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(BQ) Part 1 book Organic chemistry has contents: The basics bonding and molecular structure; families of carbon compounds functional groups, intermolecular forces, and infrared (ir) spectroscopy; an introduction to organic reactions and their mechanisms acids and bases; an introduction to organic reactions and their mechanisms acids and bases,... and other contents.
solom_fm_i-xxxiv-hr2.qxd 14-10-2009 17:19 Page xxxiv 14 IVA 15 VA 16 VIA 17 VIIA Lanthanum 138.91 89 Barium 137.33 88 Caesium 132.91 87 Francium (223) Actinium (227) # Actinide Series *Lanthanide Series Radium (226) Ra #Ac *La Ba Cs Fr 57 56 55 Zr Y Yttrium 88.906 Sr Strontium 87.62 Rb Rubidium 85.468 40 39 38 37 Ti 59 Pr Praseodymium 140.91 91 Pa Protactinium 231.04 58 Ce Cerium 140.12 90 Th Thorium 232.04 (261) Dubnium (262) Db 105 Tantalum 180.95 Ta 73 Niobium 92.906 Nb 41 Vanadium 50.942 V 23 Rutherfordium Rf 104 Hafnium 178.49 Hf 72 Zirconium 91.224 Titanium 47.867 Sc Scandium 44.956 Ca Calcium 40.078 K Potassium 39.098 22 21 20 19 Tc 43 Manganese 54.938 Mn 25 62 Hassium (277) Hs 108 Osmium 190.23 Os 76 Pm Sm 61 Bohrium (264) Bh 107 Rhenium 186.21 Re 75 (98) Ruthenium 101.07 Ru 44 Iron 55.845 Fe 26 Uranium 238.03 U 92 Neptunium (237) Np 93 Plutonium (244) Pu 94 Neodymium Promethium Samarium 144.24 (145) 150.36 Nd 60 Seaborgium (266) Sg 106 Tungsten 183.84 W 74 95.94 Molybdenum Technetium Mo 42 Chromium 51.996 Cr 24 110 Platinum 195.08 Pt 78 Palladium 106.42 Pd 46 Nickel 58.693 Ni 28 10 VIIIB 111 Gold 196.97 Au 79 Silver 107.87 Ag 47 Copper 63.546 Cu 29 11 IB 112 Mercury 200.59 Hg 80 Cadmium 112.41 Cd 48 Zinc 65.409 Zn 30 12 IIB 96 Gadolinium 157.25 Gd 64 (281) Americium (243) Curium (247) Am Cm 95 Europium 151.96 Eu 63 Meitnerium (268) Berkelium (247) Bk 97 Terbium 158.93 Tb 65 (272) Es 99 Holmium 164.93 Ho 67 Thallium 204.38 Tl 81 Indium 114.82 In 49 Gallium 69.723 Ga 31 Aluminum 26.982 Californium Einsteinium (251) (252) Cf 98 Dysprosium 162.50 Dy 66 (285) Mt Uun Uuu Uub 109 Iridium 192.22 Ir 77 Rhodium 102.91 Rh 45 Cobalt 58.933 Co 27 VIIIB S VIIB VIIIB P VIB Si VB Al IVB IIIB Mg Magnesium 24.305 Na Fermium (257) Fm 100 Erbium 167.26 Er 68 (289) Uuq 114 Lead 207.2 Pb 82 Tin 118.71 Sn 50 Germanium 72.64 Ge 32 Silicon 28.086 N (258) Mendelevium Md 101 Thulium 168.93 Tm 69 Bismuth 208.98 Bi 83 Antimony 121.76 Sb 51 Arsenic 74.922 As 33 Phosphorus 30.974 Nitrogen 14.007 O Nobelium (259) No 102 Ytterbium 173.04 Yb 70 Polonium (209) Po 84 Tellurium 127.60 Te 52 Selenium 78.96 Se 34 Sulfur 32.065 Oxygen 15.999 F Lawrencium (262) Lr 103 Lutetium 174.97 Lu 71 Astatine (210) At 85 Iodine 126.90 I 53 Bromine 79.904 Br 35 Chlorine 35.453 Cl 17 Fluorine 18.998 Radon (222) Rn 86 Xeno 131.29 Xe 54 Krypton 83.798 Kr 36 Argon 39.948 Ar 18 Neon 20.180 Ne 10 12:00 Sodium 22,990 16 15 14 13 12 11 C He Helium 4.0026 2-10-2009 Carbon 12.011 B Boron 10.811 Berylium 9.0122 Lithium 6.941 Carbon 12.011 Be 13 IIIA LI IUPAC recommendations: Chemical Abstracts Service group notation : C Symbol : Name (IUPAC) : Atomic mass : IIA H Hydrogen 1.0079 Atomic number: ELEMENTS 18 VIIIA OF THE IA P E R I O D I C TA B L E solom_ep_F01-F02v1.qxd Page SOLOMONS solom_ep_F01-F02v1.qxd 2-10-2009 12:00 Page SOLOMONS