Carbon-centered Free Radicals and Radical Cations: Structure, Reactivity, and Dynamics (Wiley Series of Reactive Intermediates in Chemistry and Biology)

Covers the most advanced computational and experimental methods for studying carbon-centered radical intermediates With its focus on the chemistry of carbon-centered radicals and radical cations, this book helps readers fully exploit the synthetic utility of these intermediates in order to prepare fine chemicals and pharmaceutical products. Moreover, it helps readers better understand their role in complex atmospheric reactions and biological systems. Thoroughly up to date, the book highlights the most advanced computational and experimental methods available for studying and using these critically important intermediates. Carbon-Centered Free Radicals and Radical Cations begins with a short history of the field of free radical chemistry, and then covers: A discussion of the relevant theory Mechanistic chemistry, with an emphasis on synthetic utility Molecular structure and mechanism, focusing on computational methods Spectroscopic investigations of radical structure and kinetics, including demonstrations of spin chemistry techniques such as CIDNP and magnetic field effects Free radical chemistry in macromolecules Each chapter, written by one or more leading experts, explains difficult concepts clearly and concisely, with references to facilitate further investigation of individual topics. The authors were selected in order to provide insight into a broad range of topics, including small molecule synthesis, polymer degradation, computational chemistry as well as highly detailed experimental work in the solid, liquid, and gaseous states. This volume is essential for students or researchers interested in building their understanding of the role of carbon-centered radical intermediates in complex systems and how they may be used to develop a broad range of useful products.

CHAPTER 1

A BRIEF HISTORY OF CARBON RADICALS

Malcolm D. E. Forbes Department of Chemistry, University of North Carolina, Chapel Hill, NC, USA

It may seem difficult to believe, but research on carbon-centered free radicals is about to close out its second century. In 1815, Gay-Lussac reported the formation of cyanogen (the dimer of •CN) by heating mercuric cyanide. Numerous experiments involving pyrolysis of organometallic compounds followed, most notably from Bunsen, Frankland, and Wurtz in the 1840s. All of these reactions suggested the existence of what we now know to be carbon-centered free radicals, but physical methods of detection were still many decades away, and the field became somewhat stagnant in the latter half of the nineteenth century. From high-temperature gas-phase dissociation reactions, it was well accepted that inorganic compounds such as elemental iodine could exist in equilibrium with their atomic "radical" forms. In 1868, Fritzsche's observation of color changes due to formation of charge transfer complexes between picric acid and benzene, naphthalene, or anthracene represented the first evidence for the existence of carbon radical cations in aromatic systems. However, the attempted isolation of neutral compounds with trivalent carbon was an idea that had definitely fallen out of favor by the 1880s. This lack of interest was amplified by the flourish of new ideas surrounding tetravalent carbon (pushed experimentally by the vapor density method for determining molecular weights) and by the geometrical insight provided by van't Hoff's proposal of tetrahedral carbon in 1874.

Because of this status quo, the field was turned completely upside down with Gomberg's report in 1900 of the preparation of the triphenylmethyl radical. Apart from the influential support of Nef, Gomberg's result was met with much skepticism. But as is typical in the scientific endeavor, healthy criticism can provoke new experiments to prove or disprove a novel result, and the carbon radical skeptics were slowly won over. The year 1900 marked the beginning of what we might call the "wet chemistry" era of research on carbon-centered free radicals, although it should be noted that there were also many gas-phase experiments that were useful in establishing radical reactivity patterns. For example, Goldstein's experiments with cathode ray tubes provided the earliest physical method of detection of carbon-based radical cations in the gas phase. On the theoretical side, strong support for the existence of carbon-centered free radicals came from G. N. Lewis in 1916, whose ideas about valence shells and the octet rule had just begun to emerge. Lewis was also the first to recognize that molecules with unpaired electrons would exhibit paramagnetism. It is rather astounding to realize that both of these hypotheses predate the advent of the quantum theory; in regard to molecular structure, Lewis had an unmatched level of insight for his time.

