The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules PDF
Preview The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules
The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules Daimay Lin-Vien Shell Development Company Houston, Texas Norman B. Colthup Stamford, Connecticut William G. Fateley Kansas State University Manhattan, Kansas Jeanette G. Grasselli Ohio University Athens, Ohio ® Academic Press San Diego New York Boston London Sydney Tokyo Toronto Find Us on the Web! http: //www.apnet.com This book is printed on acid-free paper. @ Copyright © 1991 by Academic Press All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Academic Press A Division ofHarcourt Brace & Company 525 Β Street, Suite 1900, San Diego, California 92101-4495 United Kingdom Edition published by ACADEMIC PRESS LIMITED 24-28 Oval Road, London NWI7DX Library of Congress Cataloging-in-Publication Data The Handbook of infrared and Raman characteristic frequencies of organic molecules / Daimay Lin-Vien . . . (et al.). p. cm. Includes bibliographical references and index. ISBN 0-12-451160-0 (alk. Paper) 1. Organic compounds — Spectra. 2. Molecular spectroscopy. 3. Infrared spectroscopy 4. Raman spectroscopy I. Lin-Vien, Daimay. QC462.5.H343 1991 547.3O8583-dc20 91-8611 CIP PRINTED IN THE UNITED STATES OF AMERICA 97 EB 9 8 7 6 5 4 3 Dedicated to Lionel J. Bellamy His monumental works on summarizing and explaining group frequencies in vibrational spectroscopy stand alone. His wit and his wisdom were legendary. and to Tomas Β. Hirschfeld His brilliant contributions to the theory and practice of spectroscopy enlightened us ally and were characterized by an unbounded enthusiasm and delight in the field. "If a poet at the same time be a physicist, he might convey to others the pleasure, the satisfaction, almost the reverence, which the subject inspires.—Especially is its fascination felt in the branch that deals with light. Albert A. Michelson Light Waves and Their Uses PUDDLE Our Cover The lithograph by the artist, M. C. Escher, on our cover is entitled, 'Tuddle." I purchased the original from Mr. Escher at his home in Baarn, Holland, in 1968. I believe it gives us a preview of what is to come in our interpretation of spectra. In Puddle we find two different bicycle and human tracks (are they different?) and two different auto and truck tracks. Likewise, the frequency of absorption in our spectra are the tracks for the identification of molecules. We know these frequencies provide important data about the molecules, chemical groups, and ions. It is the organization of this information, to be found in this Handbook, which elucidates the molecular structure; so let the * bracks" be your guide to molecular structure. Bill Fateley 1991 Preface Infrared and Raman spectroscopy are two of the most widely used tech niques for the determination of molecular structure and for the identifica tionofcompounds. Oneneedsonlyto glanceatthethousands ofreferences in the Fundamental Reviews on Infrared and Raman Spectroscopy published by Analytical Chemistry biennially to verify this statement. Sample handling is very simple and usually non-destructive. Instrumenta tion has improved dramatically in the last 20 years. Information can be obtained in seconds rather than hours, and energy-limited samples (low concentrationorsmallsize)thatwouldhavepresenteddifficultyin previous days are now readily examined. The "FT" revolution has involved both IR and Raman techniques, and the computer capabilities of all analytical instrumentation today provide formidable routines for data manipulation. The information content of the infrared and Raman spectra are completely complementary, and both are necessary for the vibrational analysis of a molecule. The spectroscopist, organic chemist, or physical chemist using these techniques depends on theory, on group frequency information on molecules that has been developed empirically over the years, and on evaluated collections of reference spectra. The seminal texts ofL. J. Bellamy, TheInfraredSpectraofComplexMolecules, Vols. I& II, first publishedin 1954and 1968, arestillamongthemostwidelycitedbooks in the world. Later books by Colthup, Daly and Wiberley, and A. Lee Smith continued to explore and expand on our understanding of group frequencies and how they can be used to analyze materials. The revitaliza tion of Raman spectroscopy occurred in the 1970s with the advent of the laser as a source. In 1974, the first book on CharacteristicRamanFrequen ciesofOrganicCompoundswas published by Dollish, Fateleyand Bentley. Although the Colthup et ale book is in a third edition, the Bellamy and Dollishbooks are out ofprint. It was this fact, coupled with the continuing rapid growth in the field of vibrational analysis, that led to this book. xv xvi Preface We have attempted to integrate the discussion of the infrared and Raman group frequencies for 16 classes of organic molecules as chapters in the text. Literature through 1990 was searched for information on group frequen- cies, and results of this search are evaluated and organized in the discussion. In rigorous interpretation of spectra, it is important to understand the origin of group frequencies and to recognize and assign them in the spectrum. It is equally important to understand why group frequencies shift. Our text should provide assistance, as well as references to more thorough discussions in the literature, in the use of group frequencies. We have also included a set of representative pairs of IR and Raman spectra in Chapter 18 and in the Appendices, which complement the discussion in the text by illustrating the spectral features. We gratefully acknowledge the Aldrich Chemical Co., VCH pubHshers of the B. Schräder Raman/Infrared Atlas, and the Sadtler Research Laboratories, Division of Bio-Rad Laboratories, Inc., for permission to use selections from their infrared and Raman collections in order to present the pairs of spectra for each com- pound. A summary of characteristic Raman frequencies from DoUish et