Reactive Intermediate Chemistry

1012 INDEX

Bimolecular reactions (Continued) like-charge ions, 259–261

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

triplet carbenes

excited states, 436–437 oxygen reactions, 428–429

Bimolecular trapping tetramethylenebenzene (TMB), 187 trimethylenemethane (TMM), 176–177

Biosynthesis, carbocation reactivity, 34–35 Biphenylnitrenes, structural properties, 543–544 4-Biphenylnitrenium ion

DNA damaging mechanisms, 641–644 singlet-state reactions, n nucleophile additions,

622–624

4-Biphenyphenylcarbene, tunneling reactions, elevated temperatures, 422

Biradicals

carbon atom reactivity, 487–488 electron spin resonance (ESR), 173 intra-pair reactions, 240–241 matrix isolation, 818–820

nanosecond laser flash photolysis, 855–858 non-Kekule´ molecules

vs. radical pair structure, 173 structural properties and spectroscopic

analysis, 171

organic radical ions, intra-pair reactions, 240–246

paramagnetism, Hund’s rule, 167–168 potential energy surfaces (PES)

1,2,6-heptatriene rearrangement, 953 reactive intermediate dynamics, 947–949 stepwise vs. concerted reaction, 927–931

Schlenk-Brauns hydrocarbons, 167 tetramethyleneethane derivatives, 182–185

Birch reduction, organic radical ions, bimolecular reactions, 250–256

Bis(acylperoxides), matrix isolation, 819–820 Bis(alkylidene)germirane, germylene multiple

bond addition, 680 Bis(arylthio)plumbylene, 705 Bis[octahydro-1,4,:5,8-di(ethano)-

anthryl]carbene, triplet diphenylcation protection, 443–444

Bis(Z1-pentamethylcyclopentadienyl)silane, metal-induced a-elimination reactions, 658–660

Bis[2-pyridyl-2,2-bis(trimethylsilyl)- methyl]stannylene, 697–699

Bis(silacyclopropane), silylene multiple bond addition, 676–677

Bis(silacyclopropene), silylene multiple bond addition, 676–677

Bis(silirene), silylene multiple bond addition, 676–677

Bis(tri-arylmethyls), non-Kekule´ molecules, 167 Bis(2,4,6-trichlorophenyl)carbene

halogen protection, 444–447 persistent triplet carbenes, 440–441

Bis(triisopropylsilyl)silylene multiple bond insertions, 677–680

photochemical irradiation, 657–658 1,1-Bis(trimethylsilyl)cyclopropanes,

stereomutation calculations, 994–995 Bis(trimethylsilyl)diarylgermane, photolysis,

655–656

Bis(trimethylsilyl)germanes, electronic spectra, 664–665

Bis[(trimethylsilyl)methyl]germylene, single bond insertions, 671

Bis(trimethylsilyl)methyl groups, stannylene structures, 697–699

Bis(trimethylsilyl)methyl-substituted disilenedigermane pairs, 694

Bladder cancer, nitrenium ions, 598 BLYP functionals, matrix isolation,

833–836 Bohr magneton

non-Kekule´ molecule magnetic susceptibility, 192

organic radical ion resonance, 212–214 Boltzmann distribution, triplet carbenes,

chemically induced dynamic nuclear polarization (CIDNP), 405

Boltzmann intensities, organic radical ion detection-identification, 213

Bond angle

deformation, strained hydrocarbons, 724–725 stable singlet carbenes, 343–347

triplet carbenes, singlet-triplet energy gap, preequilibrium mechanism, 396–400

Bond dissociation energies (BDE)

carbon acidity-carbanion basicity, 96–97 carbon-hydrogen radicals, 123–125 N-heterocyclic carbenes (NHC), transition metal

catalysis, 363–365 imidogen, 505–506

organic radical ions, cation reactive intermediates, 236

strained hydrocarbon bond angle deformation, 725

Bond interactions

cubyl cations, singlet dehydrocubane, 987 singlet carbenes, 274–279

Bond strength, carbanion basicity-carbon acidity, 96–97

Borane compounds, radical initiation, thermolysis, 142

Borderline reactions, nucleophilic substitution mechanisms, 42–43

aliphatic substitution, tertiary carbons, 59–65

cumyl derivatives (X-2-Y), 55–57 1-Phenylethyl derivatives (X-1-Y), 53–55 preassociation reactions, 51 ring-substituted cumyl derivatives,

