Structures of Terpenes

Introduction

• Terpenes are organic compounds that are composed of carbon and hydrogen atoms.
• They are characterised by having carbon atoms arranged in multiples of five.

Isoprene: The Building Block

• The fundamental unit in all terpenes is called isoprene, with the chemical formula C5H8.
• The systematic name for isoprene is 2-methylbuta-1,3-diene.

Formation of Terpenes

• Terpenes are unsaturated compounds formed by linking together isoprene units.
• Isoprene units can be connected in two ways:
  • Head to tail, forming linear terpenes.
  • In rings, resulting in cyclic terpenes.

Examples of Terpenes

Limonene (Cyclic Terpene):

• Found in citrus fruits.
• Composed of two isoprene units linked in a ring.
• Total carbons: 10.

B-carotene (Linear Terpene):

• Found in carrots.
• Made from 8 isoprene units linked head to tail.
• Total carbons: 40.

Menthol (Cyclic Terpenoid):

• Found in peppermint.
• It is a cyclic terpenoid, indicating it has undergone oxidation.
• Possesses a distinct aroma.

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Structures of Terpenes

Identifying Isoprene Units

• Isoprene units within terpene structures can be identified by their characteristic features:
  • Consists of 5 carbons.
  • Include a methyl branch.
  • Contain one double bond.
• When asked to identify an isoprene unit, look for a section with these characteristics and circle it.

Conclusion:

• Terpenes are organic compounds composed of carbon and hydrogen atoms.
• They contain carbon atoms in multiples of five.