Laser Flash Photolysis Generation, Spectra, and Lifetimes of Phenylcarbenium Ions in Trifluoroethanol and Hexafluoroisopropyl Alcohol. On the UV Spectrum of the Benzyl Cation

Abstract

The radical cation 2 is also able to attack the C-N double bond in imines in an intermolecular fashion, a reaction not possible for photochemical 1,3-dipolar cycloaddition.16] The reaction of azirines with imines leads to the formation of the N-substituted imidazoles.The course of the reaction is as follows: Addition of the radical cation 2 to the imine is followed by ring closure to form a dihydroimidazole. Under these reaction conditions the dihydroimidazole is not stable and undergoes subsequent aromatization, so that, even in the crude product, no dihydroimidazole is detected. Huisgen[71 did not find a dihydroimidazole under comparable conditions either. The reaction of azirines with imines offers a ready approach for the synthesis of N-substituted imidazoles with a wide variety of substituents.Since the C-N double bonds of the imine and the azirine compete for reaction, the yields of imidazoles vary rather widely ( Table 1). The remaining products are the azirine

Photochemistry of Arylmethyl Esters in Nucleophilic Solvents: Radical Pair and Ion Pair Intermediates

“…55 c Based on oxidation potentials of arylmethyl radicals in acetonitrile. 8,49 d Based on absorption spectra of arylmethyl cations in HFIP, measured for the 4-methoxybenzyl cation and estimated for the benzyl cation, 56 and on pulse radiolysis results for the benzyl cation formed from benzyl chloride. 57 e Based on absorption spectra of benzyl radicals in hexane.…”

The photochemistry of 3,3′,4,4′-tetramethoxy-and 4-hydroxy-3,3′,4′-trimethoxystilbene — models for stilbene chromophores in peroxide-bleached, high-yield wood pulps

“…Photoprotonation of phenylalkenes is well documented (22)(23)(24)(25)(26)(27)(28), and is known to be enhanced by the presence of electron-donating aromatic substituents. The process occurs with relatively low efficiency (compared to cis,trans isomerization) in 1 a n d 3, but competes effectively with phenanthrene formation and oxidative cleavage in the presence of oxygen.…”

Electronic absorptions of the benzylium cation

“…Although, both Bz + and Tr + are predicted to have distinctive electronic transitions in the visible and ultraviolet (UV) regions, until recently, only rather broad, structureless electronic absorptions had been observed for C 7 H 7 + cations in the solution phase, Ar matrix environment, and in ion traps. [5][6][7][8][9][10] Moreover, these studies are characterised by significant differences in reported band positions and assignments. For example, Ar matrix studies with benzyl chloride a) Electronic mail: evanjb@unimelb.edu.au.…”