Aromatic hydrocarbons or arenes: They are organic hydrocarbon compounds that contain at least one benzene ring. Gasoline: It is the simplest aromatic compound. The molecular formula of benzene is C6H6 The structural formula of gasoline is a regular hexagonal ring containing 6 identical carbon atoms connected to six hydrogen atoms. Inside the ring there are 3 double bonds interchangeable with 3 single bonds that are not centered in a specific position in what is called resonance. The first person to establish the structural formula for gasoline was the scientist August Kekulé, who suggested that gasoline has two formulas due to resonance. Resonance in gasoline makes it lower in energy and therefore more stable Resonance in benzene affects its chemical activity, making it more likely to react by substitution than by addition. Preparation of gasoline It is prepared in industry from destructive distillation of coal and from the polymerization of acetylene gas or the reduction of phenol. It is prepared in the laboratory by dry distillation of anhydrous sodium benzoate salt by heating it with soda lime. Benzene reacts in addition only with hydrogen (catalytic hydrogenation), forming cyclohexane, and also with chlorine in direct sunlight and high temperature, forming hexachlorocyclohexane. Benzene tends to react by electrophilic substitution, such as halogenation, sulfonation, nitration, alkylation, and acylation.