Etude par résonance paramagnétique électronique de la radiolyse en phase solide de composés cycliques perfluorés

Abstract

Perfluorocyclohexane (PFCH) and perfluoromethylcyclohexane (PFMCH) have been irradiated in the solid state by γ rays of 60Co. The electron spin resonance (e.s.r.) spectrum of PFCH irradiated at 77 °K corresponds mainly towhich is tumbling in the matrix above 160 °K and disappears at the transition point (180 °K). When γ irradiation is carried out at 200 °K, C6F11• is also produced, but reacts with PFCH giving a radicalsupposed to be [Formula: see text]The e.s.r. spectrum of PFMCH γ irradiated at 77 °K has not been identified; it might be attributable in part to (•C6F11CF3)−. Above 160–170° K, the e.s.r. spectrum corresponds only toThe equal coupling of the four γ fluorines and also the relative intensity 1:4:1 of the three main groups of lines observed above 210 °K suggest that ring inversion occurs with a high rate.We have also studied the radicals [Formula: see text]produced by γ irradiation in the presence of oxygen. The variation of their spectra with temperature, particularly near the transition points, is very characteristic of the motion involved.

E.S.R. Studies of Halogenated Pyrimidines in Gamma-irradiated Alkaline Glasses

“…of •U -S but not U • at 77°K is consistent with results reported previously byHolroyd and Glass (1968) andNazhat and Weiss (1970) on the immediate protonation of thymidine anion radical at 77°K in contrast with the thymine anion radical which does not protonate in alkaline glass until the glass is annealed in the temperature range 150°-175°K (Simpson and Zimbrick, unpublished results) .ACKNOWLEDGMENTS This research was supported by NIH grant GM 18927 and by University of Kansas General Research Fund Grant No . 3221-5038 .…”

“…The latter doublet is evidence that a small fraction of the 0 --adducts of FUr retain the halogen at C 5 which produces the observed 66 G splitting . Chachaty, Forchioni and Shiotani (1970) report a similar value for f3-fluorine splittings obtained in the solid phase by the radiolysis of perfluorinated ring compounds .…”

Rotational vibration of poly(tetrafluoroethylene) chains by the electron spin resonance method

“…This agreed well with the experimental data in Figure 4 because δ was also an increasing function of temperature. To estimate the amplitude, we substituted into eq 2 the constants b 1 = 0.9 mT and b 2 = 3.8 mT, as suggested by Chachaty et al:28 The absolute amplitude calculated from eq 3 is ambiguous for the rotational vibration of the large amplitude because the harmonic torsional oscillation is assumed. The absolute amplitude seems to be questionable.…”

Mouvements moléculaires et transitions de phases dans le perfluorométhylcyclohexane solide

“…indique l'existence d'une corrklation entre les mouvements des radicaux et ceux des molkcules de la matrice. Nous avons ainsi montrk qu'en phase I les molkcules de PFMCH sont en rkorientation quasi-isotrope et il en est de m&me pour les radicaux e F l pikgks dans cette phase (1). En phase I1 les molkcules sont en rotation autour de l'axe pseudoternaire du cycle et l'on a vu que le spectre r.p.e.…”

“…des radicaux piCgCs dans le perfluoromCthylcyclohexane (PFMCH) irradiC prCsentent d'importantes variations entre 77 OK et le point de fusion de ce composC (234 OK) (1).…”