Aromatic compounds or arenes are organic compounds "with a chemistry typified by benzene" and "cyclically conjugated." The word "aromatic" originates from the past grouping of molecules based on odor, before their general chemical properties were understood. The current definition of aromatic compounds does not have any relation to their odor. Aromatic compounds are now defined as cyclic compounds satisfying Hückel's rule. Aromatic compounds have the following general properties:Typically unreactive Often non polar and hydrophobic High carbon-hydrogen ratio Burn with a strong sooty yellow flame, due to high C:H ratio Undergo electrophilic substitution reactions and nucleophilic aromatic substitutions