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Organic Structures from 2D NMR Spectra Organic Structures from 2D NMR Spectra L D Field, H L Li and A M Magill School of Chemistry, University of New South Wales, Australia This edition first published 2015 C⃝ 2015 John Wiley & Sons Ltd Registered office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic books Designations used by companies to distinguish their products are often claimed as trademarks All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners The publisher is not associated with any product or vendor mentioned in this book Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom If professional advice or other expert assistance is required, the services of a competent professional should be sought Library of Congress Cataloging-in-Publication Data applied for A catalogue record for this book is available from the British Library ISBN: 9781118868942 Set in 12/18pt Times New Roman by Aptara Inc., New Delhi, India 2015 CONTENTS Preface List of Figures List of Tables NMR Spectroscopy Basics 1.1 1.2 One-Dimensional Pulsed Fourier Transform NMR Spectroscopy 2.3 2.4 2.5 2.6 The Chemical Shift NMR Spectroscopy 2.2.1 Chemical Shifts in H NMR Spectroscopy 2.2.2 Spin-Spin Coupling in H NMR Spectroscopy 2.2.3 Decoupling in H NMR Spectroscopy 2.2.4 The Nuclear Overhauser Effect in H NMR Spectroscopy Carbon-13 NMR Spectroscopy 2.3.1 Decoupling in 13 C NMR Spectroscopy 2.3.2 Chemical Shifts in 13 C NMR Spectroscopy Fluorine-19 NMR Spectroscopy Phosphorus-31 NMR Spectroscopy Nitrogen-15 NMR Spectroscopy 1H Two-Dimensional NMR Spectroscopy 3.1 3.2 3.3 3.4 The Physics of Nuclear Spins Basic NMR Instrumentation and the NMR Experiment 2.1 2.2 vii xi xv General Principles Proton-Proton Interactions 3.2.1 Correlation Spectroscopy – The COSY Experiment 3.2.2 Total Correlation Spectroscopy – The TOCSY Experiment 3.2.3 Nuclear Overhauser Spectroscopy – The NOESY Experiment Carbon-Carbon Interactions 3.3.1 The INADEQUATE Experiment Heteronuclear Correlation Spectroscopy 3.4.1 Heteronuclear Single Bond Correlation – The HSQC, HMQC and me-HSQC Experiments 3.4.2 Heteronuclear Multiple Bond Correlation – HMBC Miscellaneous Topics 4.1 4.2 4.3 4.4 4.5 NMR Solvents Reference Compounds and Standards Dynamic Processes 4.3.1 Protons on Heteroatoms 4.3.2 Rotation about Partial Double Bonds Second-Order Effects Effect of a Chiral Centre on NMR Spectra 9 10 15 16 16 17 18 19 22 23 25 25 28 28 30 31 35 35 37 37 38 45 45 47 48 49 50 51 51 v Contents Worked Examples 5.1 5.2 5.3 Problems Index vi General Principles Worked Example Worked Example 55 55 57 63 71 309 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 vii Preface (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 Gunther, ¨ 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 Buhlmann ¨ 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 viii H–13C me-HSQC Spectrum (C6D6, 500 MHz) H–13C me-HSQC Spectrum Expansion B 298 H–13C HMBC Spectrum (C6D6, 500 MHz) H–13C HMBC Spectrum Expansion C 299 H–13C HMBC Spectrum Expansion D 300 Problem 66 The 1H and 13C{1H} NMR spectra of haloperidol (C21H23ClFNO2) recorded in acetone-d6 solution at 298 K and 500 MHz are given below The 1H NMR spectrum has signals at δ 1.57, 1.81, 1.95, 2.43, 2.44, 2.67, 3.03, 3.86, 7.29, 7.31, 7.43 and 8.14 ppm The 13C{1H} NMR spectrum has signals at δ 22.3, 35.6, 38.4, 49.2, 57.6, 70.2, 115.3, 126.6, 127.8, 130.8, 131.4, 134.5, 149.1, 165.4 and 197.8 ppm Use the spectra below to assign each proton and carbon resonance H NMR Spectrum (Acetone-d6, 500 MHz) H NMR Expansion (Acetone-d6, 