Gerardo Caporiccio

Synthesis of fluorinated telomers. Part 1. Telomerization of vinylidene fluoride with perfluoroalkyl iodides

Abstract Thermal and redox-induced telomerizations of vinylidene fluoride (VDF) with linear (n-C 4 F 9 I) or branched (i-C 3 F 7 I) perfluoroalkyl iodides have been performed. In both cases, thermal telomerizations led to telomeric-type distributions of the first five (from linear telogen) or the first three (from branched telogen) adducts produced, with better yields at higher temperatures. The redox-initiated telomerization was more selective since it led to the first two adducts only. For both reactions, mono- and di-adducts were isolated and characterized by 1 H and 19 F NMR spectroscopy. Interestingly, both the diadducts were composed of two isomers (i.e. the expected telomer and R F CH 2 CF 2 CF 2 CH 2 I). Two mechanisms are proposed and it is assumed that the products may be obtained either by chain propagation or by stepwise telomerization. In addition, attack of the electrophilic radical on the nucleophilic side of VDF is discussed.

Controlled step-wise telomerization of vinylidene fluoride, hexafluoropropene and trifluoroethylene with iodofluorinated transfer agents

Abstract Highly fluorinated cotelomers having the structure F(TFE) w (VDF) x (HFP) y (TrFE) z I containing one or several tetrafluoroethylene (TFE), vinylidene fluoride (or 1,1-difluoroethylene, VDF), hexafluoropropene (HFP) or trifluoroethylene (TrFE) base units were synthesized by thermal step-wise cotelomerization of these fluoroolefins with perfluoroalkyl iodides. 1 H and 19 F NMR allowed one to characterize these cotelomers and to assess the defects of chaining and the molecular weights. While the monoadduct produced from VDF exclusively exhibits R F CH 2 CF 2 I structure, that prepared from TrFE was composed of R F CFHCF 2 I and R F CF 2 CFHI isomers, the ratio of which is directed from the electrophilicity of R F radical. The reactivity of the C–I bond in R F -Q-CXY-I depends on the nature of the Q spacer and on the reactivity of the fluorinated monomer (e.g., thermal initiations of VDF, TrFE and HFP were efficient from 180, 195 and 210°C, respectively). The mechanism of the addition of the radical generated from the iodinated transfer agent to the fluoroalkene is explained by means of its electrophilic attack to the more nucleophilic (i.e., the less electrophilic) side of the olefin. Ethylenation of these fluorocotelomers was successfully achieved from various initiations (thermal, redox or from peroxides) with best results from redox catalysis. Thermal properties of several fluorotelomers (glass transition temperatures, T g and melting temperatures, T m ) were assessed. They were linked to the number of consecutive CF 2 groups (for the crystalline zones) and bulky side groups which induced amorphous regions.

Synthesis of telechelic dienes from fluorinated α,ω-diiodoalkanes. Part I. Divinyl and diallyl derivatives from model I(C2F4)nI compounds

Abstract The synthesis of five fluorinated non-conjugated dienes from commercially available α,ω-diiodoperfluoroalkanes is described. Preparation of the fluorinated divinyl derivatives H2C=CH(CF2)nCH=CH2 (n = 2, 4, 6) (2,2, 2,4 and 2,6) was effected by ethylenation of these diiodinated compounds in various ways followed by dehydroiodination in ethanolic potassium hydroxide. Allyl diolefines, H2C=CHCH2(CF2)nCH2CH=CH2 (4,4 and 4,6) were produced by the α,ω-bis-telomerization of allyl acetate followed by deiodoacetoxylation in the presence of zinc. The diacetate precursors 3,4 and 3,6 of the respective diallyls 4,4 and 4,6 were obtained rather than diacetate 3,2 because of the eventual decomposition of α,ω-diiodoperfluoroethane by β-scission. These five fluorinated non-conjugated dienes have been characterized by 1H, 13C and 19F NMR spectroscopy.

Synthesis of fluorinated telomers. Part 4. Telomerization of vinylidene fluoride with commercially available α,ω-diiodoperfluoroalkanes

Abstract The synthesis of a new fluorinated αω-diiodo telomer I[(TFE)(VDF),]I (A), where TFE and VDF represent tetrafluoroethylene and vinylidene fluoride respectively, has been carried out by telomerization of VDF with αω-diiodoperfluoroalkanes. The thermal telomerization of VDF with 1,2-diiodoperfluoroethane IC2 F4I led to good yields of the monoadduct IC2F4CH2CF2I and of the diadduct which was composed of an almost equimolar ratio of ICF2CH2C2F4CH2CF2I and IC2F4(CH2CF2)2I, together with a small amount of IC2F4CH2CF2CF2CH2I and a triadduct containing I (VDF) C2F4(VDF)2I and IC2F4(VDF)3. This procedure has been applied successfully to αω-diiodo-n-perfluorobutane and α,ω-diiodo-n-perfluorohexane. The reactivity of VDF relative to the fluorinated α,ω-diiodo telogens has been studied from which it is shown that the environment of the terminal group of the telogen is a major factor affecting the reactivity.

Study of the alkylation of chlorosilanes. Part I. Synthesis of tetra(1H, 1H, 2H, 2H-polyfluoroalkyl)silanes

Abstract The synthesis and structural characterization of tetra(1 H , 1 H , 2 H , 2 H -polyfluoroalkyl)silaneswith the same or different chain lengths C n F 2 n +1 linked to Si (1⩽ n ⩽6) is reported. When the synthesis was effected from chlorosilanes and fluorinated organomagnesiumor organolithium reagents, the trialkylsilanes were obtained. The last fluorinated chainwas introduced either via a fluoroalkyllithium reagent or by hydrosilylation of thetrialkylsilanes. Some properties and characterization by 1 H, 19 F and 29 Si NMR spectroscopy of the1 H , 1 H , 2 H , 2 H -polyfluoroalkylsilanes are described.

