The Reactions of Oxygen Atoms and Monofluoromethylene Radicals with Fluorinated Ethylenes in the Gas Phase


Oxygen atoms generated in a mercury photosensitized decomposition of nitrous oxide were reacted with 1,2-difluoroethylene and trifluoroethylene and observed to form mainly monofluoromethylene (CHF) radicals and carbonyl fluoride. The CHF radicals then added to fluoroethylene to form "hot" fluorocyclopropanes which could be stabilized by collision (or isomerize or fragment). The mechanism of these reactions have been studied in detail. The main products of the reaction of CHF radical with trans- 1,2-difluoroethylene were found to be . rare 1,2,3-trifluorocyclo- ‘propane, cis- and trans- 1,2,3-trifluoropropylene whereas the reaction with cis- 1,2-difluoroethylene gave both cis- and trans- 1,2,3-trifluorocyclopropane, cis- and trans- 1,2,3-trifluoropropylene. The electronic state of CHF radical was believed to be singlet according to the stereospecific addition reaction and the lack of change in the products yield in the presence of small amount of molecular oxygen. The exothermicity of the addition reaction was estimated as 286 kJ mol‾1 <FORMULA> The reaction products of the reaction of CHF radical with trifluoroethylene were cis- and trans- 1,2,3,3-tetrafluorocyclopropane, cis- and trans- 1,2,3,3-tetrafluoropropylene, 1,1,2,3- tetrafluoropropylene, cis- and trans- 1,2-difluoroethylene, tetrafluoroethylene and pentafluorocyclopropane. Some CF2 elimination from “hot" cyclopropane occurred even at atmospheric pressure. The, _pentafluorocyclopropanes were formed by addition of CF, to the trifluoroethylene. Principal features of the mechanism are shown in the following scheme: <FORMULA> Following the detailed studies of the reaction, the systems were used to determine relative reactivities of CHF radicals with all the fluorinated ethylenes. Relative rate constants for the reaction with propylene and fluoroethylenes were measured by a competitive method. at 23 + 2°c. The results are summarized below <TABLE>

Divisions: College of Engineering & Physical Sciences > School of Infrastructure and Sustainable Engineering > Chemical Engineering & Applied Chemistry
Additional Information: Copyright © S. Rattanaphani, 1973. S. Rattanaphani asserts their moral right to be identified as the author of this thesis. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without appropriate permission or acknowledgement. If you have discovered material in Aston Publications Explorer which is unlawful e.g. breaches copyright, (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please read our Takedown Policy and contact the service immediately.
Institution: Aston University
Uncontrolled Keywords: reactions,oxygen atoms,monofluoromethylene radicals,fluorinated ethylenes,gas phase
Last Modified: 08 Dec 2023 08:03
Date Deposited: 12 Jan 2011 11:55
Completed Date: 1973
Authors: Rattanaphani, Saowanee

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