Essential Practical NMR for Organic Chemistry

by Richards, S. A.; Hollerton, J. C.

• ISBN13: 9780470976401
• ISBN10: 0470976403
• Edition: 1st
• Format: eBook
• Copyright: 2010-11-19
• Publisher: Wiley

Summary

This book describes the use of NMR spectroscopy for dealing with problems of small organic molecule structural elucidation. It features a significant amount of vital chemical shift and coupling information but more importantly, it presents sound principles for the selection of the techniques relevant to the solving of particular types of problem, whilst stressing the importance of extracting the maximum available information from the simple 1-D proton experiment and of using this to plan subsequent experiments. Proton NMR is covered in detail, with a description of the fundamentals of the technique, the instrumentation and the data that it provides before going on to discuss optimal solvent selection and sample preparation. This is followed by a detailed study of each of the important classes of protons, breaking the spectrum up into regions (exchangeables, aromatics, heterocyclics, alkenes etc.). This is followed by consideration of the phenomena that we know can leave chemists struggling; chiral centres, restricted rotation, anisotropy, accidental equivalence, non-first-order spectra etc.  Having explained the potential pitfalls that await the unwary, the book then goes on to devote chapters to the chemical techniques and the most useful instrumental ones that can be employed to combat them.

A discussion is then presented on carbon-13 NMR, detailing its pros and cons and showing how it can be used in conjunction with proton NMR via the pivotal 2-D techniques (HSQC and HMBC) to yield vital structural information. Some of the more specialist techniques available are then discussed, i.e. flow NMR, solvent suppression, Magic Angle Spinning, etc. Other important nuclei are then discussed and useful data supplied. This is followed by a discussion of the neglected use of NMR as a tool for quantification and new techniques for this explained. The book then considers the safety aspects of NMR spectroscopy, reviewing NMR software for spectral prediction and data handling and concludes with a set of worked Q&As.

Author Biography

Steve Richards graduated in Chemistry from Bangor University in 1977 and completed an MSc in Analytical Chemistry at Bristol in 1979. He joined Glaxo Group Research in 1980 and has worked in the NMR spectroscopy department ever since. He has run regular courses in NMR interpretation for new graduates and sandwich students within GSK since the late 80s.

John Hollerton joined the GSK spectroscopy department in 1980. Having spent time working with other spectroscopic techniques, he has been focused on NMR spectroscopy since 1982. He is now the manager with a staff of thirteen scientists working under his direction. John has also lectured internationally on the subject on many occasions.

Table of Contents

Introduction.

1. Getting Started.

1.1 The Technique.

1.2 Instrumentation.

1.3 CW Systems.

1.4 FT Systems.

2. Preparing the Sample.

2.1 How Much Sample Do I Need?

2.2 Solvent Selection.

2.3 Spectrum Referencing (Proton NMR).

2.4 Sample Preparation.

3. Spectrum Acquisition.

3.1 Number of Transients.

3.2 Number of Points.

3.3 Spectral Width.

3.4 Acquisition Time.

3.5 Pulse Width/Pulse Angle.

3.6 Relaxation Delay.

3.7 Number of Increments.

3.8 Shimming.

3.9 Tuning and Matching.

3.10 Frequency Lock.

3.11 To Spin or Not to Spin?

4. Processing.

4.1 Introduction.

4.2 Zero Filling and Linear Prediction.

4.3 Apodization.

4.4 Fourier Transformation.

4.5 Phase Correction.

4.6 Baseline Correction.

4.7 Integration.

4.8 Referencing.

4.9 Peak Picking.

5. Interpreting Your Spectrum.

5.1 Common Solvents and Impurities.

5.2 Group 1 – Exchangeables and Aldehydes.

5.3 Group 2 – Aromatic and Heterocyclic Protons.

5.4 Group 3 – Double and Triple Bonds.

5.5 Group 4 – Alkyl Protons.

6. Delving Deeper.

6.1 Chiral Centres.

6.2 Enantiotopic and Diastereotopic Protons.

6.3 Molecular Anistropy.

6.4 Accidental Equivalence.

6.5 Restricted Rotation.

6.6 Heteronuclear Coupling.

7. Further Elucidation Techniques – Part 1.

7.1 Chemical Techniques.

7.2 Deuteration.

7.3 Basification and Acidification.

7.4 Changing Solvents.

7.5 Trifluoroacetylation.

7.6 Lanthanide Shift Reagents.

7.7 Chiral Resolving Agents.

8. Further Elucidation Techniques – Part 2.

8.1 Instrumental Techniques.

8.2 Spin Decoupling (Homonuclear, 1-D).

8.3 Correlated Spectroscopy (2-D).

8.4 Total Correlation Spectroscopy (1- and 2-D).

8.5 The Nuclear Overhauser Effect and Associated Techniques.

9. Carbon-13 NMR Spectroscopy.

9.1 General Principles and 1-D ¹³C.

9.2 2-D Proton-Carbon (Single Bond) Correlated Spectroscopy.

9.3 2-D Proton-Carbon (Multiple Bond) Correlated Spectroscopy.

9.4 Piecing It All Together.

9.5 Choosing the Right Tool.

10. Some of the Other Tools.

10.1 Linking HPLC with NMR.

10.2 Flow NMR.

10.3 Solvent Suppression.

10.4 Magic Angle Spinning NMR.

10.5 Other 2-D Techniques.

10.6 3-D Techniques.

11. Some of the Other Nuclei.

11.1 Fluorine.

11.2 Phosphorus.

11.3 Nitrogen.

12. Quantification.

12.1 Introduction.

12.2 Relative Quantification.

12.3 Absolute Quantification.

12.4 Things to Watch Out For.

12.5 Conclusion.

13. Safety.

13.1 Magnetic Fields.

13.2 Cryogens.

13.3 Sample-Related Injuries.

14. Software.

14.1 Acquisition Software.

14.2 Processing Software.

14.3 Prediction and Simulation Software.

15. Problems.

15.1 Ten NMR Problems.

15.2 Hints.

15.3 Answers.

Glossary.

Index.