REVIEWS OF REACTIVE INTERMEDIATE CHEMISTRY REVIEWS OF REACTIVE INTERMEDIATE CHEMISTRY Edited by Matthew S Platz Department of Chemistry Ohio State University Columbus, OH Robert A Moss Department of Chemistry Rutgers University New Brunswick, NJ Maitland Jones, Jr Department of Chemistry Princeton University Princeton, NJ Copyright © 2007 by John Wiley & Sons, Inc All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada 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 Section 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, (978) 750-8400, fax (978) 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special, incidental, consequential, or other damages For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002 Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic formats For more information about Wiley products, visit our web site at www.wiley.com Wiley Bicentennial Logo: Richard J Pacifico Library of Congress Cataloging in Publication Data is available ISBN: 978-0-471-73166-5 Printed in the United States of America 10 CONTENTS PREFACE vii CONTRIBUTORS ix PART 1 REACTIVE INTERMEDIATES Tetrahedral Intermediates Derived from Carbonyl Compounds, Pentacoordinate Intermediates Derived from Phosphoryl and Sulfonyl Compounds, and Concerted Paths Which Avoid Them J.P Guthrie Silicon-, Germanium-, and Tin-Centered Cations, Radicals, and Anions 47 V.Y Lee and A Sekiguchi PART METHODS AND APPLICATIONS An Introduction to Time-Resolved Resonance Raman Spectroscopy and Its Application to Reactive Intermediates 121 123 D.L Phillips, W.M Kwok, and C Ma Time-Resolved Infrared (TRIR) Studies of Organic Reactive Intermediates 183 J.P Toscano Studies of the Thermochemical Properties of Reactive Intermediates by Mass Spectrometric Methods 207 P.G Wenthold Reactive Intermediates in Combustion 247 J.K Merle and C.M Hadad Reactive Intermediates in Crystals: Form and Function 271 L.M Campos and M.A Garcia-Garibay v vi CONTENTS The Chemical Reactions of DNA Damage and Degradation 333 K.S Gates Conical Intersection Species as Reactive Intermediates 379 M.J Bearpark and M.A Robb 10 Quantum Mechanical Tunneling in Organic Reactive Intermediates 415 R.S Sheridan INDEX 465 PREFACE In 2004, Moss, Platz and Jones edited Reactive Intermediate Chemistry This book contained chapters written by leading experts on the chemistry of the reactive intermediates commonly encountered in mechanistic organic chemistry; carbocations, radicals, carbanions, singlet and triplet carbenes, nitrenes and nitrenium ions A three-dimensional approach was offered integrating venerable methods of chemical analysis of reaction products, direct observational studies of reactive intermediates (RI’s) and high accuracy calculations of the geometries, potential energy surfaces and spectra of RI’s The book was aimed at beginning graduate students and newcomers to a particular field to provide him or her with an introductory chapter that would rapidly allow them to pursue advanced work Such is the richness and intellectual vibrancy of the field of RI chemistry that an additional book was needed to cover silicon, germanium and tin centered RI’s, as well as tetrahedral intermediates and topics of increasing importance