47–48

Born-Oppenheimer approximation, electronic structure calculations, 967–968

Branched cyclic silylsilanes, silylene synthesis, 657–658

BrCH2CD2CH2Br, femtosecond time scale, 910

BrCH2CH2CH2, femtosecond time scale, 908–910

Bridgehead double bonds, strained hydrocarbons, 728–729

Brillouins’ theorem, electron correlation, 975 Bromide ion inhibition, aliphatic nucleophilic substitution, tertiary carbons, 59

Bromine groups, halogen-protected diphenylcarbenes, 445–447

Brønsted relationship

carbon acidity-carbanion basicity, 77–78 condensed-phase vs. kinetic acidity

measurements, 94–96

organic radical ions, unimolecular reactions, 236–239

Buffer acids, elimination reactions, carbanion intermediates, 98–101

Butadiene, femtosecond time scale, retro-Diels- Alder reactions, 917–918

germylene multiple bond addition, 679–680

Butalene

p-benzyne, 753–759 hetarynes, 780–782

2-Butanone, femtosecond time scale, Norrish I intermediate, 913–914

(E)-2-(2-Butenyl)phenyldiazomethane, triplet carbene double bond additions, 433–434

tert-Butoxyl radicals, cubyl cations, hydrogen reactivity, methyl/methylcubane comparisons, 987–988

tert-Butoxyl radicals, nanosecond laser flash photolysis, 860–864

INDEX 1013

Buttressing effect, halogen-protected diphenylcarbenes, 445–447

tert-Butylallene, silylene multiple bond addition, 678–680

tert-Butylbenzene, carbon atom reactivity, 480– 484

tert-Butylcarbene

carbene mimics, 309–314 solvent effects, 313–314

intramolecular tunneling reactions, 420–421

singlet carbenes, carbene mimics, 309–314

2-Butyl cation

stable ion chemistry, 6–8 theoretical background, 7

tert-Butyl cation

aliphatic nucleophilic substitution, tertiary carbons, 59–62

solvent and solvation, 62–65 multistep radical reactions, chain reaction

sequence, 135–136

radical identification/characterization, chemical induced dynamic nuclear polarization (CIDNP) effects, 132–133

stable ion chemistry, 5–6 X-ray crystallography, 14–15

tert-Butyl 9-methyl-9-fluoreneperoxycarboxylate, picosecond spectroscopy, photolysis, 891–892

tert-Butyl radical

benzene-carbon atom reactivity, 480–484 silylenes and germylenes, singlet/triplet

ground states, 662

single bond silylene insertions, 674–675

structure, 122

tert-Butylisocyanate, acylnitrenes, 511 ‘‘Bystander assistance,’’ singlet carbenes,

intramolecular insertion reactions, 303–306

C6H5CCl

absolute rates and activation parameters, 285–289

intermolecular insertions, 297–302 C6H5COCH3, absolute rates and activation

parameters, 287–289 C6H5OCCl, philicity, 281–285

C8 adducts, nitrenium ions, DNA damaging mechanism, 644

Cage effect, matrix isolation, 802 radicals, 816–818

1014 INDEX

Calicheamicins p-benzyne, 754–759

didehydroindenes, 770–773 Canonical ensemble, potential energy

surfaces (PES) statistical kinetic models, 938

variational transition state theory (VTST), 943 Carbamoyl azide, aminonitrenes, 544–547 Carbanions

aggregation, 75–76 basicity, 76–97

carbon acidity measurements bond strengths, 96–97

condensed-phase measurements, 87–96 DMSO acidity, 88–90

gas-phase acidity, 93–94 ion-pairing, 90–93 kinetic acidity, 94–96

definitions and methodologies, 76–79 sp2 and sp hybridized C–H bonds, 86–87 sp3 hybridized C–H bonds, 79–86

chemical origins, 70–71 reactivity, 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 research background, 70

