NMR Spectroscopy Using Liquid Crystal Solvents
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NMR Spectroscopy using Liquid Crystal Solvents covers the importance of using a liquid crystal solvent in NMR to derive nuclear dipolar spin-spin coupling constants. This book is composed of ten chapters, and begins with a brief description of the features and benefits of liquid crystal in NMR spectroscopic analysis. The succeeding chapters deal with the mode of operation of nuclear spin Hamiltonian for partially oriented molecules and the analysis of NMR spectra of partially oriented molecules, as well as the determination of rigid molecule structure. These topics are followed by discussions on internal motion studies, NMR spectra from quadpolar nuclei, and the anisotropy in nuclear spin-spin coupling. The final chapters review the theoretical and experimental studies on the anisotropy in chemical shifts, nematic rotation, and the nuclear magnetic double resonance. This book will prove useful to analytical chemists.
Table of Contents
Preface
Acknowledgments
Chapter 1. Liquid Crystals
1.1 Introduction
1.2 Classification of Mesophases
1.2.1. The Nematic Mesophase
1.2.2. The Cholesteric Mesophase
1.2.3. Smectic Mesophases
1.3 Effect of Magnetic Fields on Liquid Crystals
1.4 Quantitative Description of Liquid Crystals Ordered by a Magnetic Field
1.5 Nuclear Resonance Spectra of Solutes Dissolved in Liquid Crystals
References
Chapter 2. The Nuclear Spin Hamiltonian for Partially Oriented Molecules
2.1 Introduction
2.2 The Zeeman Term
2.3 Indirect Spin-Spin Coupling
2.4 Dipolar Coupling
2.5 Nuclear Quadrupole Interaction
2.6 Total Anisotropic Spin-Spin Coupling
References
Chapter 3. Analysis of NMR Spectra of Partially Oriented Molecules
3.1 Introduction
3.2 Magnetic Equivalence
3.3 Classification of Spin Systems
3.4 Spin Systems Having Analytical Solutions
3.4.1. An
3.4.2. AB
3.4.3. AB2
3.4.4. AB3
3.4.5. AA'A''A'''
3.4.6. AA'BB'
3.4.7. AA'XX'
3.4.8. AA'A''A'''A''''
3.4.9. A3A3'
3.4.10. AA'A''A'''A''''A'''''
3.5 Analysis of Spin Systems Using the X Approximation
3.6 Computer Analysis
3.7 Multiple Solutions
3.8 Errors on Parameters Determined From Computer Analysis
References
Chapter 4. Determination of the Structure of Rigid Molecules
4.1 Introduction
4.2 Relationship between Dipolar Coupling Constants and Structure
4.3 Vibrational Averaging
4.3.1. Introduction
4.3.2. The Effective Structure
4.4 Example of Rz Structures Determined by NMR
4.4.1. Benzene
4.4.2. Benzene-dl
4.4.3. Pyridine-l5N
4.4.4. Fluorinated Aromatic Compounds
4.4.5. π-Cyclopentadienyl Compounds
4.4.6. Cyclobutadiene Iron Tricarbonyl
4.4.7. Cyclopropane
4.4.8. Cyclopentadiene
4.4.9. π-Allyl Rhenium Tetracarbonyl
4.5 Effect of the Liquid Crystal Phase on the Structure of Solutes
4.5.1. Tetrahedral Molecules
4.5.2. Acetylene
4.5.3. Norbornadiene
4.5.4. Methyl Fluoride
4.5.5. Difluoroethylenes
4.6 Molecular Complexes
4.7 Computational Methods
4.8 Survey of Results
References
Chapter 5. Studies of Internal Motion
5.1 Introduction
5.2 Averaging of Dipolar Couplings
5.2.1. Rotation between Symmetry Related Configurations
5.2.2. Rotation or Exchange between Structures with Symmetry Relationships
5.2.3. Calculation of Rotational Probabilities
5.3. Determination of Barrier Heights
5.3.1. Dependent Internal Rotos