The 1920s saw a flurry of activities in both thermal and photochemical investigations of gas-phase organic reactions, and chemists such as H. S. Taylor began to hypothesize carbon-centered radicals as reactive intermediates in certain mechanisms. In 1929, Paneth and Hofeditz reported their ingenious "mirror" experiments involving thermolysis of vapor-phase Pb(CH3)4 and other organometallic compounds. Their results clearly demonstrated that alkyl radicals were reasonable postulates as reactive intermediates in these reactions. In solution-phase organic chemistry, free radicals were beginning to be proposed as intermediates whenever "forbidden" chemistry was observed. This included reactions such as autooxidation of carbonyl compounds and the sulfite ion studied by Backström in 1927, and in other reactions by Haber and Willstätter a few years later. There was even an early suggestion by Staudinger in 1920 that free radicals were involved in the polymerization reactions of olefins. Carbon-centered radical cations were the subject of many gas-phase ion investigations in the early part of the twentieth century, led by the instrumentation developments of Thomson and Aston. Their work during these years built directly on Goldstein's cathode ray results and lay the foundation for the emerging field of organic mass spectrometry.

The year 1937 was an auspicious one for free radical chemistry, with the publication of an extensive review on solution-phase free radical mechanisms by Hey and Waters. At about the same time, Kharasch proposed the now well-accepted mechanism for anti-Markovnikov addition of HBr to alkenes in the presence of peroxides, a reaction he had initially reported with Mayo 4 years earlier. Also in 1937 came Flory's definitive paper on the kinetics of vinyl polymerization reactions, confirming the nature of these reactions as free radical propagations. This work on polymers eventually led to one of the largest spurts of industrial growth of the twentieth century. The year 1937 was noted by Walling in his excellent monograph as the beginning of the general acceptance of carbon-centered free radicals as viable reactive intermediates in solution-phase organic reactions at ordinary temperatures.

In terms of physical methods, by 1937 there had been only a few advances beyond the mirror technique of Paneth or the invoking of "forbidden reactivity" in solution to establish that a mechanism involved free radicals (or not). As noted above, mass spectrometry was one field where radicals and radical cations from organic structures were beginning to be postulated and actively studied. Optical absorption, usually carried out in frozen glasses with unstable radicals, was also a common early technique, and this was an important component of Gomberg's description of the triphenylmethyl radical. With Lewis' recognition of the link between radicals and paramagnetism, the magnetic susceptibility experiment came to be used in the study of stable free radicals. A bit later, scavenging studies were carried out to establish radical mechanisms, and the early days of flash photolysis allowed coarse structural and kinetic studies of radicals to be performed for the first time. However, prior to World War II (WWII), there were no high-resolution methods available that could definitively establish the structural (and magnetic) properties of carbon-centered radicals. The War would change this situation quickly.

The threat of airborne bombing raids on major cities during WWII led to intense efforts for the early detection of aircraft, and it was quickly recognized that radio and/ or microwave frequency electromagnetic radiation could be used for this purpose. This research in radio physics and engineering led to the availability of high-powered RF sources and sensitive detectors, the potential of which was immediately exploited by chemical physicists for the detection of magnetic resonances due to spin angular momentum in atoms and molecules. Such resonances had been predicted from the quantum theory two decades earlier, but had eluded detection. Purcell and Bloch in the United States, and Zavoisky in Russia (then the USSR), refined these RF experimental techniques to demonstrate "proof of principle" magnetic resonance spectroscopies (Purcell and Bloch discovered and reported NMR independently in 1946, while Zavoisky reported the first EPR spectrum of a paramagnetic species in 1945). While the EPR experiment is more directly relevant, both experiments played key roles in understanding mechanistic organic chemistry involving carbon-centered free radicals. The impact of these techniques on the field cannot be overestimated, and both spectroscopic methods are widely used in the study of radical reactions to the present day.

Just a few years after the discoveries of electron and nuclear magnetic resonance phenomena, commercial EPR and NMR spectrometers appeared, and the early 1950s can be considered the dawn of the "spectroscopic era" of research on free radicals. In the United States, the research groups of Weissman in St. Louis and Hutchison in Chicago were soon studying the structures and molecular dynamics of radicals and triplet states. Weissman in particular was developing workable models for simulating solution EPR spectra. In 1958, Hutchison and Mangum reported the first EPR spectrum of an organic triplet state, ending years of speculation and argument about the nature of phosphorescence (much earlier, G. N. Lewis had correctly predicted that the phosphorescent state of an organic molecule was the excited triplet).

Activity in magnetic resonance of free radicals has not let up, and a cursory literature search found almost 80,000 publications related to EPR spectroscopy at the time this book went to press. More than half of these papers are devoted to carbon-centered radicals. In 1963, new photochemical techniques and advances in spectrometer sensitivity led to the first direct observations of free radicals in liquid solution at room temperature. Soon after, it was commonplace to see g-factor (chemical shift) and isotropic electronnuclear hyperfine coupling constants for novel radicals being published on a regular basis in what we now refer to as "high-impact" journals.

