we're back again to work on our
conversion from aspirin to acetaminophen
also known as Tylenol or paracetamol in
the previous two videos we extracted
acetyl salicylic acid which is the
active ingredient of aspirin pills and
then we hydrolyzed it to salicylic acid
if you're interested in checking out
these steps I'll provide a link to the
previous two videos in the description
now we're on the third step where the
salicylic acid needs to be
decarboxylated to form phenol many
decarboxylation reactions require a base
or a catalyst to be added but luckily
for me the decarboxylation of pure
salicylic acid proceeds very smoothly
and i don't need to use any additives I
just have to crank up the heat a little
bit and it'll decarboxylate on its own
this isn't the first time that have
covered a decarboxylation reaction and I
have a few videos where I've gone over
it three chemicals that have made by
decarboxylation are benzene pyridine and
very recently cadaverine the procedure
for each of these decarboxylation x' is
pretty different and if you're
interested in checking any of them out
i've provided some links in the
description in terms of chemicals all we
need is the salicylic acid that was
prepared in part 2 which came out to be
62 point 6 grams the general procedure
that I used as a guideline was written
by the user unintentional chaos on the
science madness forum he provides a
pretty detailed write-up so if you guys
are interested in checking that out I'll
provide yet another link in the
description
to start things off I add all of the
salicylic acid to a round bottom flask
some of you might be wondering why I use
the 500 milliliter flask when everything
probably could have easily fit in a 250
I'll be using heat to decarboxylate the
salicylic acid and the phenol will be
separated by distillation this reaction
isn't exactly super efficient and we
form a fair amount of side products most
of the side products have a much higher
boiling point than phenol and in a large
flask they're going to have a hard time
making it out so basically the large
flask acts as a pseudo fractionating
column and it allows us to get a better
separation between the phenol and the
higher boiling point side products
with the salicylic acid in the flask we
now set things up for a simple
distillation what's unique about this
setup is that I don't include a
condenser the melting point or freezing
point of phenol is around forty point
five C so if we use the cold water
condenser it would very quickly get
blocked so the two options are either
not using a condenser at all or using a
condenser with warm water in it it seems
like not using a condenser work just as
well and it requires less of a setup so
I went with this method I set everything
up and then I realized I forgot a stir
bar so I just quickly dropped to an end
the apparatus was lowered into the
heating mantle and I also added a few
clips now I'm ready to start the
reaction so I turn on the heating mantle
as well as the stirring
right now the salicylic acid is a powder
and stirring won't work at all but it
should slowly melt
over the next several minutes nothing
melted but the volume of the salicylic
acid slowly diminished
eventually we reached the melting point
of salicylic acid and things started to
liquefy as the salicylic acid melted the
stir bar was liberated and it was
actually able to do its job what might
be interesting to notice here is that
the melted salicylic acid has a very
strong pinkish red color a lot of people
in the previous video commented that the
salicylic acid was still a little bit
pink and well clearly they were right
I assume the pinkness is from the dye
that they are used in the aspirin pills
but it also could be something else
anyway regardless of what it is it's
clearly pretty persistent and it's
managed to hold on even after a few
recrystallization --zz fortunately for
us though this is the last time we'll
see it and it's not going to be carried
over into the phenol product
okay so as I said before the reaction
that we're carrying out is known as a
decarboxylation when the salicylic acid
is heated up enough it will decompose
into phenol and co2 gas the co2 will
simply just diffuse a way out of the
flask and our phenol will be distilled
over one reason for loss of yield in
this reaction is that phenol will
actually react to a certain degree with
salicylic acid this type of reaction is
known as an astera fication reaction and
it'll form something called phenyl
salicylate the phenol salicylate that
forms can go on to react with more
salicylic acid to make a very crappy
polymer or it can react with itself to
forms anthone you'll see at the end of
the distillation that we'll be left with
a lot of tari crap at the bottom of the
flask and this will consist mostly of
the side products I just mentioned as
well as some unreacted salicylic acid
something that I find interesting is
that as the salicylic acid liquid is
being heated the color slowly changes
when we first started the liquid was a
pinkish red color but as things are
heated this quickly fades and were left
with a yellowish brown color we'll
eventually get some milky white liquid
dripping into the receiving flask I'm
not entirely sure what this is but I
don't think it's water or phenol it is
