Today we'll be preparing an ester, ethyl chloroacetate, and trying out an
experimental way to make ester synthesis more efficient.
To start we're using the corresponding carboxylic acid that we require, chloroacetic acid, which
as you can see is a crystalline solid.
Be careful with this because it's quite toxic and a metabolic poison.
Don't get it on your fingers.
To esterify this we're going to use an excess of ethanol.
Normally you'd use a very large excess, but we're going to try something different today
and we're only using 150 mL which is about a 3x molar excess.
We'll add the ethanol to the chloroacetic acid and dissolve it.
It takes a bit of stirring to get it all into solution, but it does eventually.
Okay.
We've set up the 500 mL flask.
We put a stir bar in there because we originally thought we'd stir the mixture, but we don't
actually need it.
Some anti-bumping granules would be a good idea, though.
We've added the chloroacetic acid in ethanol to the flask.
And now for our catalyst, we're going to use 3 mL of concentrated sulfuric acid.
We added this to the flask.
And then set up for reflux using a heating mantle.
As the reaction occurs, water is produced, and together with the ethanol this distills
off as an azeotropic mixture, condensing in our reflux condenser and then dripping back
into the mixture.
Our plan was to try to remove this water during the reflux process.
DRIPPING BACK INTO THE MIXTURE.
oxide it reacts with water to form calcium hydroxide which is also a solid
both of these compounds are insoluble in ethanol let's see it react with a few
drops of water there's no obvious reaction but the mixture heats up and
you can see some steam being given off
we put an adapter between the flask and the condenser and placed a cut down
flooded filter paper into it like this the idea is that the vapors can come
around the sides of the paper but the drops of condensing liquid will fall
into the middle and filter through the paper
and we've placed some calcium oxide into the paper so that the ethanol will drip
into this it's important though that none of the
calcium oxide makes its way into the flask calcium oxide is alkaline and will
react with both the chloride and the surfactant
acetic acid and the sulfuric acid catalyst okay let's start heating and
see what happens pretty quickly the mixture starts to boil
and we've got some reflux starting which is dripping right into the filter as
planned but it's too much the filter isn't capable of handling more than one
drip about every five seconds so we've got an overflow and some of the calcium
oxide is coming with it into the flask so we removed the middle adapter and
just set up for normal reflux after an hour we tried again using a different
configuration of filter paper and with the calcium oxide packed down tightly
you
but this also overflowed after a while so at this point we tried a different
approach so after another 30 minutes of normal refluxing we set up for simple
distillation only using calcium oxide in the receiving flask
we figured we'd collect the ethanol and water of see a trope and then try to dry
it using the calcium oxide before returning to the boiling flask
with the a seat wrote boiling off at around 80 degrees see we've got a fairly
quick distillation collecting and the temperature of the receiving flask is
getting quite warm due to the reaction of the water with the calcium oxide
after a while we poured out the mixture from the receiving flask and allowed it
to settle then we replaced the calcium oxide in the receiving flask and continue
the process
The dilution of the mixture started at 50 mg
And once the mixture had settled we placed the
alcohol back into the boiling flask
to be honest this was all a bit of a pain in the
ass because it meant constant disassembly and
reassembly of the apparatus and the product in this case was quite
lacking in which didn't help
after we continued this process for about
2 hours we decided to switch back to simple distillation editing calciumotzide
and first distilled off excess ethanol from the reaction mixture.
The ethanol was ecto-distillation temperature gradually rose and above 100°C we changed flasks and collected another fraction.
Then we collected a final fraction above 135°C, with the vapor temperature rising to 144°C at its peak.
The contents of the boiling flask began to charred and turn black towards the end of the distillation.
Once the speed of the distillation slowed down we stopped heating.
Here's our first fraction which came off above 100°C.
On adding water to this we added a second fraction.
We noticed that a bottom layer formed.
It's a little difficult to see because the color is very close to the water.
And on the right here's our slightly off-colored fraction which we collected over 135°C.
Since the product appears to be insoluble and immiscible with water we decided to combine the fractions in a separating funnel and wash with water.
The organic layer turned slightly milky.
We shook thoroughly, allowed the layers to separate, and then removed the bottom layer into a flask.
Then we added some anhydrous magnesium sulfate to dry this.
Here's our product.
55 grams of ethyl chloroacetate.
We were interested to see how much we'd get but despite our attempts at drying and recycling ethanol,
this is only a 57% yield on starting chloroacetic acid.
But this is not bad considering how much we messed around with the reaction.
Be careful with the product.
It's not as bad as bromoystone or bromopropiethanone, but it's lacrimatory and worse than benzoyl chloride in that respect.
There may be a way to use calcium oxide to make esterification more efficient,
but it's going to require some more specialized equipment.
And also having the oxide in solid granule form so it doesn't wash over.
We'll let you know if we get anywhere improving this.