Chemistry Myths and Misunderstandings

Who am I and why am I here?Dr. Sue Clarke

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IntroductionIn the 1980s I

couldn't find a suitable book on essential oil chemistry so had to write my own.

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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

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ScienceA 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

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Science:

Risk versus Benefit

Are we, and society in general, risk averse?

Regulations, Guidance and Safeguards –◦Health & Safety, COSHH, IFRA. RIFM,

MHRA

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Science:

NATURAL SUBSTANCES versus CHEMICALS

People say the strangest things …

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Science:

CAM versus MAINSTREAM MEDICINE

The importance of the House of Lords Science and Technology report on CAM in 2000 and it's implications

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Science:

IssuesAre 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.?

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ChemistryChemistry 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.

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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.

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CHEMISTRY

Isoprene

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Chemistry:

Terpenes2 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

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Chemistry:

TerpenoidsThe 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)

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Chemistry: Functional Groups

Important for the reactions and characteristics of compounds.

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Linalool

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Linalyl Acetate

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Chemistry:

What’s in a Name ?Many different and complex

names for the same compound eg. C12H20O2

Systematic (IUPAC) 3,7-dimethylocta-1,6-diene-3-yl acetate.

Trivial linalyl acetate, linalool acetate, bergamol, bergamiol, acetic acid linalool ester, linalol acetate, lynalyl acetate and another 81 recorded names.

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Chemistry:

Analysis

Quantitative and Qualitative

GC Gas Chromatography

MS Mass Spectrometry

Criteria for identification and

purity

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Chemistry:

Shapes of Molecules

Key action at membrane/cell

surfaces

Many theories for sense of smell

but specific binding with

receptors important

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Chemistry:

The SIZE of Molecules

Larger are less soluble, less volatile, less able to pass through membranes.

The skin barrier.

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Chemistry:

Variation in Natural ProductsDue to Species of the plant

Growth conditions – soil, climate, water availability, altitude

Chemotypes

Age of plant

Part of plant used

Extraction and processing method

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Chemistry:

Storage Conditions

Sunlight

Temperature

Storage vessels

Exposure to atmosphere

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How Do We Make Decisions?

Who and what can we believe ?

Lots of terminology and definition

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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

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Are You Suffering From Information Overload?Choice of materials

What can you trust ?

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5(1)

Getting Things Into Perspective

Get qualified

Follow professional guidelines

Choose your supplier carefully

Common sense

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Perspective

• Keep an open mind

• Embrace change and progress

• Be philosophical – Socrates

• Don't forget the human factor

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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