Chemical reactions which can, on demand, be switched on and off are valuable for industrial applications. In order to make the best use ofthese reactions, it is essential to have them readily available for a research chemist. The chemical literature, in general, has not yet identified or grouped such reactions. However, their existence is relatively abundant. This book is meant as a survey ofthose reactions which have potential utility in industrially useful processes. These reactions are grouped under the title ofchemical release reactions which can be triggered by heat, light, electric current, etc., to release a specific compound from, or change in the physical or chemical properties of, a unimolecular reactant. The book is divided into chapters covering ways to trigger the release of certain chemicals. Each chapter is further divided into sections, each beginning with a brief introduction ofanalogies ofthe discussed reactions and of how they were used in reported industrial processes. This survey is not meant to be absolute or exhaustive but rather to be directive, to be as complete as possible, and to provide food for further thought.

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1. Triggered Release of Gases.- 1.1. Processes Utilizing the Triggered Release of Gases.- 1.1.1. Applications within Imaging Science.- 1.1.1.1. Forming Images.- 1.1.1.2. Stabilizing Images.- 1.1.2. Applications within Polymer Science.- 1.2. Chemical Reactions for the Release of Gases.- 1.2.1. Thermally Triggered Release.- 1.2.1.1. Carbon Dioxide from Carboxylic Acids.- 1.2.1.2. Carbon Dioxide from Four-Membered Lactones.- 1.2.1.3. Carbon Dioxide from Bicyclic Lactones.- 1.2.1.4. Carbon Dioxide from Heterocycles.- 1.2.1.5. Carbon Monoxide from Ketones.- 1.2.1.6. Carbon Monoxide from Bicyclic Adducts.- 1.2.1.7. Sulfur Monoxide from Heterocycles.- 1.2.1.8. Sulfur Dioxide from Three-Membered Heterocycles.- 1.2.1.9. Sulfur Dioxide from Five-Membered Heterocycles.- 1.2.1.10. Sulfur Dioxide from Large Heterocycles.- 1.2.1.11. Sulfur Dioxide from Open-Chain Sulfones.- 1.2.1.12. Nitrogen from Azoalkanes.- 1.2.1.13. Nitrogen from Diazo Heterocycles.- 1.2.1.14. Nitrogen from Triazo Heterocycles.- 1.2.1.15. Nitrogen from Tetrazo Heterocycles.- 1.2.1.16. Nitrogen from Azides and Diazomethanes.- 1.2.1.17. Nitrogen from Diazonium Salts and N- Nitroso Compounds.- 1.2.1.18. Nitrogen from Miscellaneous Compounds.- 1.2.1.19. Carbonyl Sulfide from Xanthates.- 1.2.1.20. Oxygen from Endoperoxides.- 1.2.2. Photochemically Triggered Release.- 1.2.2.1. Carbon Dioxide from Heterocycles and Cyclic Peroxides.- 1.2.2.2. Carbon Monoxide from Bicyclic Adducts and Heterocycles.- 1.2.2.3. Carbon Monoxide from Cyclic Ketones.- 1.2.2.4. Sulfur Dioxide from Sulfonyloxy Compounds.- 1.2.2.5. Nitrogen from Azoalkanes.- 1. 2.2.6. Nitrogen from Diazonium Salts.- 1. 2.2.7. Nitrogen from Azides and Heterocycles.- 1.2.3. Electrochemically Triggered Release of Carbon Dioxide.- 1.2.4. Ultrasonic-Wave Triggered Release of Gases.- References.- 2. Triggered Release of Acids, Bases, Radicals, Nitrenes, and Carbenes.- 2.1. Processes Utilizing the Triggered Release of Acids, Bases, and Radicals.- 2.2. Chemical Reactions for the Release of Acids, Bases, Radicals, Nitrenes, and Carbenes.- 2.2.1. Thermally Triggered Release.- 2.2.1.1. Carboxylic Acids from Esters and Oxime Derivatives.- 2.2.1.2. Nitric Acid Derivatives from Nitroalkyl Derivatives.- 2.2.1.3. Ammonia and Amines from Amide Derivatives.- 2.2.1.4. Ammonia from Urea Derivatives.- 2.2.1.5. Radicals from Peroxide and Azo Derivatives.- 2.2.1.6. Nitrenes and Carbenes from Azide and Diazo Derivatives.- 2.2.2. Photochemically Triggered Release.- 2.2.2.1. Lewis Acids from Diazonium Salts.- 2.2.2.2. Brønsted Acids from Iodonium, Sulfonium, and Selenium Salts.- 2.2.2.3. Brønsted Acids from Nitrophenyl Phosphate and Sulfate Esters.