Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 1066-1076
Author(s):  
Hideo Tomioka ◽  
Junichi Nakajima ◽  
Hidehiko Mizuno ◽  
Eiji Iiba ◽  
Katsuyuki Hirai

A series of triplet 9-triptycyl(aryl)carbenes, where aryl groups are phenyl, 1- and 2-naphthyl, and 9-anthryl, is generated by photolysis of the corresponding diazomethanes and observed directly by spectroscopic means. Their structures are characterized by electron spin resonance (ESR) spectroscopy in a 2-methyltetrahydrofuran matrix at 77 K, and the reactivities are investigated by laser flash photolysis in degassed benzene solution at room temperature. Comparison of the data with other arylcarbenes bearing a series of substituents, i.e., hydrogen, phenyl, naphthyl, and anthryl groups, revealed an interesting relationship between structures and reactivities of triplet arylcarbenes.Key words: steric protection, stability of triplet carbenes, electron spin resonance, laser flash photolysis, structure-reactivity relationship.




2021 ◽  
Vol 118 (2) ◽  
pp. 022407
Author(s):  
Hideyuki Takahashi ◽  
Yuya Ishikawa ◽  
Tsubasa Okamoto ◽  
Daiki Hachiya ◽  
Kazuki Dono ◽  
...  


1984 ◽  
Vol 78 ◽  
pp. 257 ◽  
Author(s):  
Christopher D. Buckley ◽  
Andrew I. Grant ◽  
Keith A. McLauchlan ◽  
Andrew J. D. Ritchie


The electron spin resonance method was employed to study the nature, concentration and kinetics of the disappearance under varying conditions of radicals produced in polyethylene by fast electron irradiation at 77°K. The predominant radical species at 77°K is the alkyl radical —CH 2 —ĊH—CH 2 —. On being warmed to room temperature it disappears rapidly, revealing a more stable un­identified radical. The kinetics of the decay at room temperature of both radicals was observed. Their stabilities were found to vary in polyethylene samples of differing physical and chemical properties. G values for these radicals are given. Comparison was made with spectra obtained under similar conditions with two pure paraffins and a pure olefin to evaluate the effect of crystallinity branching, molecular weight and unsaturation. In the olefin there is evidence for a build-up of allyl radicals due to the encounter of an alkyl radical with main chain unsaturation. This supports the view that alkyl radicals are mobile, and cross-linking occurs when two such radicals meet.





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