Gas-Phase Pyrolytic Reactions

Preface xi

List of Abbreviations xiii

About the Author xv

1 Methodologies and Reactors 1

1.1 Static Pyrolysis 1

1.1.1 Sealed-Tube Reactor 2

1.1.1.1 Pyrolyzer 2

1.1.1.2 Reaction Tube 3

1.1.1.3 Kinetic Studies 3

1.1.1.4 Treatment of Kinetic Results 4

1.1.2 Static Apparatus 5

1.1.2.1 Reaction Chamber 6

1.1.2.2 The Pyrolysis Method 7

1.1.2.3 Treatment of the Results 7

1.2 Dynamic Flow Pyrolysis 8

1.2.1 Flash Vacuum Pyrolysis 8

1.2.2 Synthetic Applications of FVP 10

1.2.3 Gas-Flow Pyrolysis vs. STP 13

1.2.4 Limitations of FVP 13

1.2.5 Spray Pyrolysis 14

1.2.6 Falling-Solid Pyrolysis 17

1.3 Analytical Pyrolysis 19

1.3.1 Pyrolysis Gas Chromatography (Py-GC) 19

1.3.1.1 Online Py-GC 20

1.3.2 Pyrolysis Mass Spectrometry 22

1.3.2.1 Online Pyrolysis Gas Chromatography/Mass Spectrometry (Py-GC/MS) 22

1.3.3 FVP with Spectroscopy 22

1.3.4 Catalytic Gas-Phase Pyrolysis 24

References 27

2 Synthesis and Applications 31

2.1 Flash Vacuum Pyrolysis in Organic Synthesis 31

2.2 Elimination of HX 34

2.3 Elimination of CO and CO2 38

2.4 Pyrolysis of Meldrum's Acid Derivatives 54

2.5 Elimination of N2 60

2.5.1 Deazetization Reactions of Allylic Diazenes 63

2.5.2 Pyrolysis of Benzotriazole Derivatives 65

2.5.3 Pyrolysis of Triazine Derivatives 68

References 72

3 Reaction Mechanism 79

3.1 Retro-ene Reactions 79

3.1.1 Acetylenic Compounds 80

3.1.2 Acyl Group Participation 82

3.1.3 Cyanates and Isocyanates 82

3.1.4 Esters 83

3.1.5 Amides 88

3.1.5.1 Acetamides and Thioacetamides 88

3.1.5.2 Benzamides 92

3.1.5.3 N-Substituted Amides 93

3.2 Reactive Intermediates 94

3.2.1 Radicals 94

3.2.2 Diradicals 97

3.2.3 Benzynes 98

3.2.3.1 o-Benzynes 99

3.2.3.2 m- and p-Benzynes 101

3.2.4 Carbenes 101

3.2.5 Nitrenes 108

References 120

4 Structure/Reactivity Correlation 127

4.1 Diketones 127

4.2 Cyanoketones 133

4.3 Ketoamides 135

4.4 Benzotriazoles 136

4.5 Hammett Correlation in Gas-Phase Pyrolysis 148

4.6 Alkoxy versus Amino Group 153

4.6.1 Neighboring Group Participation 155

4.6.2 Amino Esters 158

References 162

5 Functional Group and Structural Frame Interconversions 167

5.1 Functional Group Interconversion 167

5.1.1 Thermal Retro-Ene Reactions 167

5.1.1.1 ?-Substituted Carboxylic Acids 173

5.1.1.2 2-Hydroxycarboxylic Acids 175

5.1.1.3 2-Alkoxycarboxylic Acids 176

5.1.1.4 2-Phenoxycarboxylic Acids 177

5.1.1.5 2-Aminocarboxylic Acids 180

5.1.1.6 2-Acetooxycarboxylic Acids 182

5.1.1.7 2-Ketocarboxylic Acids 184

5.1.1.8 ?-Substituted Esters 186

5.1.1.9 ?-Substituted Carboxylic Acids 188

5.2 Structural Frame Interconversion 191

5.2.1 Alkyl Heterocycles 195

References 197

6 Gas-Phase Pyrolysis of Hydrazones 201

6.1 Substituted Phenylhydrazones 203

6.2 N-Arylidineamino Heterocycles 213

6.3 Arylidene Hydrazine Heterocycles 221

References 231

7 Gas-Phase Pyrolysis of Phosphorus Ylides 235

7.1 Synthetic Applications 235

7.2 Haloalkynes 241

7.3 Terminal Alkynes 244

7.4 Diynes 247

7.5 Enynes and Dienes 250

7.6 Selective Elimination of Ph3PO from Di- and Tri-oxo-stabilized Phosphorus Ylides 252

7.7 Sulfonyl-Stabilized Phosphorus Ylides 257

7.8 Sulfinyl-Stabilized Phosphorus Ylides 262

7.9 Kinetic andThermal Reactivity of Carbonyl-Stabilized Phosphonium Ylides 266

References 277

Index 281

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• Química

<p>gas-phase pyrolysis; flash vacuum pyrolysis; physical organic chemistry; industrial chemistry; pyrolysis; organic synthesis; chemical process; chemical reaction; reaction mechanism; kinetics; reactive intermediates; transition states; thermal elimination; molecular reactivity; structural effect; substituent effect; neighboring group participation; pyrolytic reaction; reteroene reaction; unimolecular elimination reaction; theoretical studies; organic compounds; phosphorus ylides; green chemistry</p>