Many sophisticated techniques for the isolation and study of free radicals and carbenes in the gas phase were devised during the spectroscopic era, most of them in conjunction with the development of high-intensity CW and pulsed lasers. These experiments were not only highly complementary to magnetic resonance methods, but also had the advantage of driving computational and theoretical work because very simple structures could be studied in the absence of solvent effects with high spectroscopic resolution. An example is the landmark photodetachment experiment of Engelking et al. that led to a precise value for the singlet–triplet energy gap in methylene, the simplest carbene. This energy gap had historically been a problem for computational chemists due to its open-shell structure, but the photodetachment method provided much guidance. The electronic structure of methylene remains one of the healthiest examples ever recorded of experiment/theory convergence in physical organic chemistry. The development of pulsed lasers in the 1960s also improved the time resolution and sensitivity of the flash photolysis experiment, and this allowed the kinetics of many radical reactions in solution to be precisely measured in real time. It is fair to say that prior to the development of time-resolved magnetic resonance techniques in the 1970s, laser flash photolysis was the standard method for determining free radical lifetimes in solution.

Research on carbon-centered radical cations in solution accelerated dramatically with the development of time-resolved optical absorption and emission techniques. The research group of Th. Forster in Germany pioneered photochemical methods of production of radical cations and anions, as well as exciplexes. While the Forster group focused on structure and lifetimes, the later work of D. R. Arnold in Canada, and of H. D. Roth in the United States, reported the reactivity of photochemically generated radical cations from a mechanistic perspective. These studies of radical ion chemistry evolved into the field we now know as electron donor–acceptor interactions, a rich area of science in which carbon-centered radical cations are still actively studied.

Another burst of activity in free radical research occurred in the 1960s and 1970s, after several reports of anomalous intensities in the EPR spectra of photochemically or radiolytically produced radicals, and in the NMR spectra of the products from free radical reactions in solution. These so-called chemically induced magnetic spin polarization (CIDNP and CIDEP) phenomena provided a wealth of mechanistic, kinetic, dynamic, and structural information and were a cornerstone of carbon-centered free radical research for the better part of three decades. The umbrella term for this area of research is "spin chemistry," which is defined as the chemistry of spin-selective processes.

Many new physical methods were developed in response to needs of spin chemists. In particular, the time-resolved EPR (TREPR) and time-resolved NMR (CIDNP) techniques were found to be of unparalleled utility in terms of mechanistic understanding of radical chemistry. Theoretical work to explain CIDNP and CIDEP phenomena was able to link, for the first time, the spin physics of radical pairs to their diffusion, molecular tumbling, confinement (solvent cages versus supramolecular environments), and the effects of externally applied magnetic fields. Several chapters of this book show how magnetic field effects, as well as CIDEP and CIDNP spectral patterns, can be used to solve chemical problems. It should be noted that the study of how applied magnetic fields perturb chemical reactivity is a topic that is highly relevant to biological processes involving radical pairs, for example, photosynthesis.

Two other major instrumentation developments had a major influence on the study of carbon free radicals. In the1950s,GeorgeFeher developed electron–nuclear double resonance (ENDOR) spectroscopy, which is still used to great advantage in determination of hyperfine coupling constants in biological systems. The experiment is even run in time-resolved mode in some laboratories. Pulsed EPR has emerged in recent years as a valuable technique, but its utility in the study of organic radicals is somewhat limited by the current status of microwave pulsing technology. Only very narrow spectral widths (~100 MHz) can be excited with uniform power by such pulses without distortions of the signals. Both electron spin-echo envelope modulation(ESEEM) and FT-EPR are used in the study of biological free radicals, and as the microwave technology improves in the modern era, 2D and even 3D pulsed EPR experiments have become a reality.

It is interesting to look back on this historical perspective and note that in the "wet chemistry" era (pre-WWII), the reactivity of radicals (Backström) and synthetic applications (Kharasch) were "hot" experimental topics. Polymers were just beginning to be recognized as fertile areas for research on free radicals (Flory), and gas-phase spectroscopy was leading to some of the most insightful experimental observations of the time (Paneth). This book honors the efforts of these pioneers in that, while the experiments have become more complex, the fundamental relationship between structure and reactivity is still driving intellectual curiosity in free radical research. The level of computational precision regarding structure and reactivity of free radicals has grown incredibly since 1950 and now matches the sophistication of the modern experimental arsenal. It is clear that the complexity of the systems that can be studied with these computational methods will continue to increase.