such as quantum mechanical tunelling, conical intersections, solid-state chemistry, and combustion chemistry These topics are covered in this new book We hope Reviews of Reactive Intermediate Chemistry well captures the continuing evolution and breadth of Reactive Intermediate Chemistry, assists chemists to appreciate the state of the art and encourages new research in this area MATTHEW S PLATZ ROBERT A MOSS MAITLAND JONES, JR vii CONTRIBUTORS M J Bearpark Department of Chemistry Imperial College London South Kensington campus London SW7 2AZ UK email: m.bearpark@imperial.ac.uk L M Campos University of California, Los Angeles Department of Chemistry and Biochemistry 607 Charles E Young Drive East Los Angeles, CA 90095-1569 email: lcampos@chem.ucla.edu M Garcia-Garibay University of California, Los Angeles Department of Chemistry and Biochemistry 607 Charles E Young Drive East Los Angeles, CA 90095-1569 email: mgg@chem.ucla.edu K S Gates Department of Chemistry 125 Chem Bldg University of Missouri Columbia, MO 65211 email: GatesK@missouri.edu J P Guthrie The University of Western Ontario Department of Chemistry London, Ontario, Canada N6A 5B8 email: peter.guthrie@uwo.ca C M Hadad Department of Chemistry Ohio State University 100 West 18th Avenue Columbus, OH 43210 email: hadad.1@osu.edu W M Kwok Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong email: kwokwm@hkucc.hku.hk V Ya Lee Department of Chemistry Graduate School of Pure and Applied Sciences University of Tsukuba Tsukuba, Ibaraki 305-8571, Japan email: leevya@chem.tsukuba.ac.jp C Ma Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong email: macs@hkucc.hku.hk ix 466 INDEX β -scission fragmentation, 255 Bacteriorhodopsin, 168 Barrier, 419 Bell’s, 430 Bell-type calculation, 432 Bell-type parabolic barrier, 427 Bell-type truncated parabolic barrier, 456 Benzonorbornenyl cation, 280 Benzyl radical, 425 Benzylic (C6H5CH2•) Bergman cyclization, 258 Bertrand, 292 Bimolecular Reactions, 151 Biogenic, 248 1,3-biradical, 426, 428 Biradical intermediate, 381 Biradicals, 297, 306 bis(hydrazine) radical cations, 410 bis(methylene) adamantyl radical cation, 411 bis-carbene/diradical, 439 Boilers, 248 Bond angle, 275 Bond dissociation energies (BDEs), 249 Bond dissociation energies, 209, 218 Bond energy, 386 Bond exchange reaction, 384 Bond lengths, 275 Bond-shift isomerization of cyclobutadiene, 432 Branch and Calvin, 26 Branching space, 388, 389, 391, 399 Bronsted plot, 26 Bürgi and Dunitz, 281 C1-DNA radicals, 351 C4-sugar radicals, 353 Carbanions, 284 Carbenes as Transient Species, 317 Carbenes, 289 Carbenium ions, 276 Carbenium, 276 Carbinolamine, Carbocation, 275, 350 Carbon particles, 248 Carbon Tunneling in Singlet Carbenes, 448 Carbon tunneling, 432, 449, 451 Carbonium ions, 276 Carbonyl compounds, equilibrium constants for addition, 10 Carboxylate ester, hydrolysis mechanisms, 27 Carbyne, 261 Carbynes, 230 Catalytic antibodies, Cations of the heavier group 14 elements early studies of RRЈRЉEϩ cations: free or complexed?, 54 reactions and synthetic applications, 53 recent developments, 58 free (noncoordinated) cations, 62 acyclic tricoordinate cations, 66 cyclic conjugated cations, 62 intramolecularly coordinated