High Resolution NMR (eBook)

Front Cover 1
High Resolution NMR: Theory and Chemical Applications 4
Copyright Page 5
Table of Contents 6
PREFACE TO SECOND EDITION 12
PREFACE TO FIRST EDITION 13
ACKNOWLEDGMENTS 15
Chapter 1. Introduction 16
1.1 Historical 16
1.2 High Resolution NMR 17
Chapter 2. The Theory of NMR 24
2.1 Nuclear Spin and Magnetic Moment 24
2.2 Classical Mechanical Description of NMR 25
2.3 Quantum Mechanical Description of NMR 28
2.4 Effect of the Boltzmann Distribution 31
2.5 Spin Lattice Relaxation 33
2.6 Line Widths 35
2.7 Saturation 37
2.8 Macroscopic Magnetization 37
2.9 The Bloch Equations: Nuclear Induction 39
2.10 The Rotating Frame of Reference 40
2.11 Adiabatic Passage Ringing
Problems 43
Chapter 3. Instrumentation and Techniques 45
3.1 Basic NMR Apparatus 45
3.2 Requirements for High Resolution NMR 46
3.3 Modulation and Phase Sensitive Detection 50
3.4 Field/Frequency Control 51
3.5 Signal/Noise and Size of Sample 52
3.6 Fourier Transform Methods 55
3.7 Intensity Measurements 56
3.8 References 57
3.9 Magnetic Susceptibility Measurements 60
3.10 Frequency Calibration 61
3.11 Control of Sample Temperature 61
3.12 Useful Solvents 62
3.13 Sampling Techniques 63
3.14 Micro Techniques 66
Problems 68
Chapter 4. Chemical Shifts 70
4.1 The Origin of Chemical Shifts 70
4.2 Reference Compounds 70
4 3 Chemical Shift Scales 71
4.4 Magnetic Susceptibility Correction 74
4.5 Empirical Correlations of Chemical Shifts 76
4.6 Theory of Chemical Shifts 76
4.7 Effect of Electron Density 81
4.8 Magnetic Anisotropy and Chemical Shifts 84
4.9 Ring Currents 88
4.10 Nuclei Other Than Hydrogen 90
4.11 Carbon-13 91
4.12 Tabulations of Chemical Shifts and Spectra 91
4.13 Empirical Estimation of Chemical Shifts 93
4.14 Isotope Effects on Chemical Shifts 95
4.15 Paramagnetic Species 95
4.16 Lanthanide Shift Reagents 96
Problems 98
Chapter 5. Electron–Coupled Spin-Spin Interactions 100
5.1 Origin of Spin–Spin Coupling 100
5.2 Coupling between Groups of Equivalent Nuclei 102
5.3 First-Order Analysis 103
5.4 Signs of Coupling Constants 108
5.5 Theory of Spin–Spin Coupling 108
5.6 Some Observed Coupling Constants 109
5.7 Correlation of Coupling Constants with Other Physical Properties 117
5.8 Tabulations of Coupling Constants 120
Problems 121
Chapter 6. The Use of NMR in Structure Elucidation 123
6.1 A Systematic Approach to the Interpretation of NMR Spectra 123
6.2 Some Features of Carbon-13 Spectra 130
6.3 Structure Elucidation of Polymers 131
Problems 134
Chapter 7. Analysis of Complex Spectra 135
7.1 Notation 135
7.2 Energy Levels and Transitions in an AX System 137
7.3 Quantum Mechanical Formalism 139
7.4 Nuclear Spin Basis Functions 141
7.5 The Spin Hamiltonian 141
7.6 The Two-Spin System without Coupling 143
7.7 Factoring the Secular Equation 146
7.8 Two Coupled Spins 147
7.9 Selection Rules and Intensities 149
7.10 The AB Spectrum 150
7.11 Spectral Contributions from Equivalent Nuclei 154
7.12 Symmetry of Wave Functions 155
7.13 Summary of Rules for Calculating Spectra 156
7.14 The Three-Spin System: ABC 159
7.15 The A2B System 160
7.16 The A3B System Subspectral Analysis