TABLE 3.1 Relative Strength of Selected Acids and Their Conjugate Bases Acid Strongest acid HSbF6 HI H2SO4 HBr HCl C6H5SO3H ϩ SbF6Ϫ IϪ HSO4Ϫ BrϪ ClϪ C6H5SO3Ϫ Ϫ3.8 Ϫ2.9 (CH3)2O (CH3)2C"O CH3OH2 H3Oϩ HNO3 CF3CO2H HF C6H5CO2H C6H5NH3ϩ CH3CO2H H2CO3 CH3COCH2COCH3 NH4ϩ C6H5OH HCO3Ϫ CH3NH3ϩ H2O CH3CH2OH (CH3)3COH CH3COCH3 HC#CH H2 NH3 CH2"CH2 CH3CH3 Ϫ2.5 Ϫ1.74 Ϫ1.4 0.18 3.2 4.21 4.63 4.75 6.35 9.0 9.2 9.9 10.2 10.6 15.7 16 18 19.2 25 35 38 44 50 CH3OH H2O NO3Ϫ CF3CO2Ϫ FϪ C6H5CO2Ϫ C6H5NH2 CH3CO2Ϫ HCO3Ϫ CH3COHCOCH3 NH3 C6H5OϪ CO32Ϫ CH3NH2 OHϪ CH3CH2OϪ (CH3)3COϪ Ϫ CH2COCH3 HC#CϪ HϪ NH2Ϫ CH2"CHϪ CH3CH2Ϫ Weakest base Increasing base strength Increasing acid strength ϽϪ12 Ϫ10 Ϫ9 Ϫ9 Ϫ7 Ϫ6.5 Conjugate Base (CH3)2OH ϩ (CH3)2C"OH ϩ Weakest acid Approximate pK a Strongest base solom_fm_i-xxxiv-hr2.qxd 14-10-2009 17:19 Page i This online teaching and learning environment integrates the entire digital textbook with the most effective instructor and student resources WRÀWHYHU\OHDUQLQJVW\OH With WileyPLUS: Students achieve concept mastery in a rich, structured environment that’s available 24/7 Instructors personalize and manage their course more effectively with assessment, assignments, grade tracking, and more manage time better study smarter save money From multiple study paths, to self-assessment, to a wealth of interactive visual and audio resources, WileyPLUS gives you everything you need to personalize the teaching and learning experience » F i n d o u t h ow t o M A K E I T YO U R S » www.wileyplus.com solom_fm_i-xxxiv-hr2.qxd 14-10-2009 17:19 Page ii ALL THE HELP, RESOURCES, AND PERSONAL SUPPORT YOU AND YOUR STUDENTS NEED! 2-Minute Tutorials and all of the resources you & your students need to get started www.wileyplus.com/firstday Student support from an experienced student user Ask your local representative for details! Collaborate with your colleagues, find a mentor, attend virtual and live events, and view resources www.WhereFacultyConnect.com Pre-loaded, ready-to-use assignments and presentations www.wiley.com/college/quickstart Technical Support 24/7 FAQs, online chat, and phone support www.wileyplus.com/support Your WileyPLUS Account Manager Training and implementation support www.wileyplus.com/accountmanager MAKE IT YOURS! solom_fm_i-xxxiv-hr2.qxd 16-10-2009 11:47 Page iii TENTH EDITION Organic Chemistry solom_fm_i-xxxiv-hr2.qxd 14-10-2009 17:19 Page iv solom_fm_i-xxxiv-hr2.qxd 16-10-2009 12:22 Page v TENTH EDITION Organic Chemistry T.W GRAHAM SOLOMONS University of South Florida CRAIG B FRYHLE Pacific Lutheran University JOHN WILEY & SONS, INC solom_fm_i-xxxiv-hr2.qxd 14-10-2009 17:19 Page vi In memory of my beloved son, John Allen Solomons, TWGS To Deanna, in the year of our 25th anniversary CBF ASSOCIATE PUBLISHER Petra Recter PROJECT EDITOR Jennifer Yee MARKETING MANAGER Kristine Ruff SENIOR PRODUCTION EDITOR Elizabeth Swain SENIOR DESIGNER Madelyn Lesure SENIOR MEDIA EDITOR Thomas Kulesa SENIOR ILLUSTRATION EDITOR Sandra Rigby SENIOR PHOTO EDITOR Lisa Gee COVER DESIGNER Carole Anson COVER IMAGE © Don Paulson COVER MOLECULAR ART Norm Christiansen This book was set in 10/12 Times Roman by Preparé and printed and bound by Courier Kendallville The cover was printed by Courier Kendallville This