cations, 58 synthesis of RRЈRЉEϩ cations (E ϭ Si, Ge, Sn), 49 by cleavage of element-element bond, 51 from free radicals RRЈRЉE, 52 from halides RRЈRЉEX, 50 from heavy carbene analogs RRЈE, 52 from hydrides RRЈRЉEH, 50 from RRЈRЉE–Alkyl and RRЈRЉE– ERRЈRЉ, 51 Cavity-ring down (CRD) spectroscopy, 256 Chain-branching reaction, 251 Chain-branching, 251 Chain-propagation reactions, 251 Chain-terminating process, 252 Charge transfer (ICT) state, 398 Charge Transfer Reactions, 145 Chemical ionization (CI), 265 Chemical reactivity, 272 Chemiluminescence, 382 Chlorodiazirine, 321 Chlorophenylcarbene, 199 “Classical” carbocations, 276 13 C NMR spectra, 433 Coal, 248 Coherent anti-Stokes Raman scattering (CARS), 266 Collision-induced Dissociation, 215, 227, 229 Combustion Chemistry, 249 Compression stage, 251 Computational modeling, 266 Computational quantum chemical methods, 266 INDEX Concerted acyl transfer, 25 Concerted mechanism, 21 Concerted phosphoryl transfer, 25 Concerted reactions, 24, 26 Concerted reactions, when are they likely, 27 Concerted sulfonyl transfer, 25 Conformational Analysis, 303 Conical intersection hyperline, 387 Conical intersection intermediates, 382 Conical intersection, 380, 406 Corannulene, 260 Correlation diagram, 404 Coulomb energy, 386 (Covalent) configurations, 399 Critical point, 380 Crossed molecular beams, 265 Cross-terms, 386 Crude oil, 248 CT states, 404 Curve crossing, 384 Curved extended seam, 392 Cyclic and Polycyclic Anions, 101 Cyclization vs cleavage, 316 [2ϩ2] cycloaddition, 384 1,3-cyclobutanediyls, 429 Cyclobutadiene, 433 Cyclobutadiene—Heavy Atom Tunneling, 431 Cyclopentadienyl (c-C5H5•) radical, 256 Cyclopentadienyl (c-C5H5•) radicals, 248 Cyclopentadienyl radical, 300 Cyclopentadienyl radicals, 259 1,3-cyclopentanediyl, 426 Cyclopropylhalocarbenes, 448 Cylindricines A and B, 348 Cytochrome P450 enzymes, 258 de Broglie wavelength, 418 Deamination, 341 Decarbonylation Reactions, 307 Deglycosylation Reactions of Alkylated Bases, 338 Delocalized orbitals, 408 Density functional theory (DFT), 266 Derivative coupling, 395 Diabatic, 385, 398, 402 Diacylperoxides, 306 467 Dianions, 287 Diazirine, 321 4-diazo-3-isochromanone, 195 Dichlorocarbene, 236 Diethoxymetaphosphylium ion, 36 Differing, 430 Difluorocarbene, 236 Dimroth rearrangement, 340 Dioxocarbenium Ions, 303 Diphenylcarbene, 317 Diphenylcarbenes, 190 Dispersive TRIR spectroscopy, 185 Disproportionation, Dissociative mechanism, 21, 23 Distribution slicing, 430 di-π-methane rearrangement, 381 DNA alkylation, 350 Dot-dot, 399, 402 “Dot-Dot” configurations, 399 Double cone, 383, 390, 394 Dual fluorescence, 398 Eckart-type asymmetric barriers, 437 Eckhart-shaped barrier, 425 Electron Affinity, 211 Electron impact (EI), 265 Electron paramagnetic resonance (EPR), 248 Electron transfer, 381, 406 Electronic (VB) structure, 384 Electronic structure, 380 Electrospray ionization, 227 Elimination addition pathways, 24 Energy derivatives, 394 Engine knock, 251 Enol form, 403 Enthalpy, 309 Entropy, 309 Environmental and Solvent Effects on TR3 spectra, 140 Episulfonium ions, 344 Equilibrium constants for tetrahedral intermediate formation, estimation, 13 Ester aminolysis, 19 Ester hydrolysis, 