There are a lot of differing sub-optimal reactions that could and do occur with lower probababilities. In a perfect world, these would not occur. Taking your above example there is no accouning for the pure soot (C) which can be induced out of a flame. Such things are small parts of a reaction, such as NO. (BTW: Roger, in the text "Cumbustion and Flames" the chart was on p43, and the calculations *were* done in air, not pure oxygen, note the NO on the bottom of the chart. Though it seems that NO breaks down at the higher heats rather than being produced, I was wrong.)
Anyway, getting back to the discussion of the primary path way of hydrocarbon combustion, you can ALWAYS compute an equilibrum component. Again the stoichioistic equations gloss over any intermediates. Roger's reference was a fairly good one and typical of such texts. Overall, chemical reactions are ALWAYS are two way. This is in itself, a simplified statement of the actual events. Isomeres, sterioisomeres, and lots of other examples can be looked up, I am sure. This is also why some chemicals can be built up and some broken down in chemical plants. The conditions for a reaction usually decide which will occur most frequently, but this is NOT saying less probable reactions will NOT occur. Indeed, often the smaller fraction is what we are after, but that is seperation. Hmm, as I remember, Miller/Urey passed an electrical current through methane,and other gasses to produce all sorts of organic compounds. How? If not for reverse reactions? This seems to go against simplistic chemistry, but pchem/thermodynamics shows it does not. I am not defending such a silly thing as the equation. It is NOT an absolute description, rather an easy way to comunicate the thought to Roger and others. Do not take it lterally. Again, this is just one part of a rather complex ball wax, if you will. But one that sheds light on circulation, gas mixing, and combustion generally, that might help boil a cup of water out camping. Waste of time? Likely, hey, ha...You do not need to know that crap to boil water without breathing the exhaust fumes. Just stuff that was plugged into my head 40teen years ago.