Understanding NMR Spectroscopy
2. Edition April 2010
526 Pages, Hardcover
Practical Approach Book
Short Description
This text discusses the high-resolution NMR of liquid samples and concentrates exclusively on spin-half nuclei (mainly 1H and 13C). It is aimed at people who are familiar with the use of routine NMR for structure determination and who wish to deepen their understanding of just exactly how NMR experiments work. It demonstrates that in NMR it is possible, quite literally on the back of an envelope, to make exact predictions of the outcome of quite sophisticated experiments. The experiments chosen are likely to be encountered in the routine NMR of small to medium-sized molecules, but are also applicable to the study of large biomolecules, such as proteins and nucleic acids.
This text is aimed at people who have some familiarity with high-resolution NMR and who wish to deepen their understanding of how NMR experiments actually 'work'. This revised and updated edition takes the same approach as the highly-acclaimed first edition. The text concentrates on the description of commonly-used experiments and explains in detail the theory behind how such experiments work. The quantum mechanical tools needed to analyse pulse sequences are introduced set by step, but the approach is relatively informal with the emphasis on obtaining a good understanding of how the experiments actually work. The use of two-colour printing and a new larger format improves the readability of the text. In addition, a number of new topics have been introduced:
* How product operators can be extended to describe experiments in AX2 and AX3 spin systems, thus making it possible to discuss the important APT, INEPT and DEPT experiments often used in carbon-13 NMR.
* Spin system analysis i.e. how shifts and couplings can be extracted from strongly-coupled (second-order) spectra.
* How the presence of chemically equivalent spins leads to spectral features which are somewhat unusual and possibly misleading, even at high magnetic fields.
* A discussion of chemical exchange effects has been introduced in order to help with the explanation of transverse relaxation.
* The double-quantum spectroscopy of a three-spin system is now considered in more detail.
Reviews of the First Edition
"For anyone wishing to know what really goes on in their NMR experiments, I would highly recommend this book" - Chemistry World
"...I warmly recommend for budding NMR spectroscopists, or others who wish to deepen their understanding of elementary NMR theory or theoretical tools" - Magnetic Resonance in Chemistry
Preface to the first edition.
