Reactive Intermediate Chemistry

1052 INDEX

p-conjugated systems (Continued) triplet carbenes

electron paramagnetic resonance spectroscopy, 385–390

EPR, zero-field splitting, 391 p-donor electrons

cubyl cation formation, 986–987 organic radical ions, 215–218

cation reactions, 234–261 bimolecular reactions, 246–261

alkenes and aromatics, 246–250 like-charge ions, 259–261

protic, ionic, polar reagents, 250–256 radical anions, 256–259

intra-pair reactions, 239–246 reactive intermediates, 234–236 unimolecular reactions, 236–239

radical configuration, 122 singlet carbenes

philicity addition reaction, 281–285 transition state symmetry, 289–291

stable singlet carbenes electron-donating-electron-withdrawing

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

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

transition metal catalysis, 359–362 tetramethylenebenzene (TMB), 186–187 triplet carbenes, electronic effects, 378–379

p-orbital systems, carbon acidity-carbanion basicity, sp3 carbanions, hybridized C–H bonds, 81–86

p-p* transitions, triplet carbene oxygen reactions, matrix isolation studies, 423–425

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

Pivaloylazide acylnitrenes, 511 future research, 552

Planar structures, p-donor, 122 Planck’s constant

femtosecond laser pulses, 905–906 organic radical ion resonance, 212–214

Plateau conformation, potential energy surfaces reactive intermediate dynamics, 947–949 stepwise vs. concerted reaction, 928–931 vinylcyclopropane rearrangement, 950

Platz technique, stable singlet carbenes, single electronically active heteroatomic substituents, 341–347

Plumbanethione, 702–705

Plumbylenes, synthesis and reactions, 699–705

Point spin model, triplet carbenes, isomerism, zero-field splitting, 388–389

Polarization function

cubyl cations, hydrogen abstraction, 988 LCAO-MO approximation, 972–973

Polarized NMR signals, triplet carbenes, chemically induced dynamic nuclear polarization (CIDNP) effects, 407–408

Polar reagents

carbocation reactivity, electron-withdrawing substituents, 29–30

organic radical ions, bimolecular reactions, 250–256

Polar transition state, singlet carbenes carbon–hydrogen insertions, 299–302 stepwise addition vs. concerted reaction,

295–297

Polyaniline, nitrenium ions, 598–599 electrochemical oxidation, 618–619

Polycyclic aromatic hydrocarbon (PAH) carcinogens, carbocation reactivity, 33

Polycyclic arylnitrenes biphenylnitrenes, 543–544 naphthylnitrenes, 540–543 structural characterization, 540–544

Poly(di-n-butylsilane), photolysis, 655–656 Poly(di-n-hexasilane), photolysis, 655–656 Polymerization reactions, chain reaction

sequence, 136

Polynitrenes, structural properties, 544–545 Polynuclear aromatic carbenes, triplet structure,

448–449

Polysilabicyclosilirenes, silylene multiple bond addition, 675–677

Polysilacyclooctynes, silylene multiple bond addition, 675–677

Polysilanes

dimethylsilylene generation, 654–655 linear compound photolysis, 655–656 thermolysis, 652–654

Polysubstituted methane derivatives, carbon acidity-carbanion basicity, sp3 carbanions, hybridized C–H bonds, 83–86

Pople, John, 963, 972, 978 p orbital electrons

radical configuration, 122

singlet carbenes, philicity addition reaction, 281–285

stable singlet carbenes, singlet vs. triplet ground state, 330–332

triplet carbenes

electron paramagnetic resonance spectroscopy, 385–390

hydrogen abstraction, product studies, 402–405

hyperconjugation effects, 380–381 preequilibrium mechanism, 399–400

triplet carbenes, electronic effects, 378–379 3p orbital, electronic spectra, silylenes and

germylenes, 663–665

Positron emission tomography (PET), carbon atom generation, 465–466

Potassium complexes, carbon atom generation, 470

Potential energy surfaces (PES)

electronic structure calculations, enthalpy predictions, 965–966

organic radical ions

intra-pair reactions, 240–246 strained ring cations, 221–228

reaction dynamics

acetone radical cation generation and dissociation, 950–952

bifurcations, transition states, 932–934 conical intersections, 934–937 2,3-diazabicyclo[2.2.1]hepta-2-ene thermal

deazetization, 953–955 1,2,6-heptatriene rearrangement, 952–953 hypersurface topology, 926

molecular dynamics principles, 943–947 nonstatistical dynamics, effects of, 955–956 reactive dynamics, potential energy profile,

