Studies of Octane Properties of Mixtures of Isomeric Hexanes

The five noncyclic hexane homologs were mixed and tested for their octane qualities. The mixtures of normal hexane with the branched homologs, as well as a few of the combinations of branched species, had statistically significant higher octane quality than would be expected if the compounds responded in the CFR octane test engines as a linear combination of the individual components. It is hypothesized that this positive interaction is a reflection, of the formation of intermediates, via intermolecular hydrogen abstraction reactions, which are not able to progress along branching pathways during the combustion process. The formation of these intermediates delays the low temperature reaction kinetics, making the reaction mixture more knock resistant than expected.