Cation radical-nucleophile combination reactions. Reactions of nitrogen-centered nucleophiles with cation radicals derived from anthracenes

1991 ◽  
Vol 113 (18) ◽  
pp. 6954-6958 ◽  
Author(s):  
Bjorn Reitstoen ◽  
Vernon D. Parker
Keyword(s):  
Cation Radical ◽  
Cation Radicals

scholarly journals Methyl-Eliminierung aus dem metastabilen Homoadamantan-Radikalkation / Methyl Loss from Metastable Homoadamantane Cation Radical

1980 ◽  
Vol 35 (2) ◽  
pp. 207-211 ◽  
Author(s):  
Helmut Schwarz ◽  
Chrysostomos Wesdemiotis ◽  
Thomas Weiske ◽  
Helmut Schwarz ◽  
Chrysostomos Wesdemiotis ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Cation Radical ◽  
Model Calculations ◽  
Direct Ionization ◽  
Cation Radicals

Abstract It is demonstrated that methyl loss from ionized homoadamantane (1) yields exclusively the 1-adamantyl cation (4); there is no experimental evidence for the formation of the secondary adamantyl cation (5). From both model calculations and the investigation of [4-13C]-homoadamantane (1a) and 1(13C-methyl)adamantane (2a) it is concluded, that 24% of the metastable homoadamantane cation radicals dissociate after one isomerization (1→2); the remaining 76% are able to undergo at least a second (degenerate) isomerization cycle (2→1→2) prior to methyl loss. 78% of metastable 1-methyl-adamantane cation radical, obtained upon direct ionization of the corresponding neutral hydrocarbon, dissociate directly, whereas the loss of methyl from the remaining 22% is preceded by an isomerization 2 →1 →2.

Effect of substitution on the redox behaviour and EPR spectra of zinc(II) substituted tetraphenylporphyrin cation radicals

2000 ◽  
Vol 04 (02) ◽  
pp. 192-201 ◽  
Author(s):  
PARESH C. DAVE ◽  
D. SRINIVAS
Keyword(s):  
Ground State ◽  
Cation Radical ◽  
Molecular Geometry ◽  
Chemical Oxidation ◽  
Electronic Ground State ◽  
Epr Spectra ◽  
Redox Behaviour ◽  
Cation Radicals ◽  
First Time ◽  
Electronic Ground

Substituted tetraphenylporphyrinatozinc(II) complexes have been synthesized and characterized by various physicochemical techniques. The effects of substitution and counterions on the redox behaviour and EPR spectra have been examined. The EPR spectra revealed that chemical oxidation with bromine yields ZnT ( X - P ) P + Br - (species I) and a brominated tetraphenylporphyrin cation radical (species II). The former exhibits a labile electronic ground state (with 2 A 2 u ground state transforming into 2 A 1 u at 175 K), while the latter is characterized by a 2 A 1 u state. The lability in the electronic ground state for species I is discussed in terms of the change in molecular geometry as the temperature is lowered. The EPR spectra also revealed for the first time the formation of dimeric agglomerates of TPP cation radicals in low concentration below the electronic transition (i.e. near 170 K) wherein the paramagnetic sites are antiferromagnetically coupled.

Vicinal-diaryl interactions in stilbenoid hydrocarbons as observed in the through-space charge delocalization of their cation radicals

1999 ◽  
Vol 77 (5-6) ◽  
pp. 913-921 ◽  
Author(s):  
Rajendra Rathore ◽  
Jay K Kochi
Keyword(s):  
Space Charge ◽  
Cation Radical ◽  
Conformational Preference ◽  
Charge Delocalization ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cation Radicals ◽  
Near Ir ◽  
Aromatic Interactions ◽  
Vis Spectroscopy

The conformational preference of vicinal or 1,2-phenyl groups is probed in two classes of ring-substituted 1,2-diphenylbicyclooctene (stilbenoid) hydrocarbons 1a-1d and 2a-2c. UV-vis spectroscopy reveals, and X-ray crystallography verifies, the intramolecular (edge-to-face) orientation for the phenyl-phenyl interaction in stilbenoids 1a-1d. Most importantly, when two pairs of ortho-methyl substituents are present, the cofacial phenyl groups in the stilbenoid donors are established by X-ray crystallography and spectrally observed in the cation radicals (2a+.-2c+.) by the appearance of new bands with strong absorptions in the near IR with λmax = 1100-1315 nm, analogous to those previously observed in intermolecular (aromatic) interactions of aromatic cation radicals.Key words: stilbenoid hydrocarbon, cation radical, aryl-aryl interaction.

Oxygenation of 1-t-Butylcyclohexa-1,3-diene and Cholesta-2,4-diene in the Presence of Trityl Tetrafluoroborate

1988 ◽  
Vol 41 (4) ◽  
pp. 505 ◽  
Author(s):  
MF Arain ◽  
RK Haynes ◽  
SC Vonwiller ◽  
TW Hambley
Keyword(s):  
High Field ◽  
Cation Radical ◽  
Chemical Degradation ◽  
Crystal Data ◽  
X Ray ◽  
Cation Radicals ◽  
Crystallographic Study ◽  
The One ◽  
Allylic Radical ◽  
Tungsten Lamp

Whereas the oxygenation of 1-t-butylcyclohexa-1,3-diene (4) in the presence of catalytic amounts of trityl tetrafluoroborate in dichloromethane at -78° under irradiation from a tungsten lamp gives two dimeric epidioxides as major products, cholesta-2,4-diene (5) gives under the same conditions a monomeric endoperoxide. The structures of the dimeric epidioxides have been established by a combination of chemical degradation, high-field 1H n.m.r. and an X-ray crystallographic study on the diketone (12) derived from one of the epidioxides. A mechanism involving the generation of intermediate monomer and dimer cation radicals is used to account for the formation of the dimeric epidioxides. The dimer cation radicals are expected to be more reactive than the monomer cation radicals towards oxygen. The dimerization is assumed to take place when the diene (4) and its monomer cation radical are aligned so that one reactant lies above the other whereby π-orbital overlap between the rings is maximized; oxygen is constrained to attack the one exposed face of the allylic radical system in the dimer cation radical. This accounts for the unique stereochemistry of the epidioxide products. Crystal data for diketone (12): a 29.975(4), b 5.767(1), c 11.758(2)Ǻ, β 111.67(2)°; C2/c; Z4.

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