Synthèse de diènes téléchéliques à partir d' α,ω-diiodo-alcanes fluorés Partie II: Divinyls et diallyls présentant des motifs constitutifs tétrafluoroéthylène, fluorure de vinylidène et hexafluoropropène

Abstract Synthesis of new fluorinated non-conjugated dienes containing tetrafluoroethylene, vinylidene fluoride (VDF) and/or hexafluoropropene from α,ω -diiodofluorinated cotelomers was carried out by two methods in two steps. Divinyl monomers were obtained by α,ω -bis ethylenation of these cotelomers followed by a bis-dehydroiodination in medium yields which were lower when the cotelomers contained the VDF base unit. Diallylic olefins were produced by addition of these α,ω -diiodofluoroalkanes to allyl acetate followed by a ‘deiodoacetatization’ in high yields. Each telechelic diene was carefully characterized by 1 H and 19 F NMR.

Synthesis, characterization, and thermal properties of anhydride terminated and allyl terminated oligoimides

This study concerns the synthesis of anhydride terminated oligoimides (ANTOI) and allyl terminated oligoimides (ALTOI), in acetic acid medium, which allows a very fast reaction and an easy working out. For the preparation of ALTOIs, two methods are compared: the first one consists of adding the monofunctional compound (allyl amine) to the ANTOI already formed during a first step by reaction of a dianhydride (excess) and a diamine. The second method consists of a “one pot” reaction between the dianhydride, the diamine, and the monofunctional allyl–amine compounds, at the beginning of the reaction. The experimental results show that the best control of the molecular weights is obtained with the first method. If the amount of allyl amine is higher than the amount necessary to end cap the ANTOI, a transimidization reaction occurs. Thermal analyses of oligoimides terminated by anhydride or allyl groups have been performed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Transition and thermoresistance properties make ANTOI and ALTOI derivatives interesting as precursors for block polyimide copolymers.

Synthèse de télomères fluorés. Partie III. Télomérisation de l'hexafluoropropène avec des iodures de perfluoroalkyle

Abstract The synthesis of highly fluorinated telomers via the thermal telomerization of hexafluoropropene with branched [(CF 3 ) 2 CFI] or linear (n-C 4 F 9 I or n-C 6 F 13 I) perfluoroalkyl iodides is described. Both linear telogens led to the first three adducts with a high C n F 2 n + 1I conversion. Interestingly, the monoadduct was composed of a major normal C n F 2 n + 1 ,CF 2 CFICF 3 isomer and a minor reverse C n F 2 n + 1 CF(CF 3 )CF 2 I telomer whose ratio depended on the temperature. The activation energy for the process was determined as 27 kJ mol −1 . However, when (CF 3 ) 2 CFI was involved as the telogen in a similar reaction, the normal monoadduct was produced selectively but only in 8% telogen conversion. All these telomers were reduced to R F C 3 F 6 H, the 1 H and 19 F NMR spectra of which confirmed the structure of each derivative.

UNEXPECTED TELOMERIZATION OF HEXAFLUOROPROPENE WITH DISSYMETRICAL HALOGENATED TELECHELIC TELOGENS

Abstract The synthesis of new fluorinated α,ω-diiodo telomers I(TFE) x (VDF) y (HFP) z I (A) where TFE, VDF and HFP represent tetrafluoro-ethylene, vinylidene fluoride and hexafluoropropene, respectively, was carried out by thermal telomerization of HFP with VDF oligomers, I(TFE) x (VDF) y I, as transfer agents. Compound A was obtained in 55% yield when x = y = 1, whereas almost no reaction occurred when x = 1 and y = 2. Interestingly, HFP reacted with IC 2 F 4 CH 2 CF 2 · selectively and not with ICF 2 CH 2 CF 2 CF 2 · whereas, from IC 4 F 8 CH 2 CF 2 I, HFP could be introduced on both end-groups but produced a higher amount of I(TFE) 2 (VDF)(HFP) I. The reactivity of HFP is compared with that of VDF in reactions with fluorinated α,ω -diiodinated telogens and it is shown that the environment of the terminal C-I bond in the telogen influences the orientation of the reaction.

Synthesis of fluorinated telomers. Part 6. Telomerization of hexafluoropropene with α,ω-diiodoperfluoroalkanes

Abstract The synthesis of highly fluorinated telomers produced from the thermal bulk telomerization of hexafluoropropene (HFP) with α,ω-diiodoperfluoroalkanes is described. That involving 1,2-diiodotetrafluoroethane was unsuccessful because of the thermal decomposition of this diiodide from 190°C. An optimization of the telomerization reaction involving 1,4-diiodoperfluorobutane taking into account key parameters such as the initial [IC 4 F 8 I] 0 /[HFP] 0 molar ratio, the temperature and the time of the reaction is attempted. The conditions for the highest conversion of IC 4 F 8 I and also for directing the reaction toward the monoadduct or the diadduct are discussed. Both these telomers were reduced with tributylstannane into HC 4 F 8 (C 3 F 6 ) x H (with x =1 or 2) and H–C 3 F 6 –C 4 F 8 –C 3 F 6 –H, the 1 H and 19 F-NMR spectra of which confirmed the structure of each derivative.