As experimental evidence for a wide assortment of compounds was acquired, those incorporating this exceptionally stable six-carbon core came to be called "aromatic". For comparison, reactions of cyclohexene, a typical alkene, with these reagents are also shown (green box). Benzoic acid was eventually converted to the stable hydrocarbon benzene, C 6H 6, which also proved unreactive to common double bond transformations, as shown below.
The H:C ratio in benzoic acid is <1, again suggesting the presence of several double bonds. On treatment with hot permanganate solution, cinnamaldehyde gave a stable, crystalline C 7H 6O 2 compound, now called benzoic acid. Surprisingly, products that appeared to retain many of the double bonds were obtained, and these compounds exhibited a high degree of chemical stability compared with known alkenes and cycloalkenes (aliphatic compounds). Since double bonds are easily cleaved by oxidative reagents such as potassium permanganate or ozone, and rapidly add bromine and chlorine, these reactions were applied to these aromatic compounds. \)īecause of the low hydrogen to carbon ratio in aromatic compounds (note that the H:C ratio in an alkane is >2), chemists expected their structural formulas would contain a large number of double or triple bonds.
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