18 Estragole, 348 Ethenylperoxy, 257 Ethyl metaphosphate, 36 468 INDEX Exchange attraction, 386 Exchange integral Kij, 387, 388 Exchange repulsion, 386 Excited state minimum, 388 Excited States and Energy Relaxation, 148 Explosion, 251 Extended conical intersection seam, 403 Extended hyperline, 385, 389 Eyring transition state theory, 417 Fasicularin, 348 Femtosecond-stimulated Raman spectroscopy, 175 Flowing afterglow, 212 Fluorophenylcarbene, 199 Fossil fuels, 247 Franck–Condon geometry, 403 Fuel lean (low fuel/air ratio), 262 Fuel rich (high fuel/air ratio), 262 Fuel-NO, 262 Fullerenes, 260 Fulvene, 259 Fulvene, 392, 393 Funnel, 391 γ, 13 Gas chromatography (GC–MS), 265 Gas-phase Acidity, 211 Geometric structure, 384 Geometries of singlet carbenes, 445 Geometry relaxation, 384 Gomberg’s, 297 Gradient difference vector, 394 Green chemistry, 304 γ -Radiolysis, 362 [1,2]-H shift, 441 1,2-halo shifts, 455 H-abstraction in a perinaphthyl nitrene, 453 H-abstraction-C2H2-addition (HACA) mechanism, 259 HACA mechanism, 260 Halocarbene amides, 200 Heavy atom effects, 428 Heavy atom tunneling, 455 Heisenberg uncertainty, 418 Heme Proteins, 171 High-pressure mass spectrometry, 212 High-Temperature Mechanisms, 254 Homogeneous charge compression ignition (HCCI) engines, 267 H-shift transition states, 445 H-transfer by a phenyl-type radical, 425 H-transfer in o-tolylcarbene, 440 H-transfer, 425 Hybridization, 275 Hydride Affinity, 211 Hydrogen abstraction reactions, 438 Hydrogen Abstraction, 151, 314 Hydrogen Atom Abstraction from DNA, 351 Hydrogen Atom, 356 Hydrogen shift, 454 Hydrogen Shifts in Singlet Carbenes, 442 Hydroperoxide, 352 Hydroperoxyalkyl radical, 253 Hydroxyl radical, 255, 362 Hyperconjugation, 277 Hypervalent bonding, 22 (P)-ICT structure, 402 (R)-ICT structure, 402 (T)-ICT structures, 402 Ignition delay, 252 Imine, Imines, equilibrium constants for addition, 10 In cold organic glasses, 437 In low-temperature organic glasses, 436 [1,3]-insertion, 447 In solution, 438 Incinerators, 248 Indirect Equilibrium Constants, 11 Interaction matrix element, 410 Intersection space, 391 Intersystem crossing (ISC) reaction, 162 Intersystem crossing, 229 Intramolecular C–H insertions, 447 Intramolecular Hydrogen Abstraction by Radicals, 423 Intramolecularity, Ion cyclotron resonance, 212 Ionization energies, 210, 221 Irreducible representation, 391 iso-octane (2,2,5-trimethylpentane), 251 Isothermal, isobaric, isochoric, or adiabatic conditions, 266 Isotope exchange, 26 Isotopic exchange, INDEX Kerr-gating to reject fluorescence in picosecond TR3 spectra, 175 Keto form, 403 Kij, 386 Lachrymators, 264 Laminar flow, 264 Laser flash photolysis, 437 Laser-induced fluorescence (LIF), 266 Leaving group abilities, 18 Leinamycin, 345 Linear free energy relation, 27 Linear free energy relation, break in, Linear free energy relations, 12 Linear free energy relationships, 14, 15 Localized orbitals, 408 Locally excited (LE) state, 398 Locally excited states, 404 London formula, 386 Low-Temperature Mechanisms, 251 Marcus Theory, 19 Marcus, 19 Mass spectrometry, 208, 265 Matrix Effects, 422, 436 Matrix site, 430 McBride, 306 Mechanisms of tetrahedral intermediate formation and breakdown, 17 