5.4c. The Effect of Deuteration on Triplet Lifetime.- 5.4d. Triplet Lifetimes of Various Organic Molecules.- 5.5. Excited State Geometry.- 5.6. Spin-Orbit Coupling and Intersystem Crossing.- 5.6a. The Nature of Spin-Orbit Coupling.- 5.6b. Effect of Heavy Atoms on Intercombinational Transitions in Aromatic Compounds.- 5.6c. Effect of Heavy Atoms on Intercombinational Transitions in Carbonyl and Heterocyclic Compounds.- 5.6d. External Heavy-Atom Effects and Charge Transfer.- References.- 6 Electronic Energy Transfer.- 6.1. Excitation Transfer within a Chromophore System.- 6.1a. Internal Conversion and Intersystem Crossing Theory.- 6.1b. Radiationless Transitions: Phosphorescence Microwave Double Resonance.- 6.1c. Zero-Field Optically Detected Magnetic Resonance (ODMR).- 6.2. Theory of Excitation Transfer between Two Chromophores.- 6.2a. Radiative Transfer (Trivial Mechanism).- 6.2b. Resonance Transfer (Long-Range Transfer).- 6.2c. Energy Transfer via Exchange Interaction.- 6.2d. Exciton Transfer (Strong Coupling).- 6.3. Excitation Transfer between Two Chromophores.- 6.3a. Singlet-Singlet Energy Transfer (Förster Type).- 6.3b. Singlet-Singlet Energy Transfer via Collisions.- 6.3c. Intermolecular Triplet-Triplet Energy Transfer.- 6.3d. Application of Triplet-Triplet Energy Transfer.- 6.3e. Schenck Mechanism.- 6.3f. Intramolecular Triplet Energy Transfer.- 6.3g. Exciton Interaction.- 6.4. Exciplex Quenching.- References.- 7 Dienone and Enone Photochemistry.- 7.1. Dienone Photoreactions.- 7.2. Dienone to Cyclopropyl Ketone Formation.- 7.2a. 3–5 Bond Orders.- 7.2b. Zwitterionic vs. Diradical Intermediates.- 7.2c. Pivot vs. Slither Mechanism.- 7.3. Dienone to Hydroxy Ketone.- 7.4. Cyclopropyl Ketones.- 7.5. 2,4-Cyclohexadienones.- 7.6. Cyclohexenone Photorearrangements.- 7.6a. Aryl-Substituted Cyclohexenones.- 7.6b. Alkyl-Substituted Cyclohexenones.- Problems.- References.- 8 The Di-?-Methane Photorearrangement.- 8.1. Acyclic Di-?-Methane Photorearrangement.- 8.1a. Regiospecificity and Stereochemistry.- 8.1b. Substitution at the Central sp3 Carbon Atom and Di-?-Methane Reactivity.- 8.1c. Reaction Rate Constants.- 8.2. Aryl Di-?-Methane Photorearrangement.- 8.3. Bicyclic Di-?-Methane Photorearrangement.- 8.3a. Barrelene.- 8.3b. Benzobarrelene.- 8.3c. Naphthobarrelenes.- 8.3d. Anthrabarrelene.- 8.3e. Other Selected Examples.- 8.4. Oxa-di-?-Methane Rearrangement.- Problems.- References.- 9 Photochemical Cis-Trans and Valence Isomerization of Olefins.- 9.1. Introduction: Cis-Trans Isomerization of Stilbene.- 9.2. Potential Energy Diagrams.- 9.3. Photosensitized Stilbene Isomerization.- 9.4. Nonvertical Energy Transfer.- 9.5. Stilbene Isomerization via Direct Photolysis.- 9.5a. Vibrationally Excited Ground State.- 9.5b. Triplet State Mechanism.- 9.5c. Singlet State Mechanism.- 9.6. Substituted Stilbenes.- 9.7. Piperylene Photochemistry.- 9.8. Alkene Photoisomerization.- 9.9. Intramolecular Cycloaddition Reactions.- 9.9a. Theory.- 9.9b. Intramolecular (2 + 2) Cycloadditions and Cycloreversion Reactions.- 9.9c. Intramolecular (4 + 2) Photocycloaddition Reactions.- 9.10. Photoelectrocyclic Reactions.- 9.10a. Theory.- 9.10b. Examples of Electrocyclic Reactions.- Problems.- References.- 10 Photodimerization and Photocycloaddition Reactions Yielding Cyclobutanes.- 10.1. Photodimerization and Photocycloaddition Reactions of Olefins and Polyenes.- 10.1a. Photodimerization of Olefins and Polyenes.- 10.1b. Photocycloaddition Reactions of Olefins and Polyenes.- 10.2. Photodimerization and Photocycloaddition Reactions of Aromatic Compounds.- 10.3. Photodimerization and Photocycloaddition Reactions of ?,?-Unsaturated Carbonyls and Acid Derivatives.- 10.3a. Photodimerization of ?,?-Unsaturated Carbonyls and Acid Derivatives.- 10.3b. Photocycloaddition Reactions of ?,?-Unsaturated Carbonyls and Acid Derivatives.- 10.4. Dimerization in the Solid Phase.- References.- 11 Photoelimination, Photoaddition, and Photosubstitution.- 11.1. Photoelimination Reactions.- 11.1a. Photoelimination of Nitrogen.- 11.1b. Photoelimination of Nitric Oxide from Organic Nitrites.- 11.1c. Miscellaneous Photoeliminations.- 11.2. Photoaddition Reactions.- 11.2a. Photoaddition of Water, Alcohols, and Carboxylic Acids.- 11.2b. Miscellaneous Photoadditions.- 11.3. Photosubstitution Reactions.- References.- 12 An Introduction to Photobiology.- 12.1. Photosynthesis.- 12.1a. The Photosynthetic Apparatus.- 12.1b. A Mechanistic Model for Photosynthesis.- 12.2. The Photochemistry of Vision.- 12.2a. Anatomy of the Human Eye.- 12.2b. The Visual Pigments and the Chemistry of Vision.- 12.3. Phototaxis and Phototropism.- 12.4. Damage and Subsequent Repair by Light (Photoreactivation).- 12.4a. The Photochemistry of the Nucleic Acids.- 12.4b. Photoreactivation.- References.