book is printed on acid-free paper Copyright © 2011, 2008, 2004, 2000 John Wiley & Sons, Inc 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, scanning, or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, website www.copyright.com Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030-5774, (201)748-6011, fax (201)748-6008, website http://www.wiley.com/go/permissions Evaluation copies are provided to qualified academics and professionals for review purposes only, for use in their courses during the next academic year These copies are licensed and may not be sold or transferred to a third party Upon completion of the review period, please return the evaluation copy to Wiley Return instructions and a free of charge return shipping label are available at www.wiley.com/go/returnlabel Outside of the United States, please contact your local representative Library of Congress Cataloging-in-Publication Data Solomons, T W Graham Organic chemistry/T.W Graham Solomons.—10th ed./Craig B Fryhle p cm Includes index ISBN 978-0-470-40141-5 (cloth) Binder-ready version ISBN 978-0-470-55659-7 Chemistry, Organic—Textbooks I Fryhle, Craig B II Title QD253.2.S65 2011 547—dc22 2009032800 Printed in the United States of America 10 solom_c09_385-458hr1.qxd 14-10-2009 444 15:10 Page 444 Chapter Nuclear Magnetic Resonance and Mass Spectrometry Problems Note to Instructors: Many of the homework problems are available for assignment via WileyPLUS, an online teaching and learning solution NMR SPECTROSCOPY The following are some abbreviations used to report spectroscopic data: H NMR: s ϭ singlet, d ϭ doublet, t ϭ triplet, q ϭ quartet, bs ϭ broad singlet, m ϭ multiplet IR absorptions: s ϭ strong, m ϭ moderate, br ϭ broad 9.23 How many 1H NMR signals (not peaks) would you predict for each of the following compounds? (Consider all protons that would be chemical shift nonequivalent.) (a) (b) (d) (e) (c) (f) Br O (g) (h) (i) OH OH 9.24 How many 13C NMR signals would you predict for the compounds shown in Problem 9.23? 9.25 Propose a structure for an alcohol with molecular formula C5H12O that has the 1H NMR spectrum given in Fig 9.46 Assign the chemical shifts and splitting patterns to specific aspects of the structure you propose C5H8O 6H 1H 2H 3H dH (ppm) Figure 9.46 The 1H NMR spectrum (simulated) of alcohol C5H8O, Problem 9.25 solom_c09_385-458hr1.qxd 14-10-2009 15:10 Page 445 445 Problems 9.26 Propose structures for the compounds G and H whose 1H NMR spectra are shown in Figs 9.47 and 9.48 G, C4H9Br 4.2 4.0 2.0 1.5 TMS 1.0 dH (ppm) Figure 9.47 The 300-MHz 1H NMR spectrum of compound G, Problem 9.26 Expansions of the signals are shown in the offset plots H, C3H4Br2 TMS 6.0 dH (ppm) 5.8 5.6 4.4 4.2 4.0 Figure 9.48 The 300-MHz 1H NMR spectrum of compound H, Problem 9.26 Expansions of the signals are shown in the offset plots 9.27 Assume that in a certain 1H NMR spectrum you find two peaks of roughly equal intensity You are not certain whether these two peaks are singlets arising from uncoupled protons at different chemical shifts or are two peaks of a doublet that arises from protons coupling with a single adjacent proton What simple experiment would you perform to distinguish between these two possibilities? 