947–949

RRKM theory, 941–942 statistical kinetic models, 937–943

phase space, 937–938

statistical approximation, 940–941 transition state hypothesis, 938–939

stepwise vs. concerted controversy, 926–931 symmetry parameters, 949–950

transition state theory, 942–943 variational transition state theory, 943 vinylcyclopropane rearrangement, 950

Powder spectra, electron spin resonance (ESR), 172

Poyl(diazo)compounds, triplet polynuclear aromatic carbenes, 451–452

Preassociation reactions, nucleophilic substitution at benzylic carbons, 51–52

Preequilibrium mechanism, triplet carbenes, singlet-triplet energy gap, 395–400

Preexponential factors

diphenylcarbenes, laser flash photolysis, 409–410

elevated temperatures, tunneling reactions, 421–422

INDEX 1053

Probe continuum, picosecond lasers, 877–878 Probe pulse, time-resolved femtosecond dynamics,

903–904

Probe technique, nanosecond laser flash photolysis, 858–864

Product studies

radical identification/characterization, 126–127

triplet carbenes

excited states, 434–435 hydrogen abstraction, 402–405

hydrogen atom tunneling, 413–416 oxygen reactions, 423

Propagation reactions, radical reactions, 143–157 chain reactions, 136

composite group-transfer, 155–156 heterolytic addition, 153 heterolytic fragmentation, 153–155 homolytic addition, 148–151

homolytic atomand group-transfer, 145–148 halogen/chalcogen transfer, 146–148 hydrogen atoms, 145–146

homolytic fragmentation, 151–153 Propanes, organic radical ions, s donors,

219–221

[1.1.1]Propellane

free radical reactions, 733

inverted tetrahedral geometries, 725–726 Propellanes, small ring structures, 729–730 Propylene, femtosecond time scale, trimethylene/

tetramethylene diradicals, 915–916 Propynes

carbon-alkene reactions, 474 carbon atom reactions, 493–494

Protic solvents

carbocation lifetimes, 21–23

organic radical ions, bimolecular reactions, 250–256

Protonated cyclopropane intermediates, 734–735

Protonation, matrix isolation, 824

Proton chemically induced dynamic nuclear polarization (1H CIDNP), single bond silylene insertions, 670–671

Proton-coupled electron transfer intra-pair reactions, 242–246

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

Proton hyperfine coupling, radical compound identification

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

electron spin resonance (ESR), 129–131

1054 INDEX

Proton NMR shift methods non-Kekule´ molecules, 197

singlet carbene addition, transition state symmetry, 290–291

Pseudo-first-order rate constant

singlet carbene-alkene addition, 285–289 triplet carbenes

hydrogen atom transfer kinetics, 416–417 laser flash photolysis, 409

oxygen reactions, 427–429

TRIR UV-vis (TRUV-Vis) spectroscopy, 394 Pseudo-halogens, radical structures, homolytic

group transfers, 146–148 Pseudorotations, femtosecond time scale,

structural determinations, 919–920

Pull inductive effect, stable singlet carbenes, single electronically active heteroatomic substituents, 341–347

Pulsed lasers, femtosecond time scale, 902 Pulsed pyrolysis, matrix isolation, 818 Pulse radiolysis, radical identification/

characterization, 133–134 Pump-probe-detect strategy

femtosecond time scale, trimethylene/ tetramethylene diradicals, 915–916

time-resolved femtosecond dynamics, 903–904 Pump-probe electronic absorption spectroscopy,

picosecond lasers, 875–880 Pump pulse

femtosecond time scale, structural determinations, 919–920

time-resolved femtosecond dynamics, 903–904 ‘‘Pure’’ test molecule, non-Kekule´ molecules, 195 Push-pull carbenes, single electronically active

heteroatomic substituents, 341–347 Push-push carbenes, stable singlet carbenes, single

electronically active heteroatomic substituents, 344–347

Pyramidal structure, s-radical, 122 Pyrenylnitrenes, 543 Pyridine-2-thioenoxycarbonyl (PTOC), radical

