Organic Structures from 2D NMR Spectra E-Book

L. D. Field

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 103

Veröffentlichungsjahr: 2015

Beschreibung

The derivation of structural information from spectroscopic data is now an integral part of organic chemistry courses at all Universities.  Over recent years, a number of powerful two-dimensional NMR techniques (e.g. HSQC, HMBC, TOCSY, COSY and NOESY) have been developed and these have vastly expanded the amount of structural information that can be obtained by NMR spectroscopy.  Improvements in NMR instrumentation now mean that 2D NMR spectra are routinely (and sometimes automatically) acquired during the identification and characterisation of organic compounds.

Organic Structures from 2D NMR Spectra is a carefully chosen set of more than 60 structural problems employing 2D-NMR spectroscopy.  The problems are graded to develop and consolidate a student’s understanding of 2D NMR spectroscopy.  There are many easy problems at the beginning of the collection, to build confidence and demonstrate the basic principles from which structural information can be extracted using 2D NMR. The accompanying text is very descriptive and focussed on explaining the underlying theory at the most appropriate level to sufficiently tackle the problems.

Organic Structures from 2D NMR Spectra

• Is a graded series of about 60 problems in 2D NMR spectroscopy that assumes a basic knowledge of organic chemistry and a basic knowledge of one-dimensional NMR spectroscopy
• Incorporates the basic theory behind 2D NMR and those common 2D NMR experiments that have proved most useful in solving structural problems in organic chemistry
• Focuses on the most common 2D NMR techniques – including COSY, NOESY, HMBC, TOCSY, CH-Correlation and multiplicity-edited C-H Correlation.
• Incorporates several examples containing the heteronuclei 31P, 15N and 19F

Organic Structures from 2D NMR Spectra is a logical follow-on from the highly successful “Organic Structures from Spectra” which is now in its fifth edition.  The book will be invaluable for students of Chemistry, Pharmacy, Biochemistry and those taking courses in Organic Chemistry.

Also available: http://www.wiley.com/WileyCDA/WileyTitle/productCd-111902725X. Instructors Guide and Solutions Manual to Organic Structures from 2D NMR Spectra

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Preface

List of Figures

List of Tables

Chapter 1: NMR Spectroscopy Basics

1.1 The Physics of Nuclear Spins

1.2 Basic NMR Instrumentation and the NMR Experiment

Chapter 2: One-Dimensional Pulsed Fourier Transform NMR Spectroscopy

2.1 The Chemical Shift

2.2 1H NMR Spectroscopy

2.3 Carbon-13 NMR Spectroscopy

2.4 Fluorine-19 NMR Spectroscopy

2.5 Phosphorus-31 NMR Spectroscopy

2.6 Nitrogen-15 NMR Spectroscopy

Chapter 3: Two-Dimensional NMR Spectroscopy

3.1 General Principles

3.2 Proton–Proton Interactions

3.3 Carbon–Carbon Interactions

3.4 Heteronuclear Correlation Spectroscopy

Chapter 4: Miscellaneous Topics

4.1 NMR Solvents

4.2 Reference Compounds and Standards

4.3 Dynamic Processes

4.4 Second-Order Effects

4.5 Effect of a Chiral Centre on NMR Spectra

Chapter 5: Worked Examples

5.1 General Principles

5.2 Worked Example 1

5.3 Worked Example 2

Chapter 6: Problems

Index

Organic Structures from 2D NMR Spectra

This edition first published 2015© 2015 John Wiley & Sons Ltd

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Library of Congress Cataloging-in-Publication Data

Field, L. D.    Organic structures from 2D NMR spectra / L.D. Field, H.L. Li, and A.M. Magill.       pages cm    Includes bibliographical references and index.    ISBN 978-1-118-86894-2 (pbk.)  1. Nuclear magnetic resonance spectroscopy. 2. Spectrum analysis. I. Li, H. L. (Hsiu L.) II. Magill, A. M. (Alison M.) III. Title. IV. Title: 2D NMR spectra.    QD96.N8F54 2015    543′.66–dc23

2015008088

A catalogue record for this book is available from the British Library.

ISBN: 9781118868942

PREFACE

Obtaining structural information from spectroscopic data is an integral part of organic chemistry courses at all universities. At this time, NMR spectroscopy is arguably the most powerful of the spectroscopic techniques for elucidating the structure of unknown organic compounds, and the method continues to evolve over time.

