Photochemistry of the CX group

Sammes, Peter G.

doi:10.1002/9780470771280.ch11

Cited by 15 publications

(8 citation statements)

References 164 publications

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“…Photolysis of monohalogenated organic compounds is known to induce carbon−halogen (C−X) bond cleavage, to give products from either heterolysis or homolysis, depending on the structure of the compound, the nature of the leaving group, and the polarity and nucleophilicity of the solvent . In the case of homolytic cleavage, the final products result from radical reactions.…”

Section: Introductionmentioning

confidence: 99%

Lamp versus Laser Photolysis of a Bichromophoric Dichloroalkane: Chemical Evidence for the Two-Photon Generation of the 1,5-Diphenylpentanediyl Biradical

et al. 1996

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Low intensity (lamp) photolysis of 1,5-dichloro-1,5-diphenylpentane (1) leads to the formation of the 1-chloro-1,5-diphenylpentyl radical (7) through C-Cl bond cleavage. Radical 7 leads to the final products through typical free radical reactions. No cyclopentanes are formed under low intensity conditions. In contrast, high intensity laser irradiation leads to C-Cl photocleavage of radical 7 to yield the 1,5-diphenylpentanediyl biradical (11), which results in the formation of isomeric cis- and trans-1,2-diphenylcyclopentanes; the behavior of these biradicals agrees well with that observed when their precursor is 2,6-diphenylcyclohexanone. Two-color two-laser experiments suggest that both singlet and triplet biradicals are formed, even if only the latter are detectable with nanosecond techniques.

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Section: Introductionmentioning

confidence: 99%

Lamp versus Laser Photolysis of a Bichromophoric Dichloroalkane: Chemical Evidence for the Two-Photon Generation of the 1,5-Diphenylpentanediyl Biradical

et al. 1996

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“…Photolysis of monohalogenated organic compounds is known to induce carbon−halogen (C−X) bond cleavage, giving products from either heterolysis or homolysis. Their ratio depends on the structure of the compound, the nature of leaving group, and the polarity and nucleophilicity of the solvent. , …”

Section: Introductionmentioning

confidence: 99%

Flash Photolysis of (E)-1,2-Bis(1-chloro-1-phenylmethyl)cyclopropane. Generation of 1,5-Diphenylpentadienyl Radical and 1,5-Diphenylpentadienylium Cation

et al. 2002

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The 1,5-diphenylpentadienyl radical (5) is generated from (E)-1,2-bis(1-chloro-1-phenylmethyl)cyclopropane (1) via a two-photon process, either in cyclohexane or in acetonitrile as solvent. Two-laser two-color flash photolysis experiments show that excitation of the benzylic radical generated by homolysis of the first C-Cl bond leads, after ring-opening and proton loss, to the stabilized radical 5. This radical is also generated by photolysis of either (1E,3E)-5-chloro-1,5-diphenyl-1,3-pentadiene (6) or (1E,4E)-1,5-diphenyl-1,4-)pentadiene (7) via one-photon or two-photon processes, respectively. On the other hand, laser flash photolysis of 1 in acetonitrile also produces some 1,5-diphenylpentadienylium cation (10) generated via a one-photon process. Its formation can be explained as due to competitive photoheterolysis leading to a benzylic cation which thermally ring-opens and dehydrohalogenates. Species 10 is more efficiently generated by photolysis of 6 in acetonitrile and undergoes photoisomerization after laser excitation.

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“…The wavelength of the light absorption by this chromophore depends on both the nature of the halogen atom and the substituent on the carbon atom. For simple chloro- and fluoroalkanes, such absorptions occur below 200 nm, but increasing atomic number of the halogen and aromatic substitution cause a bathochromic shift of the absorption maximum . Absorption of light by monohaloalkanes usually induces carbon−halogen bond cleavage; the ease of homolysis is opposite to the order of the C−X bond strength, C−F < C−Cl < C−Br < C−I .…”

Section: Introductionmentioning

confidence: 99%

“…For simple chloro-and fluoroalkanes, such absorptions occur below 200 nm, but increasing atomic number of the halogen and aromatic substitution cause a bathochromic shift of the absorption maximum. 1 Absorption of light by monohaloalkanes usually induces carbon-halogen bond cleavage; the ease of homolysis is opposite to the order of the C-X bond strength, C-F < C-Cl < C-Br < C-I. 1 Although direct photolysis of the C-F bond is extremely rare, all the benzylic halides undergo light-induced cleavage.…”

Section: Introductionmentioning

confidence: 99%

“…1 Absorption of light by monohaloalkanes usually induces carbon-halogen bond cleavage; the ease of homolysis is opposite to the order of the C-X bond strength, C-F < C-Cl < C-Br < C-I. 1 Although direct photolysis of the C-F bond is extremely rare, all the benzylic halides undergo light-induced cleavage. Previous studies have shown that the initially formed radical pair can escape from the cage to participate in radical processes or undergo electron transfer to generate ionic intermediates (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

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One- vs Two-Photon Processes in the Photochemistry of 1,n-Dihaloalkanes

et al. 2001

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1,n-Dihaloalkanes can be photochemical precursors of n-haloalkyl and -allyl radicals and cations, which are generated via one-photon processes. Time-resolved techniques have provided considerable information on the structures and reactivity of these intermediates. Low-temperature matrix isolation, two-laser two-color, laser-drop, and laser-jet photolysis techniques are powerful tools to photolyze haloalkyl radicals and to generate carbenes or biradicals via two-photon processes.

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Photochemistry of the CX group

Cited by 15 publications

References 164 publications

Lamp versus Laser Photolysis of a Bichromophoric Dichloroalkane: Chemical Evidence for the Two-Photon Generation of the 1,5-Diphenylpentanediyl Biradical

Lamp versus Laser Photolysis of a Bichromophoric Dichloroalkane: Chemical Evidence for the Two-Photon Generation of the 1,5-Diphenylpentanediyl Biradical

Flash Photolysis of (E)-1,2-Bis(1-chloro-1-phenylmethyl)cyclopropane. Generation of 1,5-Diphenylpentadienyl Radical and 1,5-Diphenylpentadienylium Cation

One- vs Two-Photon Processes in the Photochemistry of 1,n-Dihaloalkanes

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