structural properties, 71–76 geometries, 71–72

magnetic properties and NMR, 75–76 stereochemistry and racemization, 72–74

Carbazoles, biphenylnitrenes, 543–544 Carbene 1,2-H shifts, singlet carbenes,

intramolecular insertion reactions, 303–306

Carbene-alkene addition reactions absolute rates and activation parameters,

285–289

carbene mimics, 311–314 philicity, 279–285

transition state symmetry, 289–291 Carbene-carbene rearrangement, triplet

diphenylcarbenes, 447–448 Carbene mimics, singlet carbenes, 308–314

Carbenes

o-benzynes, 745–747 carbon-alkene reactions, 475 carbon atom deoxygenation

carbon-hydrogen bond formation, 473 carbonyl compounds, 488–492 reactivity, mechanisms, 470

diazo precursors, 469 distonic carbene ions, 233

electron spin resonance (ESR), triplet states, 168

matrix isolation, 815–816 singlet 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 insertion reactions

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

intramolecular rearrangements, 302–306 overview, 274

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

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

reactivity, mechanisms, 347–365 research background, 330

synthesis and structural data, 335–347 transition metal complexes, catalytic

applications, 358–365

triplet vs. singlet ground state, 330–332 Wanzlick equilibrium-diaminocarbene

transition, 334–335 structure and bonding, 274–279

synthesis

diazo compound catalysis, 572–579 cyclopropanation/cyclpropenation,

573–575

diazocarbonyl compounds, 578–579 electrophilic/nucleophilic compounds,

563

insertion reactions, 575–577 ylide formation, 578

electrophilic/nucleophilic metal compounds, 563

alkylidenes, 570–571

diazo compound catalysis, 565–567 metathesis, 469–570

transition metal complexes, 567–569 Fischer carbene complexes, 579–580 ring-closing metathesis, 581–582 structural properties, 561–563

triplet carbenes

basic properties, 376–377 direct observation, 384

double bond additions, 431–434 electronic effects, 378–380 excited states, 434–439

geometry, 437–438 product studies, 434–435

reactivity differences, 438–439 spectroscopic studies, 435–437 generation and reaction, 383–384

hydrogen atom abstraction, 402–422 chemically induced dynamic nuclear

polarization, 406–408 laser flash potolysis, 408–413 product studies, 402–405 tunneling reactions, 413–422

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

hyperconjugation effects, 380–381 maxtrix-isolation spectroscopy, 385–392

electron paramagnetic resonance (EPR), 385–390

fluorescence, 391

infrared spectroscopy, 391–392 ultraviolet-visible spectroscopy, 390–391

oxygen reactions, 422–431 dimesitylketone oxide, 425–426 emission, 426–427

laser flash photolysis, 427–429

matrix isolation spectroscopy, 423–425 product studies, 423 tetramethylpiperidine N-oxide (TEMPO),

430–431

persistent triplet carbenes, 439–452 alkyl-protected diphenylcarbenes,

441–444

halogen-protected diphenylcarbenes, 444–447

high-spin polycarbenes, 449–452 polynuclear aromatic carbenes, 448–449

INDEX 1015

trifluoromethyl-protected diphenylcarbenes, 447–448

singlet carbenes

singlet-triplet equilibration, 307–308 stepwise vs. concerted addition, 293–297 structural comparisons, 377–378

singlet-triplet gap estimation, 395–402 preequilibrium mechanism, 395–400 solvent effects, 401–402 surface-crossing mechanism, 400–401

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

steric effects, 379, 381–383 time-resolved spectroscopy, room

temperature solution, 392–394 infrared (TRIR) spectroscopy, 394

ultraviolet-vis (TRUV-Vis) spectroscopy, 393–394

(D,D)-carbenes, singlet vs. triplet ground state, 331–332

Carbenic dimer, halogen-protected diphenylcarbenes, 446–447

Carbenic substituents, triplet carbenes, zero-field splitting, 386

Carbenium ions defined, 4

nonclassical carbocations, 9–12 silyl cations, 30–32 superacids, 5

Carbenoids, singlet carbene addition, transition state symmetry, 290–291

Carbocations biosynthesis, 34–35 carcinogenesis, 33–34 crystal structures, 13–15 definitions, 4

