Energetics of Organic Free Radicals PDF
Preview Energetics of Organic Free Radicals
ENERGETICS OF ORGANIC FREE RADICALS Structure Energetics and Reactivity in Chemistry Series (SEARCH series) Series Editors JOEL F. LIEBMAN Department of Chemistry and Biochemistry University of Maryland Baltimore County Baltimore, MD 21228 ARTHUR GREENBERG Department of Chemistry University of North Carolina at Charlotte Charlotte, NC 28223 The volumes in this series are comprised of state-of-the-art reviews, explicitly pedagogical in nature, in which specific topics are treated in depth. The series acronym SEARCH reflects the interplay between Struc ture, Energy And Reactivity in CHemistry and how these are also manifested in physical properties and biological activities. Others titles in the Series 1. Mesomolecules: From Molecules to Materials Edited by G. David Mendenhall, Arthur Greenberg and Joel F. Liebman 2. Active Oxygen in Chemistry Edited by Christopher S. Foote, Joan Selverstone Valentine, Arthur Greenberg and Joel F. Liebman 3. Active Oxygen in Biochemistry Edited by Joan Selverstone Valentine, Christopher S. Foote, Arthur Greenberg and Joel F. Liebman ENERGETICS OF ORGANIC FREE RADICALS EDITORS: JOSE ARTUR MARTINHO SIMOES Universidade de Lisboa ARTHUR GREENBERG University of North Carolina at Charlotte JOEL F. LIEBMAN University of Maryland Baltimore County BLACKIE ACADEMIC &. PROFESSIONAL An Imprint of Chapman & Hall London· Glasgow· Weinheim . New York· Tokyo· Melbourne· Madras Published by B1ackie Academic & Professional, an imprint of Chapman & Hall, Wester Cleddens Road, Bishopbriggs, Glasgow G64 2NZ Chapman & Hall, 2-D Boundary Row, London SEI 8HN, UK Blackie Academic & Professional, Wester Cleddens Road, Bishopbriggs, Glasgow G64 2NZ, UK Chapman & Hall GmbH, Pappelallee 3, 69469 Weinheim, Germany Chapman & Hall USA, 115 Fifth Avenue, Fourth Floor, New York NY 10003, USA Chapman & Hall Japan, ITP-Japan, Kyowa Building, 3F, 2-2-1 Hirakawacho, Chiyoda-ku, Tokyo 102, Japan DA Book (Aust.) Pty Ltd, 648 Whitehorse Road, Mitcham 3132, Victoria, Australia Chapman & Hall India, R. Seshadri, 32 Second Main Road, CIT East, Madras 600 035, India First edition 1996 © 1996 Chapman & Hall Softcover reprint of the hardcover 1st edition 1996 Typeset in 1O/12pt Palatino by Words & Graphics Ltd, Anstey, UK ISBN -13 978-94-010-6532-0 e-ISBN -13 978-94-009-0099-8 DOl 10.1007/978-94-009-0099-8 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright Designs and Patents Act, 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to the publishers at the Glasgow address printed on this page. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. A catalogue record for this book is available from the British Library Library of Congress Catalog Card Number: 94-81420 i§ Printed on permanent acid-free text paper, manufactured in accordance with ANSIINISO Z39.48-1992 (Permanence of Paper). Contents Preface Vll Series Preface IX Contributors xi 1 Free Radical Reactions 1 C. Walling 2 Heats of Formation of Organic Free Radicals by Kinetic Methods 22 Wing Tsang 3 Thermochemical Data for Free Radicals From Studies of Ions 59 J. C. Traeger and B. M. Kompe 4 Theoretical Studies of the Energetics of Radicals 110 J. S. Francisco and J. A. Montgomery, Ir 5 Photo acoustic Calorimetry of Radicals and Biradicals 150 J. L. Goodman 6 A Short and Illustrated Guide to Metal-Alkyl Bonding Energetics 169 J. A. Martinho Simoes and M. E. Minas da Piedade v vi Contents 7 Resonance and 1,2-Rearrangements in Radicals: From Alkyl Radicals to Alkykobalamins 196 A. Greenberg and J. F. Liebman 8 Solvent Effects in the Reactions of Neutral Free Radicals 224 J. M. Tanka and N. Kamrudin Suleman Index 294 Preface The current volume consists of eight chapters which interweave various aspects of the structure, energetics and reactivity of organic free radicals, all combining pedagogical insights with current research. The first is by Walling in which a personalized overview is given by one of the modern pioneers of the discipline. In the next two chapters, Tsang, and Traeger and Kompe, present key thermochemical and kinetic quantities from the complementary vantage points of the studies of neutral and cationic species. The fourth chapter by Francisco and Montgomery discusses the armamentarium of modern theory as applied to species with unpaired electrons, while the next chapter by Goodman presents the theory, methodology and results from photoacoustic calorimetry, a novel and powerful experimental technique. Martinho Simoes and Minas da Piedade interrelate organometallic and free radical chemistry, while Greenberg and Liebman consider resonance energy and rearrangements as applied to small molecules and enzyme cofactors alike. The volume ends with the chapter by Tanko and Suleman, which describes the surprising and diverse solvent effects which modulate free radical chem istry. This volume will make it apparent to entry-level graduate students and senior researchers alike that much is known and much remains to be done in both the qualitative understanding and quantitative insights of the chemistry of organic free radicals. Jose Artur Martinho Simoes Arthur Greenberg Joel F. Liebman vii Editorial Advisory Board WESTON T. BORDEN ALAN P. MARCHAND Department of Chemistry Department of Chemistry University of Washington University of North Texas Seattle, WA 98195 Denton, TX 76203 JULIAN A. DAVIES JOSE ARTUR MARTINHO SIMOES Department of Chemistry Departamento de Quimica e University of Toledo Bioquimica Toledo, OH 43606 Faculdade de Ciencias Universidade de Lisboa