Chapter 13: Basics of Essential Oil Chemistry - Cozy Buy Online

If you’ve used essential oils, you know they can be powerful allies in your wellness.  While many people stop at the basics of knowing which oils work for specific conditions, taking your knowledge a little deeper can help you to make better decisions about the oils you use.

Oils, like all substances, have a chemical makeup.  That chemistry determines how they work and bind with other substances – including the cells in your body.  Understanding their chemical nature can help you to create blends or identify oils for a specific effect.

For example, perhaps you like the respiratory support provided by eucalyptus, but the aroma sparks a headache.  Understanding the chemical nature of oils can help you to identify a substitute or another oil to blend to tone down the aromatic properties of eucalyptus.

If the last time you studied chemistry was in high school, you may feel a little intimidated by the idea of delving into essential oils chemistry.  However, you’ll find that you don’t need to a degree in chemistry to understand the basics and to harness that knowledge for your wellness.

In this report we’ll look at understanding the nature of essential oils – what they are and what they do – and we’ll discuss their basic chemistry.  You’ll be able to use this knowledge to improve your use of these gifts from nature.


The Nature of Essential Oils

What is an essential oil and what makes it “essential”?  Essential oils are the source for both the aroma and the flavor of a plant.  For example, you know when you’ve come into contact with garlic because of its telltale fragrance.  That fragrance comes from the essential oils inside of it.

When it comes to citrus fruits, the essential oil is found in high concentrations in the peel.   That’s why lemon zest is so fragrant.  In other words, the essential oils in a plant make up its “essence”.

The properties of essential oils go way beyond the fragrance and flavor, though.  For the plant itself, essential oils are important.  These oils help keep predators away and are part of the immune system of the plant.  In fact, you’ll find the highest concentrations of essential oils in parts of the plant that might become infected with microorganisms such as viruses, bacteria, and fungi.  This includes the bark, leaves, seeds, sap, and rinds of fruit.

And when humans use essential oils, we can glean these protective properties.  We can also use them to calm our minds and emotions and improve our overall wellness by stimulating natural healing.

Extracting Essential Oils

Essential oils must be extracted from plant parts.  The most common methods for doing this are steam distillation, solvent extraction, and cold press.  Plant properties determine which method will work best.

With steam distillation, boiling water creates steam that is passed through plant material.  The steam actually carries the essential oil out of the plant and into a tube where it is collected.  Then the steam is cooled and returns to its liquid state of water.  Essential oils are then separated from the water.

Solvent extraction is a method most often used to extract essential oils from flowers that are too delicate to handle other types of extraction.   To do this, the flowers are washed in a solvent mixture that pulls the compounds out.  Then the mixture is filtered to separate the plant material from the compounds.  Another process known as vacuum distillation is then used to separate the solvent from the essential oils.  Jasmine and vanilla essential oils are commonly extracted in this way.

Cold press is a method that removes essential oils without heat.  It is used for citrus fruits to remove the essential oils from the peel.  The fruit is passed over a sharp surface to break up the surface of its peel and break open the sacs that contain essential oils.  Then water is sprayed over it to collect that oil.  Eventually the water and oil mixture must be separated through another filtration process.

It takes much plant material to produce even a small amount of essential oils.  For example, it takes approximately 3,000 lemons to produce 2 pounds of lemon essential oil.  That means your 15 mL bottle of essential oil required about 75 lemons to produce.

Essential oils are highly concentrated and that is why they’re so effective compared to using the plant source material medicinally.  It’s not likely that you’ll consume that many lemons, but you can use a few drops of lemon oil to help clean the air in your home or help energize your mood.

Volatile Aromatic Compounds

Essential oils are actually made of chemicals known as volatile aromatic compounds.  These organic molecules are very small and they can change from a liquid to a gas at room temperature.  Because they can evaporate so quickly, they have a very potent fragrance.

That’s why a bottle of peppermint essential oils has a much stronger fragrance than a peppermint plant.  These compounds are highly concentrated in the essential oils.  The volatile aromatic compounds are very tiny and in one drop of essential oil you could find approximately 40 million trillion of them.

This tiny size allows them to travel quickly through the air.  In fact, you can often smell a drop or two of an essential oil from across the room.

