(GTKAM animated intro)
Shakespeare said it best: “That
which we call a rose by any other
name would smell as sweet”.
Turns out… not quite.
There are hundreds of rose species,
thousands of cultivars, many of them
smell different, others don’t smell at all.
But that rose smell we’re familiar with
from cosmetics, perfumes, foods,
rose oil and rose water?
It’s probably from a single rose species
– the damask rose.
And while that most famous rose smell
might come from a single species,
its actual scent isn’t from a single source.
Rose scent comes from a lot
of different chemicals – one has the
somewhat obviously named ‘rose oxide’.
Rose oxide produces the floral green top
note, plus a sweet, a fruity smell,
a minty smell, and a citrus scent.
So how does one chemical contribute
all those smells? Simple.
Rose oxide isn’t one chemical - it’s four.
All four rose oxides have 10 carbon atoms,
18 hydrogen atoms, and 1 oxygen atom
all connected in the same order.
How do we get four chemicals from this one setup?
It’s all about that chirality.
Think of chirality like my
left and right hand.
They’ve got the same number of fingers,
one thumb, you get the idea.
My hands are mirror image of each other.
But, if I try to superimpose my hands –
placing my left on top of my right
– it doesn’t work.
My fingers and thumbs don’t line up.
Left: 4-3-2-1-Thumb, Thumb-1-2-3-4.
They look identical, but when I try
check if they’re actually the same
– I find they are not!
The same principal applies to the four rose oxides.
All four have the same molecular formula,
same chemical connections between
the atoms, BUT not some atoms have
different arrangements in space.
And believe it or not,
that arrangement actually affects
how each rose oxide smells.
Scientists say the rose oxide known
as 2-S, 4-R stinkiest one, contributing
the most to that classic rose smell.
You only need about zero-point-five
parts per BILLION of (2-S, 4-R)-rose
oxide to be able to detect it with the ol’ sniffer.
Our other three rose oxides?
You’d need anywhere from 50 to 160 parts
per billion to pick up their scent.
All four rose oxides produce different types of smells.
Why the different scents and strength of smell? Shape!
Each rose oxide interacts differently
with an olfactory receptor in our nose.
Think of a key that fits perfectly
in a lock, versus that annoying one
you have to jiggle to make work.
Chemistry is full of these subtle differences.
Arranging atoms even slightly differently
can mean a rose by any other configuration,
DOESN’T smell as sweet.
Thanks to CAS for sponsoring this video.
And hey, if you’re really into molecules,
check out the SciFinder Future Leaders in Chemistry program.
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It’s an all-expense-paid trip where
you’ll get to see firsthand how CAS
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You’ll also get to travel to
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For details, visit cas.org/futureleaders.
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