9.28 Propose structures for compounds O and P that are consistent with the following information C6H8 H2(2 Equiv.) : C6H12 pt O 13 C NMR for Compound O Openmirrors.com P d (ppm) DEPT 26.0 124.5 CH2 CH solom_c09_385-458hr1.qxd 14-10-2009 446 15:10 Page 446 Chapter Nuclear Magnetic Resonance and Mass Spectrometry 9.29 Compound Q has the molecular formula C7H8 The broad-band proton decoupled 13C spectrum of Q has signals at d 50 (CH), 85 (CH2), and 144 (CH) On catalytic hydrogenation Q is converted to R (C7H12) Propose structures for Q and R 9.30 Explain in detail how you would distinguish between the following sets of compounds using the indicated method of spectroscopy (a) 1H NMR (b) 13C and 1H NMR O O O O (c) 13 C NMR CH3 CH3 H3C CH3 CH3 9.31 H3C Compound S (C8H16) reacts with one mole of bromine to form a compound with molecular formula C8H16Br2 The broadband proton-decoupled 13C spectrum of S is given in Fig 9.49 Propose a structure for S CH3 S, C8H16 CH3 CH C 220 200 180 160 140 CH3 CDCl3 120 100 dC (ppm) 80 C 60 40 20 TMS Figure 9.49 The broadband proton-decoupled 13C NMR spectrum of compound S, Problem 9.31 Information from the DEPT 13C NMR spectra is given above each peak MASS SPECTROMETRY 9.32 A compound with molecular formula C4H8O has a strong IR absorption at 1730 cmϪ1 Its mass spectrum is tabulated in Fig 9.43, and includes key peaks at m/z 44 (the base peak) and m/z 29 Propose a structure for the compound and write fragmentation equations showing how peaks having these m/z values arise 9.33 In the mass spectrum of 2,6-dimethyl-4-heptanol there are prominent peaks at m/z 87, 111, and 126 Propose reasonable structures for these fragment ions 9.34 In the mass spectrum of 4-methyl-2-pentanone a McLafferty rearrangement and two other major fragmentation pathways occur Propose reasonable structures for these fragment ions and specify the m/z value for each OH O solom_c09_385-458hr1.qxd 14-10-2009 15:10 Page 447 447 Problems 9.35 What are the masses and structures of the ions produced in the following cleavage pathways? (a) a-cleavage of 2-methyl-3-hexanone (two pathways) (b) dehydration of cyclopentanol (c) McLafferty rearrangement of 4-methyl-2-octanone (two pathways) 9.36 Predict the masses and relative intensities of the peaks in the molecular ion region for the following compound Br Cl 9.37 Ethyl bromide and methoxybenzene (shown below) have the same nominal molecular weights, displaying a significant peak at m/z 108 Regarding their molecular ions, what other features would allow the two compounds to be distinguished on the basis of their mass spectra? OCH3 Br 9.38 The homologous series of primary amines, CH3(CH2)nNH2, from CH3NH2 to CH3(CH2)13NH2 all have their base (largest) peak at m/z 30 What ion does this peak represent, and how is it formed? INTEGRATED STRUCTURE ELUCIDATION 9.39 Propose a structure that is consistent with each set of 1H NMR data IR data is provided for some compounds (a) (b) (c) (d) (e) (f) Openmirrors.com C4H10O C3H7Br C4H8O C7H8O C4H9Cl C15H14O d (ppm) Splitting Integration 1.28 s 9H 1.35 s 1H d (ppm) Splitting Integration 1.71 d 6H 4.32 Septet 1H d (ppm) Splitting Integration 1.05 t 3H 2.13 2.47 s q 3H 2H d (ppm) Splitting Integration 2.43 s 1H 4.58 7.28 s m 