Reactive Intermediate Chemistry

1032 INDEX

Fluorine, singlet carbenes, addition reaction rate constants and activation, 286–289

Fluorine atoms, reactive intermediate generation, reagent cocondensation, 813

Fluorocyclopropyl radicals, carbon atom reactions, 477–479

2-Fluoroenylnitrenium ion, DNA damaging mechanisms, 641–644

Fluoroenyllidene, tunneling reactions, elevated temperatures, 422

Fluoromethylidene, carbon-alkene reactions, 477–479

o-Fluorophenylnitrene

azirine cyclization, 534–536 singlet ground states, 536–538

r-Fluorophenylnitrene, singlet ground states, 537–538

Fluoro-substituted phenylnitrenes, singlet ground states, 536–538

Fock operator, wave function calculations density functional theory (DFT), 978 Hartree-Fock calculations, 969–970

Formaldehyde

carbohydrate formation, 472

carbon atom deoxygenation, 490–492 Formylalkyl radical intermediate, femtosecond

time scale, 917 Formyl radical, structure, 123 Fourier transform (FT)

EPR spectroscopy, high-spin polycarbenes, 452

picosecond systems, Raman spectroscopy, 881–882

Fragmentations alkoxycarbenes, 317–319 heterolytic radicals, 153–155 homolytic radicals, 151–153

organic radical ions, cation reactive intermediates, 236

Franck-Condon transition femtosecond time scale

cyclobutanone photolysis, 914 Norrish I intermediate, 913–914 trimethylenemethane (TMM), electron

photodetachment photoelectron spectroscopy, 179

Franklin group equivalents, strain energy calculations, 722

Free carbenes, carbon atom deoxygenation, carbonyl compounds and formation of, 491–492

Free energy barrier, singlet carbenes, addition rate constants and activation parameters, 288–289

Free energy predictions

electronic structure calculations, 966

triplet carbenes, surface-crossing mechanism, 401

Free germylenes, electronic spectra, 664–665 Free radical ions (FRI), organic radical ion

intermediates, 235–236

Free radical reactions, strained hydrocarbons, 733

Free silylene

electronic spectra, 663–665 metal-induced a-elimination reactions,

658–660

Freon, radical ions, matrix isolation, 821–823 Friedel-Crafts reaction, carbocation reactivity, nucleophilic additions, 27–28

Frontier molecular orbitals 2-methylenecyclopentane,1,3-diyls, 180 singlet carbenes, philicity addition reaction,

280–285 Fullerenes

carbon arc generation, 467

silylene multiple bond addition, 679–680 Full-valence Kekule´ isomers

Hund’s rule, 167–168 2-methylenecyclopentane,1,3-diyls, 180–181

Functionals, wave function calculations, 978–979 Furans, carbon atom reactivity with, 485–486

G2 model chemistry, strain energy calculations, 719–721

g-proton hyperfine coupling, radical compound identification, electron spin resonance (ESR), 130–131

Gap tuning, heterocyclic planar tetramethyleneethane (TME) derivatives, 188–191

Gas phase photodetachment photoelectron spectroscopy (PES)

tetramethyleneethane (TME), singlet-triplet separation, 183–185

trimethylene-methane (TMM), singlet-triplet separation, 178–179

Gas phase reaction

carbanion intermediates, 108–111 bimolecular (SN2) reactions, 108–110 nucleophilic additions, alkenes, 103 nucleophilic substitution

acyl compounds, 110–111 aromatic substitution, 104

Wittig rearrangements, 106

carbon acidity-carbanion basicity, 78–79 condensed-phase measurements

comparisons, 93–94 DMSO acidity, 89–90

hybridized C–H bonds sp2/sp carbanions, 86–87 sp3 carbanions, 79–86

organic radical ions, bifunctional/distonic radical ions, 231–234

phenylcarbene rearrangement, incarcerated carbene chemistry, 315–317

Gas phase spectroscopy, imidogen, 507 Gaussian-2/Gaussian-3 (G2/G3) methods, electron

correlation, 976 Gaussian basis sets

electronic structure calculation, LCAO/MO approximation, 972–973

wave function vs. DFT calculations, 979–981

Gaussian functions, electronic structure calculation, 963

Geometric structure carbanions, 71–72

electronic structure calculations, 964–965 triplet carbenes

annealing, zero-field splitting, 390 excited states, 437–438 isomerism, zero-field splitting,

