Re: When fuel is undergoing combustion is it losing or gaining electrons to O2?

Dear Megan -  In answering your question I enlisted the help of my friend 
Dr. Keith Hudson at the University of Arkansas, Little Rock.  He has been 
studying combustion and what follows is my translation of Dr. Hudson's 
reply. 


We will use a simple example of methane burning with oxygen.  The 
composition of methane is CH4 (one carbon and four hydrogens).  The 
combustion is a chain reaction composed of several distinct steps that can 
be classified as an initiation step, branching steps, propogation steps, 
and a termination step.  

The initiation step is the formation of radicals, for this example we'll 
assume that O2 breaks into 2 O radicals.  A radical is a atom or group of 
atoms with an odd (unpaired) electron.  The energy to form the radical 
comes from the heat of the fire or the ignition source (match, 
lighter,spark, etc.).  This is the intitiation step of the reaction.  This 
radical then reacts with the methane, oxygen or other radicals to form 
more radicals.  These reactions are the branching and propagation steps.  
Branching if you form different radicals, propagation if you form more of 
the same radical.  The termination step occurs when the radical reacts to 
form stable molecules like H2O or CO2 (combustion byproducts).  There are 
no NET loss or gain of electrons as a result of the reactions.

That said, in the flame itself there are free electrons due to the heat 
boosting some electrons into such a high energy state that the chemical 
bond is burst.  These free electons will move to neighboring atoms or 
molecules that further the combustion of our methane.  This phenomenon of 
the free electrons in a flame provides the basis of how a sensor known as 
a flame ionization detector used with gas chromatographs sense the 
presence of organic materials.  As the organic materials burns and free 
electrons are generated, an electrical current is passed through the flame 
with the amount of current proportional to the amount of organic material 
present.