2H 5H d (ppm) Splitting Integration 1.04 d 6H 1.95 3.35 m d 1H 2H d (ppm) Splitting Integration 2.20 5.08 7.25 s s m 3H 1H 10H IR 1720 cmϪ1 (strong) IR 3200–3550 cmϪ1 (broad) IR 1720 cmϪ1 (strong) solom_c09_385-458hr1.qxd 14-10-2009 448 Page 448 Chapter Nuclear Magnetic Resonance and Mass Spectrometry (g) (h) (i) (j) (k) (l) (m) 9.40 15:10 C4H7BrO2 C8H10 C4H8O3 C3H7NO2 C4H10O2 C5H10O C8H9Br d (ppm) Splitting Integration 1.08 2.07 4.23 10.97 t m t s 3H 2H 1H 1H d (ppm) Splitting Integration 1.25 2.68 7.23 t q m 3H 2H 5H d (ppm) Splitting Integration 1.27 3.66 4.13 10.95 t q s s 3H 2H 2H 1H d (ppm) Splitting Integration 1.55 4.67 d Septet 6H 1H d (ppm) Splitting Integration 3.25 3.45 s s 6H 4H d (ppm) Splitting Integration 1.10 2.10 2.50 d s Septet 6H 3H 1H d (ppm) Splitting Integration 2.0 5.15 7.35 d q m 3H 1H 5H IR 2500–3500 cmϪ1 (broad) 1715 cmϪ1 (strong) IR 2500–3550 cmϪ1 (broad) 1715 cmϪ1 (strong) IR 1720 cmϪ1 (strong) Propose structures for compounds E and F Compound E (C8H6) reacts with molar equivalents of bromine to form F (C8H6Br4) E has the IR spectrum shown in Fig 9.50 What are the structures of E and F? 100 90 E, C8H6 Transmittance (%) 80 70 60 50 40 30 20 10 4000 3600 3200 2800 2400 2000 1800 1600 Wavenumber (cm–1) 1400 1200 1000 800 650 Figure 9.50 The IR spectrum of compound E, Problem 9.40 (Spectrum courtesy of Sadtler Research Laboratories, Inc., Philadelphia © BioRad Laboratories, Inc., Information Division, Sadtler Software & Databases All rights reserved Permission for the publication herein of Sadtler Spectra has been granted by BioRad Laboratories, Inc., Informatics Division.) solom_c09_385-458hr1.qxd 14-10-2009 15:10 Page 449 449 Problems 9.41 Regarding compound J, C2HxCly, use the 1H NMR and IR data below to propose a stereochemical formula that is consistent with the data H NMR d (ppm) Splitting Integration 6.3 s — Ϫ1 IR 3125 cm 1625 cmϪ1 1280 cmϪ1 820 cmϪ1 695 cmϪ1 9.42 When dissolved in CDCl3, a compound (K) with the molecular formula C4H8O2 gives a 1H NMR spectrum that consists of a doublet at d 1.35, a singlet at d 2.15, a broad singlet at d 3.75 (1H), and a quartet at d 4.25 (1H) When dissolved in D2O, the compound gives a similar 1H NMR spectrum, with the exception that the signal at d 3.75 has disappeared The IR spectrum of the compound shows a strong absorption peak near 1720 cmϪ1 (a) Propose a structure for compound K (b) Explain why the NMR signal at d 3.75 disappears when D2O is used as the solvent 9.43 Compound T (C5H8O) has a strong IR absorption band at 1745 cmϪ1 The broad-band proton decoupled 13C spectrum of T shows three signals: at d 220 (C), 23 (CH2), and 38 (CH2) Propose a structure for T 9.44 Deduce the structure of the compound that gives the following 1H, 13C, and IR spectra (Figs 9.51–9.53) Assign all aspects of the 1H, and 13C spectra to the structure you propose Use letters to correlate protons with signals in the 1H NMR spectrum, and numbers to correlate carbons with signals in the 13C spectrum The mass spectrum of this compound shows the molecular ion at m/z 96 3H 2H 2H 1H dH (ppm) Figure 9.51 The H NMR spectrum (simulated) for Problem 9.44 Openmirrors.com solom_c09_385-458hr1.qxd 14-10-2009 450 16:25 Page 450 Chapter Nuclear Magnetic