initiation photolysis, 142–143 thermolysis, 140–142

Pyridines

carbon atom reactivity, 484 nitrosobenzene deoxygenation, 492 singlet carbenes

carbene mimics, 308–314 intramolecular insertion reactions,

302–306

reaction rate constants and activation parameters, 287–289

triplet carbenes, laser flash photolysis, 429 Pyridine ylide, carbon mimics, 308–314 Pyridinium ylide, singlet carbenes, intramolecular

reactions, 303–306 Pyridylcarbene

computational chemistry, 527–528 interconversion, 538–540

Pyridynes, hetarynes, 773–782 Pyrolysis

o-benzynes, 743–747 p-benzynes, 756–759 hetarynes, 775–782 meta-benzyne, 747–752 naphthynes, 766–769

pulsed pyrolysis, matrix isolation, 818 Pyrroles, carbon atom reactivity, 484 Pyryidylcarbenes, nitrosobenzene deoxygenation,

492

Quadratic CI calculations, electron correlation, 976

Quadricyclane, organic radical ions bimolecular reactions, 251–252 strained ring cations, 225–228 unimolecular reactions, 239

Qualitative models, electronic structure calculations, 966–967

Quantitative theory, organic radical ion detectionidentification, 213–214

Quantum chemistry

heterocyclic planar tetramethyleneethane (TME) derivatives, 188–191

tetramethylenebenzene (TMB) singlet-triplet separation, 186–187

Quantum mechanical tunneling (QMT) singlet carbenes, intramolecular insertion

reactions, 304–306 triplet carbenes

hydrogen abstraction

intramolecular reactions, 419–421 laser flash photolysis (LFP),

410–413

tunneling pathways, 418–419 temperature elevation, 421–422

Quantum mechanics, Hund’s rule, 167–168 Quantum molecular dynamics calculations,

femtosecond time scale, methyl iodide, 908

Quantum yields, nanosecond laser flash photolysis, 865–868

Quenching rate triplet carbenes

laser flash photolysis, 427–429

singlet-triplet energy gap, preequilibrium mechanism, 395–400

triplet diphenylcation protection, 444 m-Quinodimethane (MQDM)

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

non-Kekule´ molecules, electron spin resonance (ESR), 169–170

m-Quinodimethane (MQM)

electron spin resonance (ESR), 169–170 molecular connectivity, 187–188

o-Quinodimethane (MQDM)

intramolecular tunneling reactions, 419–421 triplet diphenylcation protection, 443–444

Racemization

aliphatic nucleophilic substitution, tertiary carbons, 59–60

carbanions, 72–74 cis isomers, 994

2-norbornyl cation, 10–12

triplet carbenes, hydrogen abstraction, 404 Radiation shield, matrix isolation apparatus,

803–804

Radical clock, kinetic studies, 127–128 Radical ions. See Organic radical ions

matrix isolation, 820–823 Radical pair theory

alkoxycarbene fragmentation, 317–319 carbon atom reactivity, 487–488 chemically induced dynamic nuclear

polarization (CIDNP) effects, 132–133

triplet carbenes, 406

non-Kekule´ molecules, vs. biradical structure, 173

singlet carbenes, intermolecular reactions, 297–302

Radical recombination dimers, triplet carbenes, hydrogen atom abstraction, 403

Radicals. See also Organic radical ions bond dissociation energies (BDE),

123–125 elementary reactions

closed-shell initiations, 140–143 electron transfer, 143 photolysis, 142–143 thermolysis, 140–142

propagation, 143–157

composite group-transfer, 155–156 heterolytic addition, 153 heterolytic fragmentation, 153–155 homolytic addition, 148–151

INDEX 1055

homolytic atomand group-transfer, 145–148

halogen/chalcogen transfer, 146–148 hydrogen atoms, 145–146

homolytic fragmentation, 151–153 termination, 156–157

femtosecond time scale, formylalkyl, 917 identification and characterization, 126–134

absorption spectroscopy, 133–134 chemical induced dynamic nuclear

polarization (CIDNP) effects, 132–133 electron nuclear double resonance (ENDOR)

spectroscopy, 131–132

electron spin resonance (ESR) spectroscopy, 128–131

indirect kinetic determinations, 127–128 product inference, 126–127

matrix isolation, 816–818 multistep reactions, 134–140

chain reactions, 134–136

chain reaction velocities, 136–138 nonchain reaction sequences, 138–140

stabilization energy (RSE), 123–125 stable/persistent radicals, 125–126 structural properties, 122–123

electron spin resonance (ESR) spectroscopy information, 122–123

Radical stabilization energies (RSEs), radical reactivity, 123–125

Radiochemical decay, nitrenium ions, electrochemical oxidation, 619

Radiolysis

organic radical ions, unimolecular reactions, 237–239

radical ion generation, 210–211 radical ions, matrix isolation, 821–823

Raman spectroscopy, picosecond systems, 881–882

diphenylethene (stilbene), 887

Random orientation, electron spin resonance (ESR), non-Kekule´ molecules, 168–169