an option to switch out the receiving
flask when the distillate runs clear but
I'll be running a second distillation so
I opted to just capture everything here
you'll also notice that I covered the
distillation flask with aluminum foil
and this just serves to keep things hot
I found that when I didn't use the
aluminum foil the phenol had a really
hard time making it over to help keep
the apparatus cool it's really useful to
add some damp paper towel
the boiling point of phenol is a hundred
and eighty one point seven we want to
collect everything that comes at and
below this temperature and once the
temperature starts to rise above this
the distillation is stopped on the right
here I have the final yield of phenol
from the initial distillation and on the
Left I have the tari crap that's left
over in the distillation flask
I let things cool down and the phenol
didn't freeze which indicates that it
still has quite a bit of impurities in
it
the tari crap on the left does freeze
and it forms a solid chunk at the bottom
of the flask I don't remember exactly
but I don't think it was too hard to
clean things out and I just used a bunch
of acetone to clean this now it's time
to do a second distillation to purify
the phenol so to get things started I
turn on the heating mantle as well as
the stirring it doesn't take long for
things to start coming over but like
before it's this milky white stuff this
time I decide to swap out the flask and
discard whatever this impurity is I did
this a little bit too early though and
in the new flask I was still collecting
this junk this really isn't a big deal
though and once I actually started to
get crystal clear distillate coming over
I just swapped the flasks again I
insulated the distillation flask with
some aluminum foil and now I just wait
and collect the phenol when the
temperature started to rise above the
boiling point of phenol I stopped the
distillation and I took off the aluminum
foil in our distillation flask we're
left with a goopy viscous yellow liquid
and the phenol in our receiving flask
has already started to freeze I wait for
the apparatus to cool down before taking
it apart and I'm left with a solid in
both the distillation and the receiving
flask there does appear to be a decent
amount of solid in the distilling flask
but it should be mostly unreacted
salicylic acid
because everything froze in the
receiving flask we're going to have to
melt the phenol to transfer it using a
heat gun that you can't see off-screen I
shoot the flask and the phenol very
quickly liquefies I heat up the phenol
well above its melting point and then I
quickly transfer it to a bottle the
bottle was sealed and capped and the
final yield of phenol was determined to
be twenty one point eight grams this
corresponds to a percent yield of fifty
one percent and according to the
procedure it's a little bit on the low
side
according to unintentional Kaos he says
that the typical yield is usually
between 60 and 70 percent when I
multiply out all of the percent yields
that we've gotten from each step we see
that so far the overall process is about
42 percent efficient we have something
like three more steps and each one is
going to drop the overall yield given
this I'm going to update my prediction
from I think something like 30 something
percent to 14 percent I'm hoping that it
ends up being higher than this but it's
probably going to be lower
I'm just hoping it doesn't dip into the
single digits
anyway now that I have the phenol I can
move on to the next step which is a
nitration I haven't filmed this
preparation yet though so the next video
is going to be the mercury distillation
in the straw poll it was really closed
between this video and the mercury
distillation I honestly didn't know
which one to choose but I did a separate
polling of my patrons and they by far
wanted to see this video so I decided to
release this one first so with that
being said the next video will for sure
be the mercury distillation but you guys
can vote for the one that will come
after that unfortunately I won't include
step 4 as an option because I haven't
filmed it yet and I don't want to make
any promises that I might not be able to
fulfill I do plan to film it in the next
week or so and as soon as I do I'll
include it in the polls also as an aside
in my previous video where I cleaned up
phenol by distillation I said I wasn't
sure if you could do it without a vacuum
to test things out I purposely film this
video without using vacuum and well
clearly it worked anyway that's it for
now and the next time that I see you
guys I'll be distilling some mercury
as usual I'd like to thank everyone
who's supporting me on patreon anyone
who supports me with $5 or more will get
their name at the end of the video like
you see here eventually I hope to get
some higher tears going and also add
some more rewards to the $1 and $5 tier
anyway these are the videos that have
already filmed and the ones that I
planned to film if you have any
suggestions please let me know in the
comments also if you haven't already you
can subscribe to keep up to date with
every video that I post I'm trying to
post at least one video a week
and this month there will probably be
some doubling up some weeks