it's a flavor enhancer and we're going to see if we can use it for nefarious
purposes and enhance the flavor of the chemistry in our lab
first thing we're going to do is convert this into the more useful glutamic acid
we're starting with forty grams of crystalline monosodium glutamate as you
can see here
first we've got this onto the stirrer and we're going to put a magnetic stir
bar in
and now we're going to
use seventy mils of water to get this into solution
pretty soon it dissolves forming a clear solution
now we've measured out eighteen mils of concentrated hydrochloric acid
this is twelve point eight molar and so we've calculated this should be just
enough to react completely forming glutamic acid
so let's add it to the msg solution
very rapidly the glutamic acid forms and precipitates out as a white solid
there's also a slight temperature increase we've put the thermometer into
the mixture so we can show you
stopping stirring the glutamic acid quickly falls to the bottom of the beaker
so we cover this up and chill it to ensure the maximum crystallization is achieved
of product, and then filter.
Take the time to wash with cold water and dry thoroughly.
OK here's the product.
We've got 36 grams here, which is greater than maximum yield so it's obviously still
slightly wet but likely to be a quantitative yield.
It's a very fluffy white crystalline solid.
Now we've got our glutamic acid, we can try a few different experiments with it.
Firstly we read about an interesting reaction which involves oxidizing this using hydrogen
peroxide to obtain subsinic acid.
We've included the reference for this on the screen.
We're going to start off with 25 grams of the glutamic acid that we just prepared.
We've got this in a 250ml beaker and we add a large magnetic stir bar.
Now we add 60ml of water to the beaker.
Glutamic acid isn't very soluble, so this will create a suspension.
Now we're going to convert the glutamic acid back to its soluble ammonium salt.
solution to do this but we're going to use ammonium bicarbonate. This is
available as baker's ammonia and is a useful source of ammonia in a dry and
compact form. We've weighed out 13.4 grams which should be about right to
convert all the glutamic acid into ammonium glutamate. So let's add this
carefully to the suspension. There's a reaction and carbon dioxide gas is
given off.
Don't add it fast as you don't want the mixture to bubble over. After a few
minutes you can see a clear solution forming.
So now we're ready for the hydrogen peroxide oxidation step. The
procedure calls for 2.5% very dilute peroxide but we've got 30% so we're
going to check this out. We've now switched on the hot plate and we're
warming the mixture. We've got the thermometer in here as well so we can
monitor the reaction temperature. Here's our hydrogen peroxide.
We're using 58 grams of a 30% solution which corresponds to a
three times molar ratio of peroxide to glutamic acid. Just a word of warning!
Make sure your glassware is really clean because 30% peroxide can
decompose very violently and exothermically if it touches the wrong
metallic oxide or some other compounds. Okay here's our ammonium glutamate solution.
Okay, here's our ammonium glutamate solution and it's now at around 4.5% of our ideal parameters.
65 degrees C, so time to add our first small portion of hydrogen peroxide.
About 10 ml added, and the mixture starts to bubble.
The temperature also starts to increase, and when it gets to about 80 degrees we use a
water bath to keep this under control.
And as you can see there's a yellow coloration to the reaction mixture.
Okay temperature now is back down at about 65 degrees, so we'll add another portion of
the rock side.
As before the reaction starts up and there's bubbling and a temperature increase, but not
as much as with the first portion.
Over about 30 minutes we've added all of the hydrogen peroxide.
And we're going to increase the heat slightly so that we get the mixture up to about 80
degrees C, and continue stirring for an hour and a half.
During this time some ammonia gas is produced by the mixture.
As you can see by the color.
Changed of the indicator paper.
Over the next hour and a half stirring at 80 to 85 degrees C, the ammonia boils off
and the liquid reduces slightly in volume.
Stop!
advertising.
Okay.
Two.
Okay, here we are, and the volume is now down to about 80 ml of liquid.
There's still some effervescence but there's no more ammonia coming off, and the aldehyde-like
aroma that the mixture developed has also disappeared.
We let the mixture cool right down.
In theory this now contains subsinic acid as well as probably a lot of by-products.
The original procedure says to distill the mixture to dryness, but we're not comfortable
doing this with the excess peroxide present.
So instead we're going to see if we can get some of the subsinic acid to crystallize out.
Here's 10 ml of 50% sulfuric acid.
We add this to the cooled reaction mixture.
There's no immediate precipitate which means that there can't be much glutamate remaining
in there.
With chilling the mixture the cloudiness first appears, and this then slowly becomes a crystalline
precipitate over the next two hours whilst chilling down.
Let's filter.
Okay.
Okay.
Okay.
We dry as best we can.
We've got 5.5 grams of a damp crystalline solid.
It's really hard to dry so we'll probably try to desiccate it and see if this works.
Given the solubility of subsinic acid in water this is about what we expected to get given
that the remainder would stay in solution in the filtrate.
The product is definitely acidic, and it's too soluble in water to be glutamic acid.
If it's subsinic acid then the yield is only about 25%, but there's probably more remaining
in the filtrate.
This can probably be boiled down and the further portion of product obtained will be used to
dilute it.
Well this is interesting.
The process is easy, and although it does use a lot of peroxide, the other starting
materials are cheap and plentiful.
We'll have to find a way to confirm that the product is indeed subsinic acid, but if it
is then this represents the interesting way of preparing what is normally quite a difficult
chemical to obtain.
Thanks for watching and stay tuned.
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