Basic One- and Two-Dimensional NMR Spectroscopy

Transcription

1 Horst Friebolin Basic One- and Two-Dimensional NMR Spectroscopy Third Revised Edition Translated by Jack K. Becconsall WILEY-VCH Weinheim New York Chichester Brisbane Singapore Toronto

2 Contents XV 1 The Physical Basis of NMR Spectroscopy Introduction Nuclear Angular Momentum and Magnetic Moment Nuclei in a Static Magnetic Field Directional Quantization Energy of the Nuclei in the Magnetic Field Populations of the Energy Levels Macroscopic Magnetization Basic Principles of the NMR Experiment The Resonance Condition Basic Principle of the NMR Measurement The Pulsed NMR Method The Pulse The Pulse Angle Relaxation The Time and Frequency Domains; the Fourier Transformation Spectrum Accumulation The Pulsed NMR Spectrometer Spectral Parameters: a Brief Survey The Chemical Shift Nuclear Shielding Reference Compounds and the <5-Scale Spin-Spin Coupling The Indirect Spin-Spin Coupling Coupling to One Neighboring Nucleus (AX Spin System) Coupling to Two Equivalent Neighboring Nuclei (AX 2 Spin System) Coupling to Three or More Equivalent Neighboring Nuclei (AX n Spin System) Multiplicity Rules Couplings between Three Non-equivalent Nuclei (AMX Spin System) Couplings between Equivalent Nuclei (A n Spin Systems) The Order of a Spectrum 33

3 XVIII Couplings between Protons and other Nuclei; 13 C Satellite Spectra The Intensities of the Resonance Signals J H Signal Intensities C Signal Intensities Summary "Other" Nuclides Nuclides with I=Yi Nuclides with I>Vi Bibliography for Chapter The Chemical Shift Introduction Influence of the Charge Density on the Shielding Effects of Neighboring Groups Magnetic Anisotropy of Neighboring Groups Ring Current Effects Electric Field Effects Intermolecular Interactions - Hydrogen Bonding and Solvent Effects Isotope Effects Summary 'H Chemical Shifts of Organic Compounds Alkanes and Cycloalkanes Alkenes Arenes Alkynes Aldehydes OH, SH, NH I3 C Chemical Shifts of Organic Compounds Alkanes and Cycloalkanes Alkenes Arenes Alkynes Allenes Carbonyl and Carboxy Compounds Aldehydes and Ketones Carboxylic Acids and Derivatives Relationships between the Spectrum and the Molecular Structure Equivalence, Symmetry and Chirality Homotopic, Enantiotopic and Diastereotopic Groups Summary Chemical Shifts of "Other" Nuclidess Bibliography for Chapter 2 83

4 3 Indirect Spin-Spin Coupling Introduction H,H Coupling Constants and Chemical Structure Geminal Couplings 2 /(H,H) Dependence on Bond Angle Substituent Effects Effects of Neighboring 7T-Electrons Vicinal Couplings 3 /(H,H) Dependence on the Dihedral Angle Substituent Effects H,H Couplings in Aromatic Compounds Long-range Couplings C,H Coupling Constants and Chemical Structure C,H Couplings through One Bond V(C,H) Dependence on the s-fraction Substituent Effects C,H Couplings through Two or More Bonds Geminal Couplings (i. e. 2 7(C,H) in H-C- 13 C) Vicinal Couplings (i. e. 3 7(C,H) in H-C-C- 13 C) Long-range Couplings 3+ "/(C,H) C,H Couplings in Benzene Derivatives C,C Coupling Constants and Chemical Structure Correlations between C,H and H,H Coupling Constants Coupling Mechanisms The Electron-Nuclear Interaction H,D Couplings Relationship between the Coupling and the Lifetime of a Spin State Couplings through Space Couplings of "Other" Nuclides (Heteronuclear Couplings) Bibliography for Chapter Spectrum Analysis and Calculations Ill 4.1 Introduction Ill 4.2 Nomenclature Systematic Notation for Spin Systems Chemical and Magnetic Equivalence Two-Spin Systems The AX Spin System The AB Spin System Three-Spin Systems The AX 2, AK 2, AB 2, and A 3 Spin Systems The AMX and ABX Spin Systems 121

5 4.5 Four-Spin Systems A 2 X 2 and A 2 B 2 Spin Systems The AA'XX' and AA'BB' Spin Systems Spectrum Simulation and Iteration Analysis of "C NMR Spectra Bibliography for Chapter Double Resonance Experiments Introduction Spin Decoupling in 'H NMR Spectroscopy Simplification of Spectra by Selective Spin Decoupling Suppression of a Solvent Signal Spin Decoupling in C NMR Spectroscopy !H Broad-band Decoupling The Gated Decoupling Experiment X H Off-Resonance Decoupling Selective Decoupling in 13 C NMR Spectroscopy Bibliography for Chapter Assignment of l H and 13 C Signals Introduction m NMR Spectroscopy Defining the Problem Empirical Correlations for Predicting Chemical Shifts Alkanes (Shoolery's Rule) Alkenes Benzene Derivatives Decoupling Experiments Effects of Solvent and Temperature Altering the Chemical Structure of the Sample D C NMR Spectroscopy Defining the Problem Empirical Correlations for Predicting Approximate Chemical Shifts Alkanes Alkenes x Benzene Derivatives Decoupling Experiments T\ Measurements Solvent and Temperature Effects and Shift Reagents Chemical Changes to the Sample Computer-aided Assignment of C NMR Spectra Searching for Identical or Related Compounds Spectrum Prediction Bibliography for Chapter 6 159

