C. Fraccaro

Liquid-phase fluorination of aromatic compounds by elemental fluorine

Abstract The 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: CFCl 3 3 3 OH 3 CH 2 OH 3 COOH. Interesting results were also found using particular additives (for instance, KOH or C 4 F 9 SO 3 Na 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 meta ) isomers, was found.

Electrochemical production of partially fluorinated organic compounds: N-methylmorpholine fluorination

Abstract The usual electrochemical fluorination of organic compounds in anhydrous HF produces completely fluorinated materials. In order to obtain partially fluorinated compounds, electrofluorination has been conducted under various conditions, including the use of solvents. None of the solvents lead to satisfactory results. Experiments have also been carried out with high concentrations of N-methylmorpholine in anhydrous HF and they have provided information about the selectivity and the mechanism of the reaction. Various partially fluorinated derivatives of N-methylmorpholine have been identified, and some of them separated from the reaction mixture.

Effect of reaction conditions on the radical addition of perfluorohexyl iodide to vinyl acetate

Abstract The radical addition of perfluorohexyl iodide to vinyl acetate to give an iodine-containing adduct has been studied under different conditions in order to define their influence on the reaction. Experiments have been carried out varying parameters (molar ratio of reagents, weight percent of initiator, reaction time, temperature, oxygen removal) and studying the effects on the perfluoroalkyl iodide conversion and on the adduct yield. From the experimental data obtained, the conditions required to optimize the adduct yield have been defined.

Experimental surface activity measurements of some fluorinated compounds in a non-aqueous medium

Abstract Surface activity of some fluorinated compounds having the structure R F R H (R F − = fully fluorinated group; R H− = fully hydrogenated group) in vaseline oil was experimentally determined by surface tension measurements at 20 °C. The surface tension vs concentration isotherms allow comparison of the behaviour of the tested compounds, particularly with regard to the relationship between surface activity and fluorinated group length of the solute.

Electrochemical fluorination of some cyclic tertiary amines

Abstract Electrochemical fluorination of N,N-diethylcyclohexylamine and N-ethyldicyclohexylamine gave the corresponding F-amines together with several other compounds arising from incomplete fluorination and fragmentation reactions. In the case of N,N-diethylcyclohexylamine yields of 51–52% were obtained and most of the reaction products were isolated and identified. With N-ethyldicyclohexylamine a lower yield (16%) was observed; the resultant reaction mixture was too complex to allow the identification of its components. Comments are made about the reaction mechanism, and NMR and IR data are reported for identified compounds.

Direct liquid-phase fluorination of aromatic compounds. New advances in electrophilic fluorination

Abstract Elemental fluorine is rarely used in fluorination reactions of aromatic substrates because of the uncontrollable course of reaction. The interest in a practical application of this method excited a lot of research on this matter, in order to find experimental conditions able to allow the reaction control. At present available experimental data confirm that a reaction control is possible by using operational conditions able to favour an ionic mechanism, but they also show as mono–fluorinated products are obtained in low yields. Our research was devoted to study how operational conditions influence the reaction course; a particular interest was paid to solvent and to additives able to lead to compounds having a fluorine atom bonded to an oxygen atom (ipofluorites). Fluorination by elemental fluorine of benzene, toluene, phenol, benzoic acid, 2-naphthol and pyridine was so studied in different solvents (CHCl 3 , CCI 3 F, CF 3 COOH, CF 3 CH 2 OH). The use of water and methanol, rarely used in these reactions, resulted particularly interesting: experimental data show very high yield of mono–fluorinated products and suggest interesting practical applications of the proposed method. Important remarks can also be made with regard to reaction mechanism.

Synthesis of some fluoro-hydrocarbons and their performance as surface agents in a non-aqueous medium

Abstract Some fluoro-hydrocarbons having the typical structure RF-RH can be prepared by addition of perfluoroalkyl iodides (RFI) to olefins (CH2CHR′H) by the method suggested by N.O. Brace [1] : RFI + CH2ChRH → RFCH2CHI-R′H → RFCH2CH2R′H Starting from the linear perfluoroalkyl iodides C6F13I and C8F17I, and prepared: C6F13C17, C6F13C12H25, C6F13C16H33, C8F17C12H25 and C8F17C16H33. These compounds were tested in a liquid as surface agents; measurements of the surface tension were carried out at various concentrations and temperatures (20 °C, 30 °C and 50 °C). Some of the compounds tested i.e. , C6F13C16H33) also at the highest temperature shown a poor solubility in the parraffin used. A remarkable drop of the surface tension values was shown by C8F17H33 at 20 °C. Experimental data and surface tension vs concentration diagrams are reported.

Thermal decomposition of perfluoroalkanesulfonyl fluorides: the pyrolysis of perfluoro-n-octane-1-sulfonyl fluoride

Abstract The preliminary data obtained from thermal decompositions of perfluoro- n -octane-1-sulfonyl fluoride in a continuous tubular-flow reactor are reported. The pyrolysis results in a radical reaction producing fluorocarbons, with high conversions and with yields depending on the experimental conditions. The reaction mixture composition also depends on the experimental conditions, so it is possible to obtain a prevalent formation of either light or heavy fluorocarbons.

Cloud point and pour point measurements of long chain hydrofluorocarbons solutions in a paraffin oil

Abstract Long chain hydro-fluorocarbons CF 3 (CF 2 ) n (CH 2 ) m CH 3 ( n =3, 5, 7; m =7, 11, 13, 15, 17), synthesised by free radical addition of perfluoroalkyl iodides R F I to linear 1-alkenes, showed interesting surface-active properties in a non- aqueous medium [M. Napoli, C. Fraccaro, A. Scipioni and P. Alessi, J. Fluorine Chem., 51 (1991) 103]. Pursuing the research on the physical properties of these compounds, a series of measurements of cloud point (ASTM D 2500-81) and pour point (ASTM D 97-66) was done with solutions of these hydro-fluorocarbons in a paraffin oil and the measured values were then plotted against w/w concentration. An increase of the cloud point and pour point values of paraffin, depending on the length of the perfluoroalkyl group, was generally observed.

Thermal decomposition of perfluorooctanesulfonyl fluoride

Abstract The decomposition reaction at high temperatures of perfluorooctanesulfonyl fluoride has been investigated using a continuous-tubular-flow reactor. The experiments have been carried out at different temperatures either in the empty reactor of filling the reactor with various kinds of material (copper chips, activated carbon, etc.). In all cases a mixture of homologous fluorocarbons, from C 6 to C 16 , has been obtained, whose composition depended on the experimental conditions (temperature and contact time). In particular, the best experimental conditions to obtain a reaction mixture containing higher amounts of C 9 -C 12 fluorocarbons have been searched, in view of an employment of these compounds for preparing emulsions usable as artificial blood.