Chemistry Myths and
Misunderstandings
Who am I and why am I here?
Dr. Sue Clarke
i
Introduction

In the 1980s I couldn't
find a suitable book on
essential oil chemistry
so had to write my
own.
2
A Lightning Tour
1.
Background to Scientific Approach
2.
The Chemistry
3.
How Do We Make Decisions ?
4.
Suffering from Information Overload ?
5.
Getting Things Into Perspective
iii
Science

A systematic study of nature and
behaviour of materials and the physical
universe based on observation,
experiment and measurement.
◦ Evidence based knowledge

Science, especially chemistry, underpins
the fundamental ideas and issues
important for aromatherapy
1(1)
Science:
Risk versus Benefit

Are we, and society in general, risk
averse?

Regulations, Guidance and Safeguards –
◦ Health & Safety, COSHH, IFRA. RIFM, MHRA
1(2)
1(3)
Science:
NATURAL SUBSTANCES versus
CHEMICALS

People say the strangest things …
1(4))
Science:
CAM versus MAINSTREAM MEDICINE

The importance of the House of Lords
Science and Technology report on CAM
in 2000 and it's implications
1(5)
Science:
Issues

Are risk v benefit, natural v chemical and CAM v
mainstream medicine polarised views ?

Overlap and mutual support

What is a natural product ?

Do you agree with the definition of an essential
oil as :
◦ The totally volatile product extracted by a physical
process from a single plant species that has an odour
and composition characteristic of an essential oil
from that species.?
1(6)
Chemistry

Chemistry is a vast subject that takes many
years of study building up on underpinning
knowledge.

Using IFPA syllabus will give you some
background.

The molecules found in aromatherapy are
part of the branch of chemistry called
ORGANIC CHEMISTRY.
◦ This is the chemistry of Carbon.
2(1)
2(2)
Chemistry

Molecules found in essential oils can be CLASSIFIED in a
number of ways. The most commonly used is based on the
structures of the molecules based on hydrocarbons called
TERPENES and their derivatives.

The basic structural unit is called isoprene. It is a monomer
and 'reacts' with itself to form larger polymers.

But isoprene is not the unit in the plant that gives rise to the
terpene molecules.

They form in the plant in a series of biochemical reactions
called the MEVALONIC pathway which manufactures
secondary metabolites.
2(3))
CHEMISTRY
Isoprene
2(4)
Chemistry:
Terpenes

2 isoprene units give MONOTERPENES
with 10 C atoms eg myrcene, limonene

3 isoprene units give SESQUITERPENES
with up to 15 C atoms eg farnesene,cedrene

4 isoprene units give DITERPENES with up
to 20 C atoms eg camphorene

The terpenes have names ending in ENE
2(5))
Chemistry:
Terpenoids

The TERPENOIDS are compounds derived from the
hydrocarbon terpenes but have an oxygen atom
bonded into their molecules. They are arranged into
FUNCTIONAL GROUPS (characteristic reactive
parts of molecules) such as
◦
◦
◦
◦
alcohols OH ( names ending in ol)
ketones
C=O (names end in one)
aldehydes CHO (names end in al )
esters
COOC (names end in ate or acetate)
Named after the terpene and the functional group eg
linalool & geraniol are monoterpene alcohols
 linalyl acetate is a monoterpene acetate (ester)

2(6))
Chemistry:
Functional Groups

Important for the reactions and
characteristics of compounds.
2(7)
Linalool
2(8)
Linalyl Acetate
2(9)
Chemistry:
What’s in a Name ?
Many different and complex names for
the same compound eg. C12H20O2
 Systematic (IUPAC) 3,7-dimethylocta1,6-diene-3-yl acetate.
 Trivial linalyl acetate, linalool acetate,
bergamol, bergamiol, acetic acid linalool
ester, linalol acetate, lynalyl acetate and
another 81 recorded names.

2(10)
Chemistry:
Analysis

Quantitative and Qualitative

GC Gas Chromatography

MS Mass Spectrometry

Criteria for identification and purity
2(11)
Chemistry:
Shapes of Molecules

Key action at membrane/cell surfaces

Many theories for sense of smell but
specific binding with receptors important
2(12))
2(13)
Chemistry:
The SIZE of Molecules

Larger are less soluble, less volatile, less
able to pass through membranes.

The skin barrier.
2(14)
Chemistry:
Variation in Natural Products

Due to Species of the plant

Growth conditions – soil, climate, water
availability, altitude

Chemotypes

Age of plant

Part of plant used

Extraction and processing method
2(15)
Chemistry:
Storage Conditions

Sunlight

Temperature

Storage vessels

Exposure to atmosphere
2(16)
How Do We Make Decisions?

Who and what can we believe ?

Lots of terminology and definition
3(1)
Decisions:
What is an Expert?

What exactly is meant by Studies; Research;
Investigations ; Trials ; Observations?

Who is carrying out the work ?

How are the results evaluated ?

Publication of work & peer reviews

Statistics
3(2)
3(3)
Are You Suffering From
Information Overload?

Choice of materials

What can you trust ?
4(1)
Getting Things Into Perspective

Get qualified

Follow professional guidelines

Choose your supplier carefully

Common sense
5(1)
5(2)
Perspective
•
Keep an open mind
•
Embrace change and progress
•
Be philosophical – Socrates
•
Don't forget the human factor
5(3)
True wisdom comes to
each of us when we
realise how little we
understand about life,
ourselves and the world
around us.
Socrates 469 – 399BC
5(4)