Rapid equilibrium, laser flash photolysis, 409 Rate constants

aliphatic nucleophilic substitution, tertiary carbons, 59

alkoxycarbene fragmentation, 319 chain reaction sequence, velocity measurements, 137–138 homolytic fragmentation, 151–153

radical cyclizations, homolytic addition reactions, 149–151

singlet carbenes

addition reactions, 285–289

1056 INDEX

Rate constants (Continued)

intermolecular insertion reactions, 301–302 intramolecular reactions, 303–306

triplet carbenes

excited states, 436–437

hydrogen abstraction, laser flash photolysis (LFP), 408–413

oxygen reactions, 428–429 reaction mechanisms, 383–384

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

Rate-controlling step, chain reaction sequence, velocity measurements, 137–138

Rate-equilibrium correlation, carbocation reactivity, 23–25

‘‘Reaction coordinate,’’ potential energy surfaces (PES), 926

Reaction mechanisms carbocations

azide clock, 18

basic principles, 15–16

flash photolytic generation, 18–21 Mayr’s electrophilicity/nucleophilicity

scales, 29

nucleophilic additions, 25–28 protic solvent lifetimes, 21–23 rate-equilibrium correlation, 23–25 Ritchie’s Nþ scale, 16–17

carbon atoms, 470–492 alkenes, 473–477

aromatic/heteroaromatic compounds, 479–486

C–H bonds, 473

halomethylidene formation, 477–479 deoxygenation, 486–492

inorganic substrates, 471–473 lone pair reactions, 493 reactivity properties, 470

femtosecond time scale, 900–902 nitrenium ions, 619–631

intersystem crossing, 631 singlet-state reactions

hydride donors, 628

n nucleophiles, 621–624 p nucleophiles, 624–628

singlet-state rearrangement/elimination, 619–621

triplet-state hydrogen atom transfer, 629–631 nucleophilic substitution

azide ion at benzylic carbon, concerted reaction coupling and change, 51–53

basic principles and nomenclature, 41–43 tertiary carbon, aliphatic substitution, 59–62

potential energy surfaces (PES) acetone radical cation generation and

dissociation, 950–952

bifurcations, transition states, 932–934 conical intersections, 934–937 2,3-diazabicyclo[2.2.1]hepta-2-ene thermal

deazetization, 953–955 1,2,6-heptatriene rearrangement, 952–953 hypersurface topology, 926

molecular dynamics principles, 943–947 nonstatistical dynamics, effects of, 955–956 reactive dynamics, potential energy profile,

947–949

RRKM theory, 941–942 statistical kinetic models, 937–943

phase space, 937–938

statistical approximation, 940–941 transition state hypothesis, 938–939

stepwise vs. concerted controversy, 926–931 symmetry parameters, 949–950

transition state theory, 942–943 variational transition state theory, 943 vinylcyclopropane rearrangement, 950

singlet carbenes, addition rate constants and activation parameters, 289

stable singlet carbenes, 347–365 cyclopropanation, 350–354 dimerization, 347–350

Lewis acids and bases, 354–358 triplet carbenes, 383–384

excited triplet carbene comparisons, 438–439 Reactive intermediates

carbanions, 97–101

addition reaction intermediates, 101–104 nucleophilic additions to alkenes, 101–103 nucleophilic aromatic substitution,

103–104

elimination reaction intermediates, 97–101 gas phase, 108–111

bimolecular (SN2) reactions, 108–110 nucleophilic acyl substitution, 110–111

rearrangement intermediates, 104–108 Favorskii rearrangement, 107–108 phenyl migrations, 106–107

Wittig rearrangement, 105–106 carbocations, 4–5

electronic structure calculations basic principles, 962–963 Born-Oppenheimer approximation,

