Patrick Calas

Synthesis of terminally perfluorinated long-chain alkanethiols, sulfides and disulfides from the corresponding halides

Abstract Semifluorinated n -alkanethiols, symmetrical sulfides and disulfides bearing the chain(s) F(CF 2 ) n (CH 2 ) m with n =4, 6, 8, 10, and m =2, 11 have been prepared by various synthetic methods, starting from the corresponding iodides or bromides. Methods based on sodium hydrogen sulfide, commonly used to accomplish this conversion, treatment of the Bunte salt obtained from sodium thiosulfate, the basic hydrolysis of isothiouronium salts, the hydrolysis under mild conditions of thiophosphorates formed from sodium thiophosphate and the basic hydrolysis of thiol acetic acid derivatives, have been investigated and compared relatively to the selective synthesis of the title compounds. The thiolacetic route yields essentially the thiols with some amounts of disulfides. Results from thiourea appears similar. Sodium thiophosphate constitutes an excellent route for the synthesis of thioethers, particularly when starting from the bromides. The two classical methods based on sodium hydrogen sulfide and sodium thiosulfate exhibit poor selectivity. It has been possible to obtain all the sulfur compounds reported in the pure state.

Synthesis of perfluoroalkyl carboxylic acids by reaction of perfluoroalkyl iodides with electrogenerated superoxide ion

Abstract The electrogenerated superoxide ion Of]2°- is shown to react with perfluoroalkyliodides to afford F-alkyl carboxylic acids. A mechanism is proposed on the basis of the results obtained in preparative experiments and by cyclic voltammetry.

Electrolytic reductive coupling. addition of perfluoroalkyliodides to alcenes

Abstract Addition of perfluoroalkyliodides (R F I) to alcenes has been and is extensively studied using radical initiators and UV light irradiation. In this work, the addition of R F I (R F = CF 3 (CF 2 ) n n = 4,6,8) to allylic and propargylic alcohol, and to diallyl ether is performed using and electrochemical initiation. Electrolysis is realised in two kinds of cell: 1. mercury cathode, DMF, LiClO 4 electrolyte. 2. fiber carbon cathode, water Kcl electrolyte. We obtain addition compounds and/or products resulting from the electrochemical increase of pH in the catholyte. When using an aqueous electrolyte, the organic phase is dispersed in water. This heterogeneous electrolysis appears as a very quick, high yield route, expected compounds being obtained in a pure phase. The mechanism observed when working with allylic alcohol is : The formation of the iodhydrine appears as resulting from a radical catalytic process initiated by the electrochemical reduction of R F I. When the organic phase (R F I + CH 2 = CH-CH 2 OH) is completely converted to iodhydrine, the electrolysis of the water phase produces an increase of pH in the catholyte. Consequently, the iodhydrine is converted to the epoxide: Similar reactions have been performed:

Electrochemical reduction of the perfluoro-n-Hexyl iodide on mercury, in dimethylformamide

Abstract The electrochemical reduction behaviour of perfluoro-n-hexyl iodide, C 6 F 13 I, has been studied at the mercury electrode in dimethylformamide as a solvent. The major reaction product of the controlled-potential electrolysis of C 6 F 13 I is the organomercuric compound (C 6 F 13 ) 2 Hg. Using conventional polarography and linear sweep voltammetry, it is concluded that a chemical prereaction occurs between the perfluoro-n-hexyl iodide and polarized mercury, yielding the perfluoro-n-hexyl mercury iodide C 6 F 13 HgI, which is itself reducible in two separate steps. A detailed mechanism of the electrochemical reduction of C 6 F 13 I is proposed and discussed.

New semifluorinated dithiols self-assembled monolayers on a copper platform.

