I have several questions regarding essential oils.

Question

Please answer as many questions as you can that is
within your expertise.
For each of the following naturally occurring oils:
Citronella ,eucalyptus,cinnamon
leaf,nutmeg,clove,rose,jasmine,lavender
a.how easy is it to produce for each of them
chemically as compared being extracted from natural
sources?
b.how effective the chemically produced ones for each
of them compared to the ones extracted naturally.Are
there any harmful effects using the chemically
produced ones?
c. in the market ,if one does not know the origin of a
particular oil, how likely are each of them to be
produced chemically as compared it to be the
naturally?
d. apart from laboratory tests, are there any other
way of distinguishing between the two?
e.when the lid is taken off a bottle of the oils , the
oil evaporates to fill the room with its aroma. But
after sometime, no more oil evaporates unless one
stirs it. Why is it so?
Thank you.

What you are smelling is a particular compound in the oil, and oil is a mixture of many compounds. perfumes typically have several compounds in them to produce the effect. If these compounds are put in a viscious oil, only the surface is exposed to the air, and those compounds near the surface are liberated. Because the carrier oil is viscious, the mixture is not moving, so once the compounds near the surface are evaporated, no more evaporates because the carrier oil has them trapped below. One stirs the oil to bring more near the surface.