967–968

cubyl cation formation, 985–988 cyclopropane ring opening stereochemistry,

989–997

density functional theory (DFT) calculations, 977–979

enthalpy predictions, 965–966

free energy/isotope effect predictions, 966 geometric predictions, 964–965 qualitative models, 966–967

ring expansion reactions, phenylcarbene, phenylnitrene, and phenylphosphinidene, 982–985

spectra predictions, 964 wave-function calculations, 968–977

electron correlation calculations, 973–977 configuration interaction (CI)

calculations, 974–977 perturbation theory calculations,

974–975

Hartree-Fock theory, 969–970

linear combination of atomic orbitalsmolecular orbital (LCAO-MO) calculation, 970–973

wave-function vs. DFT calculations, 979–980 low-temperature matrix studies

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

nitrenium ions, direct detection of, 638–640 non-Kekule´ molecules

basic properties, 166

connectivity theory examples, 187–191 (quinone)m-quinone derivatives, 187–188

disjoint vs. parity-based predictions, 192–194 electron spin resonance (ESR)

biradical/radical pairing, 173

Curie’s law, ground-state multiplicity, 174 matrices, 172–174

randomly oriented samples, 168–170 zero-field splitting, immobilizing media,

172–173

future research issues, 194–196 historical background, 166 Hund’s rule, 167–170

INDEX 1057

long-lived (persistent) spin isomerism, 189–191

magnetization/magnetic susceptibility measurement and interpretation, 191–192

molecular connectivity spin state, 181–185 Schlenk-Brauns hydrocarbons, 167 singlet-triplet gap, 170–171

spectroscopic structural analysis, 171 spin state structural preference, 170 tetramethylenebenzene, 185–187 tetramethyleneethane

gas-phase singlet-triplet separation, 183–185

heterocyclic planar derivatives, 188–189 molecular connectivity spin state, 181–185

trimethylenemethane bimolecular trapping, 176–177

electron spin resonance (ESR), 174–175 ring closure chemistry, 175–176 ring-constrained derivatives, 179–181 single-triplet gap, electron

photodetachment photoelectron spectroscopy, 177–179

nucleophilic substitution azide ion at benzylic carbon

liberated reaction intermediate ionization and trapping, 50

preassociation reactions, 50–51 stepwise vs. single reaction mechanisms,

41–43

picosecond lasers, 886–894 tert-butyl 9-methyl-9-

fluoreneperoxycarboxylate photolysis, 891–892

pi-bond homolysis/heterolysis, 892–894 pi-conjugated excited states, 886–891

diphenylacetylene, 890–891 1,4-diphenyl-1,3-butadiene, 888–889 1,2-diphenylethene (stilbene), 886–887 1,6-diphenyl-1,3,5-hexatriene, 889–890

potential energy surfaces (PES) profile, 947–949

vinylcyclopropane rearrangement, 950 radical cation reactions, 234–261

silyl cations, 31–32 Reactivity-selectivity relation, carbocation

reactivity, 16

Reagents, reactive intermediate generation, cocondensation, 813

Rearrangement processes

carbanion intermediates, 104–108 Favorskii rearrangement, 107–108 phenyl migrations, 106–107

1058 INDEX

Rearrangement processes (Continued) Wittig rearrangement, 105–106

carbocations, skeletal rearrangement, 8–9 nitrenium ions

Bamberger rearrangement, 500–600 single-state rearrangement, 619–621 phenylcarbene rearrangement, incarcerated

carbene chemistry, 314–317 silylene isomerization, 667–668

singlet carbenes, intramolecular insertion reactions, 302–306

Recrossing mechanisms, potential energy surfaces (PES), transition state hypothesis, 939

Redox chemistry

organic radical ions, structural analysis, 214–215

radical closed-shell structures, electron transfer, 143–144

Redox potential, radical ion generation, 211 Regiorandom adduct, 2-

methylenecyclopentane,1,3-diyls, 180 Relaxation mechanisms, femtosecond time scale,

901–902

Resistive heating, carbon atom generation, graphite vaporization, 467

Resonance

carbocation reactivity, electron-withdrawing substituents, 29–30

isotopic perturbation, 12–13

organic radical ions, detection-observation, 212–214

Retention of configuration, triplet carbenes, hydrogen abstraction, 404

Retro-Diels-Alder reactions, femtosecond time scale, 917–918

Reverse ylide formation, stable singlet carbenes, Lewis acid and base reactions, 354–358

