isoprene rule

chemical compound

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June 29, 2026

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The "isoprene rule" is a concept in organic chemistry that states many naturally occurring compounds are built from isoprene units. Isoprene itself is a volatile liquid hydrocarbon with the formula C₅H₈, used as a chemical raw material.1

Isoprenoids are a class of organic compounds made of repeating five-carbon isoprene units. These compounds play vital roles in plants and animals, serving as pigments, fragrances, vitamins, and even precursors to hormones. Natural rubber is a well-known example of a polyisoprene. The isoprene rule, proposed by Otto Wallach in 1887, helps chemists understand the structures of these diverse molecules, which range from small volatile compounds like monoterpenes to large polymers like natural rubber.213

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isoprenoid
Structural features of isoprenoids
Wallach’s proposal, called the isoprene rule, has helped chemists understand the structures of the more complex members of the class. The fundamental five-carbon unit typically has four carbon atoms in a linear chain with the fifth carbon attached at the carbon one position removed from the end of the…
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Wallach’s proposal, called the isoprene rule, has helped chemists understand the structures of the more complex members of the class. The fundamental five-carbon unit typically has four carbon atoms in a linear chain with the fifth carbon attached at the carbon one position removed from the end of the…
Read More