Resonance and Mass Spectrometry C 220 CH 200 180 160 C 140 CH2 120 100 80 60 40 CH2 CH3 20 dC (ppm) Figure 9.52 A simulated broadband proton-decoupled 13C NMR spectrum for Problem 9.44 Information from the DEPT 13C spectra is given above each peak 100 90 80 Transmittance (%) 70 60 50 40 30 20 10 4000 3000 2000 1500 –1 Wavenumber (cm ) Figure 9.53 The IR spectrum for Problem 9.44 Spectra adapted from Sigma-Aldrich Co © Sigma-Aldrich Co 1000 500 solom_c09_385-458hr1.qxd 14-10-2009 15:10 Page 451 451 Problems 9.45 Deduce the structure of the compound that gives the following 1H, 13C, and IR spectra (Figs 9.54–9.56) Assign all aspects of the 1H and 13C spectra to the structure you propose Use letters to correlate protons with the signals in the 1H NMR spectrum, and numbers to correlate carbons with the signals in the 13C spectrum The mass spectrum of this compound shows the molecular ion at m/z 148 6H 1H 2H 2H 1H 10 dH (ppm) Figure 9.54 The 300-MHz H NMR spectrum (simulated) for Problem 9.45 CH CH 200 C 180 160 CH CH3 CH C 140 120 100 80 60 40 dC (ppm) Figure 9.55 A simulated broadband proton-decoupled 13C NMR spectrum for Problem 9.45 Information from the DEPT 13C spectra is given above each peak Openmirrors.com 20 solom_c09_385-458hr1.qxd 452 14-10-2009 15:10 Page 452 Chapter Nuclear Magnetic Resonance and Mass Spectrometry 100 90 80 Transmittance (%) 70 60 50 40 30 20 10 4000 3000 2000 1500 1000 500 Wavenumber (cm–1) Figure 9.56 The IR spectrum for Problem 9.45 SDBSWeb : http://riodb01.ibase.aist.go.jp/sdbs/ (National Institute of Advanced Industrial Science and Technology, September 24, 2009) 9.46 Deduce the structure of the compound that gives the following 1H, 13C, and IR spectra (Figs 9.57–9.59) Assign all aspects of the 1H and 13C spectra to the structure you propose Use letters to correlate protons with signals in the 1H NMR spectrum, and numbers to correlate carbons with signals in the 13C spectrum The mass spectrum of this compound shows the molecular ion at m/z 204 dH (ppm) Figure 9.57 The 300-MHz H NMR spectrum (simulated) for Problem 9.46 solom_c09_385-458hr1.qxd 14-10-2009 15:10 Page 453 453 Problems 200 180 160 140 120 100 80 60 40 20 dC (ppm) Figure 9.58 A simulated broadband proton-decoupled 13C NMR spectrum for Problem 9.46 100 90 80 Transmittance (%) 70 60 50 40 30 20 10 4000 3000 2000 1500 –1 Wavenumber (cm ) Figure 9.59 The IR spectrum for Problem 9.46 SDBSWeb: http://riodb01.ibase.aist.go.jp/sdbs/ (National Institute of Advanced Industrial Science and Technology, September 24, 2009) Openmirrors.com 1000 500 solom_c09_385-458hr1.qxd 14-10-2009 454 9.47 15:10 Page 454 Chapter Nuclear Magnetic Resonance and Mass Spectrometry Deduce the structure of the compound (C5H10O3) that gives the following 1H, 13C, and IR spectra (Figs 9.60–9.62), Assign all aspects of the 1H and 13C spectra to the structure you propose Use letters to correlate protons with signals in the 1H NMR spectrum, and numbers to correlate carbons with signals in the 13C spectrum 3H 3H 2H 2H 2H dH (ppm) Figure 9.60 The 300-MHz 1H NMR spectrum (simulated) for Problem 9.47 180 160 140 120 100 80 60 40 dC (ppm) Figure 9.61 A simulated broadband proton-decoupled 13C NMR spectrum for Problem 9.47 20 solom_c09_385-458hr1.qxd 