Understanding NMR Spectroscopy

✍ Scribed by James Keeler

• Publisher: Wiley
• Year: 2010
• Tongue: English
• Leaves: 527
• Edition: 2
• Category: Library

✦ Synopsis

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

✦ Table of Contents

Cover
Title Page
Contents
Preface
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 Moving on
2.8 Further reading
2.9 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 Summary
3.9 Further reading
3.10 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 Moving on
4.13 Further reading
4.14 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 Summary
6.6 Time evolution
6.7 RF pulses
6.8 Making faster progress: the density operator
6.9 Coherence
6.10 Further reading
6.11 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 Summary
7.14 Further reading
7.15 Exercises
8 Two-dimensional NMR
8.1 The general scheme for two-dimensional NMR
8.2 Modulation and lineshapes
8.3 COSY
8.4 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 Summary
9.13 Further reading
9.14 Exercises
10Advanced 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
11Coherence 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 Examples of using gradient pulses
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
ASome mathematical topics
A.1 The exponential function and logarithms
A.2 Complex numbers
A.3 Trigonometric identities
A.4 Further reading
Index