55166-13-7Relevant academic research and scientific papers
VARIABLE TEMPERATURE ESR SPECTRA OF 1-(3,4,5-TRIMETHOXY-BENZOYL)-2,2-BIS(3,5-DI-TERT-BUTYL-PHENYL)HYDRAZYL AND ITS 1-(15)N-CONGENER
Crasovschi, Afanase,Grecu, Nicoleta,Negoita, Nicolae,Caproiu, Miron Teodor,Balaban, Alexandru T.
, p. 1335 - 1340 (2007/10/03)
The title free radicals were obtained by oxidation of the corresponding hydrazines which were synthesized and characterized by elemental analysis, IR and 1H-NMR spectra. The ESR spectra of the free radicals were recorded in toluene in the temperature range -50 deg C to +90 deg C. The simulated ESR spectra indicate a higher spin density at the tricoordinated N-2 nitrogen of the diarylamino group (hfc aN = 0.862 mT) than at the dicoordinated N-1 nitrogen atom (hfc aN = 0.830 mT). In the temperature range 0 deg C to 30 deg C the activation free energy for interconversion of conformers was determined to be ΔG(excit.) = 7.80 kcal/mol.
Factors Affecting the Stability and Equilibria of Free Radicals. 14. Unexpected Spin Densities in 1-(Trifluoroacetyl)-2,2-diarylhydrazyl Revealed by 15N Labeling
Bologa, Ursula,Balaban, Alexandru T.,Grecu, Nicoleta,Negoita, Nicolae,Caproiu, Miron T.,Walter, Robert I.
, p. 4176 - 4179 (2007/10/02)
1-(Trifluoroacetyl)-2,2-bis(3,5-di-tert-butylphenyl)hydrazyl and its congener labeled at the dicoordinated 1-nitrogen atom with 15N were prepared.ESR spectra of solutions of both compounds were recorded and hyperfine coupling constants determined by optimizing simulated spectra.Unlike all other 1,2,2-triarylhydrazyls which have been investigated, the hyperfine coupling constant for the dicoordinated nitrogen is lower (0.7 mT) than that for the tricoordinated nitrogen (1.0 mT) in this free radical.This striking result raises questions about the mode of trifluoroacetyl group participation in ? electron delocalization.
