Marjory T. Craw

A CIDEP and fluorescence study of the oxidation of vitamin E: The vitamin E radical cation

The photochemical and thermal oxidations of vitamin E in trifluoroacetic acid were investigated by the combination of electron spin resonance, chemically induced dynamic electron polarization, and fluorescence techniques. Two independent thermal pathways led to the formation of the vitamin E radical cation in which one of the paths involved the intermediate neutral semiquinone radical. Photo-oxidation, however, did not involve the neutral radicals. The fluorescence spectra of both the neutral and the charged forms of the vitamin E radicals are reported here for the first time. Some model charge transfer reactions involving the vitamin E radical cation were reported.

ELECTRON SPIN RESONANCE OF RADICAL CATIONS IN NAFION MEMBRANES

Studies of radical cations in solution at room temperature are still relatively rare and require very strongly acidic media; we report here the novel use of the superacidic membrane Nafion (having properties similar to trifluoroacetic acid) for the generation and stabilization of several radical cation species. E.s.r. spectroscopy permitted not only the detection and characterization of the radical cation species so generated but also the qualitative comparison of the effects of the semi-rigid membrane environment on radical mobility as compared to that in solution.

A novel fluorescence detection method for organosilanes

Abstract Quinones such as phenanthraquinone and anthraquinone react with organosilanes giving persistent, strongly fluorescent radicals. the reactions are photochemically initiated, rapid, and facile; detection of concentrations of silanes in the 10−7 M range are readily achieved. the starting materials do not fluoresce making the procedure simple, selective and specific.

AN ESR-CIDEP STUDY OF THE FREE-RADICAL INTERMEDIATES IN THE SULFURIZATION OF 2,5-DIMETHYL-P-BENZOQUINONE WITH LAWESSON REAGENT IN TRIFLUOROACETIC ACID

Abstract Substituted p-benzoquinones undergo rapid sulfurization with Lawesson reagent in triflouroacetic acid. The ESR observations of the radical intermediates and the time-resolved CIDEP results afford some insights into these complex reactions.

Tetrafluoro-p-Benzoquinone Radicals: Chemical Exchange as Evidenced by Cidep

Abstract The CIDEP characteristics of radicals derived from tetra-fluoro-p-benzoquinone have been studied. An alternating linewidth effect in the time-resolved CIDEP spectra was observed when a hydroxylic/non hydroxylic solvent mixture was used. The results are discussed in terms of chemical exchange between the neutral and anionic quinone radicals.