Why are aromatic compounds such as toluene and oxygenated hydrocarbons such as ethanol generally used as antiknock agents?

Question

Ellie Adams · Accepted Answer

Simply because they work.

When filling up your car with gasoline, different brands will tout different additives; most formulations would be very similar. The addition of certain additives to your hydrocarbon mix results in better performance in your combustion engine. This is the domain of an engineer, not a chemist. The presence of oxygen in alcohol additives may provide better combustion, but there is a good deal of incomplete combustion that occurs in a well-tuned internal combustion engine - as witness #CO# and particulate #C# emission.

Easton Jones · Answer

undefined Aromatic compounds like toluene and oxygenated hydrocarbons like ethanol are used as antiknock agents because they have high octane ratings, which means they resist detonation or knocking in internal combustion engines. They have a slower combustion rate compared to straight-chain hydrocarbons, allowing for more controlled and efficient combustion in the engine, thus reducing knocking and engine damage.