early research, 4

electron-withdrawing substituents, 29–30 isotopic symmetry perturbation, 12–13 matrix isolation, 824

nonclassical ions, 9–12 nucleophilic substitution, 42–43 persistent stable ions

chemistry, 5–6 superacids, 5 theory, 6–7

reactive intermediate functions, 4–5 reactivity, mechanisms

azide clock, 18

basic principles, 15–16

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

scales, 29

1016 INDEX

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

rearrangements, 8–9 silyl cations, 30–32 zeolites, 32–33

Carboethoxynitrene

phosphorylnitrene comparison, 519–520 reaction intermediates, 515–517

Carbohydrates, carbon atom reactivity, water and formation of, 472–473

Carbon acidity, carbanion basicity bond strengths, 96–97

condensed-phase measurements, 87–96 DMSO acidity, 88–90

gas-phase acidity, 93–94 ion-pairing, 90–93 kinetic acidity, 94–96

definitions and methodologies, 76–79 sp2 and sp hybridized C–H bonds, 86–87 sp3 hybridized C–H bonds, 79–86

Carbon arc studies

graphite vaporization, 466–468 historical evolution of, 464–466

Carbon atoms

energies and spin states, 466 generation techniques

chemical precursors, 468–469 graphite vaporization, 466–468 molecular beam production, 470

nucleogenic carbon and nuclear medicine, 465–466

molecular beam studies, 493–494 reaction mechanisms, 470–492

alkenes, 473–477

cycloalkenes to cyclic cumulenes, 475–477 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

structural properties, 464 Carbon–carbon bonds

cycloadditions, 733

organic radical ions, unimolecular reactions, 238–239

singlet carbene addition, carbene mimics, 311–314

transition metal cleavage, 735–736 Carbon-carbon double bond, stable singlet

carbenes, dimerization reactions, 347–350 Carbon-chloride insertion products, single bond

silylene insertions, 670–671 Carbon disulfide

bis(arylthio)plumbylene, 705

kinetically stabilized germylenes, 695–696 overcrowded diarylsilenes, 689

11Carbon, in nuclear medicine, 464 Carbon–fluorine bonds

stable singlet carbenes, single electronically active heteroatomic substituents, 343–347

trifluoromethyl-protected diphenylcarbenes, 447–448

Carbon–halogen bonds, single bond silylene insertions, 669–671

Carbon–hydrogen bonds

bond dissociation energy (BDE), strained hydrocarbon bond angle deformation, 725

carbon acidity-carbanion basicity, hybridization sp2/sp carbanions, 86–87

sp3 carbanions, 79–86 carbon atom reactivity, 473

alkene reactions, 474–475 double-bond addition vers., 486 halomethylidene formation, 477–479

Fischer-type carbenes, 580 metal carbene synthesis, 567 radical reactivity

bond-dissociation energies (BDEs), 123–125

electron spin resonance (ESR), 130–131 singlet carbene insertion reactions, 298–306

intermolecular insertion, 298–302 intramolecular insertions/rearrangements,

302–306

singlet-triplet equilibration, 307–308 triplet carbenes

hydrogen abstraction

atom transfer kinetics, 416–417 intramolecular tunneling, 420–421 laser flash photolysis (LFP), 412–413

hydrogen atom transfer kinetics, 416–417 hydrogen atom tunneling, 413–414 hydrogen product studies, 403–405

Carbonium ions. See also Nonclassical carbocations

defined, 4

1,2-Carbon migration, singlet carbenes, intramolecular reactions, 305–306

Carbon nucleophiles, carbocation reactivity, addition reactions, 26–28

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

Carbon radicals

homolytic addition reactions, 150–151 homolytic fragmentation, 151–153

Carbon suboxide photolysis, carbon atom generation, 468

Carbon–sulfur bonds, carbanion stereochemistry and racemization, 74

Carbon-13 nuclear magnetic resonance (13C NMR)

carbanions, 75–76

carbocation skeletal rearrangements, 8–9 carbon atom generation, graphite vaporization,

