Today we're going to do some chemical myth-busting. We read about a reaction .

which is able to convert an aromatic aldehyde into a nitrile, using a .

combination of iodine and aqueous ammonia as the reactants. Sounds too good .

to be true, right? There's a catch. Before we try out the reaction, let's first do a .

little experiment with iodine and ammonia and find out about that catch. So .

here's about 20 mls of about 20% aqueous ammonia solution. The fumes are pretty .

stinky and choking, so use ventilation if you need to.

And here's a very small amount of solid iodine in the bottom of this beaker.

Certainly way less than a gram. Notice that it's recycled from reactions .

and finely powdered, not the usual pellets of iodine you see us sometimes .

use. This is important. And here's a small beaker with a stir .

bar so that we can do the reaction. So we'll set this up on a magnetic stirrer .

and first we'll add the iodine.

Last of all we'll add the ammonia solution to the beaker. Washing up is .

meditation. Let's get it stirring. And we'll add the solid iodine. It looks .

pretty uneventful at this point. You might think that the iodine would .

dissolve in the alkali solution like it would in sodium hydroxide, .

but it doesn't. You can see a slight brown tint in the mixture. When solid .

iodine meets strong aqueous ammonia, it reacts forming a rather unusual compound.

A black solid, which used to be called nitrogen triiodide, but in reality it's .

actually an addition compound of nitrogen triiodide and ammonia, which .

looks like this.

The reaction doesn't take long to complete, .

switch off the stirring we've got a fine dark brown to black colored precipitate .

in here it looks like the iodine hasn't actually reacted but we'll soon find out .

so let's filter this off we're going to use a old-fashioned paper filter in a .

glass funnel as you can see there's a good reason for this as you'll find out .

we don't want the solid drying out too fast and fluted filters are cool and .

making them is very relaxing it's also good practice because once you get good .

you can make other things as well you can even attract a non-chemistry minded .

mate by demonstrating your artistic prowess and convincing them that .

there's a softer side to your character .

let's filter .

it takes some time for the majority of the .

residuals to dry out so let's filter this off and let's see how it turns out .

okay this is looking good first we'll take the damp filter paper out and place .

it onto a sheet of paper towel to dry excess liquid a bit and we've separated .

the wet black product into two piles and whilst still wet onto two sheets of .

clean filter paper we put a bit of distance between them okay you're asking .

well the catch is that this sheet of paper and this bit of product here .

spontaneously turned into this with a very large bang we didn't even touch it .

this is why you do this in two batches let's use a hot metal spatula to see how .

bad it is now that was a big bang the microphone really doesn't do just it was .

we don't normally mess with anything explosive but this is a bit of an old .

student classic the trouble is that in larger quantities and especially .

confined and with glass around it something like this happening could be .

incredibly dangerous so that's the catch on this reaction we will therefore .

proceed with some caution so let's do this the paper says that .

this works with phenolic aldehydes as well so we're going to use our favorite .

aerosol and we're going to use our favorite aerosol and we're going to use .

aromatic aldehyde as a test so here's five grams of vanillin crystals in case .

you've forgotten the structure of vanillin here it is as a reminder we use .

vanillin a lot because it's easy to obtain and a great chemical for many .

different types of reactions next here's our iodine we're using 4.5 grams which .

is a slight excess in theory to what is required stoichiometrically but not a .

long time ago .

large excess we don't want to blow ourselves up and here's the 20% ammonia .

solution we're going to use 50 mils of this to start with and more later if we .

need to in order to get a solution so we'll start off and get this into a nice .

sized beaker stirring on and first up we'll add the vanillin crystals .

you .

these start to dissolve and form a yellow colored solution typical of the .

water-soluble vanillin phenolate the original procedure calls for tetra .

hydra furon as a co solvent but we're going to experiment and try using a .

little ethanol as we know vanillin is very soluble in it so here's 15 mils of .

absolute ethanol we'll wash out the vanillin beaker and add this .

and add this .

it definitely helps solubility and there's only a few crystals in .

suspension now so we'll top the mixture up with 20% aqueous ammonia now and see .

if we can get everything dissolved .

and after about another 20 mils of ammonia we're there a pale yellow .

solution .

you .

there's quite a lot of ammonia fumes so we've switched on ventilation.

so now for the iodine.

we'll start off slowly and cautiously and add just a little bit to see what .

happens.

