Vito Tortelli

Organic hypofluorites and their new role in industrial fluorine chemistry

Abstract In this work a historical background of the synthesis and chemistry of fluorinated organic hypofluorites is given and some of the known applications of this class of compounds are reviewed. Recently, new industrial processes based on hypofluorite chemistry have been developed for the production of a variety of fluoromonomers. These processes are all based on the addition of hypofluorites having different structures to fluorinated olefins. Some mechanistic features of this key reaction are discussed, in terms of reactivity and stability of the intermediate primary radicals deriving from homolytic cleavage of the hypofluorite bond. Various aspects of these new processes are described and, in the light of these recent achievements, it is shown how hypofluorite chemistry has acquired great importance as a powerful and versatile methodology for the production of fluoromonomers of prominent industrial interest.

Thermal decomposition of branched-chain perfluoroalkanes

Abstract The pyrolysis of some branched perfluoroalkanes has been studied. Homolytic cleavageof the most hindered carbon-carbon bond occurs, followed by coupling and rearrangementof the radicals so formed. This mechanism accounts for all the reaction products. Somekinetic and thermodynamic data are presented.

A new approach to the synthesis of 2,2-difluoro-1,3-dioxolanes

Abstract A direct and versatile way to prepare halogenated 2,2-difluoro-1,3-dioxolanes through the addition of bis-(fluoroxy)difluoromethane (BDM) to halogenated alkenes (CF 2 CFCF 3 , CF 2 CFOCF 2 CF 3 , CF 2 CHCF 3 , CF 3 CFCFCF 3 , CFClCFCl, CFBrCFBr, CCl 2 CCl 2 , CHClCCl 2 , CHClCHCl, CH 2 CHCl, CF 2 CFCl, (CF 3 ) 2 CFCFCFCF 3 , CF 2 CFBr, CF 2 CF 2 ) has been discovered.

THE ADDITION OF TRIFLUOROMETHYLHYPOFLUORITE TO HEXAFLUOROPROPENE DIMERS

Abstract The reaction of trifluomethylhypofluorite with the two anionic dimers of hexafluoropropene leads to the trifluoromethylether adducts in excellent yield. The radical intermediates of the reaction have been detected using the EPR technique.

Pyrolysis of branched-chain perfluoroalkanes in the presence of halogens

Abstract The thermal decomposition of some highly branched perfluoroalkanes in the presence of molecular halogens (Cl2, Br2, I2) has been studied. The clear-cut cleavage of the most hindered carbon-carbon bond and the trapping by halogens of the intermediate radicals so formed account for the product distribution. Kinetic measurements support a mechanism based on homolytic rupture of the perfluoroalkanes as the rate-determining step, followed by the fast reaction of the intermediates with halogens.

EPR and ENDOR of perfluoroalkyl radical intermediates in the reaction between perfluorohypofluorites and perfluoroalkenes

EPR and ENDOR spectra of the reaction products of sterically hindered perfluoroalkenes with perfluoromethyl hypofluorite and with the perfluoroether hypofluorite X(CF2O)n(CF2CF2O)mCF2OF, where X is either OCF3 or a second hypofluorite group OCF2-OF, have been recorded. Tertiary and secondary free radicals are produced by the addition to the alkene double bond of a fluorine atom or of the partner radical formed by the homolysis of the hypofluorite O—F bond. Analysis of the spectra reveals that hyperfine splitting by 19F nuclei in the γ and δ positions, and even further from the radical centre, contribute spectra. The α- and β-19F hyperfine splitting are discussed in relation to the radical structure and conformation. The β-19F splittings are accounted for by the well known equation aβF=B cos2(θ); different values of the constant B have to be used according to the number of β-fluorine substituents bonded to the same α-carbon.

Perfluoro Allyl Fluorosulfate (FAFS): A Versatile Building Block for New Fluoroallylic Compounds

In this study we will present and discuss both the synthesis of CF2=CFCF2OSO2F (perfluoroallyl fluorosulfate, FAFS), focusing in particular on the important role of C3F6/SO3 ratio, reaction temperature and boron catalyst/SO3 ratio on FAFS’ yield and selectivity, as well as a wide variety of ionic and radical reactions possible with FAFS. We focused our attention on reactions of FAFS with aliphatic and aromatic alcohols, acyl halides, halides, H2O2, ketones and radicals whose synthesis and reaction mechanisms will be presented and discussed. Particular attention will be devoted to the novel diallyl-fluoroalkyl peroxide obtained. Factors such as pKa and Lowry and Pearson’s Hard/Soft Acid-Base Theory which determine the selectivity between Addition/Elimination vs. Nucleophilic Substitution reaction mechanisms on FAFS will also be presented and discussed.

Quantum Mechanical Calculations and Spectroscopic Analysis of Fluorinated Vinyl Ether Molecules

Abstract Infrared spectroscopy in connection with quantum mechanical calculations based on density functional theory (DFT) method have been used for the characterization of fluorinated vinyl ethers. A good correspondence between experimental and calculated spectra has been found. The peculiar behaviour in terms of frequency and intensity parameters relative to the CC stretching normal mode along a series of related compounds has been analysed and interpreted in terms of atomic polar tensor (APT) and equilibrium charge and charge fluxes (ECCFs) models. This study indicates that the IR intensity of the CC stretching mode is almost completely due to the flux terms, suggesting that the presence of fluorine atoms make the charge along CC bond very mobile. This approach, based on comparative analysis of experimental and theoretical data, allows a critical comparison between various chemically related molecules and provides information on the various effects of chemical substitution on the molecular charge distribution.

Synthesis of low molecular weight perfluoro oxymethylene vinyl ethers

Abstract Perfluoro oxymethylene vinyl ethers have been formed by a multi-step synthesis. The key intermediates are low molecular weight perfluoropolyether (PFPE) fluoroformates CF 3 O(CF 2 O) n COF ( I ) n =1–6 obtained from the photo-oxidation of perfluoro propene (HFP) in perfluorohexane. Under certain conditions the light-mediated fluorination of PFPE fluoroformates ( I ) gives PFPE hypofluorites CF 3 O(CF 2 O) n CF 2 OF ( II ), which can be added to sym dichlorodifluoroethene to form the dichloro adduct CF 3 O(CF 2 O) n CF 2 OCFClCF 2 Cl ( III ) which, after dechlorination, gives the desired vinyl ethers CF 3 O(CF 2 O) n CF 2 OCFCF 2 ( IV ). Every reaction step has to be properly controlled as far as the reaction variables are concerned. A mechanistic scheme is presented that is consistent with the observed experimental data.

Photolysis of perfluoroacyl fluorides

Abstract The photochemical decarbonylation and coupling of acyl fluorides containing perfluoroalkyl and perfluoro(oxa)alkyl chains have been re-examined. The reaction on either single acyl fluorides or on their binary mixtures has allowed the formation and isolation of macromolecular perfluoro(oxa)alkanes having interesting physical–chemical properties. These perfluoropolyethers are also useful as model compounds and standards to better characterize more complex mixtures of similar commercial products.