Influence Of Fluorine Substituents Research Articles

Enhanced bioaccumulation of fluorinated antibiotics in crucian carp (Carassius carassius): Influence of fluorine substituent

The negative impact of residual fluorinated antibiotics on the ecosystem and human health are of great concern. However, only a few studies have been conducted on the factors that influence the bioaccumulation of fluorinated antibiotics in aquatic organisms. To investigate the effects of fluorine substituent, environmental concentration of antibiotics, and temperature on the bioaccumulation of florfenicol (FLO), thiamphenicol (TAP), ofloxacin (OFX), and pipemidic acid (PPA), crucian carp (Carassius carassius) were exposed to different concentrations of antibiotics and different temperatures for 21 days. The liver exhibited the highest antibiotic concentrations, with 315.4 ± 13.6 ng g−1 wet weight (ww), followed by the bile (279.4 ± 12.4 ng mL−1), muscle (53.1 ± 4.3 ng g−1 ww), and gills (37.1 ± 2.6 ng g−1 ww). The FLO and OFX containing the fluorine substituent were much easier to accumulate in crucian carp compared with their isonomic TAP and PPA, respectively. The fluorine substituent increased the bioaccumulation of the targeted antibiotics in crucian carp. In addition, the lower levels of antibiotics presented higher bioaccumulation potential, but the temperature had little effect on the bioaccumulation. These findings in the present study can provide further insight into the environmental behaviors and ecological risks of fluorinated antibiotics in the aquatic environment.

Fluorinated alkali metal catalysts for the Ring-Opening Polymerization (ROP) of rac-lactide. Effect of the M···F interactions in the polymerization control

A series of lithium, sodium, and potassium complexes with different fluorinated phenoxo-imine ligands [M(O-2-(RN = CH)–C6H4] [R = 2,4,6-F3C6H2; 2,3-F2C6H3; 2-FC6H4] (1–3) (a,b,c) have been studied as catalysts for the Ring-Opening Polymerization (ROP) of rac-lactide. The sodium and potassium compounds are extremely active catalysts and reach quantitative conversions in just a couple of minutes when sodium or potassium are employed. In contrast, the lithium catalysts are slower but produce highly heterorich-PLA. The influence of fluorine substituents in the catalysts has been explored by analyzing their activity, the polymers tacticity and molecular weights in comparison to the fluorine-free derivatives [M(O-2-(RN = CH)C6H4] [R = 2-tBuC6H4; 2,6-iPr2C6H3] previously reported by us. The results show that the presence of fluorine atoms in the catalysts exerts a great influence on the polymerization reaction. The action of BnOH as chain transfer agent (CTA) has been also investigated for these ROP processes.

Influence of fluorine substituents on the properties of phenylboronic compounds

Abstract Rapid development of research on the chemistry of boronic acids is connected with their applications in organic synthesis, analytical chemistry, materials’ chemistry, biology and medicine. In many applications Lewis acidity of boron atoms plays an important role. Special group of arylboronic acids are fluoro-substituted compounds, in which the electron withdrawing character of fluorine atoms influences their properties. The present paper deals with fluoro-substituted boronic acids and their derivatives: esters, benzoxaboroles and boroxines. Properties of these compounds, i.e. acidity, hydrolytic stability, structures in crystals and in solution as well as spectroscopic properties are discussed. In the next part examples of important applications are given.

Influence of fluorine substituents on the NMR properties of phenylboronic acids

The paper presents results of a systematic NMR studies on fluorinated phenylboronic acids. All possible derivatives were studied. The experimental (1)H, (13)C, (19)F, (11)B, and (17)O spectral data were compared with the results of theoretical calculations. The relation between the calculated natural bond orbital parameters and spectral data (chemical shifts and coupling constants) is discussed. The first examples of (10)B/(11)B isotopic effect on the (19)F spectra and (4)JFO scalar coupling in organic compounds are reported.

Influence of fluorine substituents on the film dielectric constant and open-circuit voltage in organic photovoltaics

Conjugated polymers with fluorine substituents on their backbone have exhibited improved performance over their un-fluorinated analogues by lowering the polymer HOMO level, thereby increasing the open-circuit voltage (VOC). To further investigate how fluorine substituents improve device performance, three polymers with the same donor and acceptor co-monomers, but differing by the number of fluorine atoms on the acceptor unit, were synthesized. Although the HOMO levels of the mono-(P1F) and di-fluorinated (P2F) polymers are essentially the same, an increase in VOC was still observed in the OPV device incorporating P2F. This implies that correlating the VOC to the donor polymer HOMO level is inadequate to fully explain the improvement in VOC. By calculating the charge transfer exciton binding energy from the measured film dielectric constant, it was found that the increase in VOC in going from P1F to P2F matches the decrease in charge transfer exciton binding energy.

Aggregation of fluorine-substituted pyridines

The influence of fluorine substituents on the crystallisation behaviour of pyridine was investigated by crystal structure determinations. The low melting compounds 2-fluoropyridine, 2,6-difluoropyridine and 2,4,6-trifluoropyridine were crystallised by in situ crystallisation directly on the single crystal X-ray diffractometer.

New phase sequences in banana-shaped mesogens: influence of fluorine substituent in compounds derived from 2,7-dihydroxynaphthalene

The synthesis and characterization of several new banana-shaped mesogens derived from 2,7-dihydroxynaphthalene are described. Some new phase sequences such as N → B6 → B1, N → X1 → X2 → B6, N → X1 → X2 → B1 → Col? have been observed in these bent-core compounds. The influence of a lateral fluorine substituent on the occurrence as well as mesophase type have been investigated. The mesophases have been characterized using polarized light optical microscopy, differential scanning calorimetry, X-ray diffraction studies and electro-optical switching studies.

Influence of fluorine substituent on the mesomorphic properties of five-ring ester banana-shaped molecules

The synthesis and characterization of more than a hundred achiral compounds composed of banana-shaped molecules and belonging to eleven different homologous series are reported. All these symmetrical five-ring compounds are esters and are derived from resorcinol. The compounds have been systematically substituted by fluorine on the phenyl rings of the arms of these banana-shaped molecules. The mesophases exhibited by these compounds have been characterized using a combination of polarized light optical microscopy, differential scanning calorimetry and X-ray diffraction studies. Electro-optical investigations have been carried out on several compounds and both ferroelectric and antiferroelectric properties are observed. The influence of the position of the fluorine substituent on the nature of the mesophase obtained has been examined.