There is no such thing as pure gasoline in a chemical sense. The exact mix of chemicals in it depends on the petroleum source, refinery, and what regulations they have to meet. Before the ethanol mandate, some refineries were using alcohol as the octane booster. So I can't answer your question as to specific chemicals, but my understanding is that refineries can make the gasoline for E10 to a lower octane, about 85 AKI.