Mechanistic photochemistry, 382 MECI, 401 Metaphosphate, 25 Metaphosphyliumion, 39 Method of Branch and Calvin, 32, 38, 40 Methyl 2-diazo-(2-naphthyl) acetate, 195 Methylchlorocarbene (54) to vinyl chloride, 443 Methylene group, 392 Methylene, 221 Methyleugenol, 348 Methyne (HC), 261 Microwave discharge, 264 Minimum energy conical intersection (MECI), 387 Models was developed by Bell, 419 Multidimensional Marcus Theory, 19 469 Nanosecond Time-Resolved Resonance Raman, 130 Naphthalene, 259 Negative ion photoelectron spectroscopy, 230 n-heptane, 251 NIPES, 217 No Barrier Theory, 20 “Nonclassical” carbocations, 276 NO3• radicals, 262 Nonadiabatic, 381, 385, 398, 406 Nonlinear Arrhenius Plots, 420 Noradamantylcarbene, 451 Norbornenyl, 279 Norrish type I, 306 Norrish-Yang Type II, 306, 314 NOx and SOx, 261 NOx, 248, 261 n-propylperoxy (CH3CH2CH2O2•) radical, 253 Nucleophilic Sites in DNA, 335 O(1D), 262 O(3P), 263 o-benzyne, 222, 229 Octane number, 251 o-hydroxyphenyl-(1,3,5)-triazine, 403 o-hydroxyphenyl-triazine, 404 Optimization, 396 Orbital overlap, 385, 387 ortho-benzyne, 208, 237 Orthoesters, Oscillator strength, 404 Overlap, 388 2-oxepinoxy radical (1), 257 Oxidant, 248 Oxidation, 247 Oxides of nitrogen (NO, NO2, NO3, N2O4), 261 Oxocyclohexadienylcarbene, 455 Oxynitrenes, 455 Ozone (O3), 262 Ozone, 248, 264 PAH and Soot Formation, 257 Parabolic, 419 Pentacoordinate intermediate, 25, 37 Pentacoordinate species, 25 Pentacoordinate, 25, 37 470 INDEX Pericyclic Reactions, 159 1,3-perinaphthadiyl, 428 Peroxyacylnitrates (PANs, RC(ϭO)OONO2), 264 Peroxyl radical, 352 Persistence, 273 pH rate profile, Phenoxy (C6H5O •) radical, 256 Phenylacetylene, 259 Phenylchlorocarbene, 189 Phenylperoxy (C6H5O2•) radical, 256 Phosphate diester, hydrolysis mechanisms, 36, 37 Phosphate ester hydrolysis, 21 Phosphate ester, hydrolysis mechanisms, 27 Phosphate monoester, hydrolysis mechanisms, 37 Phosphoranes, 21 Phosphoranoxides, 22 Phosphoryl transfer, 25 [2ϩ2] photochemical cycloaddition of two ethylenes, 385, 387 Photochemical di-π-methane rearrangement, 387 Photochemical funnel, 382 Photochemical smog, 248 Photochemistry, 381 Photodeprotection Reactions, 162 Photodetachment, 216 Photoelectron Spectroscopy, 216 Photostabilizers, 403 pKa, 285 Point group, 391 Polycrystalline media, 320 Polycyclic aromatic hydrocarbons (PAHs), 256, 257 Potential energy curve, 379 Potential energy surface, 381, 383 Pressure dependence, 253 Primary volatile organic compounds (VOCs), 262 Product P, 273 Proton Affinity, 210, 222 Proton transfer, 404, 405 Protonation Reactions, 156 Pseudorotation, 22, 26 Puckering, 280 Pyramidalization, 394 Pyrolytic, 250 p-π-bonding, 280 π–π*, 403 Q•OOH, 253 QMT in the [1,4]-H shift of a singlet carbene, 446 QMT, 438 Quaternary centers, 313 Quinodimethane, 223 Quinoid, 400, 410 Radiationless decay, 391 Radical cation, 408 Radical chain-propagating, 251 Radicals of the heavier group 14 elements persistent radicals, 75 stable radicals, 79 stable biradicals of the heavier group 14 elements, 86 ion radicals, 83 acyclic anion radicals, 83 heavy alkene anion radicals, 83 heavy alkyne anion radicals, 85 cyclic anion radicals, 83 neutral radicals, 79 acyclic tricoordinate radicals, 81 