CHAPTER 11 Terpenes

1. CHAPTER 11Terpenes

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

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

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

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

17. 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 Sesquiterpenes H a-Selinene(celery)

21. Representative Sesquiterpenes H a-Selinene(celery)

22. Representative Sesquiterpenes a-Selinene(celery)

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

24. OH Representative Diterpenes Vitamin A

25. OH Representative Diterpenes Vitamin A

26. Representative Diterpenes Vitamin A

27. Diterpenes

28. 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