The future of the field is bright: carbon-centered free radicals in chemistry and biology continue to be of broad interest and continue to be studied experimentally with high resolution and high sensitivity. Combined with the latest computational techniques, it is now possible to consider the creation of a "cradle to grave" understanding of a free radical reaction, from the characterization of the excited-state precursor by optical techniques to the structure and dynamics of the radicals themselves by EPR spectroscopy, and finally to the kinetics of formation and structures of the products by NMR spectroscopy and other analytical methods.
(Continues...) Excerpted from Carbon-Centered Free Radicals and Radical Cations by Malcolm D. Forbes. Copyright © 2010 John Wiley & Sons, Inc.. Excerpted by permission of John Wiley & Sons.
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Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site. CARBON-CENTERED FREE RADICALS AND RADICAL CATIONS......Page 4 CONTENTS......Page 8 About the Volume Editor......Page 16 Preface to Series......Page 18 Introduction......Page 20 Contributors......Page 24 1. A Brief History of Carbon Radicals......Page 26 2.1 Introduction......Page 34 2.2.1 Cascade Reactions Initiated by Addition of C-Centered Radicals to Alkynes......Page 36 2.2.2 Cascade Reactions Initiated by Addition of O-Centered Radicals to Alkynes (Self-Terminating Radical Oxygenations)......Page 41 2.2.3 Cascade Reactions Initiated by Addition of N-Centered Radicals to Alkynes......Page 49 2.3.1 Cascade Reactions Initiated by Addition of Sn-Centered Radicals to Alkynes......Page 52 2.4.1 Cascade Reactions Initiated by Addition of S-Centered Radicals to Alkynes......Page 55 2.4.2 Cascade Reactions Initiated by Addition of Se-Centered Radicals to Alkynes......Page 61 2.5.1 Cascade Reactions Initiated by Addition of P-Centered Radicals to Alkynes......Page 62 3.1 Introduction......Page 68 3.1.1 Oxidative Carbon–Carbon Bond Cleavage......Page 69 3.1.2 Thermodynamic and Kinetic Considerations......Page 71 3.2 Electron Transfer-Initiated Cyclization Reactions......Page 74 3.2.2 Development of a Catalytic Aerobic Protocol......Page 75 3.3 Oxidative Acyliminium Ion Formation......Page 77 3.4.1 Chemoselectivity and Reactivity......Page 79 3.4.2 Reaction Scope......Page 80 3.5 Summary and Outlook......Page 83 4.1 Introduction......Page 86 4.2 Mechanism and the Origin of the Rate Acceleration......Page 87 4.3 Selectivity in Radical Cation Cycloadditions......Page 88 4.4.1 Effect of Dienophile Substituents on Chemoselectivity......Page 89 4.4.2 Effect of Sensitizers and Solvents on Chemoselectivity......Page 91 4.4.4 Effect of Electron-Rich Dienophiles on Chemoselectivity......Page 92 4.5 Regioselectivity......Page 93 4.6 Periselectivity......Page 94 4.6.1 Effects of Solvent and Concentration on Periselectivity......Page 95 4.6.2 Effect of Diene/Dienophile Redox Potentials on Periselectivity......Page 96 4.6.3 Substituent and Steric Effects on Periselectivity......Page 97 4.6.4 Quantifying Periselectivity Through Ion Pair Association......Page 99 4.7.1 Effects of Secondary Orbital Interaction and Solvents on Endo/Exo Selectivity......Page 100 4.7.2 Effect of Sensitizer on Endo/Exo Selectivity......Page 101 4.7.3 Ion Pairs and Endo/Exo Selectivities......Page 102 4.8 Conclusions......Page 104 5.1 Introduction......Page 108 5.1.1 The Consequences of Different Stability Definitions: How Stable Are Ethyl and Fluoromethyl Radicals?......Page 110 5.2 Theoretical Methods......Page 111 5.2.1 Testing the Performance of Different Theoretical Approaches: How Stable Are Allyl and Benzyl Radicals?......Page 112 5.2.2 The Application of IMOMO Schemes: How Stable Are Benzyl and Diphenylmethyl Radicals?......Page 114 5.4.1 Susceptibility to Hydrogen Atom Abstraction......Page 116 5.4.2 Assessment of Radical Stability in Other Types of Reactions......Page 125 5.5 Conclusions......Page 127 6.1 Introduction......Page 130 6.2.1 Theoretical Background......Page 132 6.2.3 Vibrational Effects......Page 133 6.2.4 Dynamical Effects......Page 134 6.3 Calculation of EPR Parameters......Page 135 6.3.1 Geometric Parameters......Page 137 6.3.2 EPR Parameters......Page 138 6.3.3.1 Glycine Radical......Page 142 6.3.3.2 Glycyl Radical......Page 144 6.3.4 Case Studies: Vibrationally Averaged Properties of Vinyl and Methyl Radicals......Page 145 6.4.1 Case Studies: Anharmonic Frequencies of Phenyl and Naphthyl Cation Radicals......Page 147 6.4.2 Case Studies: Gas and Matrix Isolated IR Spectra of the Vinyl Radical......Page 150 6.5.2 Case Studies: Vertical Excitation Energies of the Vinyl Radical......Page 151 6.6 Vibronic Spectra......Page 154 6.6.1 Theoretical Background......Page 157 6.6.3 Case Studies: Electronic Absorption Spectrum of Phenyl Radical......Page 159 6.7 Concluding Remarks......Page 162 7.1 Introduction......Page 166 7.2 The Tools......Page 167 7.2.2 EPR Parameters: Experimental and Calculated......Page 168 