466–468

electronic structure calculations, 964 isotopic perturbation, 12–13 2-norbornyl cation, 11–12

singlet carbene addition, transition state symmetry, 290–291

stable ion chemistry, 5–8

stable singlet carbenes, p-electron-donating heteroatom substituents (D-C-D), 340

strained hydrocarbons, 736 tetramethylenebenzene (TMB), 186–187

Carbonyl compounds

carbene synthesis, ylide formation, 578

carbon atom deoxygenation, carbene formation, 488–492

silylene/germylene multiple bond additions, 680–683

Carbonylnitrenes, structural properties, 511–515 nitrene esters, 515–517

phosphorylnitrenes, 518–520 sulfonylnitrenes, 517–518

Carbonyl oxides

matrix isolation, 829–830 triplet carbenes

laser flash photolysis, 427–429 oxygen reactions, 424–425

Carbonyl ylide, metal carbene synthesis, 567 Carcinogenesis

carbocation reactivity, 33–34 nitrenium ions, 597–598

Carr-Parrinello technique, potential energy surfaces (PES), molecular dynamics (MD), 945–947

CASMP2 software, multireference wave function calculations, 977

CASPT2

matrix isolation, 837–838

ring expansion reactions, electronic structure calculations, 983–985

INDEX 1017

(2,2)CASPT2/6-31G*

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

1,2-dimethylspiropentanes stereomutation, 996 (2/2)CASPT2/6-31G*, 1,1-disilylcyclopropane

stereomutation calculations, 994–995 (2/2)CASSCR/6-31G* geometry optimization,

cyclopropane stereochemistry, 990–997 Catalysis, stable singlet carbene-transition metal

complexes, 358–365 electronic structures, 359–362

Cationic structures organic radical ions

bifunctional/distonic radical ions, 229–234

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

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

chemistry, 208–209 intra-pair reactions, 239–246 n donors, 218

p donors, 215–218

reactive intermediates, 234–236 strained ring cations, 221–228 structural analysis, 214–215 unimolecular reactions, 236–239

radical cations, matrix isolation, 820–823 CBSQ model calculations, strain energy

calculations, 719–721

CCl, carbon atom reactivity with, 478 CCl2

addition reaction rate constants and activation parameters, 287–289

carbene mimics, 314 electrophilicity, 289–291 intermolecular insertions, 297–302 relative reactivities, 280–285

stepwise vs. concerted reactions, 295–297 CCl4, single bond silylene insertions,

669–671

CCSD(T), wave function vs. DFT calculations, 980–981

Cerium(IV) reagents, radical closed-shell structures, electron transfer, 143

Cesium compounds, carbon acidity-carbanion basicity, condensed-phase measurements, ion-pair acidities, 90–93

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

CF2I2, femtosecond time scale, structural determinations, 919–920

1018 INDEX

CH3CCl

carbene mimics, 314 relative reactivities, 280–285

CH3CD3 isotope effect, femtosecond time scale, Norrish I intermediate, 913–914

CH3COCH3, absolute rates and activation parameters, 288–289

philicity, 281–285

(CH3O)2C, singlet carbene philicity, 282–285 CH3OCCl, singlet carbene philicity, 282–285 (CH3OOC)2C, stepwise vs. concerted reactions,

292–297

Chain reactions, radical cations, 134–136 unimolecular reactions, 237–239 velocities, 136–138

Chalcogens, radical propagation, homolytic transfer, 146–148

Charge distribution, singlet carbenes, intramolecular insertion reactions, 303–306

Charge recombination, organic radical ions, intrapair reactions, 245–246

Chemical dynamics

femtosecond time-resolved experiments, coherence mechanisms, 904–906

femtosecond time scale, 920–921

Chemically induced dynamic electron polarization (CIDEP), organic radical ion detectionidentification, 213

Chemically induced dynamic nuclear polarization (CIDNP)

organic radical ions

bifunctional/distonic radical ions, 229–234 bimolecular reactions, 248–250 detection-identification, 213 1,5-hexadiene systems, 229

intra-pair reactions, 239–246 strained ring cations, 223–228

radical compound identification

electron spin resonance (ESR), 129–131 radical pair theory, 132–133

singlet carbenes, carbon–hydrogen insertions, 300–302

triplet carbenes, hydrogen abstraction, 406–408 Chemical oxidants, nitrenium ion generation, 614 Chemical precursors, carbon atom generation,

