Preface ...................................................... xiii
Author ......................................................... xv
Chapter 1 Nature of Organic Ion-Radicals and Their Ground-
State Electronic Structure ........................... 1
1.1 Introduction ............................................... 1
1.2 Unusual Features ........................................... 2
1.2.1 Substituent Effects ................................. 2
1.2.2 Connections between Ion-Radical Reactivity and
Electronic Structure of Ion-Radical Products ........ 7
1.2.3 Bridge-Effect Peculiarities ........................ 10
1.3 Acid-Base Properties of Organic Ion-Radicals .............. 16
1.3.1 Anion-Radicals ..................................... 16
1.3.1.1 Anion-Radical Basicity .................... 16
1.3.1.2 Pathways of Hydrogen Detachment from
Anion-Radicals ............................ 20
1.3.2 Cation-Radicals .................................... 22
1.3.2.1 Cation-Radical Acidity .................... 22
1.3.2.2 Cation-Radical Basicity ................... 29
1.3.2.3 Cation-Radicals as Acceptors or Donors
of Hydrogen Atoms ......................... 30
1.4 Metallocomplex Ion-Radicals ............................... 30
1.4.1 Metallocomplex Anion-Radicals ...................... 30
1.4.2 Metallocomplex Cation-Radicals ..................... 33
1.4.3 Bridge Effect in Metallocomplex Ion-Radicals ....... 36
1.4.4 Charge-Transfer Coordination to Metallocomplex
Ion-Radicals ....................................... 38
1.5 Organic Ion-Radicals with Several Unpaired Electrons or
Charges ................................................... 39
1.6 Polymeric Ion-Radicals .................................... 48
1.7 Inorganic Ion-Radicals in Reactions with Organic
Substrates ................................................ 53
1.7.1 Superoxide Ion ..................................... 54
1.7.1.1 Reactions of Superoxide Ion with Organic
H Acids ................................... 55
1.7.1.2 Reactions of Superoxide Ion with Organic
Electrophiles ............................. 56
1.7.1.3 Reactions of Superoxide Ion with
Biological Objects ........................ 57
1.7.1.4 Superoxide Ion-Ozone Anion-Radical
Relation .................................. 57
1.7.2 Atomic Oxygen Anion-Radical ........................ 58
1.7.3 Molecular Oxygen Cation-Radical .................... 58
1.7.4 Carbon Dioxide Anion-Radical ....................... 59
1.7.5 Carbonate Radical .................................. 60
1.7.6 Sulfur Dioxide Anion-Radical ....................... 61
1.7.7 Sulfite Radical .................................... 61
1.7.8 Sulfate Radical .................................... 62
1.7.9 Hydroxide Anion .................................... 65
1.7.10 Nitrosonium and Nitronium Ions ..................... 66
1.7.11 Tris(aryl)amine and Thianthrene Cation-Radicals .... 67
1.7.12 Trialkyloxonium Hexachloroantimonates .............. 69
1.7.13 Transition Metal Ions .............................. 69
1.8 Conclusion ................................................ 73
References ................................................ 74
Chapter 2 Formation of Organic Ion-Radicals ................. 85
2.1 Introduction .............................................. 85
2.2 Chemical Methods of Organic Ion-Radical Preparation ....... 86
2.2.1 Anion-Radicals ..................................... 86
2.2.2 Cation-Radicals .................................... 89
2.2.3 Carbenoid Ion-Radicals ............................. 92
2.3 Equilibria in Liquid-Phase Electron-Transfer Reactions .... 93
2.4 Electrochemical Methods versus Chemical Methods ........... 95
2.4.1 Charge-Transfer Phenomena .......................... 96
2.4.2 Template Effects .................................. 100
2.4.3 Adsorption Phenomena .............................. 103
2.4.4 Stereochemical Phenomena .......................... 106
2.4.5 Concentration Effects on the Fate of Ion-
Radicals at Electrodes and in Solutions ........... 110
2.4.6 Aggregation of Ion-Radical Salts .................. 1ll
2.4.6.1 Direct Influence on Electron-Transfer
Equilibrium .............................. 112
2.4.6.2 Electron-Transfer Reactions with
Participation of Ion-Radical
Aggregates ............................... 113
2.4.6.3 Kinetic and Mechanistic Differences
between Electrode and Chemical
(Homogeneous) Ion-Radical Dimerization ... 114
2.5 Formation of Organic Ion-Radicals in Living Organisms .... 115
2.6 Isotope-Containing Organic Compounds as Ion-Radical