New alpha,omega-semifluorinated dithiols HS-(CH2)11-(CF2)n-(CH2)11-SH, called DTn, and corresponding dithioacetate molecules CH3COS-(CH2)11-(CF2)n-(CH2)11-SCOCH3, called DTAn ( n = 4, 6, 8), were synthesized and used to create self-assembled monolayers (SAMs) on both untreated copper surfaces and electrochemically reduced ones. The aim of this study is to assess the organization of the resulting SAMs, particularly the effect of the presence of two perhydrogenated segments surrounding the perfluorinated one, and the ability of these difunctional molecules to bind copper substrates by only one end per molecule. In each case, the organization of the SAM is rather poor and only DTA8 molecules seem to adopt an upright position on reduced copper. In addition, the layers have been investigated by cyclic voltammetry (CV) to assess their coverage. DT4 SAMs reveal a covering ratio higher than 99%.

Unexpected selective monoadduct formation from 2-methyl-3-butyn-2-ol and α, ω-diiodoperfluorobutane

Radical chain addition of α,ω-diiodoperfluorobutane to 2-methyl-3-buten-2-ol and 2-methyl-3-butyn-2-ol has been studied. The Huang sulfinatodehalogenation system, used as initiator, gave satisfactory conversion yields of the starting diiodide when compared to more classical initiators (AIBN, Fe, triethylborane). Addition to the alkenol yields classically the bis-adduct with variable amounts of the monoadduct. On the contrary the alkynol leads exclusively to the monoadduct formation, in high yield. Some considerations are proposed for interpreting this result. The monoadduct selectively obtained constitutes a powerful intermediate for synthesis.

Synthese d'acides perfluoroalcane carboxylique et sulfinique par reduction electrochimique d'iodures de perfluoroalkyle sur cathode en fibres de carbone dans le solvant N,N dimethylformamide. Application a la synthese de perfluoro α,ω diacides.

Abstract The electrochemical reduction of C 6 F 13 I on a carbon fibre cathode in DMF as solvent and in the presence of SO 2 is studied. Depending on the water content of the solvent, perfluorohexyl sulfinic acid C 6 F 13 SO 2 H or perfluoropentyl carboxylic acid C 5 F 11 COOH are obtained. These reactions are applied to 1,4-diiodoperfluorobutane; by varying the composition of the solvent it has been possible to obtain the two diacidic compounds: HO 2 S(CF 2 ) 4 SO 2 H and HO 2 S(CF 2 ) 3 COOH.

Electroreductive synthesis of organomercurials from n-perfluorobutyl-1,4-diiodide

Abstract Electroreduction of the n-perfluorobutyl 1,4 diodide I-(CF 2 ) 4 -I, is studied in dimethylformamide as a solvent. During the electrolysis their is intermediate production of I-(CF 2 ) 4 -H and of H-(CF 2 ) 4 -Hg-I, the final product being the symmetrical mercurial H-(CF 2 ) 4 -Hg-(CF 2 ) 4 -H. The results are compared with previous studies on monoiodide CF 3 -(CF 2 ) 5 -I and the dibromide Br-(CH 2 ) 4 -Br.

Radical chain addition of iodo-perfluoroalkanes to ethylenic or acetylenic substrates. Comparison of rates of iodine atom transfer from C4F9I to σ-vinyl and σ-alkyl α-F alkyl radicals

Abstract Under electrochemical activation, the addition of C4F9I to ethylenic or acetylenic substrates proceeds via a radical chain involving addition of C4F9− radicals to the multiple bond followed by iodine-atom transfer from C4F9I to the alkyl or vinyl α-F alkyl radical thus formed. Combined use of voltammetric and electrolytic techniques allows quantitative comparison of the reactivities of alkyl and vinyl radicals versus iodine-atom transfer from C4F9I.

Synthese de perfluoro-nhexyl-2 ethanol C6F13C2H4 OH par reduction electrochimique sur fibres de carbone de perfluoro-nhexyl-2 iodo-1 ethane C6F13C2H4I dans le solvant N,N dimethylformamide.

Abstract Electrochemical reduction of 2-perfluoro-nhexyl-1-iodo-ethane at a carbon fibre cathode, in N,N-dimethylformamide as solvent, leads to the perfluoro-nhexyl-2-ethanol with perfluoro-nhexyl-2-ethylene as the major by-product. A mechanism is proposed on the basis of results obtained from macro-scale electrolysis and a study of Linear Sweep Voltammetry.