 Benzene is a colorless and highly flammable liquid with a sweet smell, and is responsible for the aroma around petrol (gasoline) stations.It is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced annually.As benzene has a high octane number, aromatic derivatives like toluene and xylene typically comprise up to 25% of gasoline (petrol).