in this video we're going to have a go at making guanidine guanidine is an

unusual compound with a structure shown and carbon surrounded by three nitrogen atoms

and the procedure we're using involves the thermal decomposition of ammonium thiocyanate

let's first look at the reaction setup we're using the 500 ml to neck flask for the reaction

and we've got the thermometer sitting in the side neck which goes down into the flask

temperature

is apparently very important for this reaction so you need to monitor this closely

in the top of the flask we've got an adapter leading to a hose

and this leads to a calcium chloride drying tube with the outlet position near our ventilation

exhaust the reaction gives off some nasty fumes so we want these carried away and at the same

time we've got to keep the reaction protected from atmospheric moisture we need to heat the mixture

quite strongly and evenly so we've got a flask and a heating mantle

okay so now for our reactant

there's only one we're going to use 100 grams of ammonium thiocyanate

we found this in the dodgy photographic supply store so it must have some use in developing photos

it's a white translucent crystalline solid we're keeping it covered up with plastic wrap because

very hydroscopic and rapidly absorbs water from the atmosphere.

We did a little test just to see how hydroscopic it is by placing a few crystals on a glass

petri dish and leaving it open to the air for a little while.

And here we are 15 minutes later.

If we zoom in close you can see there are some little puddles appearing around the crystals.

So it's fairly hydroscopic.

Definitely worth keeping covered up.

So let's get our 100 grams of ammonium hyalcyonate into our reaction flask.

Okay here we go.

So now we get the apparatus sealed back up and switch on the heating.

The reaction apparently needs a steady temperature of between 180 and 190 degrees C.

So we'll heat and then adjust as we need to.

Okay.

Pretty soon we've got some condensation appearing on the inside of the flask.

According to the literature the compound melts around 150 degrees C and apparently boils

at 170.

But we'll see what happens.

Temperature in the flask slowly rising.

Now around 150.

Soon the contents of the flask start to liquefy and we see some vapor appearing.

Temperature now at 165.

We're starting to see condensation in the adapter.

And pretty soon there's a yellow color appearing in the flask and condensing.

And we start to get a very strong smell of rotten eggs coming from the apparatus.

Hydrogen sulfide.

So it's time for ventilation to start.

And we're ready to go.

We're ready to go.

We're ready to go.

We're ready to go.

The decomposition reaction occurring is a complex one with lots of products being formed.

The main products seem to be hydrogen sulfide and ammonia gas, but apparently there's also

some carbon disulfide produced as well.

We've managed to get the temperature stable at 190 degrees C.

Soon the drying tube and hose become yellow from unpleasant stinky deposits of decomposition

products.

Well, according to the procedure we're following we need to continue heating the mixture at

this temperature for the next 20 hours.

But we have homes to go to, and jobs, and lives.

So we'll keep heating for 6 hours and we'll see what happens.

We kept the temperature pretty stable at 190 degrees for this whole time.

Here we are 6 hours later.

We've removed the flask from the heating mantle and we allow it to cool down.

As it cools there's a bright yellow deposit which appears on the sides of the flask.

The clean up job.

It wasn't actually so bad.

Lots of hot water and the apparatus cleaned very quickly and easily.

As the liquid in the flask cools it slowly begins to crystallize.

There's obviously still a large amount of ammonium thiocyanate still in here, but the

volume has decreased a bit.

Let's see what we end up with at the end of it and whether our 6 hours was really enough.

Becoming solid now.

And here's the flask completely cooled.

It's a pretty hard slightly green-colored solid remaining in there.

And it's got a very fresh alluring countryside aroma of ammonia and hydrogen sulfide.

Quite manure-like.

First thing we're going to do is digest this using 100 ml of boiling hot water.

So we need hot water.

It dissolves pretty readily forming a slightly green colored solution.

We're now going to add 15 grams of potassium carbonate to the mixture.

The theory here is that this will form potassium thiocyanate and guanidine carbonate.

Alkali-thiocyanate salts are soluble in ethanol, but the guanidine carbonate won't be.

So let's get this in.

A bit of stirring and this all seems to dissolve.

There's some dark, insoluble material in here.

So next step is to filter the mixture.

Here's the filtrate.

About 200 mils of yellow liquid.

There was some dark material left on the filter, but not much.

Our next job is to evaporate this back down to a dry solid again.

So we set up our favorite pirates evaporating oven dish.

So we set up our favorite pirates evaporating oven dish.

And got this evaporating down slowly over medium heat.

But towards the end they disappeared completely.

And we ended up with a gradually thicker white suspension of fine solid,

and eventually a completely dry solid which was quite hard and brittle in the bottom of the dish.

And eventually a completely dry solid which was quite hard and brittle in the bottom of the dish.

We created a sculpture whilst scraping the solid out.

It's entitled White Chocolate Rabbit Surprise.

And if any art collectors would like to commission a copy then we'll be happy to negotiate the fees.

Okay, let's get this into a larger beaker.

Now we're going to add absolute ethanol and dissolve out anything that's soluble including the thiocyanate salts and some other compounds.

Here's about 150 ml of ethanol.

We cover this up with plastic wrap to stop moisture getting in.

And then heat and stir the mixture to digest the solids.

The solids dissolve pretty quickly.

And stirring becomes easier.

After about 20 minutes nearly everything is in solution.

So we allow the mixture to cool slightly.

You can see there's a small amount of white solid in the bottom which won't dissolve.

So let's filter again.

The solid now needs to be washed with more ethanol until nothing more will dissolve.

Okay, so the moment of truth.

After all that we've got some insoluble residue in the filter.

A mighty 3.9 grams of it.

It really doesn't look like potassium carbonate, and it melts at too low a temperature.

So we think this has got some guanidine.

Carbonate in it.

But it's probably not pure.

But with only 3.9 grams we'll do some further tests but that's about all we can do.

So yield is pretty bad.

But even the process specifying heating for 20 hours suggests you'd only get 15 grams

or so of product at the end.

So maybe it is what it is.

It's a very slow reaction and quite a tedious work up.

We may try some other methods.

In future videos if we ever get around to it.

So stay tuned.