cyclic radicals, 79 transient species, 70 generation, 70 structure, 71 theoretical calculations, 73 electronic spectroscopy, 71 ESR spectroscopy, 72 synthetic applications, 74 Radical Pairs, 306 Radical pool, 251 Radical stabilization energy, 310 Radical, 297, 306, 352 Radical-initiation, 250 Radicals, 248 React with H2, 439 Reactant, 273 Reaction cavity concepts, 304 Reaction coordinate, 380 Reaction path, 380 Reactions in crystals, 304 Reactive intermediate, 273 Real crossing, 398, 406 INDEX Resonance Raman Scattering, 125 Resonance, 277 Reversible alkylation, 344 Ring-Opening Reactions of Alkylated Bases, 339 Safrole, 348 “Sand in a funnel” picture, 383 Sand in the funnel, 391 Scheffer, 314 Seam, 391 Secondary VOC, 264 Selected-ion flow tube, 212 Semenov mechanism, 251 Semenov, 251 Shock tube, 265 Si-, Ge-, and Sn-Centered Anions, 88 Si-, Ge-, and Sn-Centered Cations, 48 Si-, Ge-, and Sn-Centered Free Radicals, 69 Silyl cation, 283 Singlet Carbene C–H Insertions, 446 Singlet Carbenes, 290 Singlet cyclobutylhalocarbenes, 449 Singlet, 289 Singlet-triplet Energy Splittings, 229 Skeletal deformation, 392, 401, 405 Smog, 248 Solvation of carbenes, 198 Solvent-free synthesis, 313 Soot particles, 257 Soot, 248 Sooting, 258 SOx, 248, 262 Spark plug in, 251 Spark-ignition engine, 251 Spirodioxiranyl radical, 256 Spontaneous Raman scattering, 265 Squires reaction, 227, 228, 232 Stabilization, 273 Standard Bell parabolic model, 445 Static or flow reactor systems, 265 Step-scan FTIR spectroscopy, 185 Stereospecificity, 313 Stokes shifted, 265 Stretch-bond isomerism, 302 Stretched exponential, 423 Subgroup, 391 Sulfate diester hydrolysis, 24 Sulfate diester, hydrolysis mechanisms, 28 471 Sulfate ester, hydrolysis mechnisms, 27 Sulfate monoester, hydrolysis mechanisms, 31 Sulfate monoesters hydrolysis, 23 Sulfenes, 24, 107 Sulfinate ester hydrolysis, 24 Sulfonate ester hydrolysis mechanisms, 27 sulfonate ester, mechanisms of hydrolysis, 34 Sulfonyl transfe, 25 Sulfonylium cation, 34 Sulfonylium, 25 Sulfurane, 25 Sultone, 27 Superoxide Radical (O2•Ϫ), 366 Superoxide radical anion, 352 Temperature-dependent deactivation, 404 tert-Butyl carbocation, 277 tert-Butylchlorocarbene, 447 Tetrahedral intermediate, 25 Tetrahedral intermediate, mechanisms of formation and breakdown, 17 Tetrahedral intermediates, evidence for, The abasic sites, 339 The bracketing approach, 213 The kinetic method, 213 Thermal NO or Zeldovich-NO, 261 thia-Payne rearrangement, 345 This prompt NO (Fenimore-NO), 261 TICT (twisted intermolecular charge transfer)/aminobenzonitrile (ABN) compounds, 398 TICT processes, 397 Time-Resolved Resonance Raman Spectroscopy, 123, 124, 127 Tirapazamine, 362 Topochemical postulate, 304 Torsion, 394, 401 Torsional coordinate, 394 Transition State spectroscopy, 234 Transition state, 273, 388, 398, 406 Transition structure, 385 Trapezoidal distortion, 385, 388 1,3,5-tridehydrobenzene, 232 Trigonal bipyramidal intermediates, 22 1,3,5-trimethylenebenzene, 232 Trimethylenemethane, 226 Triplet 1-phenylethylidene, 441 472 INDEX Triplet aryl carbenes, 436 Triplet Carbene Intermolecular Hydrogen Abstraction Reactions, 434 Triplet Carbene Intramolecular Reactions, 440 Triplet Carbene Reactions, 