Perfumes – just a big chemistry experiment
Every aspect of our experience with perfumes is grounded in chemistry. At the center of that experience is a very well-known substance, regular old ethanol. Let’s take a closer look at ethanol and its role in the fragrance industry.
Alcohol, but not for drinking
Ethanol (C2H5OH) is the second-simplest member of the alcohol homologous series, consisting of a two-carbon chain connected to the hydroxyl (-OH) functional group.
The -OH group is what makes an alcohol an alcohol, and the only simpler member of the family is methanol, CH3OH, with just a single carbon atom.
Ethanol is a colorless and volatile liquid at room temperature, and is perhaps best known as the compound that makes alcoholic drinks alcoholic! It’s a ubiquitous chemical in a multitude of chemical industries and processes and has multiple crucial roles in the perfume industry.
Most of the alcohol used in the commercial production of perfumes is denatured alcohol, i.e., that which has been made unfit for human consumption. People wishing to produce perfumes at home may choose to use 190 proof (95%) food-grade alcohol instead, since in many instances it may be purchased without special licenses.
Smelly molecules are often not water soluble
Virtually all perfumes are combinations of several ‘smelly’ molecules, known as “volatile organic compounds,” or VOC’s, blended to create a unique fragrance. These molecules are often found in (and isolated from) naturally occurring oils, or botanical extracts. For example, take the molecule muscone.
Muscone is found in musk, which is secreted by musk deer. It has a strong aroma that has been used in perfumes for centuries.
Most of the molecules involved in creating perfumes are not particularly soluble in water, so taking each of them and dissolving them in regular H2O just isn’t an option. Besides, water is not an ideal medium for perfume, since it has a slow evaporation rate. Ethanol, on the other hand, is a great choice for dissolving aroma compounds since it more closely matches the chemistry of most VOC’s.
Volatility and other helpful properties
Ethanol also has a relatively low boiling point (78°C), allowing it to evaporate quickly. As the molecule that is responsible for carrying the fragrant molecules into the atmosphere – and ultimately the nose – this is a crucial property that is utilized in perfume manufacture. The volume of ethanol is crucial as well, since higher volumes of ethanol make the perfume more dilute, which changes the potency of the perfume.
In perfume industry speak, the a fragrance is divided into three parts: the top notes, the heart notes, and the base notes. Ethanol is a fantastic solvent for aiding each part of the experience due to its quick evaporation, relatively neutral odor, and chemical inertness with respect to most of the aroma molecules.
Which type of perfume is right?
Perfumes are typically divided into four different types: perfume, eau de parfum, eau de toilette, and eau de cologne. These terms have specific meanings that relate to their constitution. Perfume typically has 20-30% fragrant molecules, with the majority of the remainder being alcohol, but also with some water. Eau de parfum has around 15-20% fragrance, again with most of the rest being alcohol. Eau de toilette and eau de cologne come with around 5-15%, and 2-5% fragrance respectfully, once again with ethanol making up most of the remainder of the volume. The cost of these fragrances varies from the most expensive perfume, to the least expensive eau de cologne, reflecting both the concentration of fragrant molecules (greater = more expensive) and their longevity in the atmosphere, with the larger concentrations of ethanol lasting for shorter periods of time.
Making it last
Ethanol also helps in preserving perfumes. It has the property of being an antimicrobial, meaning that it suppresses the growth of bacteria. This keeps the perfume fresh and prevents the perfume from developing off-aromas or “going off.”< Back