388–389 1-Germaallene, 695–696

Germacyclopentane, germylene multiple bond addition, 679–680

Germanium chalcogen double-bond species, 693–694

Germanium-germanium bonds diarylgermylene synthesis, 693–694 overcrowded diarylsilylenes, 687–689

Germanone, 695–696 7-Germanobornadienes

electronic spectra, 664–665 thermal elimination, 653–654

Germanyl radicals, homolytic halogen/chalcogen transfer, 147–148

Germirenes, silylene multiple bond addition, 675–677

Germylenes

electronic spectra, 662–665 multiple bond insertion reactions

acetylenes, 675–677 carbonyl/thiocarbonyl compounds,

680–683

olefins, dienes, and related compounds, 677–680

singlet and triplet states, 660–662 stable structures

INDEX 1033

dialkylgermylene synthesis, 691–692 diarylgermylene synthesis, 692–694 kinetic stabilization reactions, 695–696 triplet diphenylcarbene protection, 441–444

g factor, electron spin resonance (ESR), radical compound identification, 128–131

Gibbs free energy, aliphatic nucleophilic substitution, tertiary carbons, solvation reactions, 63–65

Glyceraldehyde, carbon atom reactions, 472 Glycine, carbon atom reactions, 471–472 Gomberg’s monoradicals

Schlenk-Brauns hydrocarbons, 167 stability and persistence, 125–126 Gordy-Morehouse equation, non-Kekule´

molecules, triplet/radical pair distinction, 173

Graphite vaporization, carbon atom generation, 466–468

Grignard reagent, carbanion chemistry, 70–71

Ground-state reactions

carbocation laser flash photolysis (LFP), 21 cyclopentane-1,3-diyls, calculation and

experiments, 996–997 non-Kekule´ molecules, 170 singlet carbenes, 278–279

intramolecular reactions, 306

triplet carbene multiplicity, 377, 383–384 Group-transfer reactions

organic radical ions, intra-pair reactions, 239–246

radical composites, 155–156

Guanine bases, nitrenium ions, DNA damaging reactions, 609–611

Guanosine nucleosides, nitrenium ions, DNA damaging mechanisms, 641–644

Guoy balance technique, non-Kekule´ molecule Hund’s rule, 167–168

magnetic properties, 191–192

Halocarbon matrices, organic radical ions, unimolecular reactions, 238–239

Halogens

persistent triplet carbene protection, 444–447

radical propagation, homolytic transfer, 146–148

Halogermylenes, metal-induced a-elimination reactions, 659–660

Halomethylidenes, carbon atom reactivity, carbon–hydrogen bonds and formation of, 477–479

1034 INDEX

Halonitrenium ions, electronic configuration, 603–606

Hamiltonian matrix, electron correlation, configuration interaction (CI), 974

Hamiltonian operator

electronic structure calculations, 967 wave-function based calculations, 968

Hammett equation

carbon acidity-carbanion basicity, sp3 carbanions, hybridized C–H bonds, 80–86

nitrenium ions, 600

singlet carbenes, carbon–hydrogen insertions, 299–302

Hammett ring, nucleophilic substitution, 1- phenylethyl derivatives (X-1-Y), 44–47

Hammond postulate, carbenes, stepwise vs. concerted addition, 291–297

Hartree-Fock calculations electron correlation, 973–974 reference configurations, 977 stable ion chemistry, 5–6

tetramethyleneethane (TME), 184–185 wave function calculations, 969–970

Heat capacity corrections, electronic structure calculations, enthalpy predictions, 966 Heat of formation, strain energy calculations,

718–721

Heats of atomization, strain energy calculations, 720–721

Heavy atom effect nitrenium ions, 602–603 phenylnitrene, 532–533 phenylphosphinidines, 551

Heck coupling, N-heterocyclic carbenes (NHC), transition metal catalysis, 364–365 Heller-McConnell equation, radical compound

identification, electron spin resonance (ESR), 130–131

Helmet-like bidentate ligands, stable dialkylgermylene, 691–692

Hemicarcerand, o-benzynes, 745–747 Heptafulvene, phenylcarbene rearrangement,

incarcerated carbene chemistry, 316–317 1,2,6-Heptatriene rearrangement, potential energy

surfaces (PES), reactive intermediate dynamics, 952–953

Hetarynes, 773–782 Heteroaromatic compounds

alkenes, double bond additions, 433–434 carbon atom reactivity with, 479–486

Heteroarylnitrenium ions computational studies, 606–611 DNA damaging mechanism, 643–644

singlet-state reactions, N nucleophile additions, 623–624

Heteroatomic radicals addition reactions, 150–151

organic radical ions, bimolecular reactions, 247–250

stable singlet carbenes p-electron-donating-electron-withdrawing

heteroatom substituent (D-C-W), 335–338

single electronically active substituents, 340–347

Heteroatom-substituted germene, 695–696 Heterocumulenes, matrix isolation, 831–832 Heterocyclic arynes, 773–782

