in this video you will learn how to use
different types of formula to represent
organic molecules the formula used most
frequently in our videos has been the
displayed formula this is because
displayed formula provides the clearest
visual structure of an organic molecule
here is the molecule butene showed in
displayed formula it shows all the atoms
in the correct order with lines to
represent all single and double covalent
bonds drawing all the bonds for very
carbon molecules can be quite repetitive
for example here is butanoic acid in its
displayed formula since this is a carbon
molecule and as chemists we are clear
with the bonding arrangement of
carboxylic acid functional group we also
use structural formula to represent
organic molecules here is the structural
form as you can see the covalent bond
between the O H is not showing as we
know this arrangement anyway in fact we
could simplify this further and remove
all the displayed bonds like this
structural formula is often used when
writing equations but the formula
doesn't mean that it's always clear what
arrangement bonds are int here is
another example
first the displayed formula of propane
if we then take out the lines represents
in the covalent bonds and group our
atoms together in order they are
arranged we made the structural formula
of propane pause the video now and try
and draw both the displayed formula and
structural formula of pentane which has
5 carbon atoms
here is the displayed formula of pentane
and here is its structural formula
molecular formula is another type used
and shows us only the number of each
type of atom in the compound to work out
the molecular formula you simply add up
each type of atom for example here is
the displayed formula of hexane as you
can see it has 6 carbon atoms and it has
14 hydrogen atoms the molecular formula
of hexane is therefore c6h14 this alone
is not very useful as it does not show
us how the atoms are arranged and where
the bombs are if you look at these
molecules they all have 6 carbon atoms
and 14 hydrogen atoms although you may
not be able to name these different
molecules you can see they are very
different but all have the same
molecular formula this is the molecule
glucose pause the video now and complete
the molecular formula for glucose you
should have counted 6 carbon atoms 12
hydrogen and 6 oxygen atoms so the
molecular formula is c6h12o6 sometimes
the formula is reduced even further to
make an empirical formula the empirical
formula is the simplest whole number
ratio of atoms in a compound we need to
find the highest common factor that
being the largest whole number that is a
factor of 6 12 and 6 in this example of
glucose they all divided by 6 and so if
we do this we get C 1 H 2 or 1 we don't
show the ones and so the empirical
formula is C h2o although empirical
formula doesn't show us the molecule or
how it is arranged it does tell us the
ratio of atoms in the molecule now
at the end of this video you should
understand how to draw organic molecules
in displayed structural molecular and
empirical formula
you