scholarly journals Steric Effect on Dimer Radical Cation Formation of Poly(3,6-di-tert-butyl-9-vinylcarbazole) and Its Dimeric Model Compounds Studied by Laser Photolysis

1990 ◽  
Vol 22 (4) ◽  
pp. 319-325 ◽  
Author(s):  
Yoshinobu Tsujii ◽  
Kazukiyo Takami ◽  
Akira Tsuchida ◽  
Shinzaburo Ito ◽  
Yoshihiko Onogi ◽  
...  
Keyword(s):  
Radical Cation ◽  
Steric Effect ◽  
Laser Photolysis ◽  
Model Compounds ◽  
Tert Butyl ◽  
Dimeric Model ◽  
Dimer Radical Cation

Exterplex formation of poly(3,6-di-tert-butyl-9-vinylcarbazole) and its dimeric model compounds with dimethyl terephthalate studied by fluorescence spectroscopy

1993 ◽  
Vol 26 (6) ◽  
pp. 1411-1416 ◽  
Author(s):  
Yoshinobu Tsujii ◽  
Kazukiyo Takami ◽  
Akira Tsuchida ◽  
Shinzaburo Ito ◽  
Masahide Yamamoto
Keyword(s):  
Fluorescence Spectroscopy ◽  
Model Compounds ◽  
Tert Butyl ◽  
Dimethyl Terephthalate ◽  
Dimeric Model

Reactivity and Thermochemical Properties of the Water Dimer Radical Cation in the Gas Phase

1995 ◽  
Vol 99 (42) ◽  
pp. 15444-15447 ◽  
Author(s):  
Sam P. de Visser ◽  
Leo J. de Koning ◽  
Nico M. M. Nibbering
Keyword(s):  
Gas Phase ◽  
Radical Cation ◽  
Water Dimer ◽  
Thermochemical Properties ◽  
Dimer Radical Cation

Cleavage of the radical cations of alkenes; 1-butene and 4,4-dimethyl-1-pentene. Ab initio calculations on the interaction between the allyl and alkyl radical and carbocation moieties

1991 ◽  
Vol 69 (9) ◽  
pp. 1365-1375 ◽  
Author(s):  
Xinyao Du ◽  
Donald R. Arnold ◽  
Russell J. Boyd ◽  
Zheng Shi
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Radical Cation ◽  
Alkyl Radical ◽  
Radical Cations ◽  
Molecular Orbital Calculations ◽  
Allyl Radical ◽  
Allyl Cation ◽  
Tert Butyl ◽  
Carbon Carbon Bond

Carbon–carbon bond cleavage of the radical cations of 1-butene [Formula: see text] and 4,4-dimethyl-1-pentene [Formula: see text] will generate the allyl and alkyl radical and carbocation fragments. Alternative bonding arrangements between the allyl and methyl moieties in [Formula: see text] and between the allyl and tert-butyl moieties in [Formula: see text] possible metastable intermediates or transition states preceding complete separation of the fragments, have been investigated by ab initio molecular orbital calculations. Structures were fully optimized at the UHF/6-31G* or UHF/STO-3G levels, and some of the calculations on [Formula: see text] were expanded with single point MP2/6-31G*//UHF/6-31G* computations. The C4H8+ radical cation, having a structure similar to that of 1-butene, is more stable than the separated fragments: 183 kj mol−1 lower in energy than the sum of the energies of the allyl cation and the methyl radical, and 385 kJ mol−1 lower than the sum of the energies of an allyl radical and a methyl cation, at the MP2/6-31G* level. The corresponding values at the UHF/STO-3G level are 276 and 415 kj mol−1, respectively. There is less bonding interaction between the allyl and tert-butyl moieties in [Formula: see text] The summation of the energies of the allyl radical and tert-butyl cation is 123 kj mol−1 lower than the summation of the energies of the allyl cation and tert-butyl radical, and 115 kJ mol−1 higher in energy than the bonded radical cation [Formula: see text] at the UHF/STO-3G level. These calculated values are compared with thermochemical data and with experimental results on the cleavage of these, and related, radical cations. Key words: radical cation, cleavage, ab initio calculations, electron transfer, photochemistry.

Lignin-degrading enzymes

1987 ◽  
Vol 321 (1561) ◽  
pp. 461-474 ◽  
Keyword(s):  
Lignin Biodegradation ◽  
Major Research ◽  
Model Compounds ◽  
Peroxidase Isoenzymes ◽  
Cation Radicals ◽  
Radical Intermediates ◽  
Degrading Enzymes ◽  
Potential Applications ◽  
Full Complement ◽  
Dimeric Model

The substantial potential applications of lignin-degrading microbes and enzymes have spurred research on lignin biodegradation in recent years. As described here, that research has led to the discovery in the basidiomycete Phanerochaete chrysosporium of the first lignin-degrading enzymes and elucidation of their mode of action. A family of powerful extracellular peroxidase isoenzymes has been the focus of most investigations. The key catalytic reaction of these glycoproteins, in the presence of hydrogen peroxide, is one-electron oxidation of aromatic nuclei, generating unstable aryl cation radicals. These decompose via a number of reactions, which have been elucidated with dimeric model compounds for lignin. The involvement of carboncentred and peroxyl free-radical intermediates has been established. The peroxyl intermediates result from the addition of molecular oxygen to the C-centred radicals. Strong evidence for a classical peroxidase-type catalytic cycle of the ligninases has been obtained. The major research need is to identify the full complement of enzymes needed to degrade lignin to small fragments; this degradation is not accomplished by the isolated ligninases or by the crude extracellular mixture of enzymes secreted by cultures as they degrade lignin.

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