Carbon-centered Free Radicals and Radical Cations: Structure, Reactivity, and Dynamics (Wiley Series of Reactive Intermediates in Chemistry and Biology)

CARBON-CENTERED FREE RADICALS AND RADICAL CATIONS......Page 4
CONTENTS......Page 8
About the Volume Editor......Page 16
Preface to Series......Page 18
Introduction......Page 20
Contributors......Page 24
1. A Brief History of Carbon Radicals......Page 26
2.1 Introduction......Page 34
2.2.1 Cascade Reactions Initiated by Addition of C-Centered Radicals to Alkynes......Page 36
2.2.2 Cascade Reactions Initiated by Addition of O-Centered Radicals to Alkynes (Self-Terminating Radical Oxygenations)......Page 41
2.2.3 Cascade Reactions Initiated by Addition of N-Centered Radicals to Alkynes......Page 49
2.3.1 Cascade Reactions Initiated by Addition of Sn-Centered Radicals to Alkynes......Page 52
2.4.1 Cascade Reactions Initiated by Addition of S-Centered Radicals to Alkynes......Page 55
2.4.2 Cascade Reactions Initiated by Addition of Se-Centered Radicals to Alkynes......Page 61
2.5.1 Cascade Reactions Initiated by Addition of P-Centered Radicals to Alkynes......Page 62
3.1 Introduction......Page 68
3.1.1 Oxidative Carbon–Carbon Bond Cleavage......Page 69
3.1.2 Thermodynamic and Kinetic Considerations......Page 71
3.2 Electron Transfer-Initiated Cyclization Reactions......Page 74
3.2.2 Development of a Catalytic Aerobic Protocol......Page 75
3.3 Oxidative Acyliminium Ion Formation......Page 77
3.4.1 Chemoselectivity and Reactivity......Page 79
3.4.2 Reaction Scope......Page 80
3.5 Summary and Outlook......Page 83
4.1 Introduction......Page 86
4.2 Mechanism and the Origin of the Rate Acceleration......Page 87
4.3 Selectivity in Radical Cation Cycloadditions......Page 88
4.4.1 Effect of Dienophile Substituents on Chemoselectivity......Page 89
4.4.2 Effect of Sensitizers and Solvents on Chemoselectivity......Page 91
4.4.4 Effect of Electron-Rich Dienophiles on Chemoselectivity......Page 92
4.5 Regioselectivity......Page 93
4.6 Periselectivity......Page 94
4.6.1 Effects of Solvent and Concentration on Periselectivity......Page 95
4.6.2 Effect of Diene/Dienophile Redox Potentials on Periselectivity......Page 96
4.6.3 Substituent and Steric Effects on Periselectivity......Page 97
4.6.4 Quantifying Periselectivity Through Ion Pair Association......Page 99
4.7.1 Effects of Secondary Orbital Interaction and Solvents on Endo/Exo Selectivity......Page 100
4.7.2 Effect of Sensitizer on Endo/Exo Selectivity......Page 101
4.7.3 Ion Pairs and Endo/Exo Selectivities......Page 102
4.8 Conclusions......Page 104
5.1 Introduction......Page 108
5.1.1 The Consequences of Different Stability Definitions: How Stable Are Ethyl and Fluoromethyl Radicals?......Page 110
5.2 Theoretical Methods......Page 111
5.2.1 Testing the Performance of Different Theoretical Approaches: How Stable Are Allyl and Benzyl Radicals?......Page 112
5.2.2 The Application of IMOMO Schemes: How Stable Are Benzyl and Diphenylmethyl Radicals?......Page 114
5.4.1 Susceptibility to Hydrogen Atom Abstraction......Page 116
5.4.2 Assessment of Radical Stability in Other Types of Reactions......Page 125
5.5 Conclusions......Page 127
6.1 Introduction......Page 130
6.2.1 Theoretical Background......Page 132
6.2.3 Vibrational Effects......Page 133
6.2.4 Dynamical Effects......Page 134
6.3 Calculation of EPR Parameters......Page 135
6.3.1 Geometric Parameters......Page 137
6.3.2 EPR Parameters......Page 138
6.3.3.1 Glycine Radical......Page 142
6.3.3.2 Glycyl Radical......Page 144
6.3.4 Case Studies: Vibrationally Averaged Properties of Vinyl and Methyl Radicals......Page 145
6.4.1 Case Studies: Anharmonic Frequencies of Phenyl and Naphthyl Cation Radicals......Page 147
6.4.2 Case Studies: Gas and Matrix Isolated IR Spectra of the Vinyl Radical......Page 150
6.5.2 Case Studies: Vertical Excitation Energies of the Vinyl Radical......Page 151
6.6 Vibronic Spectra......Page 154
6.6.1 Theoretical Background......Page 157
6.6.3 Case Studies: Electronic Absorption Spectrum of Phenyl Radical......Page 159
6.7 Concluding Remarks......Page 162
7.1 Introduction......Page 166
7.2 The Tools......Page 167
7.2.2 EPR Parameters: Experimental and Calculated......Page 168
7.3 Pagodane and Its Derivatives......Page 169
7.4 Different Stages of Cycloaddition/Cycloreversion Reactions Within Confined Environments......Page 176
7.5 Extending the "Cage Concept"......Page 177
7.6 Summary......Page 179
8.1 Introduction......Page 182
8.2 The Spin-Correlated Radical Pair......Page 183
8.2.2 Intraradical Interactions......Page 184
8.2.3 Interradical Interactions......Page 185
