Gamma irradiation of hexafluorobenzene

Abstract

Mi xt ures of hexafluo robenze ne a,nd benze ne were irra di ated in li quid phase by means of a C060 cram ma o urce at 20° a nd a t '2 18° C. P crfiuoro hep tane a nd va ri ous b inar.v mix t ures involvi~g perflu o roh epta nc, h exaflu or obe ll ze ne, be nze ne, a nd cyclo hexane were a lso in'ad iated at 20° C. H exafluorob e nzene rese mb led benze ne ve ry closely in its behav ior up o n r a dio \ys is. Ge nerall y t he fluor oc arbon-h ydrocarbon mix t ur es evolved mu ch mo rc SiF4 (indi cat in g th e form at ion of J-IF, which r eac ts with th e glass vesse l) than th e pure flu orocarbon co mpon ents. The polym er from hexaflu o robe nze ne-benzrne mixtures was p r oba~ly ri ch in cyclohexadi ene a nd cycloh exe ne un its , I'cse mbiin g t hat from pu re benzene, a nd Its co mposition rat io exhib ited a strong "alte rn at in g" te nd e ncy. Th e res ults a re di scussed in te rms of fr ee-radi cal and excited-state mechanisms. r\ t 218 0 C hexaflu o robenzene a nd a lso its mixtures with benze ne showed qua litat ive difl'erences from th eir beha vior a t 20° C, a ltho ug h t he G va lues for SiF4 and p o lymer rema in ed mode rat e.

Gamma irradiation of fluorocarbon polymers

“…The radiation facility was a 2,000-curie Co 60 source having an exposure dose rate near 0.5×10 6 R/hr. Methods for calculating the absorbed dose have been described [ 10 ]. Doses were in the range 1 to 200 × 10 6 R, and irradiations were made usually at a temperature of 20±2 °C.…”

“…Gamma rays affect C 3 F 6 remarkably slowly, and high polymer is not formed [ 33 ]. When perfluoroheptane is irradiated in vacuo in dry aluminum containers, scission products are present in small amounts only, no corrosion or inorganic fluoride is seen, and the irradiated material contains coupling products [ 9 , 10 ]. In nickel tubes with glass capillary ends, small amounts of SiF 4 are seen also [ 10 ].…”

“…Most practical evaluations are made in the presence of air and moisture at 25 °C; results in vacuum can differ profoundly from these in some instances. Small fluorocarbon molecules studied in sealed containers [ 9 , 10 ] have been found to be more stable towards radiation when air is absent. Because of the influence of diffusion (of oxygen inward and degradation products outward) the observed effects may depend upon the sample dimensions.…”

The Effect of Solvent on the Acid-Base Kinetics of the Excited State of β-Naphthol1

“…In a series of papers, Weller* reported investigations of the kinetics of proton-transfer reactions in the excited state by means of fluorescence measurements.616 He was able to determine the forward and backward rate constants for the reaction k k (1) HA* + B" A A-* + HB ("+~) where HA* and A-* are the acidic and basic forms of the fluorescent compound concerned, B" is the proton acceptor (n is the charge) which may be water, acetate, hydroxide ion, etc. A detailed mechanism was also proposed.…”

“…A knowledge of the effects of changing solvent properties such as viscosity, dielectric constant, and concentration of water, for example, would help to elucidate some details of the acid-base reaction (1). In addition, the measurement of solvent effects would provide a basis for testing the mechanism proposed by Weller.…”