468–469

carbon suboxide photolysis, 468 diazo compounds, 469

low-temperature matrix-assisted cyanogen azide photolysis, 468

Chemical reactions, trimethylenemethane (TMM), 175–176

Chemiluminescence, triplet carbenes, oxygen reactions, 426–427

Chiral derivatives

aliphatic nucleophilic substitution, tertiary carbons, 59–60

carbanion structure, 72–74

Chloranil, organic radical ions, intra-pair reactions, 243–246

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

Chloride–nitrogen bond heterolysis, nitrenium ions, 601–602

Chlorine atom abstraction

singlet carbenes, intermolecular insertions, 300–302

triplet carbenes, chemically induced dynamic nuclear polarization (CIDNP) effects, 407

N-Chloroamines, nitrenium ions, 601 generation methods, 613–614 photochemical initiation, 617–618

N-Chloroaniline derivatives, nitrenium ions, 600 Chlorocyclopropylcarbene

carbene mimics, 314 intramolecular reactions, 305–306

2-Chlorodiphenylcarbene, tunneling reactions, elevated temperatures, 422

Chlorofluorocarbenes

absolute rates and activation parameters, 288–289

carbon atom reactions, 477–479 Chloronium ylide

chemically induced dynamic nuclear polarization (CIDNP) effects, triplet carbenes, 408

single bond silylene insertions, 670–671 Chlorophenylcarbene

addition rates and activation parameters, 285–289

hydrogen tunneling, 418–419 laser flash photolysis, 429

Chromium triad, carbene synthesis, 568–569 cis-1,2-dichloroethylene, single bond insertions,

671

Cisoid,cisoid diradicals, 1,1-disilylcyclopropane stereomutation calculations, 994–995

cis-trans-1,1-difluoro-2-ethyl-3- methylcyclopropanes, stereomutation, 993–994

Claisen rearrangement, triplet carbenes, 433 Classical mechanisms, hydrogen atom transfer

kinetics, 417

Close cycle cryostat, matrix isolation, 803–804 Closed-shell compounds

CASSCF/CASPT2 calculations, 976–977 heterolytic radical fragmentations, 153–155 matrix isolation, 823–824

radicals

chemically induced dynamic nuclear polarization (CIDNP) effect, 132–133

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

wave function calculations, Hartree-Fock calculations, 969–970

Cocondensation of reagents, reactive intermediate generation, 813

Coherence, femtosecond time scale, 904–906 1,3-dibromopropane, 908–910

sodium iodide, 906–907

Collision induced dissociation (CID), p-benzyne, 755–759

Combustion reactions arynes, 742 o-benzynes, 745–747 future research, 785

Common ion effect, carbocation reactivity, 15 Competition kinetics, carbocation reactivity, 16 Complete active space self-consistent field

(CASSCF) calculations

(2,2)CASSCF calculations, cyclopentane-1,3- diyl ground state calculations, 996–997

CASSCF/CASPT2 calculations, 976–977 Complete basis set calculations, electron

correlation, 976 Computational chemistry

non-Kekule´ molecules, 195–196 phenylnitrene, 525–528

singlet carbenes

intramolecular insertion reactions, 304–306 philicity, addition reaction, 282–285

triplet carbenes

infrared spectroscopy, 391–392 matrix isolation studies, 424–425

Concerted addition

hydrogen tunneling, 418–419

syn addition, 2-methylenecyclopentane, 1,3-diyls, 180

Concerted reaction mechanism azide ion at benzylic carbon

coupling and change to, 51–53 cumyl derivatives (X-2-Y), 56–57

benzyl derivatives, 57–58

potential energy surfaces (PES), 926–931

INDEX 1019

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

background, 376

hydrogen abstraction, product studies, 405 Concurrent reactions, benzyl derivatives,

57–58

Condensed-phase measurements, carbon aciditycarbanion basicity, 87–96

DMSO acidity, 88–90 gas-phase acidity, 93–94 ion-pairing, 90–93 kinetic acidity, 94–96