6 7 Relaxation Introduction Spin-Lattice Relaxation of 13 C Nuclei (7\) Relaxation Mechanisms Experimental Determination of 7\; the Inversion Recovery Experiment Relationships between T\ and Chemical Structure Influence of Protons in CH, CH 2 and CH 3 Groups Influence of Molecular Size Segmental Mobilities Anisotropy of the Molecular Mobility Suppression of the Water Signal Spin-Spin Relaxation (T 2 ) Relaxation Mechanisms Experimental Determination of T2; the Spin-Echo Experiment Line-widths of NMR Signals Bibliography for Chapter One-Dimensional NMR Experiments using Complex Pulse Sequences Introduction Basic Techniques using Pulse Sequences and Pulsed Field Gradients The Effect of the Pulse on the Longitudinal Magnetization (M z ) The Effect of the Pulse on the Transverse Magnetization Components (M x - My) The Effect of Pulsed Field Gradients on the Transverse Magnetization The /-Modulated Spin-Echo Experiment The Pulsed Gradient Spin-Echo Experiment Signal Enhancement by Polarization Transfer The SPI Experiment The INEPT Experiment The Reverse INEPT Experiment with Proton Detection The DEPT Experiment The Selective TOCSY Experiment The One-Dimensional INADEQUATE Experiment Bibliography for Chapter 8 229

7 9 Two-Dimensional NMR Spectroscopy Introduction The Two-Dimensional NMR Experiment Preparation, Evolution and Mixing, Data Acquisition Graphical Representation Two-Dimensional /-Resolved NMR Spectroscopy Heteronuclear Two-Dimensional /-Resolved NMR Spectroscopy Homonuclear Two-Dimensional /-Resolved NMR Spectroscopy Two-Dimensional Correlated NMR Spectroscopy Two-Dimensional Heteronuclear (C,H)-Correlated NMR Spectroscopy (HETCOR or C,H-COSY) Two-Dimensional Homonuclear (H,H)-Correlated NMR Spectroscopy (H,H-COSY; Long-Range COSY) Reverse Two-Dimensional Heteronuclear (H.C)-Correlated NMR Spectroscopy (HSQC; HMQC) The Gradient-Selected (gs-)hmbc Experiment The TOCSY Experiment Two-Dimensional Exchange NMR Spectroscopy: the NOESY and EXSY Experiments The Two-Dimensional INADEQUATE Experiment Summary of Chapters 8 and Bibliography for Chapter The Nuclear Overhauser Effect Introduction Theoretical Background The Two-Spin System Enhancement Factors Multi-Spin Systems From the One-Dimensional to the Two-Dimensional Experiment Experimental Aspects Applications Bibliography for Chapter Dynamic NMR Spectroscopy (DNMR) Introduction Quantitative Calculations 305

8 Complete Line-shape Analysis The Coalescence Temperature 7c and the Corresponding Rate Constant kc Activation Parameters The Arrhenius Activation Energy E A The Free Enthalpy of Activation AG X Estimating the Limits of Error Rate Constants in Reactions with Intermediate Stages Intermolecular Exchange Processes Applications Rotation about CC Single Bonds C(sp 3 )-C(sp 3 ) Bonds C(sp 2 )-C(sp 3 ) Bonds C(sp 2 )-C(sp 2 ) Bonds Rotation about a Partial Double Bond Inversion at Nitrogen and Phosphorus Atoms Ring Inversion Valence Tautomerism Keto-Enol Tautomerism Intermolecular Proton Exchange Reactions and Equilibration Processes Bibliography for Chapter Shift Reagents Lanthanide Shift Reagents (LSRs) Fundamentals Applications and Quantitative Interpretation Chiral Lanthanide Shift Reagents Chiral Solvents Bibliography for Chapter Macromolecules Introduction Synthetic Polymers The Tacticity of Polymers * Polymerization of Dienes Copolymers Bibliography for Chapter NMR Spectroscopy in Biochemistry and Medicine Introduction Elucidating Reaction Pathways in Biochemistry Syntheses using Singly 13 C-Labeled Precursors Low Levels of 13 C Enrichment High Levels of 13 C Enrichment Syntheses using Doubly 13 C-Labeled Precursors High Resolution in vivo NMR Spectroscopy

9 The Problem and its Solution P NMR Experiments m and 13 C NMR Experiments Magnetic Resonance Tomography Basic Principles and Experimental Considerations Applications Bibliography for Chapter Subject Index 375 Index of Compounds 383