7.3 Pagodane and Its Derivatives......Page 169 7.4 Different Stages of Cycloaddition/Cycloreversion Reactions Within Confined Environments......Page 176 7.5 Extending the "Cage Concept"......Page 177 7.6 Summary......Page 179 8.1 Introduction......Page 182 8.2 The Spin-Correlated Radical Pair......Page 183 8.2.2 Intraradical Interactions......Page 184 8.2.3 Interradical Interactions......Page 185 8.3.1 The Zeeman Effect......Page 187 8.4.1 Coherent Spin-State Mixing......Page 188 8.4.2 The Life Cycle of a Radical Pair......Page 190 8.5.1 "Normal" Magnetic Fields......Page 192 8.5.2 Weak Magnetic Fields......Page 194 8.5.3 Strong Magnetic Fields......Page 196 8.6.1 General Approaches......Page 197 8.6.3 The Semiclassical Approach......Page 198 8.7 Experimental Approaches......Page 199 8.7.1 Fluorescence Detection......Page 200 8.8 The Life Cycle of Radical Pairs in Homogeneous Solution......Page 201 8.8.1 Differentiating G-Pairs and F-Pairs......Page 202 8.9 Summary......Page 205 9.1 Introduction......Page 210 9.2 CIDNP Theory......Page 211 9.3 Experimental Methods......Page 215 9.4 Radical—Radical Transformations During Diffusive Excursions......Page 216 9.5 Radical—Radical Transformations at Reencounters......Page 221 9.6 Interconversions of Biradicals......Page 224 9.7 Conclusions......Page 228 10.1 Introduction......Page 230 10.2 EPR for the Isolated Ions......Page 234 10.3 Calculation Methods for EPR of the Isolated Ions......Page 236 10.3.1 Calculation of g Tensor Components......Page 237 10.3.2.1 Ab Initio Hyperfine Coupling Constants: General Notes......Page 238 10.3.2.2 Theoretical Values of Isotropic and Anisotropic Hyperfine Coupling Constants......Page 239 10.4 Implications for Spin-Relaxation in Linked Radical Pairs......Page 241 11.1 Introduction......Page 246 11.2 The Crossed Molecular Beam Method......Page 248 11.3.1 The Crossed Beam Machine......Page 249 11.3.2.1 Ablation Source......Page 252 11.3.2.3 Photolytic Source......Page 253 11.4.1 Reactions of Phenyl Radicals......Page 254 11.4.2 Reactions of CN and C(2)H Radicals......Page 261 11.4.3 Reactions of Carbon Atoms, Dicarbon Molecules, and Tricarbon Molecules......Page 262 11.5 Conclusions......Page 265 12.1 Introduction......Page 274 12.2.1 Quantum Yields of Free Radicals in Nonviscous Solutions......Page 275 12.2.2 Cage Effect Under Photodissociation......Page 277 12.2.3 The Magnetic Field Effect on Photodissociation......Page 278 12.3.1 CIDEP Under Photodissociation of Initiators......Page 279 12.3.2 Addition of Free Radicals to the Double Bonds of Monomers......Page 285 12.3.3 Electron Spin Polarization Transfer from Radicals of Photoinitiators to Stable Nitroxyl Polyradicals......Page 293 12.4.2 Representative Kinetic Data on Reactions of Photoinitiator Free Radicals......Page 295 12.6 Concluding Remarks......Page 299 13.1.1 General Considerations......Page 306 13.1.2 Escape Probability of an Isolated, Intimate Radical Pair in Liquids and Bulk Polymers......Page 308 13.2.1 General Mechanistic Considerations From Solution and Gas-Phase Studies......Page 311 13.2.1.1 Photo-Fries Reactions of Aryl Esters......Page 312 13.3 Photo-Reactions of Aryl Esters in Polymer Matrices. Kinetic Information from Constant Intensity Irradiations......Page 314 13.3.1 Relative Rate Information from Irradiation of Aryl Esters in Which Acyl Radicals Do Not Decarbonylate Rapidly......Page 315 13.3.2 Absolute and Relative Rate Information from Constant Intensity Irradiation of Aryl Esters in Which Acyl Radicals Do Decarbonylate Rapidly......Page 318 13.4 Rate Information from Constant Intensity Irradiation of Alkyl Aryl Ethers......Page 322 13.4.1.1 Results from Irradiation in n-Alkane Solutions......Page 324 13.4.1.2 Results from Irradiation in Polyethylene Films......Page 329 13.5 Comparison of Calculated Rates to Other Methods for Polyethylene Films......Page 331 13.6.1 Triplet-State Radical Pairs from the Photoreduction of Benzophenone by Hydrogen Donors......Page 333 13.6.2 Triplet-State Radical Pairs from Norrish Type I Processes......Page 336 13.7 Concluding Remarks......Page 343 14.1 Introduction......Page 350 14.2 The Photodegradation Mechanism......Page 351 14.3 Polymer Structures......Page 352 14.4 The Time-Resolved EPR Experiment......Page 354 14.5 Tacticity and Temperature Dependence of Acrylate Radicals......Page 357 14.6 Structural Dependence......Page 359 14.6.1 d(3)-Poly(methyl methacrylate), d(3)-PMMA......Page 360 14.6.4 Poly(ethyl acrylate), PEA......Page 362 14.6.5 Poly(fluorooctyl methacrylate), PFOMA......Page 363 14.6.6 Polyacrylic Acid, PAA......Page 364 14.7 Oxo-Acyl Radicals......Page 365 14.8 Spin Polarization Mechanisms......Page 368 14.9.1 pH Effects on Poly(acid) Radicals......Page 369 14.9.2 General Features for Polyacrylates......Page 370 14.10 Dynamic Effects......Page 372 14.10.1 The Two-Site Jump Model......Page 373 14.10.2 Simulations and Activation Parameters......Page 375 14.11 Conclusions......Page 377 Index......Page 384