8.3.1 The Zeeman Effect......Page 187
8.4.1 Coherent Spin-State Mixing......Page 188
8.4.2 The Life Cycle of a Radical Pair......Page 190
8.5.1 "Normal" Magnetic Fields......Page 192
8.5.2 Weak Magnetic Fields......Page 194
8.5.3 Strong Magnetic Fields......Page 196
8.6.1 General Approaches......Page 197
8.6.3 The Semiclassical Approach......Page 198
8.7 Experimental Approaches......Page 199
8.7.1 Fluorescence Detection......Page 200
8.8 The Life Cycle of Radical Pairs in Homogeneous Solution......Page 201
8.8.1 Differentiating G-Pairs and F-Pairs......Page 202
8.9 Summary......Page 205
9.1 Introduction......Page 210
9.2 CIDNP Theory......Page 211
9.3 Experimental Methods......Page 215
9.4 Radical—Radical Transformations During Diffusive Excursions......Page 216
9.5 Radical—Radical Transformations at Reencounters......Page 221
9.6 Interconversions of Biradicals......Page 224
9.7 Conclusions......Page 228
10.1 Introduction......Page 230
10.2 EPR for the Isolated Ions......Page 234
10.3 Calculation Methods for EPR of the Isolated Ions......Page 236
10.3.1 Calculation of g Tensor Components......Page 237
10.3.2.1 Ab Initio Hyperfine Coupling Constants: General Notes......Page 238
10.3.2.2 Theoretical Values of Isotropic and Anisotropic Hyperfine Coupling Constants......Page 239
10.4 Implications for Spin-Relaxation in Linked Radical Pairs......Page 241
11.1 Introduction......Page 246
11.2 The Crossed Molecular Beam Method......Page 248
11.3.1 The Crossed Beam Machine......Page 249
11.3.2.1 Ablation Source......Page 252
11.3.2.3 Photolytic Source......Page 253
11.4.1 Reactions of Phenyl Radicals......Page 254
11.4.2 Reactions of CN and C(2)H Radicals......Page 261
11.4.3 Reactions of Carbon Atoms, Dicarbon Molecules, and Tricarbon Molecules......Page 262
11.5 Conclusions......Page 265
12.1 Introduction......Page 274
12.2.1 Quantum Yields of Free Radicals in Nonviscous Solutions......Page 275
12.2.2 Cage Effect Under Photodissociation......Page 277
12.2.3 The Magnetic Field Effect on Photodissociation......Page 278
12.3.1 CIDEP Under Photodissociation of Initiators......Page 279
12.3.2 Addition of Free Radicals to the Double Bonds of Monomers......Page 285
12.3.3 Electron Spin Polarization Transfer from Radicals of Photoinitiators to Stable Nitroxyl Polyradicals......Page 293
12.4.2 Representative Kinetic Data on Reactions of Photoinitiator Free Radicals......Page 295
12.6 Concluding Remarks......Page 299
13.1.1 General Considerations......Page 306
13.1.2 Escape Probability of an Isolated, Intimate Radical Pair in Liquids and Bulk Polymers......Page 308
13.2.1 General Mechanistic Considerations From Solution and Gas-Phase Studies......Page 311
13.2.1.1 Photo-Fries Reactions of Aryl Esters......Page 312
13.3 Photo-Reactions of Aryl Esters in Polymer Matrices. Kinetic Information from Constant Intensity Irradiations......Page 314
13.3.1 Relative Rate Information from Irradiation of Aryl Esters in Which Acyl Radicals Do Not Decarbonylate Rapidly......Page 315
13.3.2 Absolute and Relative Rate Information from Constant Intensity Irradiation of Aryl Esters in Which Acyl Radicals Do Decarbonylate Rapidly......Page 318
13.4 Rate Information from Constant Intensity Irradiation of Alkyl Aryl Ethers......Page 322
13.4.1.1 Results from Irradiation in n-Alkane Solutions......Page 324
13.4.1.2 Results from Irradiation in Polyethylene Films......Page 329
13.5 Comparison of Calculated Rates to Other Methods for Polyethylene Films......Page 331
13.6.1 Triplet-State Radical Pairs from the Photoreduction of Benzophenone by Hydrogen Donors......Page 333
13.6.2 Triplet-State Radical Pairs from Norrish Type I Processes......Page 336
13.7 Concluding Remarks......Page 343
14.1 Introduction......Page 350
14.2 The Photodegradation Mechanism......Page 351
14.3 Polymer Structures......Page 352
14.4 The Time-Resolved EPR Experiment......Page 354
14.5 Tacticity and Temperature Dependence of Acrylate Radicals......Page 357
14.6 Structural Dependence......Page 359
14.6.1 d(3)-Poly(methyl methacrylate), d(3)-PMMA......Page 360
14.6.4 Poly(ethyl acrylate), PEA......Page 362
14.6.5 Poly(fluorooctyl methacrylate), PFOMA......Page 363
14.6.6 Polyacrylic Acid, PAA......Page 364
14.7 Oxo-Acyl Radicals......Page 365
14.8 Spin Polarization Mechanisms......Page 368
14.9.1 pH Effects on Poly(acid) Radicals......Page 369
14.9.2 General Features for Polyacrylates......Page 370
14.10 Dynamic Effects......Page 372
14.10.1 The Two-Site Jump Model......Page 373
14.10.2 Simulations and Activation Parameters......Page 375
14.11 Conclusions......Page 377
Index......Page 384