GAUTAM R. DESlRAJU 1700 Lisboa, Portugal School of Chemistry University of Hyderabad JOAN MASON Hyderabad, India 500134 Department of Chemistry Open University FRANC;:OIS N. DIEDERICH Milton Keynes MK7 6AA, UK Laboratorium fUr Organische Chemie ETH-Zentrum ROBERT A. MOSS Universitatstrasse 16 Department of Chemistry CH-8092 Ziirich, Switzerland Rutgers University Piscataway, NJ 08855 DENNIS A. DOUGHERTY Department of Chemistry BRUCE E. SMART California Institute of Technology E. I. Du Pont de Nemours & Co., Inc. Pasadena, CA 91125 Central Research and Development Experimental Station RICHARD D. GANDOUR Wilmington, DE 19880-0328 Department of Chemistry Virginia Polytechnic and State JOAN SEL VERSTONE VALENTINE University, Department of Chemistry and Blacksburg, VA 24601 Biochemistry University of California, Los Angeles SHARON G. LIAS Los Angeles, CA 90095 Chemical Kinetics and Thermodynamics Division DEBORAH VAN VECHTEN National Institute of Standards and Space Sciences Division Technology Naval Research Laboratory Gaithersburg, MD 20899 Washington, DC 20375 Series Preface The purpose of this series is the presentation of the most significant research areas in organic chemistry from the perspective of the interplay and inseparability of structure, energetics, and reactivity. Each volume will be modeled as a text for a one-semester graduate course and will thus provide groundwork, coherence, and reasonable completeness. In this context, we have made the editorial decision to defer to the authors the choice of the desired blend of theory and experiment, rigor and intuition, practice and perception. However, we asked them to engage in the spirit of this venture and to explain to the reader the basis of their understanding and not just the highlights of their findings. For each volume, and each chapter therein, we have aimed for both a review and a tutorial of a major research area. Each volume will have a single theme, unified by the common threads of structure, energy, and reactivity for the understanding of chemical phenomena. Structure, energetics, and reactivity are three of the most fundamental, ubiquitous, and therefore seminal concepts in organic chemistry. The concept of structure arises as soon as even two atoms are said to be bonded, since it is there that the concept of bond length and interatomic separation begins. Three-atom molecules already introduce bond angle into our functioning vocabulary, while four atoms are needed for the introduction of the terms planarity, nonplanarity, and dihedral angles. Of course, most organic chemists are interested in molecules of more than four atoms, so new shapes (tetrahedra, cubes, dodecahedra, prisms, and numerous exotic polyhedra) and new degrees of complexity arise. These ix x Series Preface new molecular shapes, in turn, function as templates for the next molec ular generation. Still, the basic assumption remains: molecular structure determines energy and reactivity, and even though Van't Hoff, LeBel, and Sachse explained chemical reality with palpable molecular models over a century ago, we still do much the same thing on the screens of personal computers. The concept of energetics arises in chemistry as soon as there is a proton and an electron and remains with us throughout our discipline. There are the fundamental, experimentally measurable quantities of bond energies, proton affinities, ionization potentials, pKa values, and heats of formation. There are the derived quantities such as strain and resonance energies, acidity, and basicity. There are also the widely used, generally understood, and rather amorphous concepts such as delocalization, conjugation, and aromaticity. Indeed, the shape, conformation, and there fore function of a protein are determined by a balance of energetics con tributions - resonance in the peptide linkage, hydrogen bonding, hindered rotation of a disulfide, Van der Waals forces, steric repulsion, Coulombic interactions and salt bridges, and solvent interactions. The concept of reactivity inseparably combines structure and ener getics and introduces more concepts and words: stereospecificity, intra molecularity, nucleophilicity, catalysis, entropy of activation, steric hindrance, polarizability, hard and soft acids and bases, Hammettrraft parameters. Reac tivity is a more difficult concept than structure and energetics. One must specify reaction conditions and usually accompanying reagents, since reactivity generally refers to two species or at least two seemingly disjoint parts of the same molecule. Structure, energetics, and reactivity in chemistry have been probed by a plethora of experimental and theoretical methods. These tools have different degrees of accuracy and applicability, and consensus is rare as to when our understanding is deemed adequate. Indeed, diverse approa ches - heats of hydrogenation and Hartree-Fock calculations, line inten sities and LDso values, ease of substitution and of sublimation, coupling constants and color - all contribute to the special blend of rigor and intuition that characterizes modern organic chemistry. As people, and not just as scientists and editors, we wish to acknowl edge the unity of the intellect and the emotions. We are grateful for the love and support of our families and for the inspiration, agitation, and stimulation from our mentors, colleagues, and students, and so we dedicate these volumes "To Research and to Reason, To Family and to Friendship. " JOEL F. LIEBMAN ARTHUR GREENBERG Baltimore, Maryland Charlotte, North Carolina
The list of books you might like