Precursors ............................................... 117
2.6.1 Kinetic Isotope Effects in Electron-Transfer
Reactions ......................................... 118
2.6.2 Behavior of Isotope Mixtures in Electron-
Transfer Reactions ................................ 120
2.7 Organic Ion-Radicals in Solid Phases ..................... 126
2.7.1 Organic Ion-Radicals in Frozen Solutions .......... 126
2.7.2 Organic Ion-Radical as Constituents of Solid
Salts ............................................. 130
2.8 Formation and Behavior of Ion-Radicals within Confines ... 130
2.8.1 Micellar Media .................................... 130
2.8.2 Porous Media ...................................... 131
2.8.3 Capsule Media ..................................... 133
2.9 Conclusion ............................................... 135
References ............................................... 136
Chapter 3 Electronic Structure-Reactivity Relationship in
Ion-Radical Organic Chemistry ...................... 143
3.1 Introduction ............................................. 143
3.2 Principle of "Detained" Electron That Controls Ion-
Radical Reactivity ....................................... 144
3.2.1 Frontier-Orbital Control .......................... 144
3.2.2 Steric Control over Spin Delocalization ........... 153
3.2.3 Unpaired Electron Localization in the Field of
Two or More Atoms ................................. 155
3.2.4 Spin-Charge Separation (Distonic Stabilization
of Ion-Radicals) .................................. 161
3.2.4.1 Distonic Stabilization of Anion-
Radicals ................................. 163
3.2.4.2 Distonic Stabilization of Cation-
Radicals ................................. 165
3.2.5 Ion-Pair Formation ................................ 168
3.2.5.1 Detention of Unpaired Electron in
a Framework of One Specific Molecular
Fragment ................................. 169
3.2.5.2 Formation of Closed Contour for
Unpaired Electron Delocalization ......... 170
3.3 Principle of "Released" Electron That Controls Ion-
Radical Reactivity ....................................... 178
3.3.1 Effects of Spread Conjugation in Ion-Radicals
Derived from Molecules with Large Contours of
Delocalization .................................... 180
3.3.2 Spin Delocalization in Ion-Radicals Derived from
Molecules of Increased Dimensionality ............. 183
3.4 Biomedical Aspects of Ion-Radical Organic Chemistry ...... 186
3.4.1 Cation-Radical Damage in Deoxyribonucleic Acid .... 186
3.4.1.1 Ionization Potentials of Carcinogens ..... 187
3.4.1.2 Localization of Charges and Spins in
Cation-Radicals of Carcinogens ........... 187
3.4.2 On Geometrical and Spatial Factors Governing the
Behavior of Ion-Radicals in Biological Systems .... 189
3.4.3 Ion-Radical Repair of Damaged Deoxyribonucleic
Acid .............................................. 191
3.4.4 Cation-Radical Intermediates in Metabolism of
Furan Xenobiotics ................................. 194
3.4.5 Behavior of Anion-Radicals in Living Organisms .... 194
3.5 Conclusion ............................................... 196
References ............................................... 197
Chapter 4 Discerning Mechanism of Ion-Radical Organic
Reactions .......................................... 205
4.1 Introduction ............................................. 205
4.2 Why Do Reactions Choose Ion-Radical Mechanism? ........... 205
4.3 Chemical Approaches to Identification of Ion-Radical
Organic Reactions ........................................ 209
4.3.1 Identification According to Structure of Final
Products .......................................... 209
4.3.2 Identification According to Correlation within
Reaction Series ................................... 213
4.3.3 Identification According to Disturbance of
"Leaving-Group Strength" Correlation .............. 215
4.3.4 Kinetic Approaches to Identification of Ion-
Radical Reactions ................................. 216
4.3.4.1 Kinetic Isotope Effect ................... 216
4.3.4.2 Other Kinetic Approaches ................. 217
4.3.5 Positional Reactivity and Distribution of Spin
Density in Substrate Ion-Radicals ................. 219
4.3.6 Identification by Methods of Chemical Probes ...... 223
4.3.6.1 Initiation of Polymerization of Vinyl
Additives ................................ 223
4.3.6.2 Method of Inhibitors ..................... 224
4.3.6.3 Method of Radical and Spin Traps ......... 227
4.4 Physical Approaches to Identification of Ion-Radical
