Warning: This experiment uses corrosive hydrochloric acid.
Wear gloves when handling it.
This experiment also generates flammable and explosive hydrogen gas.
Work outside or in a fume hood.
Greetings fellow nerds.
In this video we're going to make anhydrous iron (II) chloride also known as anhydrous
ferrous chloride.
This is useful for those reactions where you can't have any water but still want ferrous
chloride.
An example is the synthesis of chlorotoluene I showed in a previous video.
Now a quick reminder, this is for making iron (II) chloride or ferrous chloride.
This is not for making iron (III) chloride also known as ferric chloride.
Anhydrous ferric chloride requires a different process involving chlorine gas and cannot
be produced by the method in this video.
Okay, now you're probably thinking, hydrated ferrous chloride is easy enough to make,
just react iron and hydrochloric acid and let it dry.
Can't we just heat that up and remove the water of crystallization to make anhydrous
ferrous chloride?
The answer is yes and no.
While you can heat ferrous chloride tetrahydrate,
it will partially decompose as it reacts with air to form ferric chloride and ferric oxide.
What you'll get is a mixture of ferric chloride and oxides as well as ferrous chloride.
Let me break this up.
You can clearly see the red ferric oxide interspersed with the ferrous chloride.
Now if your chemistry can accept ferric oxide and chlorides then i suppose this is all you need.
If however your chemistry is more demanding, we're going to have to do better.
So let's get started with an improved method using a few lab tricks.
First we're going to have to make fresh ferrous chloride.
Start with 57 g of iron metal.
I'm using some old iron nails.
Now add to it 300 mL methanol.
This is optional and water would work just as well.
Just methanol is faster and easier to boil away later.
Now to this, add 200 mL of 30% or higher hydrochloric acid.
What's happening is the iron is reacting with the hydrochloric acid to produce hydrogen gas.
and a solution of iron (II) chloride also known as ferrous chloride.
Since i'm using nails this will take overnight.
If you want to go faster you can use an equivalent weight of steel wool and be done in a few hours.
If after awhile you notice no more hydrogen bubbling, but the iron still present,
you'll have to add some hydrochloric acid to restart it.
Once everything is dissolved, filter the mixture to remove any solid particles.
Iron usually contains small bits of carbon and silica leftover from the smelting process.
I must say ferrous chloride has a very nice shade of green.
Now drop in a couple of large iron nails.
Doesn't matter if they're rusted, just as long as they're large and iron.
I'll explain their function in a minute.
Now set up a simple distillation apparatus around the flask.
Use ground glass joints for all the glassware and grease or PTFE tape to seal them so no
air can get in.
On the distillation adapter at the upper right, attach a long hose so hydrogen gas can escape,
but slows down the return of air since the hose is very long.
If you have a one-way check-valve that would also help.
Now turn on the stirring and the heating and start distilling the solvents.
Now the air in the system will convert some of the ferrous chloride to iron (III) or ferric
chloride which we don't want.
To reverse this we used the iron nails we added previously as a redox scavenger to reduce
any ferric chloride into ferrous chloride.
The iron nails also continue reacting with the hydrochloric acid
and release hydrogen gas like the iron we added previously.
The hydrogen gas displaces the air in the system and thus helps to prevent further air oxidation.
Finally the nails are also a convenient magnetic stir bar for our magnetic hotplate stirrer.
We didn't use steel wool or smaller iron nails
because we want them to last all the way to the end of the distillation.
We also want to minimize the amount of insoluble impurities coming from the iron.
The larger iron nails with their smaller surface area are ideal for this purpose.
To further exclude air, and speed up the distillation, you can attach the exhaust hose to a vacuum system.
Although as you can see in my system,
foaming might be a problem so you'll have to turn down the heating to control it.
Anyway, keep heating until you've removed most of the methanol and water.
As the ferrous chloride starts drying you may want to wrap your flask in foil to keep the heat in
and prevent condensation from remaining in the flask at the end.
Turn the heating to maximum and let the ferrous chloride thoroughly dry.
Then, while the flask is still hot, quickly disconnect it from the still head and stopper it.
Unfortunately a tiny amount of air will get in but this unavoidable.
Now let it cool to room temperature.
And there we have our anhydrous ferrous chloride.
You can see a very light shade of red on the surface due to the air getting in earlier
but this is minor.
The cake is actually quite fragile and some hard shaking will break it up.
You can see these chunks of ferrous chloride are much cleaner and uniform than the air
dried ferrous chloride i showed earlier.
If you keep shaking you can break up the ferrous chloride into a powder.
I recommend keeping the ferrous chloride stoppered in the flask to prevent air getting in and
only opening it when you need it.
While the nails are still in here i say leave them.
Just remember to remove them when you get the ferrous chloride.
And that's how you make anhydrous ferrous chloride.
Conceptually simple, but requires a few tricks in practice.
This stuff can be used for make organometallic complexes
and for electrophilic halogenation reactions as i've shown in a previous video.
Thanks for watching
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