Preface to the Second Edition ................................ xvii
Preface to the First Edition .................................. xix
1 General Aspects .............................................. 1
1.1 Defining Acidity ........................................ 1
1.1.1 Acids and Bases .................................. 1
1.1.2 The pH Scale ..................................... 3
1.1.3 Acidity Functions ................................ 4
1.2 Definition of Superacids ................................ 6
1.2.1 Range of Acidities ............................... 7
1.3 Types of Superacids ..................................... 9
1.3.1 Primary Superacids .............................. 10
1.3.2 Binary Superacids ............................... 10
1.3.3 Ternary Superacids .............................. 10
1.3.4 Solid Superacids ................................ 10
1.4 Experimental Techniques for Acidity Measurements
(Protic Acids) ......................................... 11
1.4.1 Spectrophotometric Method ....................... 11
1.4.2 Nuclear Magnetic Resonance Methods .............. 13
1.4.2.1 Chemical Shift Measurements ............ 15
1.4.2.2 Exchange Rate Measurements Based on
Line-Shape Analysis (DNMR: Dynamic
Nuclear Magnetic Resonance) ............ 18
1.4.3 Electrochemical Methods ......................... 20
1.4.4 Chemical Kinetics ............................... 20
1.4.5 Heats of Protonation of Weak Bases .............. 22
1.4.6 Theoretical Calculations and Superacidity
in the Gas Phase ................................ 22
1.4.7 Estimating the Strength of Lewis Acids ... 23
1.4.8 Experimental Techniques Applied to
Solid Acids .............................. 27
References .................................................. 29
2. Superacid Systems ........................................... 35
2.1 Primary Superacids ..................................... 35
2.1.1 Brønsted Superacids ............................. 35
2.1.1.1 Perchloric Acid ........................ 35
2.1.1.2 Chlorosulfuric Acid .................... 36
2.1.1.3 Fluorosulfuric Acid .................... 37
2.1.1.4 Perfluoroalkanesulfonic Acids .......... 38
2.1.1.5 Hydrogen Fluoride ...................... 40
2.1.1.6 Carborane Superacids H(CB11HR5X6) ....... 41
2.1.2 Lewis Superacids ................................ 42
2.1.2.1 Antimony Pentafluoride ................. 42
2.1.2.2 Arsenic Pentafluoride .................. 44
2.1.2.3 Phosphorus Pentafluoride ............... 44
2.1.2.4 Tantalum and Niobium Pentafluoride ..... 44
2.1.2.5 Boron Trifluoride ...................... 44
2.1.2.6 Tris(pentafluorophenyl) Borane ......... 45
2.1.2.7 Boron
Tris(trifluoromethanesulfonate) ........ 46
2.1.2.8 Apr otic Organic Superacids
(Vol'pin's Systems) .................... 46
2.2 Binary Superacids ...................................... 47
2.2.1 Binary Brønsted Superacids ...................... 47
2.2.1.1 Hydrogen Fluoride-Fluorosulfuric
Acid ................................... 47
2.2.1.2 Hydrogen
Fluoride-Trifluoromethanesulfonic
Acid ................................... 47
2.2.1.3 Tetra(Hydrogen Sulfato)Boric Acid-
Sulfuric Acid .......................... 47
2.2.2 Conjugate Brønsted-Lewis Superacids ............. 47
2.2.2.1 Oleums-Poly sulfuric Acids ............. 47
2.2.2.2 Fluorosulfuric Acid-Antimony
Pentafluoride ("Magic Acid") ........... 49
2.2.2.3 Fluorosulfuric Acid-Sulfur Trioxide .... 53
2.2.2.4 HSO3F-MFn(SO3F)5-n; n = 3,4,
M = Nb, Та ............................. 53
2.2.2.5 Fluorosulfuric Acid-Arsenic
Pentafluoride .......................... 54
2.2.2.6 Perfluoroalkanesulfonic Acid-Based
Systems ................................ 54
2.2.2.7 Hydrogen Fluoride-Antimony
Pentafluoride (Fluoroantimonic
Acid) .................................. 56