Rhodium complexes

catalysts, carbene synthesis, diazo compounds, 574–575

rhodium(II)

carbene insertion reactions, 575–577 metal nitrenes, organic synthesis, 584–586

stable singlet carbenes, transition metal catalysis, 361–362

Rhombic structures, organic radical ions, strained ring cations, 224–228

Rice-Ramsperger-Kassell-Marcus (RRKM) model, potential energy surfaces (PES)

limitations, 956–957

stepwise vs. concerted reaction, 928–931 theoretical principles, 941–942 transition state hypothesis, 938–939

Ring closing metathesis (RCM), carbene synthesis, 570

applications, 581–583 Ring closure chemistry

cyclic polysilanes, 656–657 trimethylene-methane (TMM), 175–176

Ring-constrained derivatives trimethylene-methane (TMM)

2-methylenecyclopentane,1,3-diyls, 179–181

triplet carbenes, hydrogen abstraction, product studies, 405

Ring expansion reactions

electronic structure calculations, phenylcarbene, phenylnitrene, and phenylphosphinidene, 982–985

matrix isolation, 832–836

Ring-opening metathesis polymerization (ROMP), carbene synthesis, 569–570

Ring opening reactions

cyclopropanes, stereochemistry, 989–997 singlet carbenes

carbene mimics, 309–314

stepwise addition vs. concerted reaction, 294–297

Ring strain, carbanion basicity-carbon acidity, 80–81

Ring-substituted derivatives, nucleophilic substitution, azide ion at benzylic carbon

cumyl derivatives, 47–48 1-phenylethyl derivatives, 44–47

Ritchie’s Nþ scale, carbocation reactivity, 16–17

nucleophilic addition, 25–28

Room temperature solutions, triplet carbenes, time-resolved spectroscopy, 392–394

Rotomeric structures, triplet carbene geometrical isomerism, 388–389

Ruthenium complexes, stable singlet carbenes, transition metal catalysis, 362–365

Rydberg states, femtosecond time scale methyl iodide, 908

Norrish I intermediate, 912–914

Sabinene radical cations, bimolecular reactions, 252

Samarium diiodide (SmI2), radical closed-shell structures, electron transfer, 143–144

Scaling factors, wave function vs. DFT calculations, 979–981

Schlenk-Brauns hydrocarbons molecular connectivity, 182 non-Kekule´ molecules, 167

Schmidt reactions, imidogen, 506

Schmittel cyclization, didehydroindenes, 770–773 Schrock-type carbene complexes, transition metal

catalysis, electronic structure, 359–362 Schro¨dinger equation

electronic structure calculations, 967 femtosecond laser pulses, 905–906 femtosecond time scale, methyl iodide, 908

SD(Q)-C*/6-31G*, 1,1-difluorocyclopropane, 993–994

Secondary deuterium isotope effect, cyclopropane stereochemistry, 990–997

Second-order processes

Jahn-Teller distortion, strained ring compound radical ions, 222

nanosecond laser flash photolysis, 864–865 kinetic studies, 869

Selective bleaching, matrix isolation, 829–830 Selectivity values

carbene synthesis, 562

carbocation reactivity, Ritchie’s Nþ scale, 17 nitrenium ions, spectroscopic analysis,

633–634

ring-substituted cumyl (X-2-Y) derivatives, 47–48

triplet carbenes, abstraction-recombination insertion, 404

Selenagermiranes, 695–696 Self-consistency

Hartree-Fock electronic structure calculations, 970

linear combinations of atomic orbitalsmolecular orbital (LCAO/MO) approximation, 971–973

Self-consistent field (SCF) theory

Hartree-Fock electronic structure calculations, 970

silylenes and germylenes, electronic spectra, 664–665

Self-dissociation, carbon acidity-carbanion basicity, 76–77

Self-repulsion energy, wave function calculations, 978–979

Semibullvalene, radical cations, 229 Semiclassical trajectory calculations cyclopropane stereochemistry, 992

