this word is
polymorph
polymorphs are crystals of the same
compound but where the parts the
molecules in the crystal are arranged in
a different way so chemically they're
identical but usually not always they're
salts and the way that the positive and
the negatively charged ions fit together
in the crystal structure is different
is particularly common with
pharmaceutical compounds because
pharmaceutical compounds tend to be
quite complicated molecules so they
don't fit together very well in the
crystal they're not like the round
sodium and chloride ions in sodium
chloride so why does it matter why are
people interested in
polymorphs the problem is that different
polymorphs of the same compound often
have different solubilities say in water
or in acid so if you imagine you take a
pharmaceutical compound as a pill you
swallow it if it's one polymorph it will
dissolve much more quickly in your
stomach than another one so your dose
would be
different so in the pharmaceutical
industry it's very important that you
always produce the same polymorph of the
compound that you're going to sell as a
pharmaceutical
product the difficulty is that when you
have something
crystallizing the
crystallization begins often with a tiny
Crystal that starts as a nucleus that
sets everything else off once something
decides to crystallize in a polymorph
nearly the whole batch will go in that
way and there's several stories about
factories that are making a polymorph of
a particular pharmaceutical and a
different Factory that is getting the
wrong
polymorph somebody comes from that
factory to the other one and says show
me how to do it and
suddenly the factory that could do it
gets the wrong polymorph too because the
visitor has some micr crystals or
whatever in his clothes his hair or
whatever so understanding how things
crystallize is really quite an important
part of chemistry especially when you're
trying to make pH tical products I think
in fact that many if not most
pharmaceutical compounds have more than
one polymorph sometimes it's really good
because you can patent one polymorph and
then when the patent's beginning to run
out you can patent another one which
somehow is more effective so the
lifetime of your patent
continues but also I read an article
once which says the number of polymorphs
on a
compound really depends on the amount of
of money you spend studying it and the
longer you study it the more polymorphs
you can find because these are
complicated compounds and small changes
in the crystallization procedure can
change the polymorph I've heard of
things called allotropes how is an
allotrope different from a polymorph an
allotrope is a form of an element
graphite and
Diamond oxygen and ozone in those cases
is the
molecules have the atoms bonded together
in different ways in a polymorph or in
polymorphs the way that the atoms are
bonded together in the molecule or ions
are identical it's just the way that
they're stacked up that is
different and the difference in
solubility may not be very great but if
one thing is twice as soluble as another
when you eat it you get twice as big a
dose and twice as big a dose is quite
serious