al., and the Colthup correlation charts for infrared frequencies are presented in Appendix Three. The purpose of this book is to provide a reference to aid in the interpreta- tion of the infrared and Raman spectra of organic compounds. We hope it accomplishes that. Although excellent instrumentation and software are now readily available to chemists everywhere, it is perhaps more important than ever that the interpretations of the data are based on sound spectroscopic principles. There is still no better way to do this than to use and understand the group frequencies of organic molecules. D. Lin-Vien N. B. Colthup W. G. Fateley J.G. GrasseUi Acknowledgment The authors wish to thank Mr. Dick Nyquist for the wonderful help and guidance he has provided us in the preparation of this book. For many years he has published outstanding papers on the relationship between vibrational group frequencies and structure in molecules. It is work such as this that made this book possible Many thanks to you, Dick! All of us CHAPTER 1 Introduction Infrared (IR) and Raman spectroscopies provide information on molecular vibrations. These methods cause molecules to undergo changes in vibra- tional energy state by subjecting them to excitation radiation in selected spectral regions. IR and Raman spectroscopy differ in the means by which photon energy is transferred to the molecule and in the instrumentation used. Thus, the information extracted exhibits different characteristics. Infrared and Raman spectroscopy are complementary rather than com- peting techniques. The molecular vibrational frequencies observed by both techniques are nearly the same, but the vibrational band intensities differ (sometimes markedly so) because of the different excitation mechanisms and therefore different selection rules. 1-1. PRINCIPLES AND SELECTION RULES The theory and selection rules of IR and Raman transitions have been discussed by Herzberg [1] and Steinfeld [2] in detail. Fateley et al. [19] have discussed the infrared and Raman selection rules for molecular and lattice vibrations by the correlation method. Considerations on the selection rules from the view of molecular symmetry are given by Cotton [3] and Drago [4]. Only qualitative descriptions of the principles and selection rules of IR Raman spectroscopies are given here. 2 Chapter 1 : Introduction 1 -1 · 1 · I nfrared Spectroscopy In IR spectroscopy, the vibrational excitation is achieved by radiating the sample with a broad-band source of radiation in the infrared region, which is generally 4000-200 cm~^ (2.5-50/im). The wavenumber, ν in cm"\ is the number of waves per centimeter. It is equal to the reciprocal of the wave- length λ in cm, and is equal to the frequency ν divided by c, the velocity of light (cm sec"^). In the IR region, the wavelength λ is given in micrometers μνα or 10"^ m. As illustrated in Fig. 1-1, the molecule is excited to a higher vibrational state by directly absorbing the infrared radiation. The transmit- tance at a given wavenumber can be calculated according to Eq. 1. The transmission spectrum is then obtained by plotting the transmittance versus the IR wavenumber. Similarly, the absorbance at a given wavenumber can be obtained by using the Beer-Lambert equation (Eq. 2). A plot of absor- bance versus wavenumber yields an absorption spectrum. Τ ^ γ. (1) Λ = log(^ = abc, (2) where Τ is transmittance, A is absorbance, /q is the intensity of the entering radiation (before sample absorption), / is the intensity of the transmitted Hght (after sample absorption), a is absorptivity, b is cell thickness, and c is concentration. 1-1.2. Raman Spectroscopy The origin of Raman spectroscopy is an inelastic scattering effect. In this case, the excitation radiation source is monochromatic and is much more energetic than infrared radiation. Elastic and inelastic scattering of radia- tion by the sample is observed in a Raman experiment. In elastic scattering (Rayleigh scattering), the molecule is excited to a virtual state, and then relaxes to the original vibrational state by re-emitting a photon at the same frequency as the incident light. The molecule **absorbs" no energy from the incident radiation in this case. See Fig. 1-1. Only a very small fraction of molecules undergo inelastic scattering (Raman scattering). When Raman scattering occurs, the excited molecule relaxes to a different vibrational level, rather than to the original state. The energy carried by an inelastically scattered photon is different from that of 1 -1. Principles and Selection Rules VIRTUAL STATES VIBRATIONAL STATES V= 4 - V= 3 — V= 2- v=i- —I v = o - STOKES RAYLEIGH ΑΝΤΙ - STOKES IR RAMAN Fig. 1-1. Energy states involved in IR and Raman spectroscopies. the incident Hght. In a Raman spectrum, the energy difference between the incident and scattered Hghts appears as a frequency shift between the scat- tered Hght v' and the excitation frequency v. These two frequencies, ν and v', are related to the vibrational energy by the following equation (see also Fig. 1-1): hv = hv' + Ä£,ibration (3) It should be noted that in Raman experiments, the final vibrational state of the molecule can be either higher or lower in energy than the original state. In the case where the final vibrational state is lower in energy than the original one, the scattered photon will exhibit a higher frequency than the incident radiation. Thus, a blue shift from the excitation frequency is observed. Raman bands of this type are called anti-Stokes lines. Similarly, a red shift from the incident radiation is observed when the final state exhibits higher energy than the original state; these Raman bands are referred to as Stokes lines. Since most of the molecules are at ground vibra- tional state (υ = 0) at room temperature, the Stokes lines exhibit higher Raman intensity than the corresponding anti-Stokes lines, which originate from an elevated vibrational state {υ = 1). Therefore, the Stokes lines are more commonly used for molecular characterization.
The list of books you might like
