Essential Oils — Beyond the Pleasing Aromas

Written by: | May 2, 2016 | 17 responses

Essential Oils — More than Just A Pleasing Aroma

Essential Oils are fabulous. We all love them for their amazing power to uplift, calm, delight, and fascinate our spirits. We blend them together to get a unique scent profile for ourselves, and even for our pets! I love using our Pet EO Blend of Cypress, Cedarwood, Citronella, Lemongrass, Lavender, and Tea Tree in shampoos and bedding sprays. Sometimes a single note is exactly what we want — like Lavender, Rose, or Jasmine. But as great as EOs are for creating aromatherapy combinations and beautiful scent profiles, there’s a lot more behind an EO that many of us don’t realize.  So today we’re going to talk a little about the chemistry behind EOs.

Essential Oil Chemistry 101

As someone who successfully avoided Chemistry throughout high school and in college, imagine how surprised I was to be confronted with the subject as an adult formally studying Aromatherapy! Though it was difficult, studying the chemistry of Essential Oils provided me with an in-depth understanding of their complex chemical compositions and their proper usage.  I also learned that it would be nearly impossible to create an Essential Oil in a lab, as each and every chemical constituent that we know and love is already included by nature.

What gives an Essential Oil its Properties?

Each EO has unique multiple chemical properties that influence the aroma they give off.  When you can break down an Essential Oil into to its distinct properties, you can begin to understand how that Oil gets its scent and how the different constituents work together. Essential Oils consist of hundreds (sometimes thousands) of chemical constituents, also known as Organic molecules and chemical compounds or “building blocks” that include hydrogen, oxygen, and carbon. Each of the Oil’s properties works in tandem with the other to rebalance a variety of conditions.

In general, Essential Oils fall into two distinct groups of chemical constituents; the hydrocarbons, which are made up almost exclusively of terpenes (monoterpenes, sesquiterpenes, and diterpenes), and the oxygenated compounds which are mainly esters, aldehydes, ketones, alcohols, phenols, and oxides.

Below is an abbreviated list of the constituents in an Essential Oil, beginning with Terpenes, which are evident in nearly all Essential Oils.

Hydrocarbons (Terpenes)

Terpenes (/ˈtɜːrpn/) are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers and as well, Cannabis sativa plants. Comprised of Hydrocarbons, Terpenes found in most of the Oils and include Monoterpenes and Sesquiterpenes. I have always referred to Monoterpenes as the ‘sunny’ constituents.  Monoterpenes provide a warming or “sunshine” sensation to the skin and call to mind aromas of Citrus.  Pinene and Limonene are the two most common of all of the constituents that make up Essential Oils.

Oils containing Monoterpenes include:

  • Limonene- found in Bergamot, Carrot, Fennel, Lemon, Neroli , Orange and other Citrus Oils
  • Pinene- found in Coriander, Cypress, Eucalyptus, Pine, Black Pepper, Oregano
  • Camphene-found in Juniper, Fir, Spruce, and Pine

Next, we have Sesquiterpenes: I refer to Sesquiterpenes as the ‘calming and soothing’ constituents. When I smell oils with a high percentage of Sesquiterpene, I feel immediate relaxation. I always carry a dram of Clary Sage Essential Oil with me; it’s my go-to EO for helping me relax after a stressful day.

Oils containing Sesquiterpenes include:

  • Carophyllene- found in Lavender, Clary Sage, Marjoram
  • Azulene & Chamazulene- found in Chamomile
  • Cadinene- in Patchouli, Lemon, Cedarwood

Oxygenated Compounds

Oxygenated Compounds mainly include Aldehydes, Phenols, Alcohols, and Esters.

  • Aldehydes– When I smell oils with a considerable amount of Aldehydes I think of Citronella candles burning on a Spring evening– hopefully providing an aroma that will give bugs something interesting to think about rather than sharing their venom! Not all Aldehydes provide this fruity aroma, however. Aldehydes are actually one of the compounds that drive the scent of an Essential oil and include:
    Cinnamaldehyde Acid – prevalent in Cinnamon Bark Oil, also in Patchouli
    Anisaldehyde- prevalent in Anise Oil
    Benzaldehyde- in Bitter Almond Oil
    Citronellal-in Lemongrass, Lemon Balm (aka Melissa)
    Citral- Bergamot, Lemongrass, Cistus
    Geranial- Lemon, Lemongrass, Cistus and Lemon Balm
  • Phenols– I tend to think of a Medicinal/Herbal aroma when I think of oils that are high in Phenols. Two kinds of Phenols exist in Essential Oils- one is naturally occurring and the other occurs in the distillation process.
  • Eugenol– is very prevalent in Clove oil. (You might recall the scent of Clove when undergoing a dental procedure). Other oils that contain Eugenol are Bay, Basil, Cinnamon, Rose, Ylang Ylang
  • Thymol– in Thyme Oil, Sage Oil
  • Methyl Chavicol– in Basil Oil, Fennel, Hyssop, Marjoram, Anise
  • Anthethole- Fennel
  • Carvacrol-in Black Pepper, Marjoram, Thyme, Fennel
  • Alcohols-A very large functional group of constituents which are categorized as “Monoterpenic”, “Sesquiterpenic” and “Di-Terpenic”, the latter in small amounts and the first mentioned the most common.
    Geraniol- in Bergamot, Geranium, Melissa, Neroli, Grapefruit
    Menthol- -in Lavender, Peppermint
    Linalool- in Basil, Bergamot, Clary Sage, Lavender, Marjoram, Neroli, Thyme, Ylang Ylang, Coriander, Ginger, Oregano
    Borneol- in Juniper, Frankincense, Lavandin, Hyssop
  • Esters – Essential Oils that contain Esters are quite fragrant with a fruity type of Aroma to my nose. When I smell oils with a high Ester Content I feel automatically relaxed, perhaps it is due to the intense aromas of these organic compounds or more so because I simply love ester-heavy oils.
    • Linalyl Acetate- in Lavender, Bergamot, Clary Sage, Geranium, Lavandin, Jasmine, Petitgrain
    • Benzyl benzoate- Benzoin, Jasmine, Ylang Ylang, Balsam Peru
    • Geranyl acetate- in palmarosa, lemon grass, petit grain, neroli, geranium, coriander, carrot
    • Borneol Acetate- in Yarrow, Rosemary, Pine, Juniper

When thinking about creating your own Essential Oil blends, I hope this gives you a little insight into the WHY behind the fabulous aromas you envision.

Happy Creating,


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