14-10-2009 15:10 Page 455 455 Challenge Problems 100 90 80 Transmittance (%) 70 60 50 40 30 20 10 4000 3000 2000 1500 1000 500 Wavenumber (cm–1) Figure 9.62 The IR spectrum for Problem 9.47 SDBSWeb: http://riodb01.ibase.aist.go.jp/sdbs/ (National Institute of Advanced Industrial Science and Technology, September 24, 2009) Challenge Problems 9.48 The 1H NMR examination of a solution of 1,3-dimethylcyclopentadiene in concentrated sulfuric acid shows three peaks with relative areas of 6:4:1 What is the explanation for the appearance of the spectrum? 9.49 Acetic acid has a mass spectrum showing a molecular ion peak at m/z 60 Other unbranched monocarboxylic acids with four or more carbon atoms also have a peak, frequently prominent, at m/z 60 Show how this can occur 9.50 The 1H NMR peak for the hydroxyl proton of alcohols can be found anywhere from d 0.5 to d 5.4 Explain this variability 9.51 The 1H NMR study of DMF (N,N-dimethylformamide) results in different spectra according to the temperature of the sample At room temperature, two signals are observed for the protons of the two methyl groups On the other hand, at elevated temperatures (Ͼ130°C) a singlet is observed that integrates for six hydrogens Explain these differences 9.52 The mass spectra of many benzene derivatives show a peak at m/z 51 What could account for this fragment? 9.53 Consider the following information Br Ha O Hb Hc Jab ϭ 5.3 Hz Jac ϭ 8.2 Hz Jbc ϭ 10.7 Hz (a) How many total 1H NMR signals would you expect for the above molecule? (b) Ha appears as a doublet of doublets (dd) at 1.32 ppm in the 1H NMR spectrum Draw a labeled splitting tree diagram for Ha using the coupling constant values given above Openmirrors.com solom_c09_385-458hr1.qxd 456 14-10-2009 15:10 Page 456 Chapter Nuclear Magnetic Resonance and Mass Spectrometry Learning Group Problems Given the following information, elucidate the structures of compounds A and B Both compounds are soluble in dilute aqueous HCl, and both have the same molecular formula The mass spectrum of A has Mиϩ 149 (intensity 37.1% of base peak) and Mиϩ ϩ 150 (intensity 4.2% of base peak) Other spectroscopic data for A and B are given below Justify the structures you propose by assigning specific aspects of the data to the structures Make sketches of the NMR spectra (a) The IR spectrum for compound A shows two bands in the 3300–3500-cmϪ1 region The broadband protondecoupled 13C NMR spectrum displayed the following signals (information from the DEPT 13C spectra is given in parentheses with the 13C chemical shifts): 13 C NMR: d 140 (C), 127 (C), 125 (CH), 118 (CH), 24 (CH2), 13 (CH3) (b) The IR spectrum for compound B shows no bands in the 3300–3500-cmϪ1 region The broadband protondecoupled 13C NMR spectrum displayed the following signals (information from the DEPT 13C spectra is given in parentheses with the 13C chemical shifts): 13 C NMR: d 147 (C), 129 (CH), 115 (CH), 111 (CH), 44 (CH2), 13 (CH3) Two compounds with the molecular formula C5H10O have the following 1H and 13C NMR data Both compounds have a strong IR absorption band in the 1710–1740-cmϪ1 region Elucidate the structure of these two compounds and interpret the spectra Make a sketch of each NMR spectrum (a) 1H NMR: d 2.55 (septet, 