Heterocyclic planar tetramethyleneethane (TME) derivatives, biradical analysis, 188–191

Heterocyclobutadienes, stable singlet carbenes, cyclopropanation, 353–354

N-Heterocyclic carbenes (NHC), transition metal catalysis, 358–365

catalytic properties, 362–365 electronic structure, 359–362

Heterogeneous catalysis, N-heterocyclic carbenes (NHC), transition metal catalysts, 365

Heteroleptic plumbylene, 701–705 Heterolysis, picosecond spectroscopy, p bonds,

892–894 Heterolytic radicals

addition reactions, 153

alkoxycarbene fragmentation, 317–319 fragmentation, 153–155

1,5-Hexadiene systems, organic radical ions, 228–229

Hexafluoroisopropanol (HFIP)

aliphatic nucleophilic substitution, tertiary carbons, solvation reactions, 63–65

carbocation lifetimes, 21–23 carbocation reactivity, 19–21

carbocation reactivity, nucleophilic additions, 26–28

photoprotonation, 19–21 silyl cations, 31–32

Hexamethylsilirane, thermal elimination, 653–654 1,3(Z),5-Hexatriene, femtosecond time scale,

structural determinations, 919–920

(Z)-3-hexene-1,5-diyne, femtosecond time scale, 910–911

Highest occupied molecular (HOMO) organic radical ions

detection-observation, 211–214 n donors, 218

p donors, 215–218

strained ring cations, 221–228 structural analysis, 214–215

silylenes and germylenes, singlet and triplet states, 661–662

singlet carbenes, philicity in addition reaction, 280–285

stable singlet carbenes, cyclopropanation, 352–354

tetramethylenebenzene (TMB), 187 High-spin polycarbenes

persistent triplet carbene structure, 449–452 triplet polynuclear aromatic carbenes,

450–452

Hoffman b-elimination, triplet carbenes, chemically induced dynamic nuclear polarization (CIDNP) effects, 408

Hoffman rearrangement, acylnitrenes, 511–512

Hohenberg-Kohn theorem, wave function calculations, 978

Homoallylic cations, nonclassical structures, 11–12

Homo-chrysanthemol, organic radical ions, protic, ionic, and polar solvents, 256

Homocubylidenes, carbon mimics, 312–314 Homolytic reactions

alkoxycarbene fragmentation, 317–319 elementary radicals, 140–142

picosecond spectroscopy, p bonds, 892–894 radical atomand group-transfer reactions,

145–148 radical structures

addition reactions, 149–151 fragmentation, 151–153 halogen/chalcogen transfer, 146–148 hydrogen atoms, 145–146

‘‘Hot atom chemistry,’’ carbon atoms, 464 Hu¨ckel calculations, stable singlet carbenes, cyclopropanation, 353–354

Hund’s rule

non-Kekule´ molecules

electron spin resonance (ESR), 168–170 historical background, 167–168

singlet carbenes, structure and bonding, 276–279

wave function calculations, 968

Hybridized C–H bonds, carbon acidity-carbanion basicity

sp2/sp carbanions, 86–87 sp3 carbanions, 79–86

Hybrid orbitals, radical configuration, 122 Hydrazoic acid, imidogen, 506

matrix isolation spectroscopy, 507

INDEX 1035

Hydrides nitrenium ions

singlet-state reactions with donors, 628 singlet-state rearrangement/elimination,

619–621

radical reactions, homolytic hydrogen atom transfer, 145–146

Hydride shifts, singlet carbenes, intramolecular insertion reactions, 303–306

Hydrocarbon structures carbocation reactivity, 36

organic radical ions, bifunctional/distonic radical ions, 231–234

singlet carbenes, intramolecular insertion reaction, 305–306

stability-reactivity, 729–732 dimerization, 731–732 thermal reactivity, 730–731

strained hydrocarbon structures angle deformation, 724–725

inverted tetrahedral geometries, 725–726 reactivity

cycloaddition reactions, 733 cyclopropanes, electrophilic cyclobutanes,

733–735

electronic spectra, 736 free radical reactions, 733 NMR spectra, 736

transition metal carbon-carbon bond cleavage, 735–736

vibrational spectra, 737 steric strain, 726–727 torsional strain, 726

twisted double bonds, 727–729

triplet carbenes, product studies, 402–405 Hydrogen atom abstraction

cubyl cations, 987–988

diphenylcarbenes, laser flash photolysis, 409 triplet carbenes, 402–422

chemically induced dynamic nuclear polarization, 406–408

laser flash potolysis, 408–413 product studies, 402–405 tunneling reactions, 413–422

atomic transfer kinetics, 416–417 intramolecular reactions, 419–421 pathway determination, 417–419 product studies, 413–416 temperature elevations, 421–422