Reactions ................................................ 232
4.4.1 Radiospectroscopy ................................. 232
4.4.1.1 Electron Spin Resonance Methods .......... 232
4.4.1.2 Nuclear Magnetic Resonance Methods ....... 233
4.4.2 Optical Spectroscopy Methods ...................... 236
4.4.2.1 Electron Spectroscopy .................... 236
4.4.2.2 Vibration Spectroscopy ................... 238
4.4.3 Other Physical Methods ............................ 238
4.4.3.1 Magnetic Susceptibility .................. 238
4.4.3.2 Mass Spectrometry ........................ 238
4.4.3.3 Electrochemical Modeling of Ion-Radical
Reactions ................................ 238
4.4.3.4 X-Ray Diffraction ........................ 239
4.5 Examples of Complex Approaches to Discernment of
Ion-Radical Mechanism of Organic Reactions ............... 240
4.5.1 Oxidative Polymerization of Anilines .............. 240
4.5.2 Reactions of Hydroperoxides with Phosphites and
Sulfides .......................................... 241
4.5.3 ter Meer Reaction ................................. 243
4.5.4 Aromatic Nitration ................................ 247
4.5.4.1 System of HNO3 and H2SO4 with Catalytic
Amounts of HNO2 .......................... 251
4.5.4.2 System of HNO3 and (CH3CO)2O ............. 253
4.5.4.3 System of NaNO2 and CF3SO3H .............. 253
4.5.4.4 Systems of Metal Nitrites with
Oxidizers ................................ 255
4.5.4.5 Systems of Metal Nitrates with
Oxidizers ................................ 256
4.5.4.6 Systems with Tetranitromethane as
Nitrating Agent .......................... 257
4.5.4.7 Systems with Participation of Nitrogen
Dioxide .................................. 258
4.5.4.8 Nitration and Hydroxylation by
Peroxynitrite ............................ 259
4.5.4.9 Gas-Phase Nitration ...................... 260
4.5.5 Meerwein and Sandmeyer Reactions .................. 262
4.6 Conclusion ............................................... 263
References ............................................... 264
Chapter 5 Regulating Ion-Radical Organic Reactions ........... 271
5.1 Introduction ............................................. 271
5.2 Physical Effects ......................................... 271
5.2.1 Effect of Light ................................... 271
5.2.2 Effect of Electric Field .......................... 274
5.2.3 Effect of Magnetic Field .......................... 277
5.2.4 Effect of Microwave Field ......................... 278
5.2.5 Effect of Acoustic Field .......................... 279
5.2.6 Effect of Mechanical Action ....................... 281
5.2.6.1 Mechanochromism .......................... 282
5.2.6.2 Mechanopolymerization and Mechanolysis ... 283
5.3 Effect of Chemical Additives ............................. 286
5.4 Solvent Effects .......................................... 295
5.4.1 Static Effects .................................... 295
5.4.1.1 General Solvation ........................ 295
5.4.1.2 Selective Solvation and Solute-Solvent
Binding .................................. 297
5.4.2 Dynamic Effects ................................... 301
5.4.2.1 Solvent Reorganization ................... 301
5.4.2.2 Solvent Polarity and Polarization ........ 303
5.4.2.3 Solvent Internal Pressure ................ 304
5.4.2.4 Solvent Conformational Transition ........ 305
5.4.2.5 Solvent Temperature ...................... 306
5.4.3 Liquid Crystals and Ionic Liquids as Solvents ..... 306
5.5 Salt Effects ............................................. 308
5.5.1 Salt Effect on Spin Density Distribution .......... 308
5.5.2 Salt-Cage Effect Interplay ........................ 310
5.5.3 Salt Effect on Course of Ion-Radical Reactions .... 312
5.6 Conclusion ............................................... 316
References ............................................... 317
Chapter 6 Stereochemical Aspects of Ion-Radical Organic
Reactions .......................................... 323
6.1 Introduction ............................................. 323
6.2 Problem of Steric Restrictions ........................... 323
6.3 Reflection of the Ion-Radical Step in Reaction Steric
Results .................................................. 328
6.4 Conformational Transition of Ion-Radicals ................ 331
6.5 Space Structure and Skeletal Isomerization of Ion-
Radicals ................................................. 341
6.6 Conclusion ............................................... 344
