Chapter 2: Essential Oil Organic Chemistry
Sesquiterpenes can have
a straight-chain backbone,
one ring, or two rings (see
figure 2.4). Sesquiterpenes
aren’t quite small enough
to pass through the cell
membrane as efficiently as
monoterpenes, but they have
unique shapes that allow
Figure 2.4: Some common sesquiterpenes
them to adhere to pockets
include germacrene (top left), guaiene
in three-dimensional protein
(top right), and farnesene (bottom).
structures, affecting protein
activity. Sesquiterpenes are known to activate various cell surface
receptors.
2.3 INTRODUCTION TO FUNCTIONAL GROUPS
Another way to characterize essential oils is based on functional
groups. Functional groups are easy to spot on a skeleton diagram
because they are spelled out, in contrast to the carbon and hydrogen
molecules, which are omitted. For instance,
the letters “O” and “H” (representing
oxygen and hydrogen) are spelled out in
the carbon skeleton diagram of an alcohol,
which is one specific kind of functional
group (see figure 2.5).
Functional groups are distinct groups of
atoms within a molecule, but they have
characteristic properties that manifest
themselves regardless of the other
atoms contained within the molecule. For
instance, menthone and carvone are both
ketones, meaning that somewhere in their
Figure 2.5: A monoterpene
with an alcohol functional
group
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