This text Organic Structures from 2D NMR Spectra builds on the popular series Organic Structures from Spectra, which is now in its fifth edition. The aim of Organic Structures from Spectra is to teach students to solve simple structural problems efficiently by using combinations of the major spectroscopic and analytical techniques (UV, IR, NMR and mass spectroscopy). Probably the most significant advances in recent years have been in the routine availability of quite advanced 2D NMR techniques. This text deals specifically with the use of more advanced 2D NMR techniques, which have now become routine and almost automatic in almost all NMR laboratories.

In this book, we continue the basic philosophy that learning how to identify organic structures from spectroscopic data is best done by working through examples. Solving real problems as puzzles is also addictive – there is a real sense of achievement, understanding and satisfaction. About 70% of the book is dedicated to a series of more than 60 graded examples ranging from very elementary problems (designed to demonstrate useful problem-solving techniques) through to very challenging problems at the end of the collection.

The underlying theory has been kept to a minimum, and the theory contained in this book is only sufficient to gain a basic understanding of the techniques actually used in solving the problems. We refer readers to other sources for a more detailed description of both the theory of NMR spectroscopy and the principles underpinning the NMR experiments now in common use.

The following books are useful sources for additional detail on the theory and practice of NMR spectroscopy:

(i) T. D. W. Claridge, High-Resolution NMR Techniques in Organic Chemistry, 2nd edition, Elsevier, Amsterdam, 2009. ISBN 978-0-08-054628-5.

(ii) J. Keeler, Understanding NMR Spectroscopy, 2nd edition, John Wiley & Sons, UK, 2010. ISBN 978-0-470-74609-7.

(iii) H. Friebolin, Basic One- and Two-Dimensional NMR Spectroscopy, 5th edition, Wiley-VCH, Weinheim, 2011. ISBN 978-3-527-32782-9.

(iv) H. Günther, NMR Spectroscopy: Basic Principles, Concepts and Applications in Chemistry, 3rd edition, Wiley-VCH, Weinheim, 2013. ISBN 978-3-527-33000-3.

In this book, the need to learn data has been kept to a minimum. It is more important to become conversant with the important spectroscopic techniques and the general characteristics of different types of organic compounds than to have an encyclopaedic knowledge of more extensive sets of data. The text does contain sufficient data to solve the problems, and again there are other excellent sources of data for NMR spectroscopy.

The following collections are useful sources of spectroscopic data on organic compounds:

(i)http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/cre_index.cgi?lang=eng, maintained by the National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.

(ii)http://webbook.nist.gov/chemistry/, which is the NIST Chemistry WebBook, NIST Standard Reference Database Number 69, June 2005, Eds. P. J. Linstrom and W. G. Mallard.

(iii) E. Pretch, P. Bühlmann and M. Badertscher, Structure Determination of Organic Compounds, Tables of Spectral Data, Springer-Verlag, Berlin/Heidelberg, 2009. ISBN 978-3-540-93810-1.

ASSUMED KNOWLEDGE

The book assumes that students have completed an elementary organic chemistry course, so there is a basic understanding of structural organic chemistry, functional groups, aromatic and non-aromatic compounds, stereochemistry, etc. It is also assumed that students already have a working knowledge of how various spectroscopic techniques (UV, IR, NMR and mass spectroscopy) are used to elucidate the structures of organic compounds.

The following books are useful texts dealing with the elucidation of the structures of organic compounds by spectroscopy:

(i) L. D. Field, S. Sternhell and J. R. Kalman, Organic Structures from Spectra, 5th edition, John Wiley & Sons, UK, 2013. ISBN 978-1-118-32545-2.

(ii) R. M. Silverstein, F. X. Webster, D. J. Kiemle and D. L. Bryce, Spectrometric Identification of Organic Compounds, 8th edition, John Wiley & Sons, USA, 2014. ISBN 978-0-470-61637-6.

STRUCTURE OF THE BOOK

Chapter 1

deals with the basic physics of the NMR experiment and the hardware required to acquire NMR spectra.

Chapter 2

deals with the general characteristics of NMR spectroscopy for commonly observed nuclei. While most NMR deals with

1

H or

13

C NMR spectroscopy, this chapter also provides an introduction to

19

F,

31

P and

15

N NMR.

Chapter 3

deals with 2D NMR spectroscopy. First the principles, and then a basic description of the commonly used 2D NMR experiments – COSY, NOESY, TOCSY, INADEQUATE, HSQC/HMQC and HMBC.

Chapter 4

covers a group of special topics which are important in interpreting NMR spectra. Topics include (i) the common solvents used for NMR; (ii) the standard reference materials used for the observation of the spectra of different nuclei; (iii) the effects of molecular exchange and molecular motion on NMR spectra; and (iv) the effect of chirality on NMR spectra.