2.2.2.8 Hydrogen Fluoride-Phosphorus
Pentafluoride .......................... 59
2.2.2.9 Hydrogen Fluoride-Tantalum
Pentafluoride .......................... 60
2.2.2.10 Hydrogen Fluoride-Boron
Trifluoride (Tetrafluoroboric Acid) .... 60
2.2.2.11 Conjugate Friedel-Crafts Acids
(HX-AIX3, etc.) ........................ 61
2.3 Ternary Superacids ..................................... 62
2.3.1 HSO3F-HF-SbF5 ................................... 62
2.3.2 HSO3F-HF-CF3SO3H ................................ 63
2.3.3 CF3SO3H-HF-Lewis Acid ........................... 63
2.3.4 HSO3F-SbF5-SO3 .................................. 63
2.4 Solid Superacids ....................................... 63
2.4.1 Zeolitic Acids .................................. 64
2.4.2 Polymeric Resin Sulfonic Acids .................. 65
2.4.2.1 Lewis Acid-Complexed Sulfonic Acid
Resins ................................. 65
2.4.2.2 Perfluorinated Polymer Resin Acids ..... 66
2.4.3 Enhanced Acidity Solids ......................... 68
2.4.3.1 Brønsted Асid-Modified Metal
Oxides: TiO2-H2SO4; ZrO2-H2SO4 .......... 68
2.4.3.2 Lewis Acid-Modified Metal Oxides
and Mixed Oxides ....................... 69
2.4.3.3 Lewis Acid-Complexed Metal Salts ....... 70
2.4.4 Immobilized Superacids (Bound to Inert
Supports) ....................................... 71
2.4.4.1 Superacids Immobilized on Solid
Supports ............................... 11
2.4.4.2 Graphite-Intercalated Superacids ....... 72
2.4.4.3 SbF5Fluorinated Graphite,
SbF5-Fluorinated Al2O3 .................. 74
References .................................................. 75
3 Carbocations in Superacid Systems ........................... 83
3.1 Introduction ........................................... 83
3.1.1 Development of the Carbocation Concept: Early
Kinetic and Stereochemical Studies ..................... 83
3.1.2 Observation of Stable, Long-Lived
Carbocations .................................... 84
3.1.3 General Concept of Carbocations ................. 85
3.2 Methods of Generating Carbocations in Superacids
Systems ................................................ 87
3.3 Methods and Techniques in the Study of Carbocations .... 88
3.3.1 Nuclear Magnetic Resonance Spectra in
Solution ........................................ 88
3.3.2 13C NMR Chemical Shift Additivity ................ 89
3.3.3 Isotopic Perturbation Technique ................. 90
3.3.4 Solid-State 13C NMR ............................. 90
3.3.5 X-ray Diffraction ............................... 91
3.3.6 Tool of Increasing Electron Demand .............. 91
3.3.7 Core Electron Spectroscopy ...................... 91
3.3.8 Infrared and Raman Spectroscopy ................. 92
3.3.9 Electronic Spectroscopy ......................... 92
3.3.10 Low-Temperature Solution Calorimetric
Studies ......................................... 92
3.3.11 Quantum Mechanical Calculations ................. 93
3.4 Trivalent Carbocations ................................. 93
3.4.1 Alkyl Cations ................................... 93
3.4.1.1 Early Unsuccessful Attempts ............ 93
3.4.1.2 Preparation from Alkyl Fluorides in
Antimony Pentafluoride Solution and
Spectroscopic Studies .................. 94
3.4.1.3 Preparation from Other Precursors ..... 108
3.4.1.4 Observation in Different Superacids ... 112
3.4.2 Cycloalkyl Cations ............................. 112
3.4.3 Bridgehead Cations ............................. 116
3.4.4 Cyclopropylmethyl Cations ...................... 120
3.4.5 Alkenyl Cations ................................ 123
3.4.6 Alkadienyl and Polyenylic Cations .............. 125
3.4.7 Arenium Ions ................................... 126
3.4.8 Ethylenearenium Ions ........................... 132
3.4.9 Propargyl and Allenylmethyl Cations