500 MHz) H{19F} NMR Expansion (Acetone-d6, 300 MHz) 301 13 C{1H} NMR Spectrum (Acetone-d6, 125 MHz) 13 C{1H} NMR Expansion (Acetone-d6, 125 MHz) 13 C{1H} NMR Expansion (Acetone-d6, 125 MHz) 19 F{1H} NMR Spectrum (Acetone-d6, 282 MHz) 302 H–1H COSY Spectrum (Acetone-d6, 500 MHz) H–1H COSY Spectrum Expansion A 303 H–1H COSY Spectrum Expansion B H–13C me-HSQC Spectrum (Acetone-d6, 500 MHz) 304 H–13C me-HSQC Spectrum Expansion C H–13C me-HSQC Spectrum Expansion D 305 H–13C HMBC Spectrum (Acetone-d6, 500 MHz) H–13C HMBC Spectrum Expansion E 306 H–13C HMBC Spectrum Expansion F 307 Proton Chemical Shift (ppm) Carbon C1 H2 C2 H3 C3 C4 C5 H6 C6 H7 C7 H8 C8 H9 C9 H10 C10 C11 C12 H13 C13 H14 C14 C15 OH 308 Chemical Shift (ppm) Index Deshielding, Amides restricted rotation, 50 by aromatic rings, Chemical shift, 13 C NMR, 18 19 F NMR, 19 by alkenes, nitro and carbonyl compounds, by π-electrons, Diastereotopic protons, 51 Distortionless Enhancement by Polarisation H NMR, 15 N NMR, 23 31 P NMR, 22 Transfer, 17 Exchange with deuterium, 49 Chiral centre effect on NMR spectra, 51 effect on NMR spectra, 48 Coalescence point, 48 effect of temperature, 49 Correlation spectroscopy, 28 protons on heteroatoms, 49 pulse sequence, 28 FID, see Free induction decay COSY, see Correlation spectroscopy Fourier transformation, Coupling Free induction decay, in 1H NMR, 10 FT, see Fourier transformation long range in H NMR spectra, 15 Heteronuclear multiple bond correlation n+1 rule, 10 apparent one-bond correlations, 42, 43 second order, 14, 51 in aromatic systems, 40 Coupling constant 19 effect of symmetry, 42, 43 F– C, 21 one-bond artefacts, 43 13 H–19F, 19 Heteronuclear multiple quantum coherence, 37 H– P, 23 Heteronuclear single quantum coherence, 37 31 aliphatic, 12 multiplicity-edited, 37 alkenes, 13 HMBC, see Heteronuclear multiple bond aromatic, 13 correlation geminal, 12 HMQC, see Heteronuclear multiple quantum Coupling patterns coherence 1,4-disubstituted benzene rings, 14 disubstituted benzene rings, 13 trisubstituted benzene rings, 14 Decoupling HSQC, see Heteronuclear single quantum coherence INADEQUATE, 35 Karplus relationship, 12 broad-band H in C NMR, 17 13 selective in 1H NMR, 15 in 19F spectra, 19 Larmor equation, Degree of unsaturation, 55 Magnetic anisotropy, DEPT, see Distortionless Enhancement by Magnetic moment, Polarisation Transfer Magnetogyric ratio, 1, 3, Organic Structures from 2D NMR Spectra L D Field, H L Li and A M Magill © 2015 John Wiley & Sons, Ltd Published 2015 by John Wiley & Sons, Ltd me-HSQC, see Heteronuclear single quantum correlation spectroscopy, 28 coherence detection period, 25 Multiplicity, 10 evolution period, 25 H NMR, 10 mixing sequence, 25 Multiplicity-edited heteronuclear single quantum preparation sequence, 25 coherence, see Heteronuclear single quantum Reference compounds, 47 coherence Relaxation, Natural abundance, 2, Resonance frequencies, NMR solvents, 45 Shielding, chemical shift, 46 by aromatic rings, common coupling patterns, 47 by π-electrons, NOE, see Nuclear Overhauser effect Spin quantum number, NOESY, see Nuclear Overhauser spectroscopy TOCSY, see Total correlation spectroscopy Nuclear Overhauser effect, 16, 31 Total correlation spectroscopy, 30 Nuclear Overhauser spectroscopy, 31 Two-dimensional NMR Nuclear spin, contour plot, 27 Paramagnetism magnitude spectra, 27 effect on NMR spectra, 6, Prochiral centre, 51 Pulse sequence, 25 310 phase-sensitive spectra, 27 stacked plot, 26 WILEY END USER LICENSE AGREEMENT Go to www.wiley.com/go/eula to access Wiley’s ebook EULA
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