References ............................................... 345
Chapter 7 Synthetic Opportunities of Ion-Radical Organic
Chemistry .......................................... 349
7.1 Introduction ............................................. 349
7.2 Reductive and Oxidative Reactions ........................ 349
7.2.1 Transformation of Ethylenic Ion-Radicals .......... 349
7.2.1.1 Anion-Radicals ........................... 349
7.2.1.2 Cation-Radicals .......................... 352
7.2.2 Reduction of Ketones into Alcohols ................ 352
7.2.3 Preparation of Dihydroaromatics ................... 354
7.2.4 Synthetic Suitability of (Dialkylamino)benzene
Cation-Radicals ................................... 357
7.3 Ion-Radical Polymerization ............................... 358
7.3.1 Anion-Radical Polymerization ...................... 358
7.3.2 Cation-Radical Polymerization ..................... 359
7.3.2.1 Formation of Linear Main Chains .......... 359
7.3.2.2 Formation of Cyclic and Branched
Chains ................................... 360
7.4 Ring Closure ............................................. 362
7.4.1 Cation-Radical Ring Closure ....................... 362
7.4.2 Anion-Radical Ring Closure ........................ 369
7.4.3 Ring Closure Involving Cation- and Anion-
Radicals in Linked Molecular Systems .............. 377
7.5 Ring Opening ............................................. 378
7.6 Fragmentation ............................................ 379
7.6.1 Selective Oxidation ............................... 379
7.6.1.1 Selective Oxidation of Alkylbenzenes ..... 379
7.6.1.2 Selective Oxidation of
Dimethylimidazole ........................ 381
7.6.2 Cation-Radical Route to Group Deprotection ........ 382
7.6.2.1 Removal of Butoxycarbonyl Protective
Group .................................... 382
7.6.2.2 Removal of Methoxybenzyl Protective
Group .................................... 383
7.6.2.3 Removal of Trimethylsilyl Protective
Group .................................... 384
7.6.3 Scission of Carbon-Carbon Bonds ................... 384
7.6.4 Synthon-Influential Bond Scission ................. 387
7.7 Bond Formation ........................................... 388
7.8 Opportunities Associated with SRN1 Reactions ............. 392
7.8.1 Substrate Structure ............................... 393
7.8.2 Nature of Introducing Groups ...................... 394
7.8.3 Reaction Medium ................................... 394
7.8.4 Dark SRN1 Reactions ............................... 395
7.9 Conclusion ............................................... 398
References ............................................... 398
Chapter 8 Ion-Radical Organic Chemistry in Its Practical
Applicability ...................................... 403
8.1 Introduction ............................................. 403
8.2 Organic Ion-Radicals in Microelectronics ................. 403
8.2.1 Ion-radical Approach to Molecular Switches and
Modulators ........................................ 403
8.2.2 Cation-Radicals of Triarylamines in Optical-
Recording Media ................................... 407
8.2.3 Ladder Polymerization of Fluoranthene-Based
Cation-Radicals as Route to Electrochromic
Materials ......................................... 408
8.3 Organic Metals ........................................... 409
8.4 Semiconductors ........................................... 418
8.5 Organic Magnets .......................................... 420
8.6 Lubrication in Terms of Ion-Radical Organic Chemistry .... 424
8.7 Ion-Radical Organic Chemistry in Its Contributions to
Wood Delignification and Fossil-Fuel Desulfurization ..... 428
8.7.1 Paper Fabrication ................................. 428
8.7.2 Manufacture of Commercial Products from
Delignification Wastes ............................ 433
8.7.3 Desulfurization of Fossil Fuels ................... 434
8.8 Conclusion ............................................... 435
References ............................................... 435
Chapter 9 General Outlook .................................... 441
9.1 Importance of Ion-Radical Organic Chemistry .............. 441
9.2 Scientometric Notes ...................................... 441
9.3 Prospects ................................................ 442
References .................................................... 443
Author Index .................................................. 445
Subject Index ................................................. 471
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