(Mesomeric Vinyl Cations) ....................... 134
3.4.10 The Phenyl Cation .............................. 139
3.4.11 Arylmethyl and Alkylarylmethyl Cations ......... 140
3.4.12 Carbodications and Polycations ................. 147
3.4.13 Aromatic Stabilized Cations and Dications ...... 157
3.4.14 Polycyclic Arene Dications ..................... 162
3.4.15 Fullerene Cations .............................. 164
3.4.16 Heteroatom-Stabilized Cations .................. 167
3.4.16.1 Halogen as Heteroatom ................. 167
3.4.16.2 Oxygen as Heteroatom .................. 172
3.4.16.3 Sulfur as Heteroatom .................. 192
3.4.16.4 Nitrogen as Heteroatom ................ 195
3.4.17 Carbocations Complexed to Metal Atoms .......... 204
3.5 Equilibrating (Degenerate) and Higher (Five or Six)
Coordinate (Nonclassical) Carbocations ................ 206
3.5.1 Alkonium Ions (Protonated Alkanes СnH2n+3+) ..... 206
3.5.1.1 The Methonium Ion (CH5+) .............. 207
3.5.1.2 Multiply Protonated Methane Ions
and Their Analogs ..................... 212
3.5.1.3 Varied Methane Cations ................ 214
3.5.1.4 Ethonium Ion (C2H7+) and Analogs ...... 216
3.5.1.5 Proponium Ions and Analogs ............ 218
3.5.1.6 Higher Alkonium Ions .................. 219
3.5.1.7 A daman tonium Ions ................... 224
3.5.2 Equilibrating and Bridged Carbocations ......... 225
3.5.2.1 Degenerate 1,2-Shifts in
Carbocations .......................... 225
3.5.2.2 The 2-Norbornyl Cation ................ 229
3.5.2.3 The 7-Norbornyl Cation ................ 239
3.5.2.4 The 2-Bicyclo[2.1.1]hexyl Cation ...... 240
3.5.2.5 Degenerate Cyclopropylmethyl and
Cyclobutyl Cations .................... 241
3.5.2.6 Shifts to Distant Carbons ............. 246
3.5.2.7 9-Barbaralyl
(Tricyclo[3.3.1.02,8]nona-3,
6-dien-9-yl) Cations and
Вicyclo[3.2.2] nona-3,6,8-trien-2-yl
Cations ............................... 253
3.5.2.8 The 1,3,5,7-Tetramethyl- and 1,2,3,5,
7-Pentamethyl-2-adamantyl Cations ..... 257
3.5.3 Homoaromatic Cations ........................... 258
3.5.3.1 Monohomoaromatic Cations .............. 259
3.5.3.2 Bishomoaromatic Cations ............... 260
3.5.3.3 Trishomoaromatic Cations .............. 265
3.5.3.4 Three-Dimensional Homoaromaticity ..... 266
3.5.4 Pyramidal Cations .............................. 267
3.5.4.1 (CH)5+-Type Cations ................... 267
3.5.4.2 (CH)62+-Type Dications ................ 270
References ................................................. 273
4 Heterocations in Superacid Systems ......................... 311
4.1 Introduction .......................................... 311
4.2 Oniumlons ............................................. 311
4.2.1 Oxonium Ions ................................... 311
4.2.1.1 Hydronium Ion (H3O+) .................. 311
4.2.1.2 Primary Oxonium Ions [ROH2+] .......... 313
4.2.1.3 Secondary Oxonium Ions [RR'OH+] ....... 319
4.2.1.4 Tertiary Oxonium Ions ................. 322
4.2.1.5 Aurated Oxonium Ions .................. 328
4.2.1.6 Hydrogen Peroxonium Ion (H3O2+)
and Derivatives ....................... 329
4.2.1.7 Ozonium Ion(HO3+) ...................... 330
4.2.2 Sulfonium Ions ................................. 331
4.2.2.1 Hydrosulfonium Ion (H3S+) .............. 331
4.2.2.2 Primary Sulfonium Ions ................ 332
4.2.2.3 Secondary Sulfonium Ions .............. 334
4.2.2.4 Tertiary Alkyl(Aryl)Sulfonium Ions .... 335
4.2.2.5 Halosulfonium Ions .................... 340
4.2.2.6 Sulfonium Ions with Other
Heteroligands ......................... 342
4.2.3 Selenonium and Telluronium Ions ................ 350
4.2.3.1 Hydridoselenonium and
Hydridotelluronium Ions ............... 350
4.2.3.2 Acidic Selenonium and Telluronium
