First of all though, here's some sodium nitrite.
Let's do a quick recap of how this reacts with acids.
First of all we'll take some dilute sulfuric acid and drip it on.
Lots of brown fumes.
That's nitrogen dioxide formed because as the nitrite reacts with sulfuric acid forming
nitrous acid,
nitrous acid is very unstable and decomposes forming nitrogen oxides.
So now let's do something different.
Here's a little bit of concentrated 36% hydrochloric acid.
This time we're going to add the sodium nitrite to the excess acid.
At first you might say it's the same.
But the color is quite different.
There's a golden yellow color and yellow fumes produced rather than the brown NO2.
What's happened is that the nitrous acid and nitrogen oxides formed have gone on and reacted
with the excess HCl, forming a compound called nitrosyl chloride.
And this is what we're interested in today, because there's an interesting reference that
we found on the Science Madness online forum whereby nitrosyl chloride can react with an
organic amino acid to form the carbon dioxide.
If true, this might enable glycine to be converted into chloroacetic acid.
We figured it's worth a try.
So here's the set up of reagents we're using for this reaction.
First up, here's the glycine.
This is 15 grams of glycine, otherwise known as aminoacetic acid.
It's the free amino acid.
Next we've got 22 grams of hydrochloric acid.
of sodium nitrite which is a 1.6 molar ratio to the glycine as per the
procedure we're following and here's 100 mils of 36% concentrated hydrochloric
acid first we've got a large 500 mil beaker set up with a magnetic stir bar
good stirring is important for this reaction to work first we're going to
add 4 ice cubes approximately 60 grams to the beaker and now we'll add the
hydrochloric acid and now the glycine powder the glycine can form a salt with
the acid glycine hydrochloride and this will be soluble in the mixture but it's
going to need some stirring to get it to dissolve
so we're going to add the hydrochloric acid and now we're going to add the
glycine powder so let's set this up some wrap to stop fumes from escaping
and on to the magnetic stirrer it takes a little while to dissolve maybe about
five to ten minutes okay here we go now we're going to take this solution and
we're going to place in the freezer to chill it down to about zero degrees C
while we're doing this we'll set up for the reaction you're going to need a
really cold and substantial water bath so we've got some water lots of ice and
we'll add salt to this as well to reduce the temperature once the beaker
containing the acid and glycine is cool we place this into the bath we've got a
small funnel stand to hold the beaker in place in the ice water so it doesn't tip
over
we've got a thermometer inserted into the liquid in the beaker so we can
carefully measure the temperature and we've kept the wrap on the beaker just to
try and contain any nasty fumes generated so let's start stirring and
we'll watch and wait for the temperature in the beaker to stabilize at around zero
degrees C just below zero now so let's kick it off
just a tiny bit of the nitrite on each addition you can see the beautiful gold
and yellow color formed and not much in the way of brown fumes we keep adding
but watch the temperature closely as the reaction is quite exothermic once it
gets up to above about seven degrees C we wait and allow the mixture to cool
again before adding more sodium nitrate to the beaker and we'll wait for the mixture to cool again before adding more sodium nitrate to the beaker
warming up now so we'll let it cool and now we'll start addition again you can
start to see the color of the mixture turning slightly darker as well and soon
it starts to change to a green blue color what's interesting is that on
adding the nitrite there's an initial reaction as it hits the acid then lots
of
after a few seconds and another reaction occurring then it dies down again and
the color changes from yellow back to green something funky is definitely
going on in the original reference which uses alanine a slightly different amino
acid with an extra carbon the nitrosyl chloride reacts with the amine group in
the compound presumably first creating an unstable diazo type compound this
then releases nitrogen gas and what remains is the corresponding chloro acid
there doesn't seem to be a clear understanding of the mechanism though as
you can see we're getting bubbles of colorless gas produced which could well
be nitrogen so this is a good sign
you
we won't spoil the surprise but we will come clean and admit that for glycine
which we're using the result of the reaction isn't actually the chloro acid
for some reason the reaction doesn't work on glycine but we didn't know this
until after we'd finished the experiment instead something else is produced
something far more interesting and sinister than chloroacetic acid although
not as useful addition is pretty slow in order to keep the temperature around the
five
five
degree mark it takes about an hour in total about halfway now and you can see
the blue color is becoming more intense
let's chill out with some smooth tunes and enjoy the rest of the reaction
you
you
you
you
you
you
with stirring out of the ice bath okay here we are up at room temperature let's
switch off stirring and allow this to settle there's a fine white precipitate
in the mixture which we suspect is sodium salts which have separated out so
the first thing we're going to do with the reaction mixture is filter it
through a cinter and remove the solids
so here's what we've got a very pretty blue colored solution a little like
copper sulfate but a slightly different shade of blue if you're going to repeat
this experiment here's a word for it
of warning from this point onwards exercise extreme care don't allow this
solution or especially more concentrated ones to come into contact with your skin
we'll explain why later and we'll show you why it's difficult not to
okay well we tried using dichloromethane to extract the blue color but it didn't
work and it stayed in the aqueous layer to extract the blue compound the only
solvent we found that worked was diethyl ether
so here's about 17 mils of diethyl ether we'll add this to the beaker and
see if we can extract to minimize exposure we used a pipette to mix the
liquids together rather than use a sep funnel definitely got the blue color
moving into the top ether layer
ok this will do most of the color is now in the ether so now we'll use the pipette
and separate the top ether layer into a separate container
and here we go an ether solution of the blue
mystery compound and here's where the weirdness starts whatever it is that's
blue is somehow able to evaporate as colorless fumes along with the ether and
condense like a limestoneØ
in the beaker let's have a go and see if we can evaporate off some of the ether
whilst leaving the blue stuff behind you'll see why we need the paper towels
not only does the blue liquid condense on the sides of the evaporating dish but
it also has a strong tendency to creep out and escape pick up the dish or
beaker and you have an instant permanent blue stain which goes through latex
gloves even after scrubbing with soap the blue stain on your finger starts to
itch and hurt after a few minutes then in real time you can see your skin dying
and turning white and flaking off it's like concentrated nitric acid only it
pretends to be blue and cute and it likes to escape there's also a highly
irritating vapor coming off
we think we've got most of the ether off now maybe five mils of very dark blue
colored but watery liquid so what could this be well we found a possible answer
from a helpful user on science madness apparently this reaction has been
studied and the blue color is suspected to be caused by a chloronitroso compound
possibly the one you can see here
the author
notes that it can be extracted using ether and on removing the ether forms an
emerald green color which isn't far from what we've got looking closely
but it's pretty nasty stuff and you've got to handle with care cleaning up is
also difficult as you can see it's a chemical escape artist
okay a few tests let's drop some in warm water
sinks to the bottom then rapidly dissolves now let's try dilute sodium
hydroxide
a reaction and an intense yellow-brown color is formed let's try solid sodium
hydroxide vigorous reaction it looks like the compound is quite acidic and
nature let's burn some the report says it's highly explosive
not exactly but it does seem to burn vigorously with no residue and after a
while you can see that it starts to decompose slightly there are some heavy
brown fumes of nitrogen dioxide starting to accumulate in the beaker and
An interesting experiment and a scary product. Stay tuned.