Prisoners of Scent Symphonies: The Chemistry of Perfumes and Fragrances

The chemistry of perfumes is more than interesting – molecules that in different doses can smell differently, different natural or synthetic substances… Nature does not know the terms “odor” and “stink”. For some, Mugler’s Angel is a fragrance, and for some (including me) it stinks, but that’s just a subjective experience. Anyone who has a dog knows that the smell of something black is attractive to them like perfume, while cats frown at the smell of oranges. What we perceive as pleasant or unpleasant smells, for nature, are just molecules that convey some information. In order for something to have a smell, it must be volatile, because by evaporation, the odor molecules mix with the air and can “run” on our smell receptors. What does not evaporate, we cannot smell.

Aldehyde in Chanel No5

What we experience in perfumes as a powdery note or, depending on the concentration, freshness, is actually the smell of aldehyde molecules. It has already become a legend that Chanel No 5 owes its timelessness to the fact that the assistant of Ernest Beaux, who was asked by Coco Chanel to create a perfume that “will not smell like a rose or a lily of the valley ” instead of a 10% solution of aldehyde, mistakenly put 100 % aldehyde.

Another perfume, Guerlain’s Mitsouko, contains a substance codenamed C-14 (gamma-undecalactone), which smells creamy-peach. This substance is sometimes mistakenly called an aldehyde, but it is actually a lactone. In general, various esters are mainly responsible for fruity-floral scents in nature.

Aldehydes are a broad group of compounds, and all have in common that they have an aldehyde group -COH (basically, it’s a carbonyl group, the same as ketones). However, no one from Chanel ever gave a single word about which aldehyde it was, we only know that this aldehyde “smelled very much of Arctic freshness” (the words of Constanin Weriguin, Beaux’s student).

Rainsmell

What we call “the smell of rain”, the smell of freshness when it rains after a dry period, scientists call petrichor, which is a mixture of oils that plants produce during drought to protect themselves from excessive evaporation of water and the smell of earth – geosmin molecules produced by some bacteria (actinobacteria, namely gram-positive Streptomyces ) in the country. If the rain is accompanied by lightning, then some oxygen in the air turns into ozone – an allotropic variant of oxygen, whose molecule has three oxygen atoms instead of two, and we feel some of that smell in the atmosphere.

Many people are against synthetics in perfumes. This “natural” trend has spread from food to perfumery. Women want to smell like flowers and everyone is horrified by the use of synthetic components in perfumes, not knowing the secret of Chanel No 5.

Perfume chemistry: synthetic molecules

There is no need to run away from synthetic molecules. Just as Ernest Beaux used an aldehyde and created a legend, so the Escentric Molecules brand created an unusual component that they called Iso E Super ® in some of their magnificent Escentric Molecules perfumes (for example, Molecule 01, which consists exclusively of Iso E Super ® ). This scent component has pheromone properties, and sometimes it smells fresh, like a mixture of cut grass and ozone, sometimes vaguely woody, to some like sandalwood, to others like cedar, but it is neither sandalwood nor cedar, and it has the ability to disappear from the skin, then come back again. This code name stands for 7-acetyl, 1,2,3,4,5,6,7,8-octahydro-1,1,6,7-tetramethyl naphthalene.

Almost everything that smells – whether we like that smell or not – belongs to the world of organic chemistry. Of course, inorganic compounds can also have a smell – just remember the smell of hydrochloric acid, but in our world of messages, pheromones, perfumes, musks, spices, seduction and warning – most smells are organic compounds.
This means that they are mainly composed of only a few types of atoms – carbon, hydrogen, oxygen, nitrogen and sulfur atoms. Only five elements of the Periodic Table form all those fantastic, less fantastic and horrible smells.

Some compounds with specific, not to say unpleasant, smells have names that match them. Putrescine smells like decomposed garbage with a note of feces, i.e. according to the IUPAC nomenclature, butane -1,4 – diamine. For those who have never dealt with organic chemistry, let me explain: “butane” means that the molecule has 4 carbon atoms connected by single bonds and that the first (1) and fourth carbon atom (4) have attached amino groups, in total, two of them (diamine). Another compound with a horrible smell and a name that refers to it is cadaverine, according to the IUPAC pentane -1,5 – diamine (all the same as putrescine, only one more carbon atom, which smells like a corpse. However, one molecule has a nice name, and it smells very strange In large doses, as a pure component, indole.

It smells like feces and of course it is there. In small amounts, it smells floral and almost all white flowers, especially tuberose, contain this volatile component.

Rotten & seductive

Indole is a heterocyclic compound whose molecule consists of 2 rings – one benzene ring and one pyrrole ring. Another digression for those who did not have organic chemistry – heterocycle means that the ring itself does not consist exclusively of carbon atoms, but also of some other atom, in this case nitrogen atom, in the above illustration colored blue. Indole is a degradation product of the amino acid tryptophan, it is found in excrement, but also in tar, and, as I have already said, in the essence of some flowers. It got its name from indigo, from which it was first derived. By “some flowers” I mean the already mentioned tuberose, white jasmine/sambac, lily, lily of the valley, gardenia and orange blossoms. The jasmine flower has an incredible 2.5% indole. However, this should not deter you from buying jasmine.

Many perfumes with a strong jasmine note do not contain jasmine at all, and this jasmine note is called “non-indolic”, such as Bulgari’s jasmine perfumes, Armani Sensi and Jasmine White Moss by E. Lauder. Chanel No 5 contains real jasmine.

The smell of tuberose (Polyanthes tuberosa), citrus-floral, with a mushroom-like undertone, is an indole oil. In the Victorian era, young girls were forbidden to smell tuberose – and God forbid anyone give this flower to a young girl! – because there was a belief that by smelling this flower, the imagination of innocent girls could be polluted and that they could experience an orgasm. In Italy too, they believed that the smell of tuberose would lead young girls into decadence. For the rest – non-virgins and non-virgins – tuberose was considered an aphrodisiac (I almost didn’t write “aphrozodiac”). Perfumes that contain a lot of tuberose are Dior’s Hypnotic Poison and Robert Piguet’s Fracas and Boucheron’s Tubéreuse de Madrasand Amouage Honor Woman. Also, the slightly musty, vintage old lady’s closet note in Elizabeth Arden 5th Avenue comes from the hefty amount of tuberose in the middle notes.

Indole is a real Eros/Thanatos thing, the note of that “there is something rotten in the country of Denmark” – in perfumes it has the effect of a slightly animalic, even slightly rotten note, but by carefully arranging the composition of the fragrant pyramid, the animalic, but not vulgar qualities of the perfume are obtained, while the mistakes in the selection of components – too much musk and indole together, they give vulgar results and evoke the association of the toilet.

Otherwise, animal components in perfumes until the 30s of the last century – all those musks, civets, ambergris – were reserved for “friends of the night”, for the infamy, while those women who wanted to present themselves to society as “fine” wore single-component florals perfumes. So, they smelled boring, like some flower. Scents define us and dictate some of our decisions on a hidden subconscious level. The smell of leather can excite, but also repel, like, after all, all other smells. Very often illness, but also pregnancy, change the perception of smells, and patients and pregnant women cannot stand some smells that are perfectly fine to other people. First of all, we communicate with smells, we perceive the environment. That is why, in a way, we are prisoners of these molecular telegrams.