Chapter 5

contains two worked solutions as an illustration of a logical approach to solving problems. However, with the exception that we insist that students should perform all routine measurements first, we do not recommend a mechanical attitude to problem solving – intuition has an important place in solving structures from spectra.

INSTRUMENTATION

The NMR spectra presented in the problems contained in this book were obtained under conditions stated on the individual problem sheets. Spectra were obtained on the following instruments:

(i) 300 MHz 1H NMR spectra, 75 MHz 13C NMR spectra and 283 MHz 19F spectra on a Bruker DPX-300 spectrometer;

(ii) 400 MHz 1H NMR spectra, 100 MHz 13C NMR spectra and 376 MHz 19F spectra on Bruker Avance III 400 spectrometers;

(iii) 500 MHz 1H NMR and 125 MHz 13C NMR spectra on a Bruker Avance III 500 spectrometer;

(iv) 600 MHz 1H NMR and 150 MHz 13C NMR spectra were obtained on Avance III 600 or Avance III HD 600 Cryoprobe spectrometers.

There is a companion Instructor’s Guide which provides a comprehensive step-by-step solution to every problem in the book.

Bona fide instructors may obtain a list of solutions (at no charge) by emailing the authors at [email protected] or fax [phone]).

We wish to thank Dr Donald Thomas and Dr James Hook at the Mark Wainwright Analytical Centre at the University of New South Wales, and Dr Joanna Cosgriff and Dr Roger Mulder at CSIRO Materials Science and Engineering who helped to assemble the additional samples and spectra used in this book. Thanks are also due to Dr Samantha Furfari and Dr Manohari Abeysinghe who helped with the synthesis of several of the compounds used in the problems.

L. D. FieldH. L. LiA. M. MagillJanuary 2015

LIST OF FIGURES

2.1 1H NMR spectra (a) time domain spectrum (FID); (b) frequency domain spectrum obtained after Fourier Transformation of (a).

2.2 Approximate 1H chemical shift ranges for protons in organic compounds.

2.3 1H NMR spectrum of bromoethane (simulated at 90 MHz, CDCl3) showing the multiplicity of the two 1H signals.

2.4 1H NMR spectrum of 1,2,4-trichlorobenzene (500 MHz, CDCl3) showing the multiplicity of the three 1H signals.

2.5 The dependence of vicinal coupling constants (3JHH, Hz) on dihedral angle (φ) (Karplus relationship).

2.6 Characteristic aromatic splitting patterns in the 1H NMR spectra of some disubstituted benzene rings.

2.7 1H NMR spectrum of 1-chloro-4-nitrobenzene (500 MHz, CDCl3).

2.8 Characteristic aromatic splitting patterns in the 1H NMR spectra for some trisubstituted benzenes.

2.9 1H NMR spectrum of bromoethane (simulated at 90 MHz, CDCl3) (a) basic spectrum showing all coupling; (b) with irradiation at H1; (c) with irradiation at H2.

2.10 13C NMR spectra of 1-iodo-3-methylbutane (CDCl3, 100 MHz): (a) broad-band 1H decoupling; (b) no decoupling; (c) DEPT spectrum.

2.11 Approximate 13C chemical shift ranges for carbon atoms in organic compounds.

2.12 Approximate 19F chemical shift ranges for fluorine atoms in organic compounds, relative to CFCl3.

2.15 Approximate 31P chemical shift ranges for phosphorus atoms in organic compounds, relative to 85% H3PO4.

2.16 Approximate 15N chemical shift ranges for nitrogen atoms in organic compounds.

3.1 Acquisition of a 2D NMR spectrum. (a) A series of individual FIDs are acquired; (b) Each individual FID is subjected to a Fourier transformation; (c) A second Fourier transformation in the remaining time dimension gives the final 2D spectrum.

3.2 Representations of 2D NMR spectra: (a) Stacked plot; (b) Contour plot.

3.3 Representations of phase-sensitive 2D NMR spectra.

3.4 1H–1H COSY spectrum of 3-methyl-1-butanol (500 MHz, CDCl3).

3.5 TOCSY spectrum of ethyl valerate (600 MHz, C6D6).

3.6 1H–1H NOESY spectrum of trans-ß-methylstyrene (500 MHz, DMSO-d6). The diagonal has been plotted with reduced intensity.

3.7 1H–1H NOESY spectrum of cis-ß-methylstyrene (500 MHz, DMSO-d6). The diagonal has been plotted with reduced intensity.

3.8 INADEQUATE spectrum of 2-methyl-1-butanol (125 MHz, CDCl3).

3.9 Multiplicity-edited HSQC spectrum of 3-methyl-1-butanol (500 MHz, CDCl3). Positive contours (CH/CH3