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0:04
So far we have
considered the way
atoms are bonded
to each other in
a molecule so the
topology and how
this is translated into a
computer-readable form.
Now let's go a step further to
the 3D arrangement and the
3D formation of molecules.
0:23
Before we come to coding 3D
information with a computer,
here's just a short overview or
a summary of the different
types of stereochemistry.
I think the chemists should
be familiar with this
and I will not go any
further into detail.
0:42
Here we can see again
in a flow chart
how stereoisomers
can be classified.
By computer handling,
we have to decide if
the empirical formula
is the same or not
and then if they have
the same connectivity,
they are stereoisomers;
if not, they
are constitutional
isomers and then we have
to split into conformers or
configurational isomers also
considering the chirality.
If the isomers are chiral,
they have special properties and
they are different
compounds as we can see on
the next slide with
different arrangements of
the groups in the space.
1:23
They have equal topology
so in the 2D space but
different topography
in the 3D space
and they should behave
like mirror images.
This can be seen in
the figure below
and also that we can depict
this 3D information either
in a coordinate system
or in this special
representation
called the Natta projection.
If we go back to the
configurational isomers again,
we see that there are
always pairs of molecules.
For example, E and
Z or R and S, and
this pairwise appearance
makes it very
comfortable by bitwise computer
handling of the information.
The wedged or hashed
representations
we have seen in this
Natta projection are
just simplifications of
a spatial depiction for
describing the
actual arrangements
of all atoms in 3D space,
two different methods are
commonly used corresponding to
two different coordinate systems
as we will see in
the next slides.