Hydrogen atom transfer diphenylcarbenes, laser flash photolysis,

409–410

triplet-state nitrenium ions, 629–631

1036 INDEX

Hydrogen bonding, carbon acidity-carbanion basicity, condensed-phase measurements, ion-pair acidity, 92–93

Hydrogen chloride abstraction, single bond silylene insertions, 669–671

Hydrogen/deuterium (H/D) exchange

carbanion stereochemistry and racemization, 74 elimination reactions, carbanion intermediates,

99–101

Hydrogen migration, triplet carbenes, hydrogen atom tunneling, 414–416

Hydrogen molecules, femtosecond time scale, 902

Hydrogen nuclear magnetic resonance (1H NMR)

carbanions, 75–76

carbocation skeletal rearrangements, 8–9 2-norbornyl cation, 11–12

stable ion chemistry, 5–6

triplet carbenes, dimesitylketone oxide, 426 1,2-Hydrogen shift

carbocations, skeletal rearrangement, 8–9 nitrenium ioins, hydrogen atom transfer,

629–631

singlet carbenes, intramolecular reactions, 303–306

trimethysilyl groups, cyclopropane stereomutation, 994–995

1,4-Hydrogen shift, triplet diphenylcation protection, 443–444

Hydrogen structures

carbon atom reactivity, inorganic substrates, 471 organic radical ions

bifunctional/distonic radical ions, 230–234 intra-pair reactions, 243–246

radical reactions, homolytic atomic transfer, 145–146

triplet carbenes, 402–422

chemically induced dynamic nuclear polarization, 406–408

laser flash potolysis, 408–413 product studies, 402–405 tunneling reactions, 413–422

atomic transfer kinetics, 416–417 intramolecular reactions, 419–421 pathway determination, 417–419 product studies, 413–416 temperature elevations, 421–422

N-Hydroxyaniline, nitrenium ion singlet-state reactions, p nucleophiles, 624–628

Hydroxycarbenes, carbohydrate formation, 472 Hydroxylamine esters, nitrenium ion generation, photochemical initiation, 617–618

N-Hydroxylamines, nitrenium ion generation, 611–614

DNA damaging mechanisms, 641–644 Hydroxymethyl radical, structure, 123 Hyperconjugation reactions

cubyl cation formation, 986–987 cyclopentane-1,3-diyl ground state calculations,

997

cyclopropane stereochemistry, 989–997 1,1-difluorocyclopropane stereochemistry,

992–994

1,2-dimethylspiropentanes stereomutation, 995–996

1,1-disilylcyclopropane stereomutation calculations, 994–995

isotopic perturbation, 12–13

singlet carbenes, carbon–hydrogen insertions, 300–302

tetramethyleenethane, 185 triplet carbenes, 380–381 X-ray crystallography, 14–15

Hyperfine coupling

organic radical ions, p donors, 217–218 radical identification/characterization

electron nuclear double resonance (ENDOR) spectroscopy, 131–132

electron spin resonance (ESR), 128–131 Hyperfine interaction, organic radical ion

resonance, 212–214 Hyperfine splitting

non-Kekule´ molecules, ESR zero-field splitting, 172–173

trimethylene-methane (TMM), electron spin resonance (ESR), 174–175

Hypersurface typology, potential energy surfaces (PES), 926

‘‘Hyperthermal nozzle,’’ matrix isolation, 818 H-ZSM-5 zeolite, radical ion generation,

209–211

IF2C–CF2, femtosecond time scale, structural determinations, 919–920

IF2C–CF2I, femtosecond time scale, structural determinations, 919–920

Imidazol-2-ylidenes, stable singlet carbenes Lewis acids and bases reactions,

355–358

p-electron-donating heteroatom substituents (D-C-D), 338–340

transition metal catalysts, 362–365 Imidogen (NH)

gas-phase spectroscopy, 506 matrix isolation spectroscopy, 507

nitrenium ion classification, 594 phenylnitrene, 525–528 structural properties, 502–506 vinylnitrene structures, 521–522