1H), 2.10 (singlet, 3H), 1.05 (doublet, 6H) 13 C NMR: d 212.6, 41.5, 27.2, 17.8 (b) H NMR: d 2.38 (triplet, 2H), 2.10 (singlet, 3H), 1.57 (sextet, 2H), 0.88 (triplet, 3H) 13 C NMR: d 209.0, 45.5, 29.5, 17.0, 13.2 Openmirrors.com 1H or can be caused by is caused by Shielding Induced local magnetic fields from circulation of sigma or pi electrons results from For n = leads to For n = leads to For n = leads to For n = leads to a quartet a triplet a doublet a singlet The n + rule (where n = # of equivalent hydrogen atoms separated by three or fewer bonds) Electron-donating groups Higher electron density around a nucleus Magnetic anisotropy Electron-withdrawing groups Decreased electron density around a nucleus Deshielding Upfield [toward smaller d (ppm) values] signals result from Downfield [toward larger d (ppm) values] follows Lead to enantiomers if substituted Lead to the same compound if substituted The number of hydrogen atoms producing a given signal is proportional to Lead to diastereomers if substituted Have different chemical shifts (except for coincidental overlap) and split each other’s signal Diastereotopic nuclei Have the same chemical shift and not split each other’s signal Enantiotopic nuclei Homotopic nuclei COSY Spectra is correlated in Integration of Signal Area 15:10 or Spin–spin coupling is caused by Is quantified by the coupling constant (J) in Hz Signal Splitting provides structural information based on Indicates the number of hydrogen atoms on adjacent carbons NMR Spectroscopy 14-10-2009 can be described as The position of an NMR signal [measured in d or ppm units relative to TMS (tetramethylsilane)] is Chemical Shift A CONCEPT MAP solom_c09_385-458hr1.qxd Page 457 Concept Map 457 220 1H OH 160 OR C N 140 C C C 12 11 C H O 10 C OH O C N H H d H (ppm) C C OH 120 100 dC (ppm) NMR Approximate Chemical Shift Ranges 180 C C R,H 200 O O C O 60 C C CH Ar CH C CH O C C H C OH C OH, NHn X,O,N CH 80 C C C OR C N C Cl, Br CH2 CH 3Њ,2Њ,1Њ 40 CH C 20 CH3 Absence of signal splitting and peak integration information in routine 13C NMR spectra 15:10 O 1H indicate HETCOR Spectra Correlation of NMR signals with 13C NMR signals (i.e., which hydrogen atoms are bonded to which carbon atoms) NMR Spectroscopy 458 NMR Approximate Chemical Shift Ranges Number of hydrogen atoms bonded to a given carbon and its carbon chemical shift indicate the DEPT Spectra 13C 14-10-2009 13C One signal for each magnetically distinct carbon atom exhibit Broadband Decoupled Spectra B CONCEPT MAP solom_c09_385-458hr1.qxd Page 458 Chapter Nuclear Magnetic Resonance and Mass Spectrometry ... Argon 39.948 Ar 18 Neon 20 .18 0 Ne 10 12 :00 Sodium 22,990 16 15 14 13 12 11 C He Helium 4.0026 2 -10 -2009 Carbon 12 . 011 B Boron 10 . 811 Berylium 9. 012 2 Lithium 6.9 41 Carbon 12 . 011 Be 13 IIIA LI IUPAC... 1. 17 How to Interpret and Write Structural Formulas 41 1 .18 Applications of Basic Principles 46 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1. 9 1. 10 1. 11 1 .12 Families of Carbon Compounds Functional Groups,... 11 15 24 .10 Lysozyme: Mode of Action of an Enzyme 11 16 THE CHEMISTRY OF Carbonic Anhydrase: Shuttling the Protons 11 19 24 .11 Serine Proteases 11 20 24 .12 Hemoglobin: A Conjugated Protein 11 22