Radiotracers in fluorine chemistry. Part VIII. Fluorine-18 exchange reactions involving uranium(VI) or uranium(V) fluorides. Evidence for surface complexation and comparisons with ligand exchange reactions [1]

Investigation of fluorinated surfaces by means of radio-labelled probe molecules

“…An aqueous solution of 18 F À is transported to Glasgow and converted as previously described to solid Cs 18 F (typically 50-450 MBq) [11]. Although the closest medical cyclotron to Glasgow is the John Mallard Scottish PET Centre, Aberdeen, the time loss as a result of the 3 h road journey to Glasgow is offset by the higher specific activities Cs 18 [3,[11][12][13][14][15][16]. These exchange reactions have the advantage of occurring relatively quickly at moderate temperatures (typically temperatures in the range 323-373 K are used) but, because normally all F atoms are exchangeable, the radio-label is distributed statistically throughout and, as a result, specific activities may be relatively low.…”

Activation Energy for Isotope Exchange Reaction between 235UF5 Nanoparticles and 238UF6 Gas

“…We then investigated the origin of such a difference. It is a straightforward way to assume the following mechanism for the isotope exchange reaction between 235 UF 5 particles and 238 UF 6 . First, a 238 UF 6 molecule adsorbs on the surface of the outermost layer of the 235 UF 5 particle, and then a fluorine atom in the 238 UF 6 gas molecule transfers to a 235 UF 5 molecule on the surface of the UF 5 particles via a transitional state as shown in eq 3.…”

Silicon-[18F]Fluorine Radiochemistry: Basics, Applications and Challenges

“…It seems that C- 18 F radiochemistry has reached its limits and alternative strategies have to be found to advance the field further in terms of convenience, applicability and reliability. The use of Si-F bond formation in radiochemistry dates back to 1958 [19] and a few more papers on that subject have been published before the first in vivo application was reported [20][21][22].…”