Atomic Inversion - Chemical Bonding Video Lecture | Inorganic Chemistry

everyone's professor Davis here
answering a question that was posed on
the YouTube channel can a means be Kyle
centers and why is it that we often
treat them as though they're not even
though they clearly have a tetrahedral
electron domain geometry to begin
answering this question I've drawn
ammonia molecule here with nitrogen
represented in blue and its lone pair
electrons represented by the pink
coloured substituents so we have three
hydrogen's and one lone pair about this
nitrogen center and although this is not
chiral or even apparently chiral
molecule I want to show you first the
phenomenon that we're going to rely on
to explain this simply using something
like ammonia what happens here is lone
pair electrons on the nitrogen center
are contained in sp3 hybridized orbitals
and because they have a little bit of
that s character there that means that
that lone pair of electrons can actually
move through the center of this molecule
to the other side of the nitrogen so
unlike the chemical bonds it can
relocate itself to the opposite side now
let's take a look at what happens when
that occurs as you can see the three
hydrogen's are flipping back and forth
sort of like an umbrella being inverted
and this is the effect that causes most
nitrogen containing compounds to be a
chiral even though they actually do have
two sets of enantiomers now let me show
you using a chiral Center what that
looks like
so shown here is our nitrogen-containing
molecule but I replaced the hydrogen's
with three different colored
substituents again we have our nitrogen
center in blue our lone pairs of
electrons shown as the pink and then
three distinct substituents leading to a
chiral center however recall that the
lone pair of electrons can go through
the center causing it to flip back and
forth if this exchange happens rapidly
on the timescale of our experiments in
the lab we'll have a mixture of these
two handed versions of our nitrogen
molecules no matter what we do even if
we could isolate one of the two it would
rapidly begin interconverting with the
other enantiomer which means that
although a means may be technically
chiral centers it's very difficult to
make an enantiomeric we pure sample of
one and only in rare cases do we see
this happen I hope this has answered
your question and we'll see you next
time we upload