While all essential oils have these compounds, there are many different subgroups of them.  An essential oil might be made up of one type of volatile aromatic compound or it might have 1000 different types within it.  We call each one of these types a constituent.

Each constituent of an essential oil can be identified by its size, shape, and the way its chemical bonds are arranged.  The constituents of essential oils determine their specific properties.

For example, lavender essential oil contains over 100 constituents, but there are a few that make up its main components including linalyl acetate, a-pinee, limonene, and cis-ocimene.  Peppermint essential oil contains many different constituents but has a high concentration of menthol which accounts for its strong fragrance.

What makes these constituents work the way they do?  The secret can be found in their chemical structures.  As you read on, you’ll learn about some of the most distinguishing characteristics of these structures and how they affect essential oil function.


Grouping Essential Oils

We can use chemistry to group essential oils and categorize them.  Organic chemistry, specifically, is the study of organic molecules.  Organic molecules are those that are made up from carbon molecules.

Carbon Molecule Basics

Every aromatic molecule is made up of carbon atoms that are joined together through chemical bonds.  The chain of carbon atoms linked to hydrogen atoms that make up an aromatic molecule is called a carbon backbone.  The carbon backbone alone would have limits on what it could do.  But functional groups added to the carbon backbone allow it to have additional properties.

They also have atoms within their molecule known as functional groups.  These are structures of molecules in addition to carbon and hydrogen that have the same function no matter where they are found.  They affect the properties of that molecule and help us to classify it.

Understanding Terpenes

The aromatic molecules made by plants are called terpenes because of their carbon backbones.  Plants have enzymes that help build these carbon compounds.  There are three main types of terpenes including monoterpenes, diterpenes, and sesquiterpenes.

The two main terpenes in essential oils are monoterpenes and sesquiterpenes.  Diterpenes can be found in essential oils, but when they’re found it’s usually in very small amounts.

Monoterpenes are so common that almost all essential oils have them.  They’re very small and because of that small size, they can react quickly to heat and to exposure to the air.  They also can be broken down very quickly.  Their tiny size also allows them to pass through the cell membrane and get inside the cell.  As a result, they can have a direct effect on targets within the cell.

Sesquiterpenes are more stable and are less common in essential oils than monterpenes.  They aren’t able to pass through cell membranes, but they can stick to pockets in protein structures and affect how the protein functions.  They can also bind to receptors on the surface of the cell and affect activities that way as well.

Functional Groups 101

As we discussed earlier, carbon backbones need functional groups to determine their specific properties.  There are eight functional groups that can be attached to a carbon backbone.  In this section we’ll go over the basics of each.

Each group is differentiated because of its structure and attachment to a carbon backbone.  The types of atoms it contains as well as where it bonds to the carbon backbone cause each group to have unique properties.

Some of these functional groups are very commonly found in essential oils while others occur more rarely.  While you can spend hours and hours memorizing carbon skeletons and structures, it really isn’t necessary in order to understand the basics.

Here we’ll look at the basic functional group, how you can recognize it when looking at names of molecules, how it can affect essential oil function, and which essential oils contain it.

This information will be helpful when trying to analyze the constituents of essential oils and make decisions about creating blends and using oils medicinally.


Alcohols are any molecules that have an alcohol functional group.  You can recognize alcohols when looking at molecule names because they end in the suffix “-ol”.  For example, menthol and linalool are alcohols found in essential oils.

When used aromatically alcohols produce relaxing aromas and can be soothing to anxiety.  When used topically, alcohols cleanse, can be repellant, and can improve skin health.  Internally, alcohols from essential oils can calm the nervous system and improve circulation.

Oils that contain a high concentration of alcohols include basil, lavender, melaleuca, geranium, patchouli, and cedarwood.


Aldehydes are molecules that contain an aldehyde functional group.  You can identify them with the suffix “-al” or “-aldehyde”.  For example, geranial and cinnamaldehyde are both aldehydes found in essential oils.

When used aromatically, aldehydes have the properties of being calming, relaxing, and protecting.  When used topically, they can support healthy skin and a healthy mouth.  They can also be responsible for a warming sensation on the skin.

Oils that contain many aldehydes include cinnamon, lemongrass, lime, and cassia.


