From: poutnik@privacy.net   
      
   Dne 20/01/2018 v 06:23 thisguy2529@gmail.com napsal(a):   
   > octane has nothing to do with molecular weight... sorry to be the downer   
   >   
      
   Octane has, the octane number has not.   
      
   Octane, particularly "isooctane"   
   as the octane isomer 2,2,4-trimethylpentane   
   is used as the point 100 of the "octane scale",   
   has molecular weight cca 8*12+2*8+1=112 g/mol.   
      
   n-heptane, used as the point 0 of the "octane scale"   
   has molecular weight cca 7*12+2*7+1=97 g/mol.   
      
   The "octane scale" relates to the stability and reactivity   
   of hydrocarbon radicals and speed of oxidation by air oxygen.   
      
   n-heptane has a linear chain and its radicals are unstable and reactive.   
   As consequence, it burns too fast wrt the mechanical engine cycle.   
      
   OTOH, isooctane or aromatics* has more stable   
   and less reactive radicals, that burns more slowly,   
   what fits the engine fuel purpose better,   
   as it avoids high pressure spikes of low octane fuel.   
      
   * e.g. benzene or toluen has octan number > 100 .   
      
      
   --   
   Poutnik ( The Pilgrim, Der Wanderer )   
      
   A wise man guards words he says,   
   as they say about him more,   
   than he says about the subject.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)