‘‘Imidonium ions.’’ See Nitrenium ions Iminium salt, stable singlet carbenes, single

electronically active heteroatomic substituents, 342–347

Immobilization techniques, non-Kekule´ molecules, singlet-triplet separation, 171

Immobilizing media, electron spin resonance (ESR), zero-field splitting, 172–173

In-cage recombination, triplet carbenes, chemically induced dynamic nuclear polarization (CIDNP) effects, 407

Incarcerated carbenes, phenylcarbene rearrangement, 314–317

Indene, carbon-alkene reactions, 474–475, 477 Independent-particle model, wave function

calculations, 969

Indirect kinetic studies, radical identification/ characterization, 127–128

Inert free radicals, triplet diphenylcation protection, 444

Infrared absorption spectroscopy, picosecond lasers, 883–885

>1500-cm 1 region, 883–884 fingerprint region, 884–885

Infrared (IR) spectroscopy

electronic structure calculations, 964 matrix isolated compounds, 830–836 nitrenium ions, 636–638

radical identification/characterization, 133–134

stable ion chemistry, 6–8 triplet carbenes

matrix isolation, 391–392 oxygen reactions, 423–425

Initiation mechanisms, radical reactions chain reactions, 134–136 closed-shell compounds, 140–143

electron transfer, 143 photolysis, 142–143 thermolysis, 140–142

Inlet systems, matrix isolation apparatus, 807–809

Inner-sphere reduction pathway, nitrenium ion singlet-state reactions, 622–624

Inorganic substrates, carbon atom reactivity, 471 amino acid precursors, ammonia reactions,

471–472

carbohydrate formation, water reactions, 472–473

INDEX 1037

Inosine, nitrenium ions, DNA damaging mechanisms, 641–644

Insertion reactions

carbene synthesis, dirhodium(II) catalysts, 575–577

carbon atom reactions, carbon–hydrogen bond insertion, 486

carbon–hydrogen bonds, singlet carbenes, 298–306

intermolecular insertion, 298–302 intramolecular insertion/rearrangement,

302–306

metal nitrenes, organic synthesis, 585–586 silylenes and germylenes

multiple bond insertion reactions acetylenes, 675–677 carbonyl/thiocarbonyl compounds,

680–683

olefins, dienes, and related compounds, 677–680

single bond insertions, 668–675 C-O and Si-O bonds, 671–673

oxygen-hydrogen, nitrogen-hydrogen, and carbon-halogen bonds, 669–671

Si-H and Si-Si bonds, 673–675 stable diarylgermylenes, 692–694

triplet carbenes, hydrogen abstraction, product studies, 403–405

In situ generation, reactive intermediates, 814–815

Interconversion rate constant silylenes isomerization, 666–668

triplet carbenes, singlet-triplet energy gap, solvent effects, 402

Intermediate neglect of differential overlapconfiguration interaction (INDO-CI) calculations

matrix isolation, 837–838

m-quinone derivative connectivity, 187–188 Intermolecular reactions, singlet carbenes

carbene mimics, 314 carbon–hydrogen insertions, 298–302 philicity addition, 283–285

Intermolecular vibrational relaxation, picosecond spectroscopy, p bond homolysis/ heterolysis, 892–894

Internal return, carbon acidity-carbanion basicity, 78

Interradical distance, non-Kekule´ molecules, 173 Interstellar molecules, carbon atom reactions, 473 Intersystem crossing (ISC)

acylnitrenes/carbonylnitrenes, 513–515 alkylnitrenes, 509–511

1038 INDEX

Intersystem crossing (ISC) (Continued) arylnitrenes, 516–517

carbon atom reactivity, benzene/substituted benzenes, 482–484

imidogen, matrix isolation spectroscopy, 507 nitrenium ions, 631

organic radical ions, intra-pair reactions, 241–246

phenylnitrene, 531–532 ortho-/meta-substituted derivatives, 533–534 para-substituted derivatives, 532–533

phosphorylnitrene, 519–520

radical structures, chemically induced dynamic nuclear polarization (CIDNP) effects, 132–133

singlet carbenes, stepwise vs. concerted addition, 291–297

triplet carbenes

hydrogen atom transfer kinetics, 416–417 hydrogen atom tunneling, 414–416 intramolecular tunneling reactions, 420–421 reaction mechanisms, 384