7.17 The ABX System 164
7.18 Analysis of an ABX Spectrum 167
7.19 Relative Signs of 7AX and JBX in an ABX Spectrum 173
7.20 ABX Patterns Deceptively Simple Spectra
7.21 "Virtual Coupling" 178
7.22 The AABB' and AA'XX' Systems 182
7.23 Other Complex Spectra 186
7.24 Aida in the Analysis of Complex Spectra 187
7.25 Carbon-13 Satellites 189
7.26 Effects of Molecular Asymmetry 189
7.27 Polymer Configuration 193
7.28 Use of Liquid Crystals as Solvents 194
Problems 196
Chapter 8. Relaxation 199
8.1 Molecular Motions and Processes for Relaxation in Liquids 199
8.2 Nuclear Magnetic Dipole Interactions 203
8 3 Relaxation via Chemical Shift Anisotropy 205
8.4 Spin–Rotation Relaxation 205
8.5 Electric Quadrupole Relaxation 207
8.6 Scalar Relaxation 207
8.7 Relaxation by Paramagnetic Substances 209
8.8 Some Chemical Applications 209
8.9 Measurement of Relaxation Times 212
Problems 213
Chapter 9. Theory and Application of Double Resonance 214
9.1 Notation and Terminology 214
9.2 Experimental Techniques 215
9.3 Theory of Double Resonance 217
9.4 The Nuclear Overhauser Effect 221
9.5 Structure Elucidation 223
9.6 Location of "Hidden" Lines 226
9.7 Determination of Chemical Shifts 227
9.8 Relative Signs of Coupling Constants 228
9.9 Determination of Energy Level Arrangements 231
9.10 "High Resolution'' Spectra in Solids 234
Problems 235
Chapter 10. Pulse Fourier Transform Methods 237
10.1 RF Pulses and the Free Induction Decay 237
10.2 Fourier Transformation of the FID 240
10.3 Instrumental Requirements 243
10.4 Data Processing in the Computer 244
10.5 Sensitivity Enhancement by Time Averaging 246
10.6 Measurement of Relaxation Times 247
10.7 Two-Dimensional FT-NMR 252
Problems 254
Chapter 11. Exchange Processes: Dynamic NMR 255
11.1 Spectra of Exchanging Systems 255
11.2 Theory of Chemical Exchange 258
11.3 Collapse of Spin Multiplets 260
11.4 More Complete Theories of Exchange 262
11.5 Double Resonance and Pulse Techniques 263
11.6 CIDNP 264
Problems 267
Chapter 12. Solvent Effects and Hydrogen Bonding 268
12.1 Medium Effects on Chemical Shifts 268
12.2 Solvent Effects on Coupling Constants 270
123 Solvent Effects on Relaxation and Exchange Rates 271
12.4 Hydrogen Bonding 271
Problems 273
Chapter 13. Use of NMR in Quantitative Analysis 274
13.1 Advantages of NMR in Quantitative Analysis 274
13.2 Drawbacks and Problems in the Use of NMR in Quantitative Analysis 275
13.3 Some Analytical Uses of NMR 278
Chapter 14. Contemporary Developments in NMR 281
14.1 Solids 281
14.2 Multinuclear NMR 283
14.3 Biochemical Studies 283
14.4 NMR Imaging 284
References 286
Appendix A: General NMR References 293
A. Comprehensive Treatments 293
B. Introductory Books 293
C. NMR Techniques 293
D. Organic Applications 294
E. Biochemical Applications 294
F. Serial Publications 294
G. Compilations of Data 295
Appendix B: Nuclear Spins, Magnetic Moments, and Resonance Frequencies'' 296
Appendix C: Proton and Carbon-13 NMR Spectra of "Unknowns" 307
Appendix D: Answers to Selected Problems 354
Chapter 2 354
Chapter 3 355
Chapter 4 356
Chapter 5 356
Chapter 7 357
Chapter 8 357
Chapter 9 358
Chapter 10 359
Appendix C 359
Index 364