433 Triplet carbenes can abstract H from H2, 438 Triplet Carbenes, 296 Triplet ground state, 317 Triplet, 289 Triradical, 230 Trityl radical, 297 Troposphere, 248 Tunneling in a Cyclopropene to Triplet CarbeneRearrangement, 455 Tunneling in Nitrene Reactions, 452 Tunneling in Reactions of Biradicals, 426 Tunneling in Singlet Carbene Reactions, 442 Tunneling through a parabolic barrier, 430 Tunneling, 428, 454 Turbulent flows, 264 Ultrafast TRIR methods, 185 Unavoided crossing, 395 Unpaired electron, 408 Ultrafast Time-Resolved Resonance Raman, 132 ZEKE, 218 Zwitterionic configurations, 399 Valence bond, 380, 384 Vertical excitation, 384, 404 Vibrational Spectroscopy and Functional Groups, 134 Vinyl cation, 283 Vinylbenzene, 259 Vinylidene (R2CϭC:) carbene, 260 Volatile organic compounds (VOCs), 248 Wave function, 400 Wheland intermediate, 379 Winstein, 279 Wolff rearrangement, 194 Woodward–Hoffmann [2sϩ2s] cycloaddition, 388 X-ray diffraction, 274 Xylylene, 223 Figure 7.4 Top: Schematic representation of the reaction to form the cation-anion Me-5ϩ, Sb2F11Ϫ Bottom: Two different views of the X-ray structure of the Me-5ϩ, showing the important structural parameters (Adapted from reference 27.) Figure 7.24 Solid-state photochemical decarbonylation model for ketones The dashed path corresponds to the experimentally determined energies of acetone (in kcal/mol).128 The effects of substituents with radical stabilizing energies (RSEs) are illustrated by the solid line in the reaction coordinate Ph Ph Ph Ph OH hν OH Ph Ph OH OH O OH 52 hν 51 Scheme 7.14 bond rotation OH 53 5′ HO C5′ O C4′ O O B O C1′ C3′ – HO B C2′ O O – O P O O O B 3′ HO DNA Backbone B=DNA Base OH P O O B HO OH RNA Backbone Major Groove Major Groove CH3 H N N R O H N N3 N H R 1N O N N N R H N N3 N H R 1N O H N N H O A-T G-C Minor Groove Minor Groove R=DNA Backbone Figure 8.1 H Figure 9.3 Cartoon of a “classic” double cone conical intersection, showing the excited state reaction path and two ground state reaction paths Energy R* X3 X2 X1 P R Figure 9.9 A cartoon showing the conical intersection hyperline traced out by a degeneracypreserving coordinate X3 The system remains degenerate as one traverses the coordinate X3, but the energy and the shape of the double-cone must change in X1 X2 Figure 9.10 The conical intersection hyperline traced out by a coordinate X3 plotted in a space containing the coordinate X3 and one coordinate from the degeneracy-lifting space X1 X2 Figure 9.22 The geometries in Figure 9.21 located in the cone which changes shape along the conical intersection hyperline (adapted from reference 14) ...REVIEWS OF REACTIVE INTERMEDIATE CHEMISTRY REVIEWS OF REACTIVE INTERMEDIATE CHEMISTRY Edited by Matthew S Platz Department of Chemistry Ohio State University Columbus, OH Robert A Moss Department of. .. breadth of Reactive Intermediate Chemistry, assists chemists to appreciate the state of the art and encourages new research in this area MATTHEW S PLATZ ROBERT A MOSS MAITLAND JONES, JR vii CONTRIBUTORS... 23 24 24 26 36 Reviews of Reactive Intermediate Chemistry Edited by Matthew S Platz, Robert A Moss, Maitland Jones, Jr Copyright © 2007 John Wiley & Sons, Inc TETRAHEDRAL INTERMEDIATES DERIVED