2nd EuCheMS Chemistry Congress – 2008 September 16-20 – Torino, Italy

Simplified kinetic study of the reaction between perfluoro-methyl-hypofluorite and perfluoro-olefins

Navarrini Walter ^a*, Venturini Francesco ^a, Sansotera Maurizio ^a, Metrangolo Pierangelo ^a, Resnati Giuseppe ^a, Galimberti Marco ^b, Barchiesi Emma ^b, Dardani Patrizia ^b .

^a Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, 7, via Mancinelli, I-20131, Milano, Italy.

^b Solvay-Solexis, R &D Centre, 20, viale Lombardia, I-20021 Bollate (MI), Italy.

In the reaction between perfluoroolefins and perfluoroalkylhypofluorites [1] the existence of two different free radical reaction mechanisms is demonstrated by the presence of characteristic by-products.

In particular in the reaction between trifluoromethyl hypofluorite and highly reactive perfluoroolefins like CF₂=CFOCF₃ and CF₂=CF₂, the free radical oligomerization and dimerization products can be suppressed by utilizing the opportune experimental conditions.

These experimental conditions are characterized by the presence of hypofluorite during the addition reaction and can be performed by adding the olefin to the hypofluorite, these conditions herein referred as ”Reverse hypofluorite addition” are different from the standard methodologies described in the literature where generally the hypofluorite is added to the olefin.

The main products of the addition of CF₃OF to CF₂=CFOCF₃ are perfluoro-2,2-bis-(methoxy)-ethane and perfluoro-1,3-bis-(methoxy)-ethane [2] in the molar ratio of 20% and 80% respectively.

We found experimental evidence for the termination products peroxide CF₃OOCF₃ and perfluoroethersC₈F₁₈O₄respectively. The first termination product CF₃OOCF₃ was present at high amount in the reaction where the CF₃OF concentration was maintained always above zero and substantially constant, on the contrary the termination products C₈F₁₈O₄ were completely absent. In this conditions the oligomerization and polymerization of the perfluoroolefins were also suppressed, as well as in the case of the very reactive TFE.

[1] W. Navarrini, V. Tortelli, A. Russo, S. Corti, J. Fluorine Chem. 95(2),(1999)27-39.

[2] W. Navarrini, G. Resnati, P. Metrangolo, M. Cantini, F. Venturini, IT Patent app. MI2007A001384 (2007).

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15th European Symposium on Fluorine Chemistry – Prague – July 15-20, 2007

New Advances in Perfluoroalkytation of Aromatics: Products and Mechanism

Sansotera ^a, P. Metrangolo ^a, W. Navarrini ^a, G. Resnati ^a, I. Wlassics ^b

^a Dip-CMIC ”Giulio Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milan, Italy;

^b R&D Centre, Solvay Solexis, viale Lombardia 20, 20021 Bollate (MI), Italy

E-mail: maurizio.sansotera@polimi.it; walter.navarrini@polimi.it

Thermal decomposition of perfluorodiacyl peroxides in the presence of aromatic compounds leads to the synthesis of perfluoroalkylated aromatic derivatives. C₃ and C₄-perfluorodiacyl peroxides have been synthesized starting from C₃ and C₄-perfluoroacyl halides with H₂O₂ in alkaline conditions and have been employed in reactions with several aromatic substrates. The capability of perfluorodiacyl peroxides to generate perfluoroalkyl free radicals is at the basis of the perfluoroalkylation process. Perfluoroalkyl radical reacts with the aryl via an electron-transfer propagation process. During the formation of the perfluoroalkylated intermediate the aromatic substrate loses its aromaticity and another molecule of peroxide oxidizes the intermediate. Finally a proton removal restores the aromaticity. Competitive mechanistic pathways are responsible for the perfluoroalkyl radical formation: primarily the concerted dissociation with a three-bond fission, and secondarily the stepwise decomposition through primary homolytic cleavage of O-O peroxidic bond and subsequent decarboxylation. Stability of the oncoming radicals and temperature are the important parameters to discriminate the decomposition pathway. The analyses of reaction main-products and by-products allowed to draw a more complete mechanism pathway that can be applied to the whole family of aromatic compounds.

18th International Symposium on Fluorine Chemistry – Bremen (DE) – July 30 – August 4, 2006

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