Covers the most advanced computational and experimental methods for studying carbon-centered radical intermediates

With its focus on the chemistry of carbon-centered radicals and radical cations, this book helps readers fully exploit the synthetic utility of these intermediates in order to prepare fine chemicals and pharmaceutical products. Moreover, it helps readers better understand their role in complex atmospheric reactions and biological systems. Thoroughly up to date, the book highlights the most advanced computational and experimental methods available for studying and using these critically important intermediates.

Carbon-Centered Free Radicals and Radical Cations begins with a short history of the field of free radical chemistry, and then covers:

• A discussion of the relevant theory
  
  

• Mechanistic chemistry, with an emphasis on synthetic utility
  
  

• Molecular structure and mechanism, focusing on computational methods
  
  

• Spectroscopic investigations of radical structure and kinetics, including demonstrations of spin chemistry techniques such as CIDNP and magnetic field effects
  
  

• Free radical chemistry in macromolecules
  
  

Each chapter, written by one or more leading experts, explains difficult concepts clearly and concisely, with references to facilitate further investigation of individual topics. The authors were selected in order to provide insight into a broad range of topics, including small molecule synthesis, polymer degradation, computational chemistry as well as highly detailed experimental work in the solid, liquid, and gaseous states.

This volume is essential for students or researchers interested in building their understanding of the role of carbon-centered radical intermediates in complex systems and how they may be used to develop a broad range of useful products.