Ions .................................. 351
4.2.3.3 Tertiary Selenonium and Telluronium
Ions .................................. 352
4.2.3.4 Haloselenonium and Halotelluronium
Ions .................................. 356
4.2.3.5 Aurated Selenonium and Telluronium
Ions .................................. 357
4.2.3.6 Polychalcogen Dications ............... 358
4.2.4 Halonium Ions .................................. 360
4.2.4.1 Acyclic (Open-Chain) Halonium Ions .... 362
4.2.4.2 Cyclic Halonium Ions .................. 372
4.2.5 Oniurn Ions of Group 15 Elements ............... 381
4.2.5.1 2-Azoniaallene and Derived Cations .... 381
4.2.5.2 Diazonium Ions ........................ 383
4.2.5.3 Nitronium Ion (NO2+) .................. 390
4.2.5.4 Nitrosonium Ion (NO+) ................. 392
4.2.5.5 Ammonium, Phosphonium, Arsonium,
and Stibonium Ions .................... 394
Enium Ions ............................................ 397
4.3.1 Enium Ions of Group 13 Elements ................ 397
4.3.1.1 В or enium Ions ....................... 397
4.3.1.2 Alumenium Ions ........................ 400
4.3.2 Enium Ions of Group 14 Elements ................ 401
4.3.2.1 Silicenium Ions ....................... 401
4.3.2.2 Germenium Ions ........................ 411
4.3.2.3 Enium Ions of Other Group 14
Elements .............................. 413
4.3.3 Enium Ions of Group 15 Elements ................ 415
4.3.3.1 Nitrenium Ions ........................ 415
4.3.3.2 Phosphenium Ions ...................... All
4.3.3.3 Enium Ions of Other Group 15
Elements .............................. 423
4.3.4 Enium Ions of Group 16 Elements ................ 424
4.3.4.1 Oxenium Ions .......................... 424
4.3.4.2 Enium Ions of Other Group 16
Elements .............................. 425
4.4 Homo- and Heteropolyatomic Cations .................... 426
4.4.1 Halogen Cations ................................ 427
4.4.1.1 Iodine Cations ........................ 4ll
4.4.1.2 Bromine Cations ....................... 430
4.4.1.3 Chlorine Cations ...................... 432
4.4.2 Interhalogen Cations ........................... 433
4.4.2.1 Triatomic Interhalogen Cations ........ 433
4.4.2.2 Pentaatomic Interhalogen Cations ...... 436
4.4.2.3 Heptaatomic Interhalogen Cations ...... 437
4.4.3 Polyatomic Cations of Group 16 Elements ........ 438
4.4.3.1 The O2+ Cation ........................ 438
4.4.3.2 Polysulfur Cations .................... 439
4.4.3.3 Polyselenium Cations .................. 441
4.4.3.4 Polytellurium Cations ................. 444
4.4.3.5 Polyheteroatom Cations ................ 445
4.4.4 Mixed Polyheteroatom Cations of Group 15, 16,
and 17 Elements ................................ 447
4.4.4.1 Polyheteroatom Cations of Nitrogen
and Sulfur ............................ 441
4.4.4.2 Polyheteroatom Cations of Halogens
with Oxygen or Nitrogen ............... 448
4.4.4.3 Polyheteroatom Cations of Chalcogens
with Halogens ......................... 450
4.5 Cations of Group 6-12 Elements ........................ 453
4.5.1 Homoleptic Metal Carbonyl Cations .............. 453
4.5.2 Other Cations of Group 6-12 Elements ........... 456
4.6 Miscellaneous Cations ................................. 460
4.6.1 Hydrogen Cations ............................... 460
4.6.1.1 H+ Ion ................................. 460
4.6.1.2 H3+ Ion ................................ 460
4.6.2 Cations of Noble Gases ......................... 460
References ............................................ 465
5 Superacid-Catalyzed Reactions .............................. 501
5.1 Conversion of Saturated Hydrocarbons .................. 501
5.1.1 Sigma-Basicity: Reversible Protonation or
Protolysis of C-Hand C-C Bond .................. 503
5.1.1.1 Deuterium-Hydrogen Exchange