5.4 Comparison Between Structures Determined by NMR and Microwave Spectroscopy for a Molecule with Internal Rotation
5.5 Averaging of Dipolar Couplings Over Ring Puckering Motion
5.6 Valence Isomerisation
5.7 Survey of Results
References
Chapter 6. NMR Spectra From Quadrupolar Nuclei
6.1 Introduction
6.2 Spectra of Nuclei With I=l
6.2.1. A Single Nucleus
6.2.2. A Single Deuterium Coupled to other Nuclei
6.2.3. Two Deuterium Nuclei
6.2.4. Three Nuclei A3 with Symmetry
6.3 Relationship between qzz and Components of q in a Molecule-Fixed Axis System
6.4 Determination of Quadrupole Coupling Constants
6.4.1. Introduction
6.4.2. Examples of Determination of Quadrupole Coupling Constants
6.5 Survey of Results
6.5.1. Deuterium
6.5.2. Nitrogen
6.6 Determination of Orientation From Quadrupole Coupling Constants
6.6.1. Solute Orientation
6.6.2. Orientation of Pure Liquid Crystals
References
Chapter 7. Anisotropy in Nuclear Spin-Spin Coupling
7.1 Introduction
7.2 Theory of Spin-Spin Coupling
7.2.1. The Hamiltonian
7.2.2. Methods of Calculation
7.2.3. Expressions for Jnn, in the Sum Over States Method
7.3 Experimental Determination of Jij aniso
7.3.1. Molecules With Internuclear Vectors Related by a C4 or Higher Axis
7.3.2. Molecules Containing Parallel Internuclear Vectors
7.3.3. Comparison of Observed Dipolar Couplings with those Calculated From a Geometry
7.4 Survey of Experimental Results and Theoretical Calculations
7.4.1. lH-lH Coupling
7.4.2. lH-l3C Coupling
7.4.3. lH-l9F Coupling
7.4.4. lH-X Coupling
7.4.5. l9F-l9F Coupling
7.4.6. l9F-l3C Coupling
7.4.7. l3C-l3C Coupling
7.4.8. l9F-3lP Coupling
References
Chapter 8. Anisotropy in Chemical Shifts
8.1 Introduction
8.2 Theory
8.3 Experimental Methods of Measuring Chemical Shift Anisotropy
8.3.1. Medium Effects on Chemical Shift Anisotropy
8.3.2. Comparison of Chemical Shifts in Nematic and Isotropic Phases
8.3.3. Measurement of Δσ From Dependence of Chemical Shift on Orientation
8.3.4. Measurement of Δσ by Application of an Electric Field
8.3.5. Measurement of Δσ by Sample Rotation
8.3.6. Use of Smectic Phases to Obtain
8.4 Survey of Results
8.4.1. Proton Shielding Anisotropies
8.4.2. Fluorine Shielding Anisotropies
8.4.3. Carbon Shielding Anisotropies
8.4.4. Phosphorus Shielding Anisotropies
8.4.5. Shielding Anisotropies of Other Nuclei
References
Chapter 9. Rotation of Nematic Samples
9.1 Introduction
9.2 Theory
9.3 Separation of Anisotropic From Isotropic Interactions by Sample Rotation
9.3.1. Separation of Jij from Tij
9.3.2. Determination of Chemical Shift Anisotropies by Sample Rotation
References
Chapter 10. Nuclear Magnetic Double Resonance
10.1 Introduction
10.2 Theory
10.3 Spin-Tickling and INDOR
10.3.1. An - {X} With Both Nuclear Spins ½
10.3.2. A3 - {X} System with Both Spins ½
10.3.3. A3 - {X} System with IA = ½, IX = l
10.4 Spin Decoupling
10.4.1. All Nuclei with Spin ½
10.4.2. Systems in Which Irradiated Spins Have S = l
10.4.3. Spin Decoupling With Modulated Irradiating Fields
References
Appendix Recent Publications Not Included in the Text
Index
Product details
- No. of pages: 386
- Language: English
- Copyright: © Pergamon 1975
- Published: January 1, 1975
- Imprint: Pergamon
- eBook ISBN: 9781483279947
About the Authors
JW Emsley
J. C. Lindon
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