1. HC
CHEMISTRY HC
CHEMISTRY
NATURES’ CHEMISTRY
(E) Fragrances

2. HC HC (E) Fragrances Isoprene Unit
CHEMISTRY HC
CHEMISTRY
(E) Fragrances
Isoprene Unit
After completing this lesson you should be able to :
Terpenes are unsaturated compounds formed by joining together isoprene (2- methylbuta-1,3-diene) units.
Terpenes can be oxidised within plants to produce some of the compounds responsible for the distinctive aroma of spices.

3. b) Terpenes Learning intention
Learn about the chemistry and uses of terpenes, a key group of unsaturated molecules based upon isoprene.

4. Terpenes
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The name ‘terpene’ is derived from the Greek word ‘terebinth’.
Terebinth is a type of pine tree from which terpene-containing resins are obtained.
Pistacia palaestina is a tree or shrub common in the Levant region (especially Palestine, Israel and Syria). It is called terebinth in English, a name also used for Pistacia terebinthus, a similar tree from the western Mediterranean Basin.

5. Terebinth
In the book Voyage of the Dawn Treader, C. S. Lewis named one of the fictional islands "Terebinthia"; Lewis scholar Marvis. D. Hinten posits "Lewis, the renowned medieval scholar, naturally knew that terebint was Middle English for the tree used in the Middle Ages to produce turpentine." Katherine Paterson, the author of the 1977 novel Bridge to Terabithia noted she had probably unintentionally taken the name of her fictional world from C. S. Lewis, who had likely taken the name from the tree.

6. Terpenes to steroids
Essential oils of many plants and flowers are obtained by distilling the plant with water. The water-insoluble oil that separates usually has an odor characteristic of the particular plant (rose oil, geranium oil and others). Compounds isolated from these oils contain multiples of five carbon atoms (that is, 5, 10, 15 and so on) and are called terpenes. They are synthesised in the plant from acetate by way of an important biochemical intermediate, isopentyl pyrophosphate. The five-carbon chain and a one-carbon branch at C-2 is called an isoprene unit.

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

8. Essential oils contain terpenes
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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.

9. Spices contain terpenes
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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.

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

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

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Isoprene
One isoprene unit contains five carbon atoms

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

14. Myrcene – a linear terpene
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Myrcene – a linear terpene
Head
Tail
Head
Tail
Myrcene is a component of plants, including bay, ylang-ylang and thyme.

15. Limonene – a cyclic terpene
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Limonene – a cyclic terpene

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

17. Absinthe – a cyclic terpenoid
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Absinthe – a cyclic terpenoid
This terpene has been
oxidised to a terpenoid
Thujone is a ketone and a monoterpene Though it is best known as a chemical compound in the spirit absinthe, absinthe contains only small quantities of thujone, so thujone is unlikely to be responsible for absinthe's alleged psychedelic effects. Thujone, as a component of several essential oils, is also used in perfumery. Thujone podcast

18. Camphor – a cyclic terpenoid
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Camphor – a cyclic terpenoid

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

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

21. Squalene
6 isoprene units
30 carbon atoms

22. Questions Which unit makes up every terpene?
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Questions
Which unit makes up every terpene?
How many carbons are there in an isoprene unit?
What is the systematic name for isoprene?
What is an oxidised terpene known as?

23. Answers COPY Which unit makes up every terpene? Isoprene unit
How many carbons there are in an isoprene unit?
Five
What is the systematic name for isoprene?
2-methylbuta-1,3-diene
What is an oxidised terpene known as?
Terpenoid

24. COPY
Summary
Terpenes are unsaturated compounds formed by joining together isoprene units.
Terpenes are components in a wide variety of fruit and floral flavours and aromas.
Terpenes can be oxidised within plants to produce the compounds responsible for the distinctive aroma of spices.