Chemistry drives the world around us and serves as the liaison between all other branches of science—even physics, biology, physiology, and geology. In fact, all things are composed of chemicals and undergo constant chemical reactions. Even essential oils are composed of a complex blend of chemical constituents. In plants, these constituents offer many protective and reproductive benefits. In humans, these constituents are what give the oil functionality, determining their mechanism of physiologic action, and in turn, the resulting health benefit.

Each individual essential oil constituent is made up of atoms, the building blocks of all chemicals. Carbon is the most prevalent element in essential oils with approximately 70–80 percent of the whole essential oil being composed of just this single element! Hydrogen, oxygen, nitrogen, and sulfur also play important roles in essential oil composition and chemistry; however, they are present in far lesser quantities. Covalent bonds are created between atoms to increase their stability. Although it seems as though there are endless combinations of atoms that could come together to form molecules, there are actually just a few distinct patterns found in nature. The most commonly found classes of essential oil constituents are:

  • Monoterpenes. A hydrocarbon group composed of 10 carbon atoms; this is the most prevalent variety of constituent found in essential oils. Monoterpenes are characterized by their low molecular weight and high volatility
  • Sesquiterpenes. This constituent forms when an additional isoprene unit is added to a monoterpene forming a molecule with a total of 15 carbons atoms. Although less prevalent than monoterpenes, sesquiterpenes offer potent health benefits such as cleansing properties and the ability to support health.*
  • Diterpenes. Diterepenes represent the heaviest constituents found in essential oils. They are composed of 20 carbon atoms, or two monoterpene units combined. Because of their high molecular weight, they are rarely found in essential oils.
  • Alcohols. Alcohols have a functional group that contains one oxygen atom and one hydrogen atom (-OH) bonded to a carbon chain. This important class of constituents is known for its, cleansing properties.
  • Phenols. Phenols feature an alcohol group bonded to an aromatic benzene ring. This class of constituent is considered especially potent and possesses benefits such as its ability to support health and its antioxidant properties.*
  • Aldehydes. Featuring a double bonded oxygen group (C-H-O) at the end of a carbon chain, aldehydes have distinct and potent aromas. In fact, aldehydes are often the key contributor to an essential oil’s overall fragrance profile.
  • Ketones. Similar to aldehydes, ketones feature a double-bonded oxygen that is located in the middle of a carbon chain. This class of constituent is great for supporting health.*
  • Esters. Esters contain a carbon atom with the following bonds: a double-bonded oxygen, a single-bonded oxygen, and a single-bonded carbon atom. Many esters are renowned for their calming and relaxing properties, as well as their ability to support health.*
  • Oxides. A unique functional group, oxides always include an oxygen atom that is part of a closed ring structure. Oxides are most commonly known for their powerful ability to promote feelings of clear breathing.

The chemical profile of essential oils is very complex containing up to hundreds of individual constituents. Many studies have been conducted examining both the synergistic action of the whole oil as well as the individual action of isolated constituents. These studies have verified that there is increased benefit and safety from using the whole oil, rather than just an individual constituent. In other words, oils are best used in their whole form—with the exact composition designed by nature—nothing added, removed, or isolated.

You should have completed Module 4: Chemistry of Essential Oils, before continuing with this module.  


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