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

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

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…)

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

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%

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

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!

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

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. www.chemsoc.org

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.

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

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.

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.

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?

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

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

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

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)

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

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

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

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

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

Chemical analysis Extraction Separation Identification/analysis

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?

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

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

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

Identification: Mass Specrometry

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

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