From hogue@canada.den.mmc.com  Tue May  4 12:21:33 1993
Date: Tue, 4 May 93 18:21:33 MDT
From: hogue@canada.den.mmc.com (Pat Hogue 1-2183)
Message-Id: <9305050021.AA03470@canada.den.mmc.com>
To: chemistry@ccl.net
Subject: Dehalogenation


Opinions are solicited on the possible mechanism for dehalogenation described below.

     Perfluoropolyethers (PFPEs) have been shown to react even at cryogenic 
temperatures with atomically clean aluminum and iron surfaces.  PFPEs also react with (most probably) Lewis acid surface sites at elevated temperatures.  In 
both cases AlF3 or FeF3 and carbonyl fluoride (COF2) is observed.  There is also some evidence for ALF6-3 species.  

     Is fluorine anion abstraction to Lewis acid site the initiating step?  Or  is atomic fluorine transferred instead? 

     My AM1 model of the small polyether represented by
 F3COCF2OCF2CF2OCF2*CF2OCF2CF3 (where the asterisk represents the location of
 the Fluorine anion abstracted, it has the largest HOMO coefficient)
 indicates that these coefficients changed from a state of delocalization 
over the central portion of the molecule to a state
 where the coefficients are concentrated on the three terminal fluorines and 
oxygen at one end of the molecule.

     I propose that three fluorine atoms leave the terminal -O-CF3 group to form FeF3.  I think the resulting carbon triradical can undergo rearrangement with 
oxygen to produce carbon monoxide (also reported by some workers). 

 Any opinions?  How about a second three atom transfer to form the hexavalent 
fluoride?