1. Tim Harrison Bristol ChemLabS Director of Outreach
Perfume Chemistry
-where Chemistry meets Art!

2. Tim Harrison Bristol ChemLabS Director of Outreach
Fragrance Chemistry
-where Chemistry meets Art!

5. Smelly Chemistry!
As well as being sold as perfumes, fragrance chemicals are added to hundreds of products
Household products (cleaners, laundry, air fresheners…)
Cosmetics (makeup, shampoo,
moisturisers…)

6. The basic science What is and what isn’t a chemical reaction
Gases and vapours
Sense of smell

7. CH3CH2OH What is Perfume? Simply – an alcoholic mixture Essential oils
Denatured ethanol (ethyl alcohol)
CH3CH2OH
Perfume
22%
Eau de Parfum
15 to 22%
Eau de Toilette
8 to 15%
Eau de Cologne 4%

8. Why use Ethanol? It is a good solvent It hardly has any smell
Few people are allergic to it
It’s volatile (vaporises quickly)
Image: Dr. Podesta

9. Denatured Alcohol Add denatonium benzoate, Bitrex®
Alcohol is no longer subject to taxes, as it would be if it were fit to drink
Safety – to stop toddlers drinking perfumes!

10. Olfaction: the sense of smell
Odours are detected by the olfactory epithelium
The exact mechanism of olfaction is not clear
Shape?
Vibration?
Compounds must be volatile to be detected

11. How do Perfumes Work? This occurs when the fragrance molecules
Molecules leave the perfume solution and diffuse to your nose.
This occurs when the
fragrance molecules
are weakly bonded to
the solvent or skin.

12. Perfumes and Fragrances
Fragrance chemistry closely related to flavour chemistry
Most of what we perceive as ‘flavour’ is actually ‘odour’ !
The tongue can sense only a few flavours sweet, bitter, sharp, salt and monosodium glutamate . The rest of flavours are odours.

13. How do Perfumes Work?
The strength of Intermolecular bonding dictates which molecules evaporate first.
Head or top-notes – last a few minutes
Heart or middle-notes – last a few hours
Base, foundation or end-notes – last longest

14. Fragrance Families Ambers: Includes the scents of tropical flowers,
woods, vanilla, spice and animals.
Chypre: (Cyprus in French) Fragrances built on a
similar base consisting of bergamot, vetiver,
jasmine and oakmoss.
Citrus: Notes such as orange, lemon,
petit grain bergamot, and tangerine.
Floral: As the name suggests this family is
dominated by the scent of flowers such
as rose, jasmine or lavender.

15. Fragrance Families
Fougère: Fragrances, characterized by herbaceous and woody scents.
Leather: A family of fragrances which features a leather-like scent and the scents honey, tobacco and wood tars.
Woody: Fragrances that are dominated by the woody scents, e.g. sandalwood and cedar and patchouli.

16. Memory and Smells
Humans are good at remembering smells-smells are also remind us places, people, events
We are going to give you a few fragrances. Can you recognise each one?

17. Complex Mixtures
A fragrance will contain a mixture of many compounds :
Individual compounds
Plant/animal extracts (already contain mixtures)

18. Essential Oils
Obtained from plants by several common extraction processes:
Steam Distillation
Solvent Extraction
Expression
Enflureage

19. Essential Oils
Extraction processes require a lot of labour and often give low yields.
Sometimes the oils are impossible to extract or very expensive
Five to six tons of roses are needed to obtain one kilo of essential oil, with an approximate annual production of rose oil of about 20 tonnes

20. Chemistry at Work!
Chemists can make extraction methods more efficient.
Organic chemists synthesise substitutes or create totally artificial fragrance molecules e.g. Lilly of the Valley)

21. Chemistry at Work! Fragrance storage
Being a complex mixture of compounds reactions can still occur in the bottle;
Light
Temperature
Head space
Small bottles not large!
Age –choose your shop carefully –high turnover

22. Examples of common fragrance compounds
cis-hex-3-en-1-ol
cut grass
1-octen-3-ol
mushroom
hexanal
green, waxy odours
benzaldehyde
almond, cherry

23. Examples of common fragrance compounds
ethyl butanoate
strawberry
3-methylbutyl ethanoate
banana
2-prop-1-enyl hexanoate
pineapple
d-octalactone
coconut

24. Sensory analysis: Describing odours
vanillin
vanilla
eugenol
cloves
nerol
citrus
geraniol
floral

25. Choosing a fragrance –top tips
Fragrance changes depending on:
Time of appliance –top notes or base notes??
What fragrances you are already wearing
What you have just eaten
Whether you are ill or not
Menstruation /pregnant

26. Chemical analysis
Extraction
Separation
Identification/analysis

27. Extraction
In order to analyse odour compounds, we need to extract them out of their current setting
eg plant materials, foodstuffs, cosmetics
There may be hundreds of other compounds there – how do we extract the odour compounds whilst leaving the others behind?

28. Extraction: headspace analysis
fibre with polymer coating which traps odour molecules
headspace
odour compound
sample

29. Separation: Gas Chromatography
silica capillary column coated on inside with polymer layer He
flame ionisation detector
temperature controlled oven
Response
Time
Chromatogram

30. Separation: Gas Chromatography
How can we identify all these peaks?
1. Retention time comparison
2. Odour port analysis
3. Mass spectrometry

31. Identification: Mass Specrometry

32. Identification: Mass Spectrometry
High energy electron
Mass spectrum
106
105 77
106
Relative intensity 51
105
ionised molecule with too much energy
m/z
(mass to charge ratio
effectively the mass) 77 51

33. The End! Thanks to John Stephan of the Cotswold Perfumery
Bristol ChemLabS
Prof David Grayson, Trinity College Dublin