Intramolecular reactions addition-elimination reactions, 156 organic radical ions

nucleophilic capture, 255–256 unimolecular bond formation, 237–239

radical propagation, 147–148 homolytic additions, 149–151

singlet carbenes, insertion reactions, 302–306 carbene mimics, 313–314

singlet-triplet equilibration, 307–308 stable diarylgermylenes, 692–694 triplet carbenes

double bond additions, 434 hydrogen tunneling, 419–421

Intramolecular vibrational energy redistribution (IVR)

femtosecond time scale, 902

potential energy surfaces (PES), statistical approximations, 940–941

Intra-pair reactions, organic radical ions, 239–246

Intrinsic reaction coordinate (IRC), potential energy surfaces (PES)

2,3-diazabicyclo[2.2.1]hept-2-ene, 954–955 transition states and bifurcations, 932–934 Inversion reactions, metal-induced a-elimination

reactions, 659–660

Inverted tetrahedral geometries, strained hydrocarbons, 725–726

Invisible carbenes

laser flash photolysis, 409

TRIR UV-vis (TRUV-Vis) spectroscopy, 393–394

Iodonium ylides, metal carbene synthesis, 567 Ion cyclotron resonance (ICR), carbanion

intermediates, gas phase reactions, bimolecular nucleophilic substitution (SN2), 108–110

Ionic reagents, organic radical ions, bimolecular reactions, 250–256

Ionization, reactive intermediates, 814 Ionization potentials (IP)

singlet carbenes, philicity addition, 283–285 triplet carbenes, excited state spectroscopy,

436–437

Ion pairing, alkoxycarbene fragmentation, 319 Ion-pairing, carbon acidity-carbanion basicity, 77

condensed-phase measurements, 87–88, 90–93 (i-Pr3Si)3SiH, photochemical irradiation,

657–658

Iridium(I) complex, stable singlet carbenes, transition metal catalysis, 363–365

Isocarbazoles, biphenylnitrenes, 543–544 Isocyanates

acylnitrenes, 512 carbonylnitrenes, 514–515

singlet carbenes, philicity of addition, 284–285 Isodesmic reactions

strain energy calculations, 721 triplet carbenes, 382–383

Isomerism

organic radical ions

intra-pair reactions, 241–246 unimolecular reactions, 237–239

silylenes, 665–668

triplet carbenes, zero-field splitting, 388–389 Isonitriles, overcrowded diarylsilenes, 689 Isopentenyl disphosphate:dimethylallyl

diphosphate isomerase, carbocation reactivity, 34–35

Isoprene pathway

carbocation biosynthesis, 34–35 silylene-isonitrile complexes, 690–691

Isopropyl cation, stable ion chemistry, 6 2-Isopropylidenecyclopentane-1,3-diyl

electron spin resonance (ESR), 179–181 non-Kekule´ molecules, structural properties and

spectroscopic analysis, 171 Isothiocyanates, kinetically stabilized germylenes,

695–696 Isotope effects

benzene-carbon atom reactivity, 483–484 carbanion intermediate elimination reaction,

99–101

carbon atom reactivity, 487–488 electronic structure calculations, 966 femtosecond time scale, 922

singlet carbenes, transition state symmetry, 289–291

Isotope exchange

carbanion basicity-carbon acidity, 77–78 condensed-phase reactions, 95–96

carbanion intermediate elimination reaction, 99–101

Isotope labeling, triplet carbene oxygen reactions, matrix isolation studies, 424–425

Isotopic perturbation of resonance/equilibrium, carbocation symmetry, 12–13

Isotopic tracers, 2-norbornyl cation, 10–12

Jahn-Teller (JT) distortion femtosecond time scale, structural

determinations, 919–920 organic radical ions

s donors, 219–221

strained ring cations, 223–228

Kasha’s rule, diphenylacetylene (DPA), picosecond spectroscopy, 890–891

Ketenes, matrix isolation, 829–830 Ketenimine

biphenylnitrenes, 544

nanosecond time-resolved infrared (TRIR) spectroscopy, 551–552

naphthylnitrenes, 541–543 phenylnitrene, 523–525

azirine cyclization, 534–536 computational chemistry, 527–528 laser flash photolysis (LFP), 528–529 singlet dynamics, 530–531

