Perfumes: The fragrances of chemistry

"A woman's perfume, with the scent of a woman.". It was based on this audacious request by the French fashion designer Gabrielle Chanel, better known as Coco Chanel, that the renowned chemist and perfumer Ernest Beaux created Chanel No. 5 in 1921. The mixture combined flower essences with aldehydes, substances obtained by chemical synthesis. The perfumer used around 80 substances to satisfy the designer's demands and the result was an intense and very sensual perfume.

The use of synthetic ingredients marked the beginning of modern perfumery at the end of the 19th century and enriched the perfumers' palette with new fragrance notes. In the 1920s, the study of molecules was the passport to the production of fragrances on an industrial scale. Today, manufacturers have more than three thousand synthetic perfume molecules at their disposal and the perfume industry is worth seven billion euros annually.

The fragrance of a perfume is a complex system of substances, which were originally extracted from plants or wild animals. To get an idea, it takes five tonnes of roses to obtain one kilo of this essential oil and eight million jasmine trees to obtain the same quantity. The marketing of natural musk oil, on the other hand, is limited to 300 kilos per year, in order to preserve the musk deer species.

In fact, the hunting of this small deer was banned by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 1979, although some countries, such as Russia, have national laws authorising it within certain limits.

Concern for the conservation of biodiversity, particularly of endangered species of flora and fauna, has led the perfume industry to chemical laboratories, where today synthetic products are created as an alternative to those of vegetable or animal origin. And these are perhaps the two greatest contributions of synthetic chemistry to the perfume industry: the preservation of biodiversity and the massification of perfumes since the synthesis of aromas in the laboratory has made their production considerably cheaper.

Launched on 5 May 1921, Chanel No. 5 is still a success today. A symbol of refinement and elegance, the perfume's formula contains rosewood, Grasse jasmine, orange blossom and sandalwood essential oils. A century after its launch, it remains both a classic and contemporary perfume, and is the best-selling perfume in the world.

She was a woman and worked as a cook at the Royal Palace. And it was at the kitchen counter that, using cooking utensils, she developed techniques for making beer, but also for perfumes, ointments, and cosmetics. Tapputi-Belatekallim, was born in Babylon in 1200 BC and is considered to be the first female perfumer and the first woman in the field of Chemistry. 

A clay tablet found by archaeologists, dating from around 1200 BC, shows that this woman adapted cooking equipment and used different plants to create various aromatic essences. Her experiments were based on trial and error, leaving records of how certain elements reacted when combined, the dosages required and the temperatures desired.

Tapputi was also responsible for cleaning the palace and created perfumed oils. To achieve these results, she boiled water several times, diluting different combinations of flowers, leaves and myrrh. These oils were also used to perfume deceased kings and nobles, so that the odour of their bodies remained bearable until the end of long and elaborate funeral rituals.

It is said that the famous queen of Egypt - Cleopatra (60 BC - 30 BC) - had perfumes, oils, and creams to protect herself from the arid desert climate. During the Roman Empire (27 B.C. - 476 A.D.), the wealthier population, who enjoyed comfort, used perfumed essences and oils in their baths.

It is not known for sure when the concept of perfume arose. The word derives from the Latin per fumun or pro fumun, meaning 'through smoke'. With the fall of the Roman Empire and the advent of Christianity, the use of perfumes as an additive to the body was banned, as it was associated with pagan rituals.

The resurgence of perfumery in the West was due to merchants travelling to the Indies in search of spices such as cinnamon, pepper and musk. In the 16th century and after the discovery of the distillation of raw materials, the demand for perfumes was so high that Dominican friars began to devote themselves to this process in the monasteries in Florence. Catherine de Medici (1519-1589), Queen of France, had her own group of perfumers from Italy. It was the beginning of the perfume industry in France.

In the 18th century, perfumes were already manufactured in special stores run by pharmacists. It was at this time that at the hands of Italians living in the city of Cologne in Germany, "Cologne water" was created and became very popular.

The production of a perfume basically comprises the following components: denatured ethanol (C2H6O), essence or fragrance, fixative, propylene glycol (C3H8O2) and distilled water (H20). The fragrance, on the other hand, can be synthetic or natural.

Essences from natural sources are being replaced by synthetic compounds, as a result of the awareness for sustainability that is transversal to all sectors of activity. It is estimated that of the 3,000 fragrances available to perfumers, less than 5% come directly from natural sources, according to the article “Chemistry Perfumes your Daily Life” published in the Journal of Chemical Education. This means that in addition to greater resource compatibility, there is greater cost efficiency. According to the same article, thanks to this choice of synthetic compounds, fragrance now only represents 3% of the price of a perfumed product, with obvious repercussions on the final cost and making perfumes accessible to all.

Basically, a perfume is made up of a combination of fragrances, distributed according to an olfactory pyramid. The so-called "notes" of a perfume vary according to the volatility of its compounds.

The future of perfumery depends on chemistry and its scientists to invent molecules never before synthesised or smelt. If it is the perfumer's job to create a perfume using the available fragrance notes, it is up to the chemist to expand the palette of notes to be used.

However, grouping scents, or molecules by molecules, is far from being simply a way of providing cheaper copies of natural smells. Adding subtle nuances to raw materials - which could be a simple flower, for example - gives them character and an interpretation that can result in a unique perfume. And that is what makes the work of the chemical scientist so exciting in the art of perfumery.

Perfumers can create the scent of a non-existent abstract flower by combining fragrances, but it is synthetic chemistry that offers the potential to create completely new smells. It was exactly this combination of natural essences with the concentration of synthetic aldehydes, whose scent is not found in nature, that made Chanel No. 5 so special.

Sometimes the smell of a perfume, a flower or an orange cake is enough for us to travel back in time to a happy memory. The least studied of our senses - our sense of smell - is intimately linked to our emotions and behaviour and is what allows us to decipher chemical odour messages.

We cannot smell all the smells - only the elements that release chemical particles into the atmosphere. We can smell an apple, for example, but not glass or metal.

Smells are volatile odour molecules that spread through the air, penetrate the nostrils, and reach a group of olfactory cells that are found in the olfactory epithelium, the innermost part of the nose, near the base of the skull.

Olfactory cells have specific receptor molecules for certain odour molecules and when the two meet, the olfactory cell transforms the chemical message carried by the odour molecule into electrical impulses that reach the brain via the olfactory bulb. But it is in the olfactory cortex that odour information is interpreted, identifying the smell that has entered through the nose.

Sensory information is stored by the hippocampus to be remembered later and is also sent to the hypothalamus, which allows us to search for food, for example, through smell.

Like every sensory experience, olfactory perception awakens emotional and behavioural experiences in human beings. In fact, after all this, what we really want to say is that "chemistry" begins with our sense of smell...