1. Terpenes: The Isoprene Rule4

2. Isoprene Links Heads or Tails?
Head to tail couplings are most common.

3. Common Carbon Backbone

4. Some Common Terpenes

5. Terpenes
Classification of Terpenes
Class Number of carbon atoms
Monoterpene 10
Sesquiterpene 15
Diterpene 20
Sesterpene 25
Triterpene 30
Tetraterpene 40

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

7. Representative SesquiterpenesH
a-Selinene (celery)

8. Representative DiterpenesOH
Vitamin A

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

11. Terpenes
isoprenyl (C5) --> geranyl (C10)
geranyl (C10) --> farnesyl (C15)
farnesyl (C15) --> squalene (C30)
Generic: C10 monoterpenes, C15sesquiterpenes, C20 diterpenes, C30 triterpenes, C40 tetraterpenes

12. Rings form by intramolecular carbon-carbon bond formation.
Cyclization
Rings form by intramolecular carbon-carbon bond formation. +
OPP
OPP
E double bond
Z double bond

13. Limonene H – + + OH
H2O
a-Terpineol