Conductivity studies, organic radical ions, like charge reactions, 259–261

Configuration interaction (CI) electron correlation, 974

coupled-cluster/quadratic CI calculations, 975–976

size consistency, 975

wave function calculations, 969 Conformational barriers

acyclic radicals, 122–123 alkoxycarbene fragmentation, 319

Conical intersections, potential energy surfaces (PES), 934–937

Conjugated ring systems, carbon acidity-carbanion basicity, sp3 carbanions, hybridized C–H bonds, 84–86

Conrotation

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

cyclopropane stereochemistry, 990–997 1,1-difluorocyclopropane stereochemistry,

993–994

1,2-dimethylspiropentanes stereomutation, 995–996

Conservation of angular momentum, cyclopropane stereochemistry, 992

Contact radical ion pairs (CRIP)

heterolytic radical addition and fragmentation, 153–155

organic radical ions, 235–36 intra-pair reactions, 239–246

Continuous wave (CW) lasers, picosecond systems, Raman spectroscopy, 882

Cook’s kinetic method, carbon acidity-carbanion basicity, sp3 carbanions, hybridized C–H bonds, 79–86

Cope rearrangement CASSCF/CASPT2 calculations, 977 cubyl cation formation, 986–987

organic radical ions, unimolecular reactions, 237–239

1020 INDEX

Copper complexes

catalysts, carbene synthesis, diazo compounds, 574–575

radical closed-shell structures, electron transfer, 143

Coulombic repulsion imidogen, 505–506 triplet carbenes, 377–378

wave function calculations, 968–969 Coulomb operator

Hartree-Fock calculations, 969–970 wave function calculations

density functional theory (DFT), 978 functionals, 978–979

Coupled-cluster theory, electron correlation, configuration interaction (CI) calculations, 975–976

Coupled rotation, 1,1-difluorocyclopropane, 993–994

Coupling reactions

nucleophilic substitution at benzylic carbon, concerted reaction mechanism, 51–53

radical-radical closed-shell compounds, 156–157

Criegee intermediates, triplet carbene oxygen reactions, 423

‘‘Cross’’ cycloaddition, organic radical ions, unimolecular reactions, 237–239

Cross-metathesis, carbene synthesis, 570 ring closing metathesis (RCM), 582–583

Cross-over reactions, singlet carbenes, philicity, additions, 283–285

Cross-products, triplet carbenes, laser flash photolysis, 413

Cryogenic temperatures, triplet carbenes, hydrogen tunneling, 421–422

Cryostats, matrix isolation, 803–804 Crystalline hosts

non-Kekule´ molecules matrix ESR, 172 spectroscopic analysis, 171

trimethylenemethane (TMM), ESR spectra, 174–175

Crystal structures, carbocations, 13–15 Cubane structures, 729–730

Cubene structures dimerization, 732 structural properties, 729

Cubyl cations

electronic structure calculations, 985–988 hydrogen reactivity, methyl/methylcubane

comparisons, 987–988 singlet dehydrocubane, 987

MP2 calculations, 985–987

Cumene derivatives, singlet carbenes, carbon– hydrogen insertions, 299–302

Cumulenes. See also Cyclic cumulenes carbon-alkene reactions, 474

Cumyl derivatives (X-2-Y), nucleophilic substitution, azide ion at benzylic carbon, 47–48

borderline reactions, 55–57

More O’Ferral reaction coordinate diagrams, 48–50

Curie’s law

heterocyclic planar tetramethyleneethane (TME) derivatives, 189

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

singlet-triplet separation, 184 trimethylenemethane (TMM), ESR spectra,

175

triplet carbenes, electron paramagnetic resonance spectroscopy, 386–390 Curie-Weiss law, non-Kekule´ molecules,

ground-state multiplicity, 174 Curtius bis(carbene)-acetylene, stable singlet

carbene state, 332–334

Curtius rearrangement, acylnitrenes, 511–512 Curve crossing techniques

femtosecond laser pulses, sodium iodide, 907 organic radical ions, protic, ionic, and polar

solvents, 254–256

Cyanoaromatic radical anions, intra-pair reactions, 243–246

Cyanocyclopentadienyl radical, phenylnitrene, 524–525

Cyanogen azide photolysis, carbon atom generation, 468

Cyanonitrene, cyanogen azide photolysis, 468 9-Cyanophenanthrene, radical anion, intra-pair

reactions, 244–246 o-Cyanophenylnitrene, azirine cyclization,

535–536 Cyclic carbenes

aromatic carbenes, preequilibrium mechanism, 398

singlet-triplet energy gap, preequilibrium mechanism, 398–400

triplet carbenes, steric effects, 382–383 Cyclic cumulenes, carbon atom reactivity with

cycloalkenes, 475–477

Cyclic diarylcarbenes, singlet-triplet energy gap, preequilibrium mechanism, 399–400

