Kinetic modelling of the low‐temperature photo‐oxidation of hexafluoropropene

Abstract

By kinetic simulation, the significant features of the mechanism of the low‐temperature photo‐oxidation of hexafluoropropene were elucidated and the rate constants for the major elementary reactions of the intermediate fluorinated peroxy and alkoxy radicals were determined through a best‐fit procedure. Comparison with analogue reactions in non‐fluorinated systems showed a significant increase in reactivity for the self‐reaction and double bond addition by peroxy radicals and β‐scission by alkoxy radicals, which are discussed in terms of fluorine substituent effects.

The chemical effects of ionizing radiations on fluorinated ethers

“…In our investigations, the EPR study was extended to the poly(perfluoroethers) Krytox TM , Fomblin TM Y, Demnum TM and Fomblin TM Z and a more efficient EPR methodology was adopted based on both matrix isolation and spin trapping techniques [11][12][13][14][15][16][17][18][19][20]. The major radical intermediates in the poly(perfluoroethers) radiolysis are accounted for in terms of C-O scissions, C-C and C-F bonds ruptures in decreasing order of importance (Table 2 and Figs.…”

“…Because of these applications and the interest stemming from their structure, the effects of radiations on poly(perfluoroethers) and their related model compounds has been the subject of several investigations aimed to cover the need of information on the radiolytic stabilities and the basic feature of the radiolysis mechanisms. Because of the chemical phenomenology inherent to the action of ionizing radiations, these studies have also afforded significant advances in the understanding of unexplored aspects of the free radical and ion chemistry of the perfluoroether function [9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. In this work the state of art in this research field is reviewed and novel results pertaining the investigations carried on in our laboratories concerning also low molecular weight model analogues of formula shown below are reported: …”

Kinetics and mechanism of the thermal gas‐phase oxidation of perfluorobutene‐2 in presence of trifluoromethyl hypofluorite

“…The perfuoroalkoxy radicals decompose via the CC bond cleavage 48, 49, this decomposition being the atmospheric fate of these radicals. The perfluoroalkoxy radicals containing ether groups and a relatively weak β‐bond CC in the OCR 2 C(O)FCF 3 group, where R = F or CF 3 , decompose principally by the β‐scission, giving shorter perfluoroalkyl radicals and CF 3 C(O)F as products 2, 3. Rates of β‐scission are determined by the stability of the radicals produced, depending on the nature and degree of substitution at the radical center 3, 50.…”

“…The perfluoroalkoxy radicals containing ether groups and a relatively weak β‐bond CC in the OCR 2 C(O)FCF 3 group, where R = F or CF 3 , decompose principally by the β‐scission, giving shorter perfluoroalkyl radicals and CF 3 C(O)F as products 2, 3. Rates of β‐scission are determined by the stability of the radicals produced, depending on the nature and degree of substitution at the radical center 3, 50. It appears that the oxygen atoms attached to the adjacent carbon atoms in the CC bond, as in the OCC(O) group of the CF 3 OCF(CF 3 )C(O) • FCF 3 radical, enhance the weakening of this bond, favoring β‐scission (reaction (13)).…”

“…The fluid perfluoropolyethers are used as lubricants for the computer hard disks because of their good performance as a protective layer between the hard disk surface and the magnetic head. The major route utilized for their commercial production is the photooxidation 1–5 of perfluoroolefins (CF 2 CF 2 , CF 3 CFCF 2 ) in liquid phase at 233 K or lower, initiated by UV light. These lubricants are mixtures of species with different relative molecular masses, containing CF 2 O and CF(CF 3 )O groups.…”