Chapter 26: Lipids

Terpenes

• Terpenes commonly occur in the oils that give plants their fragrance.
• Originally the term terpene was resricted to hydrocarbons, it is now used to include substituted derivatives too.
• The fundamental building block of terpenes is the isoprene unit, C₅H₈
• The larger structures are "assembled" from several isoprene units, usually by "head-to-tail" linked isoprene units.

fundamental unit	a simple terpene	See how myrcene contains the skeletons of 2 isoprene units connected head-to-tail

• Terpenes can be cyclic or acyclic, with a large range of structural variations. A few examples are given below.
• More than 23,000 terpene systems are known.
• Monoterpenes are based on two isoprene units and so have the molecular formula C₁₀H₁₆
• Other terpenes have multiples of C₅ units so C₁₅, C₂₀, C₂₅, C₃₀  etc.

© Dr. Ian Hunt, Department of Chemistry