Cyclic molecular ions, unimolecular reactions, 239 Cyclic polysilanes, ring contraction, 656–657

Cyclic voltammetry (CV) nitrenium ions, 602–603 radical ion generation, 210–211

Cyclization

phenylnitrene to azirines, 534–536 radical homolytic additions, 149–151

Cyclo[6]-carbon, 784 [1þ2]cycloadditions

masked silylenes, 689–691 overcrowded diarylsilylenes,

688–689

[1þ3]cycloadditions, kinetically stabilized germylenes, 695–696

[1þ4] cycloadditions

dialkylsilylene synthesis and isolation, 685–687

silylene-isonitrile complexes, 690–691 [2þ1] cycloadditions, dialkylsilylene synthesis

and isolation, 685–687 Cycloadditions

carbene synthesis, 579 2-methylenecyclopentane,1,3-diyls, 180 organic radical ions

bimolecular reactions, 248–250 intra-pair reactions, 243–246 unimolecular reactions, 237–239

strained hydrocarbons, 733 Cycloalkanes, heats of formation, 720–721 Cycloalkenes, carbon atom reactivity,

475–477

Cycloalkenylidenes, steric effects, 382 Cyclobutadiene

p-benzyne, 754–759 matrix isolation, 826–827

unimolecular reactions, 238–239 Cyclobutane

bond angle deformation, 724–725 femtosecond time scale, trimethylene/

tetramethylene diradicals, 915–916 organic radical ions, strained ring cations,

223–228

strained hydrocarbon reactivity, 733–735

thermal decomposition, 732 Cyclobutanone, femtosecond time scale

Norrish I intermediate, 913–914 photolysis, 914 trimethylene/tetramethylene diradicals,

915–916

2,2,4,4-d4-cyclobutanone, femtosecond time scale,

914

3,3-d2-cyclobutanone, femtosecond time scale,

914

INDEX 1021

Cyclobutenes, singlet carbenes, stepwise addition vs. concerted reaction, 294–297

Cyclodecanone, femtosecond time scale, Norrish I intermediate, 913–914

Cyclohepta-1,2,4,6-tetraene, incarcerated carbenes, 317–319

ring expansion reactions, electronic structure calculations, 982–985

Cycloheptatetraene

carbon atom reactivity, 479–484, 481–484 phenylcarbene rearrangement, incarcerated

carbene chemistry, 316–317 Cycloheptatrienylidene, incarcerated carbenes,

316–317

Cycloheptyne derivatives, silylene multiple bond addition, 675–677

1,3-Cyclohexadiene, femtosecond time scale, structural determinations,

919–920 1,4-Cyclohexadiene

excited state spectroscopy, 437–438 femtosecond time scale, 911

Cyclohexadienyl radical, femtosecond time scale, 911

Cyclohexane-1,4-diyl, radical cation structure, 229

Cyclohexanone, femtosecond time scale, Norrish I intermediate, 914

Cyclohexene, femtosecond time scale, retro-Diels-Alder reactions, 917–918

Cyclohexylamine, carbon acidity-carbanion basicity, condensed-phase measurements, 87–88

gas phase vs., 94 ion-pair acidities, 90–93 kinetic acidity, 94–96

Cyclononapentaene, carbon-alkene reactions, 477

Cyclooctane, steric strain, 726–727 Cyclooctatetraene radical anion

carbon atom reactions, 477

organic radical ions, like charge reactions, 260–261

Cyclopentadiene, carbon acidity-carbanion basicity, sp3 carbanions, hybridized C–H bonds, 84–86

Cyclopentadienylidene, matrix isolation, 816

1,3-Cyclopentane-diyl diradical, femtosecond time scale, trimethylene/tetramethylene diradicals, 916