Studies ............................... 505
5.1.2 Electrochemical Oxidation in Strong Acids ...... 520
5.1.3 Isomerization of Alkanes ....................... 524
5.1.4 Cleavage Reactions (β-Cleavage versus C-C
Bond Protolysis) ............................... 539
5.1.5 Alkylation of Alkanes and Oligocondensation
of Lower Alkanes ............................... 543
5.2 Alkylation of Aromatic Hydrocarbons ................... 554
5.2.1 Alkylation with Alkenes ........................ 554
5.2.2 Alkylation with Alcohols and Cyclic Ethers ..... 560
5.2.3 Alkylation with Alkyl Halides .................. 566
5.2.4 Alkylation with Carbonyl Compounds and
Derivatives .................................... 577
5.2.5 Alkylation with Acid Derivatives ............... 585
5.2.6 Isomerization and Transalkylation of
Alkylbenzenes .................................. 586
5.2.7 Alkylation with Miscellaneous Reagents ......... 589
5.2.8 Cyclialkylation ................................ 595
5.3 Acylation of Aromatics ................................ 608
5.4 Carboxylation ......................................... 618
5.5 Formylation ........................................... 627
5.6 Thio- and Dithiocarboxylation ......................... 632
5.7 Sulfonation and Sulfonylation ......................... 633
5.8 Nitration ............................................. 636
5.9 Nitrosonium Ion (NO+)-Induced Reactions ............... 643
5.10 Halogenation .......................................... 647
5.10.1 Halogenation of Nonaromatic Compounds ......... 647
5.10.2 Halogenation of Aromatic Compounds ............ 655
5.11 Amination ............................................. 659
5.12 Oxyfunctionalization .................................. 660
5.12.1 Oxygenation with Hydrogen Peroxide ............. 661
5.12.1.1 Oxygenation of Alkanes ................ 663
5.12.1.2 Oxygenation of Aromatics .............. 663
5.12.1.3 Oxygenation of Natural Products ....... 666
5.12.2 Oxygenation with Ozone ......................... 667
5.12.3 Oxygenation Induced by Nafion Resins ........... 672
5.12.4 Oxygenation by Other Methods ................... 674
5.13 Superacids in Protection Group Chemistry .............. 676
5.14 Superacids in Heterocyclic Chemistry .................. 680
5.14.1 Synthesis of Heterocycles ...................... 680
5.14.1.1 Preparation of Oxacycloalkanes ........ 680
5.14.1.2 Synthesis of Nitrogen Heterocycles .... 685
5.14.1.3 Heterocycles with Two or Three
Heteroatoms ........................... 689
5.14.2. Ring-Opening of Oxygen Heterocycles ........... 696
5.15 Dehydration ........................................... 698
5.16 Superacids in Carbohydrate Chemistry .................. 700
5.17 Rearrangements and Cyclizations ....................... 706
5.17.1 Rearrangements and Cyclizations of Natural
Products ....................................... 706
5.17.2 Phenol-Dienone Rearrangements .................. 722
5.17.3 Other Rearrangements and Cyclizations .......... 724
5.18 Ionic Hydrogenation ................................... 727
5.19 Esterification and Ester Cleavage ..................... 734
5.20 Additions ............................................. 735
5.20.1 Cycloadditions ................................. 735
5.20.2 Other Additions ................................ 738
5.21 Ritter Reactions ...................................... 742
5.22 Polymerization ........................................ 744
5.23 Miscellaneous Reactions ............................... 750
References ................................................. 756
Outlook ....................................................... 789
Index ......................................................... 791
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