- 2.2.2.4. Brønsted Acids from Intramolecular Cyclization.- 2.2.2.5. Carboxylic Acids from Benzyl Esters.- 2.2.2.6. Carboxylic Acids from Phenacyl, Sulfenyl, and Benzoin Esters.- 2.2.2.7. Carboxylic Acids from Amide Derivatives.- 2.2.2.8. Carboxylic Acids from Quinone Diazides, Aryl Azides, and Unsaturated Carbonyl Compounds.- 2.2.2.9. Amines from Nitrobenzyl, Benzyloxycarbonyl, Phenyloxycarbonyl, Phenacyl, and Sulfonamide Derivatives.- 2.2.2.10. Nitrenes from Azide Derivatives.- 2.2.2.11. Carbenes from Diazo Derivatives.- 2.2.2.12. Radicals from Onium Salts and Other Compounds.- 2.2.3. Electrochemically Triggered Release.- 2.2.3.1. Acids and Bases from Ester and Amine Derivatives.- References.- 3. Triggered Release of Other Monomeric Species.- 3.1. Processes Utilizing the Triggered Release of Monomeric Species.- 3.2. Chemical Reactions for the Release of Monomeric Species.- 3.2.1. Thermally Triggered Release.- 3.2.1.1. Olefins from Esters, Ethers, Lactones, and Amine Oxides.- 3.2.1.2. Aliphatic and Aromatic Hydrocarbons from Diazonium Salts, Aryl Ethers, Heterocycles, Peroxides, and Azo Alkanes.- 3.2.1.3. Heterocycles from Other Heterocycles.- 3.2.1.4. Other Small Molecules from Heterocycles, Phenols, Amides, and Ketones.- 3.2.2. Photochemically Triggered Release.- 3.2.2.1. Olefins from Electrocyclic Reactions.- 3.2.2.2. Aromatic and Aliphatic Compounds from Diazonium Salts and Ketones.- 3.2.2.3. Phenol and Its Derivatives from Ethers and Esters.- 3.2.2.4. Alcohols from Amides, Esters, Ketones, and Azide Derivatives.- 3.2.2.5. Ketones from Silyl Ethers, Ketals, and Thioketal Derivatives.- 3.2.2.6. Heterocycles from Other Heterocycles, Aryl Ketones, and Nitrone Derivatives.- 3.2.3. Electrochemically Triggered Release.- References.- 4. Triggered Reactions of Polymers.- 4.1. Processes Utilizing the Triggered Reactions of Polymers.- 4.2. Chemical Reactions for the Release of Modified Polymers and Monomers.- 4.2.1. Thermally Triggered Release.- 4.2.1.1. Polyimides from Polyamides.- 4.2.1.2. Polyheterocycles from Polyoximes, Polyhydrazides, and Their Derivatives.- 4.2.1.3. Macro Radicals from Polyperoxides.- 4.2.1.4. Macro Radicals from Azo Polymers.- 4.2.1.5. Monomers from the Depolymerization of Polymers.- 4.2.1.6. Polymers with Reactive Pendant Groups from Protected Derivatives.- 4.2.2. Photochemically Triggered Release.- 4.2.2.1. Crosslinked Polymers via Intermolecular Addition.- 4.2.2.2. Polymers via Polymeric Rearrangements.- 4.2.2.3. Polymeric Fragments via Molecular Fragmentation.- 4.2.2.4. Photochromic Polymers.- References.- 5. Triggered Isomerization and Color Change.- 5.1. Processes Utilizing Triggered Isomerization and Color Change.- 5.1.1. Imaging Science.- 5.1.2. Polymer Science.- 5.2. Chemical Reactions for Color Change.- 5.2.1. Thermally Triggered Release.- 5.2.1.1. Thermochromic Spiropyrans.- 5.2.1.2. Thermochromic Ethylenic Compounds.- 5.2.1.3. Thermochromic Disulfide Derivatives.- 5.2.1.4. Miscellaneous Thermochromic Compounds.- 5.2.1.5. Isomerization about Aliphatic and Aromatic C,C-Double Bonds.- 5.2.1.6. Isomerization about C,N- and N,N-Double Bonds.- 5.2.1.7. Thermally Irreversible Color Change.- 5.2.2. Photochemically Triggered Release.- 5.2.2.1. Photochromic Anils or Schiff's Bases.- 5.2.2.2. Photochromic Arylhydrazones.- 5.2.2.3. Photochromic Osazones and Semicarbazones.- 5.2.2.4. Photochromic Stilbene and Thiosulfonate Derivatives.- 5.2.2.5. Fulgides and Azo Dye Derivatives.- 5.2.2.6. Photochromic Indigo Dyes.- 5.2.2.7. Photochromic Triphenylmethane and Camphor Derivatives.- 5.2.2.8. Photochromic o-Nitrobenzyl Derivatives.- 5.2.2.9. Photochromic Spiro Compounds.- 5.2.2.10. Photochromic Anthrones and Sydnones.- 5.2.2.11. Other Photochromic Compounds.- 5.2.2.12. Photo-isomerization about Aromatic C,C-Double Bonds.- 5.2.2.13. Photo-isomerization about C,N- and N,N-Double Bonds.- 5.2.2.14. Photochemically Irreversible Color Change.- References.