1,720,964 research outputs found
Electrochemical fluorination: state of the art and future tendences
No full textA brief survey of the ECF process for the preparation of perfluorinated organo-compounds is given. The yield of perfluorinated products depends on the experimental conditions and on the nature of the starting material. Some useful rules are reported in order to optimise the ECF process. An improved operational technique allowed to obtain high yield of perfluorodimorpholinepropane (PFDMP) by simultaneous fluorination of dimorpholinepropane and N-methylmorpholine. (C) 2003 Elsevier B.V. All rights reserved
Liquid-phase fluorination of aromatic compounds by elemental fluorine
No full textThe fluorination of aromatic compounds (benzene, toluene, phenol and benzoic acid) by elemental fluorine diluted with nitrogen has been investigated in various solvents (Freon 11, chloroform, methanol, trifluoroacetic acid, 2,2,2-trifluoroethanol, water) in order to define the influence of the experimental conditions on the reaction. Experiments have been carried out by varying the temperature, the substrate concentration in solution, the molar ratio of fluorine to substrate, and the concentration of fluorine in the fluorine/nitrogen mixture. In all cases, the effects on the yield of fluorinated products were studied. Monofluorinated compounds were mainly found in the reaction mixture, the isomers formed being in accord with the mechanism for electrophilic substitution. The highest yield of monofluorinated products was obtained with polar solvents and the following order was found: CFCl3 < CHCl3 < CH3OH < CF3CH2OH < CF3COOH. Interesting results were also found using particular additives (for instance, KOH or C4F9SO3Na in methanol) or water as the solvent. A direct relationship was observed between the yield of monofluorinated compounds and the molar ratio of fluorine to substrate, which has to be less than one in order to obtain high yields. In contrast, low selectivity, expressed as the yield ratio of ortho to para (or metal isomers, was found
Evaluation of commercial and purified Pluronic (R) F-68 in a human blood neutrophil bioassay
No full textThe effects have been studied of commercial grade Pluronic(R) F-68 or its purified fractions, prepared by passage through silica gel resin (SGR) or by supercritical fluid fractionation (SFF), on human polymorphonuclear leucocyte (PMNL) chemiluminescence in vitro. The mean (+/- s.d., n = 3) total chemiluminescence following stimulation of neutrophils with phorbol 12-myristate 13-acetate in saline controls, was 190 +/- 3 mV x min. Commercial Pluronic(R) inhibited chemiluminescence by a maximum of 26% (P < 0.05), whilst, in contrast, Pluronic(R) F-68 fractions prepared by SGR or SFF stimulated chemiluminescence by up to 53% over control (P< 0.05). The total chemiluminescence with Pluronic(R) F-68 prepared by SA followed by SGR was not significantly. different to that produced by saline (0.9% w/v NaCl). These results reinforce previous suggestions that trace impurities in commercial preparations of the Pluronic(R) F-68 are responsible for reported adverse biological effects
Perfluoroalkanesulfonylimides and their lithium salts: synthesis and characterisation of intermediates and target compounds
No full textECF processes have been extensively experienced and developed since early 1970s at the Fluorine Chemistry Laboratory of Padua University: several classes of perfluorinated inert and functional compounds have been obtained, in particular perfluoro heterocyclics and perfluorinated acid fluorides.
Recently the demand for electrolyte salts, applied in lithium batteries, drove our interest to investigate on the perfluoroalkanesulfonylimides.
A series of the perfluoroalkanesulfonylfluoride precursors has been obtained by ECF and their metathesis to the related imides and lithium salts has been investigated.
A number of representative products has been obtained and characterized in their structure and ionic conductivity
Evaluation of some mitochondrial functions following liver perfusion with perfluorotributylamine emulsions.
No full textEffects of diltiazem on liver mitochondria of rats: a reconsideration.
No full text1. The effects of the Ca-channel blocker diltiazem (a drug of the benzothiazepine family) on bioenergetic metabolism have been assessed on isolated rat liver mitochondria. 2. Millimolar concentrations of diltiazem induced a decrease of both the ADP- and the uncoupler-stimulated respiration and a concomitant slight increase of the resting respiration. 3. Under the same experimental conditions diltiazem decreased the transmembrane electrical potential while leaving calcium uptake unaffected. 4. Micromolar concentrations of diltiazem, which are close to therapeutic haematic levels, were without effect
Mass Spectrometry of Some Fluornated Alcohols
No full textThe 70 eV electron impact mass spectrometric behaviour of some fluorinated alcohols, i.e. 2-fluoroethanol, 2,2,2,-trifluoroethanol, 2,2,3,3-tetrafluoropropan-1-ol and 1,3-difluoropropan-2-ol, was studied in detail by means of mass-analysed ion kinetic energy spectrometry, deuterium-labelling experiments and comparison with unfluorinated analogues. Composite metastable peaks related to HF losses were rationalized by invoking the presence of two concurrent decomposition pathways, the first consisting in a 1,2-elimination and the second requiring the implication of hydroxyl hydrogen. This last process and other decomposition routes suggest the presence of H bridging between the hydroxyl oxygen atom and fluorine
Diblock semifluorinated n-alkanes purification by gel phase formation in organic solvent :C8F17C18H37 in alcohols
No full textThe formation of a gel-like phase observed with some diblock semifluorinated n-alkanes dissolved in organic solvents was investigated as a purification method for these compounds. Experiments were carried out with F(CF2)(8)(CH2)(18)H by using absolute ethanol or methanol as solvent. Starting from samples with different initial degrees of purity, and using a very strict methodology, the amount of solvent giving the highest yield of purification was determined. The different solubilizing power of the solvents used did not greatly influenced the purification process. Different cooling rates were also investigated, but only small influences on the treatment effectiveness were observed
Regioselective ring opening of [(perfluoroalkyl)methyl] oxiranes with N-nucleophiles
No full textThe reactions of C8F17CH2CHCH2O with some primary and secondary aliphatic amines affording selective ring opening at C-beta are reported. The reactions with secondary amines (HNRR2)-R-1 (R-1 = R-2 = Et; R-1 = Bu-t, R-2 = CH2CH2O(CO)C(CH3)=CH2; R-1 = Et, R-2 = CH2CH2OH; R-1 =R-2 =CH2CH2OH) gave the corresponding C8F17CH2-CH(OH)-CH2-(NRR2)-R-1 derivatives. For R-1 = Et, R-2 = CH2CH2OH; R-1 =R-2 = CH2CH2OH, the reactions proceed through the selective nucleophilic attack of the NH moiety with no evidence of reactivity of the OH group. The reactions with the primary amines, allylamine and n-hexamethylenediamine, gave different products depending on reaction conditions. (c) 2005 Elsevier B.V. All rights reserved
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