Alkenes are molecules that actually don’t contain any functional groups.  However, they have at least one double bond between any of their carbon backbone molecules.  You’ll recognize alkenes by the suffix “-ene”.  Some examples of alkenes include alpha-pinene, limonene, and zingiberene.

Alkenes are known for being antioxidants.  Because of their chemical structure, they are able to accept electrons belonging to free radicals and keep them from attacking the body.

When used aromatically, alkenes have a pleasant fragrance.  Topically, alkenes benefit the skin and other tissues because of their antioxidant properties.  Internally, antioxidants from alkenes can benefit most organs in the body.

Oils high in alkenes include frankincense, ylang ylang, black pepper, lemon, bulue tansy, and wild orange.


Esters are functional groups that occur when an alcohol and an aicd react to each other.  Esters are made up of carbon molecules that actually have two carbon chains.  Because of this unique structure, they often have two names.

You’ll recognize them in the naming because they end in the suffix “-ate”.  For example, linalyl acetate, methyl salicylate, and benzyl acetate are all esters.

Esters provide relaxation and balancing when used aromatically.  When they’re used topically on the skin, they can be rejuvenating and soothing to those tissues.  They can also protect against some environmental threats to the skin.

When internally used, esters can support heart health, the immune system, and the nervous systems.  However, some esters should not be used internally.  You’ll need to carefully research essential oils you use to determine if they are safe internally.

Lavender, wintergreen, and roman chamomile are all essential oils that contain a high number of esters.


Ethers are molecules that aren’t very commonly attached to monoterpenes.  However, sesquiterpenes frequently have ether groups attached to them.  Eucalyptol is the most commonly found ether in essential oils.

Ethers are used aromatically to soothe emotions as well as clear airways.  Topically, they help to clean the surface of the skin and improve its appearance.  When used internally, ethers can support a healthy immune system.  But some ethers aren’t safe for internal use.

Oils that are high in ethers include eucalyptus, peppermint, melaleuca, and rosemary.


Ketones are a lot like aldehydes in the way they bond to a carbon backbone.  The difference is where they’re placed on that backbone.  Aldehydes are found at the end of the carbon chain and ketones are found somewhere in the middle.

You can recognize ketones most of the time by their suffix “-one”.  Menthone and carvone are both exmaples of ethers.  However, camphor is also a ketone, but its name doesn’t fit that pattern.

When used aromatically, many ketones are uplifting and energizing.  Still other ketones are grounding and stabilizing.  Some can also help open airways.  Topically, ketones can help skin hygiene as well as repel microbes.  Most ketones support digestive health and nervous system function.  However, some are not recommended for internal use.

Some examples of oils that are high in ketones include spearmint, peppermint, dill, caraway, and frankincense.


Phenols are actually a subtype of alcohols.  This is an alcohol group that is attached to a hydrocarbon ring known as a benzene ring.  Since phenols are also alcohols, they also end in the suffix “-ol”.  Some examples of phenols include carvacrol, eugenol, and thymol.  These usually occur in monoterpenes and are very uncommon in sesquiterpenes.

When used aromatically, phenols tend to have an invigorating aroma. Topically, they are cleansers.  Internally, phenols provide antioxidant support and can support most of the body systems.  You’ll recognize essential oils that contain phenols as coming from plants we commonly eat.

Oils that are high in phenols include oregano, thyme, clove, cinnamon, and basil.


The final functional group is phenylpropenes.  These are commonly found in monoterpenes but aren’t very common in essential oils.  The most common phenylpropenes are anethole and chavicol.

Those essential oils that do have them can provide an energizing aroma when used aromatically.  When used topically they can improve skin health and appearance.  And used internally they can support your heart health by promoting blood flow.

Essential oils that contain phenylpropenes include fennel, anise, basil, and myrtle.


Essential Oil Chemistry and You

Understanding essential oil chemistry can help you to become a better consumer of it.  First, you’ll be able to understand the constituent profile and how that affects the aroma.  This can help you to create a good oil blend.

Second, essential oil chemistry knowledge can help you to determine how oils will work therapeutically.  You’ll be able to understand how oils work alone and with other oils to improve your health.

Finally, understanding oil chemistry is important to help you choose oils that are safe for you and your family.  We’ve gone over some of the very basics of essential oil chemistry to get you started on the road of this science.

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