1. CHAPTER 11 Terpenes

2. Learning outcomes
Terpenes are unsaturated compounds formed by joining together isoprene units.
Terpenes are components of a wide variety of fruit and floral flavours and aromas.
Terpene derivatives are responsible for the distinctive aroma of spices.

3. Terpenes
The name ‘terpene’ is derived from the Greek word ‘terebinth’.
Terebinth is a type of pine tree from which terpene-containing resins are obtained.

4. What are terpenes? Natural organic compounds.
Components of a variety of fruit and floral flavours and aromas.
Used in perfumes, essential oils and medicines.

5. Essential oils contain terpenes
Lavender – used to relieve tension.
Ylang-ylang – used to treat anxiety.
Lemon oil – aids good circulation.
Essential oils often contain a mixture of terpenes.

6. Spices contain terpenes
Terpenes in plants can be oxidised to produce the compounds responsible for the distinctive aroma of spices.
Terpenes containing oxygen or other functional groups are known as ‘terpenoids’.
Common spices containing terpenes include cloves, cinnamon and ginger.

7. Terpenes are unsaturated
Terpenes are unsaturated compounds.
All terpenes are built up from units of isoprene.

8. Isoprene
Isoprene is the common name for
2-methylbuta-1,3-diene

9. Building terpenes from isoprene
Isoprene units can be linked:
head to tail to form linear terpenes
in rings to form cyclic terpenes.

10. Isoprene

11. Head
Isoprene
Tail
Head
Tail

12. Head
Isoprene
Tail
Head
Tail

13. Classification of Terpenes
Isoprene units
Carbon atoms 1
Monoterpenes 2 10
Sesquiterpenes 3 15
Diterpenes 4 20
Sesterterpenes 5 25
Triterpenes 6 30
Carotenoids 8 40 7
Rubber
> 100
> 500

14. The Isoprene Unit
The isoprene units of myrcene are joined "head-to-tail."
head
tail
tail
head

15. a-Phellandrene (eucalyptus)
Representative Monoterpenes OH O H
a-Phellandrene (eucalyptus)
Menthol (peppermint)
Citral (lemon grass)

16. a-Phellandrene (eucalyptus)
Representative Monoterpenes OH O H
a-Phellandrene (eucalyptus)
Menthol (peppermint)
Citral (lemon grass)

17. a-Phellandrene (eucalyptus)
Representative Monoterpenes
a-Phellandrene (eucalyptus)
Menthol (peppermint)
Citral (lemon grass)

18. Limonene – a cyclic terpene

19. Menthol – a cyclic terpenoid
This terpene has been
oxidised to a terpenoid

20. Representative SesquiterpenesH
a-Selinene (celery)

21. Representative SesquiterpenesH
a-Selinene (celery)

22. Representative Sesquiterpenes
a-Selinene (celery)

23. a-Selinene – a cyclic terpene
3 isoprene units
15 carbon atoms

24. Representative DiterpenesOH
Vitamin A

25. Representative DiterpenesOH
Vitamin A

26. Representative Diterpenes
Vitamin A

27. Diterpenes

28. Squalene (shark liver oil)
Representative Triterpene
tail-to-tail linkage of isoprene units
Squalene (shark liver oil)

29. β-carotene – a linear terpene
8 isoprene units
40 carbon atoms