Ketones

non-Kekule´ molecules, electron spin resonance (ESR), 168

triplet carbenes, oxygen reactions, 424–425

a,b-unsaturated ketone radical anion, intra-pair reactions, 243–246

Ketyl anions, organic radical ions, like charge reactions, 259–261

Kinetic acidity measurements, carbon aciditycarbanion basicity, 77–78

condensed-phase measurements, 94–96 sp3 carbanions, hybridized C–H bonds,

79–86

Kinetic analysis, triplet carbenes, TRIR UV-vis (TRUV-Vis) spectroscopy, 393

INDEX 1039

Kinetic energy

organic radical ions, time resolved spectroscopy, 261

persistent triplet carbenes, 439–441 radical structures

absorption spectroscopy, 133–134 indirect determination, 127–128

singlet carbene-alkene addition, rate constants and activation parameters, 286–289

trimethylenemethane (TMM), electron photodetachment photoelectron spectroscopy, 177–178

Kinetic isotope effects

electronic structure calculations, 966 singlet carbenes

addition, transition state symmetry, 290–291

carbon–hydrogen insertions, 299–302 intermolecular insertion reactions, 301–302 intramolecular reactions, 303–306

triplet carbenes

hydrogen abstraction, product studies, 404–405

laser flash photolysis, 410–413

tunneling reactions, elevated temperatures, 421–422

Kinetic stabilization

persistent triplet carbenes, 439–441 triplet diphenylcation protection, 443–444

Kinetic studies, nanosecond laser flash photolysis, 853–858

second-order processes, 869

Kohn-Sham theorem, wave function calculations, 978

Koopman’s theorem, wave function calculations, Hartree-Fock calculations, 969–970

Labeling experiments, silylene isomerization, 667–668

Lamp irradiation, excited state, 435 Lapis lapzuli, radical anions, 206–207

Laser apparatus, nanosecond laser flash photolysis, 850–852

Laser evaporation, carbon atom generation graphite vaporization, 468

molecular beams, 470, 493–494 Laser flash photolysis (LFP)

alkoxycarbene fragmentation, 318–319 p-benzyne, 756–759

biphenylnitrenes, 543–544 carbocation generation, 18–21 carbocation reactivity

azide clock, 18

1040 INDEX

Laser flash photolysis (LFP) (Continued) nucleophilic addition, 25–28

electronic structure calculations, 964 imidogen, 506

nucleophilic substitution, 1-phenylethyl derivatives (X-1-Y), 46–47

phenylnitrene, 528–529 silyl cations, 31–32 singlet carbenes

addition rates and activation parameters, 285–289

carbene mimics, 308–314

intermolecular insertion reactions, 301–302 intramolecular insertion reactions, 302–306 singlet-triplet equilibration, 307–308

singlet-triplet equilibrations, 307–308 triplet carbenes

alkyl-protected triplet diphenylcarbenes, 443–444

excited states, 435–437 halogen-protected diphenylcarbenes,

444–447

hydrogen abstraction, 408–413 atomic transfer kinetics, 417

oxygen reactions, 427–429 singlet-triplet energy gap, preequilibrium

mechanism, 395–400 time-resolved spectroscopy, 392–394

time-resolved ultraviolet-vis (TRUV-Vis), 393–394

zeolite carbocations, 32–33 Laser-induced fluorescence

femtosecond time-resolved experiments retro-Diels-Alder reactions, 918 sodium iodide, 907

Laser power, triplet carbene excited state, 435 ‘‘Least-notion’’ symmetry, singlet carbenes,

289–291 Leaving groups

carbocation generation, laser flash photolysis (LFP), 19–21

heterolytic radical fragmentations, 153–155 nucleophilic additions, carbanion intermediates,

alkenes, 102–103 silyl cations, 32

Leveling effect, carbon acidity-carbanion basicity, 76

Lewis acids and bases

silylenes and germylenes, electronic spectra, 663–665

stable singlet carbenes, reaction mechanisms, 354–358

Lewis structures, nonclassical carbocations, 9–12

Liberated reaction intermediates, nucleophilic substitution, stepwise ionization and trapping, 50

Lifetime parameters

aliphatic nucleophilic substitution, tertiary carbons, 61–62

cyclopentane-1,3-diyl ground state calculations, 997

nitrenium ions, spectroscopic analysis, 631–640 nucleophilic substitution, 1-phenylethyl

derivatives, 45–47 trifluoromethyl-protected diphenylcarbenes,

447–448

triplet carbenes, excited states, 436–437 Like charge radical ions, organic radical ion

reactions, 259–261 Lindemann-Hinshelwood model, potential energy

surfaces (PES), 941–942

Linear combinations of atomic orbitals-molecular orbital (LCAO/MO) approximation, electronic structure calculations, 971–973