.

.

.

.

.

.

.

.

.

.

.

.

though most of it has dissolved. Just some black specks remaining.

So we keep the addition going and add the iodine in portions, making sure that it's .

mostly dissolved before adding the next one.

Addition takes about .

15 minutes, and towards the end the mixture gets dark and there's some buildup of the .

black solid.

We're worried for a moment that this is nitrogen triiodide, but soon we notice that it's also .

dissolving and disappearing into the mixture.

And after about 5 more minutes of stirring we notice a white deposit on the bottom of .

the beaker, and some precipitate forming.

We let the mixture stir for another 15 minutes, so a total reaction time of about 40 minutes, .

and then we let the mixture settle.

Then we cover it up and place it in the fridge for an hour to chill it down.

The thinking here was to see if we could maximize the precipitate.

There's obviously been some sort of reaction, so we'll start with the precipitate and try .

to separate this.

So here we are.

Here we are an hour later.

Nice and chilled.

Not much more precipitate has come off though.

So let's filter.

.

with ice water a number of times until there was no more ammonia aroma .

it takes a lot of drying and even after an hour on the pump we still had a paste .

it does have a faint vanillin aroma but that could just be due to some residual .

vanillin it's a pale tan color to get this dry we made up a makeshift .

desiccator and placed the beaker into this over phosphorus pentoxide for a few .

days and this did the job while we were .

waiting though we did a quick qualitative test to give us a clue as to .

what this is we made up a saturated solution of sodium hydrogen sulfide .

in a little bit of water we know that vanillin and many of its derivatives are .

aldehydes and as a result for a ducts with sodium bisulfite unlike with .

benzaldehyde these are highly soluble in water so let's add some of the tan .

colored paste if it's an aldehyde then it should dissolve if it's a nitrile .

then it's unlikely to .

to begin with it doesn't dissolve easily but after a bit of stirring .

most of the tan solid does dissolve in the solution forming a slightly yellow .

colored solution so this isn't looking good for a successful reaction at least .

for the precipitate we obtained okay let's go back and look at the .

filtrate now we'll go through the process quickly .

we first tried extracting the amber colored filtrate using diethyl ether as .

recommended by the original prep after shaking well we've got a slightly orange .

colored ether layer and we're ready to go to the next step which is to extract the .

layer so we separated this off and then evaporated it down to see if it .

contained anything on evaporating we've got a flaky cream colored solid but only .

a tiny amount and it smells a bit like creosol which we made in a previous .

video by reducing vanillin there's not enough here to analyze so this might be .

our elusive vanillyl nitrile but if it is then the yield is tiny so we decided .

to take the aqueous ammonia layer and add a little bit of aqueous ammonia to the .

layer and acidify this firstly using citric acid crystals and then using .

sulfuric acid until strongly acid the heat generated by neutralization caused .

some residual ether to boil off we're getting a white emulsion produced as the .

sulfuric acid neutralizes that last of the ammonia and then some red colored .

oil which floats to the surface and dances around in interesting patterns so .

So we extracted this mixture, again using diethyl ether.

And now the red color has extracted completely into the ether layer.

We evaporated the solvent to see what remains.

Once the ether had evaporated we were left with a oily red residue.

Probably a couple of mils in total.

But this had a very strong aroma of vanillin.

Washing with sodium thiosulfate also didn't remove the brown color, .

so our guess is that this is just vanillin with some impurities in as well.

So now back to our original precipitate.

It's dried a fair amount after a few days, although still a little clumpy.

So what could it be? .

Well we weighed it and it's pretty dense.

There's just over 4 grams here.

And although it's not totally dry this is a surprisingly high weight.

The only explanation we can come up with is that this is a product which has chemically absorbed some of the iodine, .

hence leading to a large weight increase.

The previous test we did suggests it's an aldehyde so our guess is that this is 5-io-dovanillin.

The same product that we made in a previous video.

It looks the same, it's just as hard to dry, it's about the same density.

So this is interesting.

Perhaps it was the conditions we used which varied slightly from the procedure.

But our suspicion is that in reality vanillin is just too reactive towards electrophilic attack by the iodine, .

especially with a base like ammonia around to absorb the H I produced for this reaction to work successfully with it.

We might come back to this in the future when we have a less reactive aldehyde to try.

But at least we got an excuse to blow up some nitrogen triodide.

Stay tuned.