Transcript Higher Chemistry

Terpenes
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.
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.
What are terpenes?

Natural organic compounds.

Components of a variety of fruit and
floral flavours and aromas.

Used in perfumes, essential oils and
medicines.
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.
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.
Terpenes are unsaturated

Terpenes are unsaturated compounds.

All terpenes are built up from units of
isoprene.
Isoprene

Isoprene is the common name for
2-methylbuta-1,3-diene
C H3
H2C
C
H3C
CH
C H2
C
C H2
H2C
CH
Isoprene
Head
T a il
C H2
C H3
C
CH
=
C H2
Iso p re n e
(2 -m e th ylb u ta -1 ,3 -d ie n e )
One isoprene unit contains five carbon atoms
Building terpenes from isoprene
Isoprene units can be linked:

head to tail to form linear terpenes

in rings to form cyclic terpenes.
Myrcene – a linear terpene
Head
C
C
CH
H3C
Tail
C H 2 H CC H 2
3
C HH23 C
H3C
H2C
Head
Tail
CC
CH
CH
H2
C
2
CH
H
C
HH22CC
• Myrcene is a component of plants, including bay,
ylang-ylang and thyme.
Limonene – a cyclic terpene
C H2
H3C
C
CH
H2C
C H2
H2C
CH
C
C H3
L im o n e n e
(s k in o f c itru s fru its )
Menthol – a cyclic terpenoid
C H3
H3C
This terpene has been
oxidised to a terpenoid
CH
CH
OH
H2C
CH
H2C
C H2
CH
C H3
M e n th o l
(p e p p e rm in t)
Absinthe – a cyclic terpenoid
CH3
H3C
This terpene has been
oxidised to a terpenoid
CH
C
H2C
CH2
HC
C
CH
C H3
T h u jo n e
(A b sin th e )
O
Camphor – a cyclic
terpenoid
C H3
H3C
C
CH
C H2
CH2
C
H2C
H3C
C
O
Camphor
(C a m p h o r tre e )
a-Selinene – a cyclic terpene
C H3
CH2
H2C
H2C
C
CH
C
3 isoprene units
C H2
C H2
C
C H2
C H2
C
H
C H3
a -S e lin e n e
CH2
15 carbon atoms
β-carotene – a linear terpene
C H2
H3C
H3C
C
C
H2C
C
C H2
CH
C
CH
H2C
CH
C H2
C
C H2
C H3
C H3
CH3
C
CH
CH
CH
CH
C
8 isoprene units
40 carbon atoms
CH
C
C
CH
H3C
CH3
CH3
CH
CH
CH
CH
CH
C
 -ca ro te n e
C H3
C H3
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?
Answers




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
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.