femtosecond time scale, 922 Semiempirical calculations

heterocyclic planar tetramethyleneethane (TME) derivatives, 188–191

nitrenium ions, DNA damaging reactions, 609–611

tetramethylenebenzene (TMB), 186

INDEX 1059

Septet-state benzene-1,3,5-tris(phenylmethylene), triplet polynuclear aromatic

carbenes, 452 Sertraline, carbene synthesis

diazo compounds, 574–575 insertion reactions, 577

Shell higher olefins process (SHOP), carbene synthesis, 569–570

Shock waves, nanosecond laser flash photolysis, 869

Sigma-dot substituent constants, triplet carbene delocalization, 386–387

sbonds

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

stable singlet carbenes

single electronically active heteroatomic substituents, 342–347

singlet vs. triplet ground state, 330–332 transition metal catalysis, 359–362

scomplexes, nitrenium ion detection, 638–649

sdonor electrons

carbon acidity-carbanion basicity, sp3 carbanions, hybridized C–H bonds, 82–86

cubyl cation formation, 987 nonclassical carbocations, 9–12 organic radical ions, 219–221

cation reactions, 234–261 bimolecular reactions, 246–261

alkenes and aromatics, 246–250 like-charge ions, 259–261

protic, ionic, polar reagents, 250–256 radical anions, 256–259

intra-pair reactions, 239–246 reactive intermediates, 234–236 unimolecular reactions, 236–239

radical configuration, 122

singlet carbenes, philicity addition reaction, 281–285

tetramethylenebenzene (TMB), 186–187 triplet carbenes, 377–378

double bond additions, 433–434 electronic effects, 378–379

s-electron-withdrawing substituent, cubyl cation formation, 986–987

sþ substituent constant scale, carbocation lifetimes, 21–23

s-substituent constant scale, carbocation lifetimes, 21–23

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

1060 INDEX

1,3-Sigmatropic rearrangements, potential energy surfaces (PES), stepwise vs. concerted reaction mechanisms, 928–931

2,3-Sigmatropic rearrangements, single bond silylene insertions, 670–671

3,3-Sigmatropic rearrangements, potential energy surfaces (PES), stepwise vs. concerted reaction mechanisms, 929–931

[2,3]-Sigmatropic rearrangement, carbene synthesis, ylide formation, 578

Sigmatropic shifts, organic radical ions protic, ionic, and polar solvents, 251–256 unimolecular reactions, 236–239

7-Silanorbornadienes, thermal elimination, 653–654

Silacarbonyl ylide, silylene multiple bond additions, 680–683

Silacyclobutadiene, silylene isomerization, 666–668

1-silacyclohexadienes, silylene multiple bond addition, olefins and dienes, 678–680

2,5-silacyclohexadienes, silylene multiple bond addition, 678–680

Silacyclopentanes, metal-induced a-elimination reactions, 658–660

1-Silacyclopropenylidene, isomerization, 667–668

1-Silacyclopent-1,3-diene, isomerization, 666–668

1-Silacyclopent-2,4-diene, silylene isomerization, 666–668

1-Silacyclopent-3-ene

silylene isomerization, 666–668 silylene thermal elimination, 654

Silaketenimine, 689 Silanimine, isomerization, 668

‘‘Silanone transfer agent,’’ single bond silylene insertions, 671–673

7-Silanobornene, branched cyclic silylsilanes, 657–658

Silathiocarbonyl ylide, silylene multiple bond additions, 681–683

Silaylide, single bond silylene insertions, 668 Silicon-hydrogen bonds, single bond silylene

insertions, 673–675

Silicon nuclear magnetic resonance (29Si NMR) dialkylsilylene synthesis and isolation, 686–687 silyl cations, 31–32

Silicon-oxygen bonds, single bond silylene insertions, 671–673

Silicon-silicon bonds

linear polysilane photolysis, 655–656 overcrowded diarylsilylenes, 687–689 silylene extrusions, 652–654

single bond silylene insertions, 673–675 Silirene, silylene thermal elimination, 654 2-Silolenes, 689–691

3-Silolenes, 690 Silver photocathode

femtosecond time-resolved experiments dynamics, 904

femtosecond time scale, structural determinations, 919–920

Silylcarbene, isomerism, 665–668

Silyl cations, reactivity mechanisms, 30–32 Silylene-isonitrile complexes

masked silylenes, 689–691 overcrowded diarylsilenes, 689

Silylenes

multiple bond insertion reactions acetylenes, 675–677

carbonyl/thiocarbonyl compounds, 680–683 olefins, dienes, and related compounds,

677–680

single bond insertion reactions, 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 structure reactions and dimerizations, 684–691

