The hydrogenation technique can be used by chemists to convert from benzene to cyclohexane by saturating the benzene ring with missing hydrogens.Ī special catalyst is required to hydrogenate benzene rings due to its unusual stability and configuration. In other words, cyclohexane is not the same as benzene! These two compounds have different molecular formulas and their chemical and physical properties are not the same. In order to stabilize this structure, 3 conjugated π (double) bonds are formed in the benzene ring in order for carbon to have four adjacent bonds. In contrast, benzene is only saturated with one hydrogen per carbon, leading to its molecular formula of C 6H 6. Since the carbons in the cyclohexane ring is fully saturatedwith hydrogens (carbon is bound to 2 hydrogens and 2 adjacent carbons), no double bonds are formed in the cyclic ring. If you were to count the number of carbons and hydrogens in cyclohexane, you will notice that its molecular formula is C 6H 12. Structure comparison between cyclohexane and benzene For a modern, chemical definition of aromaticity, refer to sections Aromaticity and Hückel’s Rule.įigure 3. Despite this inconsistency, however, the term aromatic continues to be used today in order to designate molecules with benzene-like rings in their structures. On the other hand, benzene itself gives off a rather strong and unpleasant smell that would otherwise invalidate the definition of an aromatic (sweet-smelling) compound. This is false, since non-aromatic compounds, such as camphor, extracted from the camphor laurel tree, release a strong, minty aroma, yet it lacks the benzene ring in its structure (Figure 1). There is a misconception amongst the scientific community, however, that all aromatics are sweet smelling and that all sweet smelling compounds would have a benzene ring in its structure. For this reason, organic compounds containing benzene rings were classified as being “aromatic” (sweet smelling) amongst scientists in the early 19th century when a relation was established between benzene derived compounds and sweet/spicy fragrances. Benzene derived products are well known to be pleasantly fragrant.
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