Chemistry?!? Are your eyes glazed over yet? It happens...yet if you're interested at all in the therapeutic use of essential oils, a little primer on their chemistry can be very useful. Not only will you better understand how and why essential oils work, but the great importance of using natural, high-quality oils - oils that are pure, properly distilled, AND smell nice - will be made clear. It's not just an aromatherapy sales pitch; essential oils with exceptional bouquets have different chemical make-ups than flat or otherwise uninteresting oils. The differences can significantly affect the healing potency of therapeutic applications for you, your family and/or your clients. Much of the time, you can discern the difference of therapeutic value between two oils just by their aroma - one needn't always have the proof of fancy, expensive machines to make an educated choice.
So, why are essential oils called 'oils' anyway? They don't feel greasy, and they tend to evaporate completely, unlike common 'fixed' oils (such as olive, grapeseed, hazelnut and the like). Essential oils and fixed oils share a similar chemical foundation: their structures are based on the linking of carbon and hydrogen atoms in various configurations. But this is really where the similarity ends. Fixed oils are made up of molecules comprised of three long chains of carbon atoms bound together at one end, called a triglyceride. Every fixed oil is made up of just a few different triglyceride arrangements - olive oil, for example, is primarily made up of oleic, linoleic and linolenic acids (the names of particular carbon-hydrogen chains forming the triglycerides). Their long-chain shape holds them in a liquid state which does not easily evaporate.
Essential oils are 'volatile' oils - oils that DO easily evaporate. Their chains of carbon atoms to which the hydrogens attach are not as long or heavy, and are much more complex. Many essential oil structures are not really chains, but ring, or multi-ringed shapes with diverse sub-units - called 'functional groups' - sticking out in various directions. Like their fixed oil counterparts, essential oils are lipophillic - meaning 'fat liking'. The fat-liking nature of both fixed and essential oils makes them easily absorbed by our bodies. Because of their typically smaller structures however, essential oils are absorbed more rapidly than fixed oils, and can easily penetrate deep into the body. Despite their plant origins, this lipophillic nature of essential oils makes their profound healing action on the human body possible.
Most of the therapeutic activity of an essential oil can be attributed to the functional groups of the individual chemicals that make up the oil. There can be over a hundred identifiable molecules in one essential oil. Each of these molecules, as mentioned earlier, is a chain or ring (or multiple-ring) structure of carbon atoms linked together with hydrogen atoms bonded to them in various configurations. Every chain or ring has a functional group attached - a functional group is defined by Salvatore Battaglia in 'The Complete Guide to Aromatherapy' as: "a single atom or group of atoms that...has a profound influence upon the properties of the molecule as a whole. It is often referred to as the chemically active center of the molecule".