Linear free energy, singlet carbene philicity, 282–285

Lithium naphthalenide, cyclotrisilane photolysis and thermolysis, 656–657

Lithium salts, aggregation, 75–76

Living radical polymerization, nonchain radical reaction sequence, 140

Local density approximation, matrix isolation, infrared spectroscopy, 833–836

Lone pair electrons, carbon atom reactivity, 493 Long-lived (persistent) spin isomerism, non-

Kekule´ molecules, 189–191 Long-range interaction

1,1-difluorocyclopropane, 993–994

1,2-dimethylspiropentanes stereomutation, 996 diradical energy calculations, 998 1,1-disilylcyclopropane stereomutation

calculations, 994–995 Lossen rearrangement

acylnitrenes, 511 nitrenes, 502

Low-activation parameters, hydrogen atom transfer kinetics, 417

Low-energy electron diffraction (LEED), o-benzynes, 747

Lowest unoccupied molecular orbital (LUMO) cubyl cation formation, 986–987

organic radical ions detection-observation, 211–214

protic, ionic, and polar solvents, 253–256 strained ring cations, 221–228

structural analysis, 214–215

radical configuration, 122–123

silylenes and germylenes, singlet and triplet states, 661–662

singlet carbenes, philicity addition reaction, 280–285

stable singlet carbenes, cyclopropanation, 352–354

tetramethylenebenzene (TMB), 187 triplet carbenes, singlet-triplet energy gap,

preequilibrium mechanism, 399–400 Low-temperature matrices

carbon atom generation, cyanogen azide photolysis, 468

matrix isolation, 798

silylene multiple bond additions, 681–683 Low-temperature spectroscopy. See Matrix

isolation spectroscopy

Magnetic dipole interactions, triplet carbenes, EPR spectroscopy, 385–386

Magnetic field effects, intra-pair reactions, 239

Magnetic measurements, triplet polynuclear aromatic carbenes, 450–452

Magnetic properties, carbanions, 75–76 Magnetic susceptibility measurements non-Kekule´ molecules, 191–192

Hund’s rule, 167–168

organic radical ions, like charge reactions, 259–261

pentamethylenepropane (PMP), 193–194 Manganese(III) acetate, radical closed-shell structures, electron transfer, 143–144

Many-electron wave functions, electronic structure calculations, 967, 968

‘‘Masked’’ diborylcarbenes, stable singlet carbenes, singlet vs. triplet ground state, 332

Masked silylenes, 689–691

Mass selected ion beams, radical ions, matrix isolation, 821–823

Mass spectrometry (MS)

carbon acidity-carbanion basicity, 78–79 organic radical ions, bifunctional/distonic

radical ions, 232–234 radical ion detection-observation,

211–214

Matrix deposition, stable ion chemistry, 6 Matrix isolation

applications, 799–801 benzadiynes, 783–784

o-benzynes, parent structure, 743–747 p-benzynes

INDEX 1041

parent structure, 756–759 substituent effects, 762–764

defined, 798 dimesitylsilylenes, 663–665

electronic structure calculations, 964 hetarynes, 775–782

imidogen, 507 limitations, 801–802 meta-benzynes

parent structure, 748–752 substituent effects, 761–762

naphthynes, 766–769

non-Kekule´ molecules, electron spin resonance (ESR)

biradical/radical pairing, 173

Curie’s law, ground-state multiplicity, 174 2,4-dimethylenecyclobutane diyl, 170 matrices, 172–174

randomly oriented samples, 168–170 structural properties, 171

zero-field splitting, immobilizing media, 172–173

reactive intermediate generation bent triple bonds, 825 biradicals, 818–820 carbenes, nitrenes, 815–816 closed-shell ions, 823–824 cyclobutadiene, 826–827

dehydrohalogenations, 825–826 low-temperature studies, 812

external generation, 812–813 reagent cocondensation, 813 in situ generation, 814–815

probing techniques, 827–838 infrared spectroscopy, 830–836

ultraviolet-visible spectroscopy, 836–838 radical ions, 820–823

radicals, 816–818

techniques and equipment, 802–811 cryostat apparatus, 803–804 inlet systems, 807–809

sample holders, spectroscopic windows, 804–806

sample preparation lines, 809 spectrometers, 811

trolleys, 810

vacuum equipment, 809–810 triplet carbenes, 385–392

electron paramagnetic resonance (EPR), 385–390

fluorescence, 391

hydrogen atom tunneling, 414–416 infrared spectroscopy, 391–392