Functional imaging using fluorine ((19)F) MR methods: basic concepts

Kidney-associated pathologies would greatly benefit from noninvasive and robust methods that can objectively quantify changes in renal function. In the past years there has been a growing incentive to develop new applications for fluorine ((19)F) MRI in biomedical research to study functional changes during disease states. (19)F MRI represents an instrumental tool for the quantification of exogenous (19)F substances in vivo. One of the major benefits of (19)F MRI is that fluorine in its organic form is absent in eukaryotic cells. Therefore, the introduction of exogenous (19)F signals in vivo will yield background-free images, thus providing highly selective detection with absolute specificity in vivo. Here we introduce the concept of (19)F MRI, describe existing challenges, especially those pertaining to signal sensitivity, and give an overview of preclinical applications to illustrate the utility and applicability of this technique for measuring renal function in animal models. This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis

Synthesis of novel fluorinated 4H-benzo[h]chromen-4-one and 4H-pyranol[3,2-h]quinolin-4-one derivatives.

International audienc

The thermal transformations of bicyclopropylidene and methylenespiropentane revisited

The overall and the individual rate constants of the unimolecular thermal isomerization of methylenespiropentane (4) to 1,2- and 1,3-dimethylenecyclobutanes (7 and 8) have been determined to be lg (k(-4)/s(-1)) = (13.78 +/- 0.06) - (49.7 +/- 0.2) kcal mol(-1)/RT.ln 10, lg(k(7)/s(-1)) = (13.03 +/- 0.19) - (48.0 +/- 0.6) kcal mol(-1)/RT.ln 10 and lg(k(8)/s(-1)) = (14.15 +/- 0.19) - (52.4 +/- 0.5) kcal mol(-1)/RT.ln 10, respectively. The activation energies are significantly lower than that for the rearrangement of the parent spiropentane. ((c) Wiley-VCH Verlag GmbH & Co

Radical Terpolymerization of 1,1,2-Trifluoro-2-pentafluorosulfanylethylene and Pentafluorosulfanylethylene in the Presence of Vinylidene Fluoride and Hexafluoropropylene by Iodine Transfer Polymerization

International audienceIodine transfer terpolymerization of two monomers bearing an SF5 group, i.e., 1,1,2-trifluoro-2- pentafluorosulfanylethylene (F2CdCFSF5) and pentafluorosulfanylethylene (H2CdCHSF5), with 1,1-difluoroethylene (or vinylidene fluoride, VDF) and hexafluoropropylene (HFP) is presented. These pentafluorosulfanyl monomers present a peculiar reactivity. They do not homopolymerize by conventional radical polymerization, but they co- and terpolymerize with the above fluorinated olefins. The resulting fluorinated terpolymers were characterized by 19F and 1H NMR spectroscopies which enabled the assessment of the molar percentages of the three comonomers. Size exclusion chromatography and NMR characterizations were also used to assess the molecular weights, Mn, ranging between 260 and 8400 g/mol. Interestingly, both these pentafluorosulfanyl monomers exhibit different behaviors in that radical terpolymerization in the presence of C6F13I as a degenerative chain transfer agent. Thus, CF2CFSF5 can be terpolymerized with VDF and HFP with a good control of molecular weight leading fluoropolymers bearing SF5 groups with low polydispersity index (PDI). Unexpectedly, only two iodide functionalities of the terpolymers namely two end groups (-CH2CF2I and -CF2CH2I) were observed and their proportions were influenced by the number of VDF units. Indeed, -CH2CF2I functionality decreased when the number of VDFs per chain increased. In contrast to 1,1,2-trifluoro-2-pentafluorosulfanyl ethylene, H2Cd CHSF5 could not be terpolymerized by ITP but led to C6F13[(CH2CF2)(CH2CH(SF5)]nI alternating cooligomers of low molecular weight in poor yields (5-20%). The formation of byproduct (C6F13CHdCHSF5 monoadduct obtained by dehydrofluorination) was also observed, which corresponds to the elimination of HI from the 1:1 adduct. In the last part, the thermal properties are discussed. The presence of SF5 group decreases the Tg of fluoropolymers whereas the thermal stabilities depended on the molecular weights

Perfluoro-tert-butyl, a reactive, neutral, electrophilic carbon-centered radical par excellence

Absolute rate constants for (CF3)3C. addition to terminal olefins increase by roughly a factor of 30 for every 1 eV decrease in the ionization potential (IP) of the alkene. A similar decrease in IP increases the rate of addition of CF3. and n-C3F7. by a factor of only 3 or 4. The perfluoro-tert-butyl radical is, therefore, the most electrophilic, neutral carbon-centered radical to have been studied to date.Peer reviewed: YesNRC publication: Ye