1 What this book is about and who should read it.
1.1 How this book is organized.
1.2 Scope and limitations.
1.3 Context and further reading.
1.4 On-line resources.
1.5 Abbreviations and acronyms.
2 Setting the scene.
2.1 NMR frequencies and chemical shifts.
2.2 Linewidths, lineshapes and integrals.
2.3 Scalar coupling.
2.4 The basic NMR experiment.
2.5 Frequency, oscillations and rotations.
2.6 Photons.
2.7 Further reading.
2.8 Exercises.
3 Energy levels and NMR spectra.
3.1 The problem with the energy level approach.
3.2 Introducing quantum mechanics.
3.3 The spectrum from one spin.
3.4 Writing the Hamiltonian in frequency units.
3.5 The energy levels for two coupled spins.
3.6 The spectrum from two coupled spins.
3.7 Three spins.
3.8 Further reading.
3.9 Exercises.
4 The vector model.
4.1 The bulk magnetization.
4.2 Larmor precession.
4.3 Detection.
4.4 Pulses.
4.5 On-resonance pulses.
4.6 Detection in the rotating frame.
4.7 The basic pulse-acquire experiment.
4.8 Pulse calibration.
4.9 The spin echo.
4.10 Pulses of different phases.
4.11 Off-resonance effects and soft pulses.
4.12 Further reading.
4.13 Exercises.
5 Fourier transformation and data processing.
5.1 How the Fourier transform works.
5.2 Representing the FID.
5.3 Lineshapes and phase.
5.4 Manipulating the FID and the spectrum.
5.5 Zero filling.
5.6 Truncation.
5.7 Further reading.
5.8 Exercises.
6 The quantum mechanics of one spin.
6.1 Introduction.
6.2 Superposition states.
6.3 Some quantum mechanical tools.
6.4 Computing the bulk magnetization.
6.5 Time evolution.
6.6 RF pulses.
6.7 Making faster progress: the density operator.
6.8 Coherence.
6.9 Further reading.
6.10 Exercises.
7 Product operators.
7.1 Operators for one spin.
7.2 Analysis of pulse sequences for a one-spin system.
7.3 Speeding things up.
7.4 Operators for two spins.
7.5 In-phase and anti-phase terms.
7.6 Hamiltonians for two spins.
7.7 Notation for heteronuclear spin systems.
7.8 Spin echoes and J-modulation.
7.9 Coherence transfer.
7.10 The INEPT experiment.
7.11 Selective COSY.
7.12 Coherence order and multiple-quantum coherences.
7.13 Further reading.
7.14 Exercises.
8 Two-dimensional NMR.
8.1 The general scheme for two-dimensional NMR.
8.2 Modulation and lineshapes.
8.3 COSY.
8.4 Double-quantum filtered COSY (DQF COSY).
8.5 Double-quantum spectroscopy.
8.6 Heteronuclear correlation spectra.
8.7 HSQC.
8.8 HMQC.
8.9 Long-range correlation: HMBC.
8.10 HETCOR.
8.11 TOCSY.
8.12 Frequency discrimination and lineshapes.
8.13 Further reading.
8.14 Exercises.
9 Relaxation and the NOE.
9.1 The origin of relaxation.
9.2 Relaxation mechanisms.
9.3 Describing random motion - the correlation time.
9.4 Populations.
9.5 Longitudinal relaxation behaviour of isolated spins.
9.6 Longitudinal dipolar relaxation of two spins.
9.7 The NOE.
9.8 Transverse relaxation.
9.9 Homogeneous and inhomogeneous broadening.
9.10 Relaxation due to chemical shift anisotropy.
9.11 Cross correlation.
9.12 Further reading.
9.13 Exercises.
10 Advanced topics in two-dimensional NMR.
10.1 Product operators for three spins.
10.2 COSY for three spins.
10.3 Reduced multiplets in COSY spectra.
10.4 Polarization operators.
10.5 ZCOSY.
10.6 HMBC.
10.7 Sensitivity-enhanced experiments.
10.8 Constant time experiments.
10.9 TROSY.
10.10 Double-quantum spectroscopy of a three-spin system.
10.11 Further reading.
10.12 Exercises.
11 Coherence selection: phase cycling and field gradient pulses.
11.1 Coherence order.
11.2 Coherence transfer pathways.
11.3 Frequency discrimination and lineshapes.
11.4 The receiver phase.
11.5 Introducing phase cycling.
11.6 Some phase cycling 'tricks'.
11.7 Axial peak suppression.
11.8 CYCLOPS.
11.9 Examples of practical phase cycles.
11.10 Concluding remarks about phase cycling.
11.11 Introducing field gradient pulses.
11.12 Features of selection using gradients.
11.13 Using gradient pulses for coherence pathway selection.
11.14 Advantages and disadvantages of coherence selection with gradients.
11.15 Suppression of zero-quantum coherence.
11.16 Selective excitation with the aid of gradients.
11.17 Further reading.
11.18 Exercises.
12 Equivalent spins and spin system analysis.
12.1 Strong coupling in a two-spin system.
12.2 Chemical and magnetic equivalence.
12.3 Product operators for AXn (InS) spin systems.
12.4 Spin echoes in InS spin systems.
12.5 INEPT in InS spin systems.
12.6 DEPT.
12.7 Spin system analysis.
12.8 Further reading.
12.9 Exercises.
13 How the spectrometer works.
13.1 The magnet.
13.2 The probe.
13.3 The transmitter.
13.4 The receiver.
13.5 Digitizing the signal.
13.6 Quadrature detection.
13.7 The pulse programmer.
13.8 Further reading.
13.9 Exercises.
A Some mathematical topics.
A.1 The exponential function and logarithms.
A.2 Complex numbers.
A.3 Trigonometric identities.
A.4 Further reading.
Index.