dialkylsilylene synthesis and isolation, 684–687

overcrowded diarylsilylene generation and reactions, 687–691

silylene-isonitrile complex reactions, masked silylene, 689–691

structures

electronic spectra, 662–665 isomerization, 665–668 singlet/triplet states, 660–662

thermally induced a-elimination and photoextrusion, 652–660

branched cyclic silylsilanes, 657–658 cyclotrisilane/cyclotrigermane photolysis and

thermolysis, 656–657 dimethylsilylene generation, polysilanes/

oligosilanes, 654–655

linear polysilane photolysis, 655–656 metal-induced eliminations, 658–660 polysilane/oligosilane thermolysis, 652–654

triplet diphenylcarbene protection, 441–444 Silylene-silene rearrangements, isomerism,

665–668

Silylenoids, metal-induced a-elimination reactions, 658–660

Silylmethylsilyene, 686–687

Silyl radicals

homolytic halogen/chalcogen transfer, 147–148 radical cations, 258–259

1-Silylsilaethene, 686–687 a-Silylsilenes, isomerization, 667–668

Simmons-Smith reaction, carbene synthesis, 562 alkylidines, 571–572

Single/double excitation configurational interaction (SD-CI) calculations

cyclopentane-1,3-diyl ground state calculations, 996–997

electron correlation, 974 size consistency, 975

tetramethyleneethane (TME), 185

Single electron transfer, radical ions, matrix isolation, 820–823

Single-point calculations

cyclopropane stereochemistry, 990–997 enthalpy predictions, 965–966

Singlet carbenes. See Carbenes; Singlet ground state

Singlet dehydrocubane, electronic structure calculations, 987

Singlet diradicals, CASSCF/CASPT2 calculations, 976–977

Singlet state arylnitrenes, 523

p-benzynes, substituent effects, 762–764 carbenes

addition reactions overview, 274 philicity, 279–287

rates and activation parameters, 285–289 stepwise vs. concerted addition, 291–297 transition state symmetry, 289–291

alkoxycarbene fragmentation, 317–319 carbene mimics, 308–314

solvent effects, 313–314 future research issues, 320–321

hydrogen atom tunneling, 415–416 insertion reactions

carbon-hydrogen, 298–306 intermolecular reactions, 298–302

intramolecular rearrangements, 302–306 overview, 274

intramolecular hydrogen tunneling, 420–421 oxygen reactions, 425

phenylcarbene rearrangement, 314–317 singlet-triplet equilibration, 307–308 stable singlet carbenes

Curtius bis-(carbene)-acetylene- (phosphino)(silyl)carbene transition, 332–334

INDEX 1061

reactivity mechanisms, 347–365 research background, 330

synthesis and structural data, 335–347 triplet vs. singlet ground state, 330–332 Wanzlick equilibrium-diaminocarbene

transition, 334–335

stepwise vs. concerted addition, 291–297 structure and bonding, 274–279

carbon atoms, inorganic substrates, 471 Coulombic repulsion, 377 didehydrotoluene biradical, 771–773 o-fluorophenylnitrene, 536–538 fluoro-substituted phenylnitrenes, 536–538 methylene, 274–279

methylnitrene, 507–511 naphthylnitrenes, 540–543 nitrenium ions

aryland heteroarylnitrenium ions, 607–611 density functional calculations, 637–638 historical background, 601–603

hydride donors, 628

n nucleophiles, 621–624

parent, alkyland halonitrenium ions, 603–606

photochemical initiation, 615–618 p nucleophiles, 624–628 rearrangement/elimination, 619–621

non-Kekule´ molecules, ground-state multiplicity, Curie law, 174

phenylnitrene, 525

computational chemistry, 526–528 dynamics, 529–531

laser flash photolysis (LFP), 529

p bond homolysis/heterolysis, picosecond spectroscopy, 892–894

silylenes and germylenes, 660–662 single bond silylene insertions, 670–671 tetramethylenebenzene (TMB), 186–187 trimethylenemethane (TMM)

electron spin resonance (ESR), 175 ring closure chemistry, 176 ring-constrained derivatives, 180–181

Singlet-triplet energy gap benzadiynes, 783–784 o-benzynes, 745–747 p-benzynes

parent structure, 758–759 substituent effects, 762–764

didhydroindenes, 771–773 hetarynes, 773–782

heterocyclic planar tetramethyleneethane (TME) derivatives, 188–191

imidogen, 503–506