Warning: Diethyl ether is highly flammable.
Sodium is a reactive flammable metal.
Fire safety protocols must be in place.
Greetings fellow nerds.
In an upcoming video i'm going to be making grignard reagents and performing grignard reactions.
Now grignard reagents are notoriously sensitive to water, reactive impurities, as well as air.
So before we begin we need to dry and purify our solvent diethyl ether.
So here is our diethyl ether.
This particular batch has been recovered from multiple experiments
so it's full of impurities including water, organic peroxides, small amounts of alcohols, esters,
halogenated compounds, acids and so on.
In fact if you look at it very carefully you can see droplets of water in the bottom.
Let me see if can zoom in for you.
As you can see this is not good solvent and would certainly ruin our grignard reactions if we used it.
Now the first step in purifying it is to add in some potassium hydroxide.
I'm using about 30g for my 500mL.
This will absorb water and highly polar impurities like alcohol as well as react with any acids and neutralize them.
As you can see this ether is so impure that the reaction with potassium hydroxide is generating enough heat to boil it.
Now for the most part this shouldn't happen with most sources of ether.
Just mine happens to be grossly impure since it was recovered from other experiments.
Chances are very little will happen with your ether.
Anyway, let this sit for a few hours until stops bubbling.
Now we add in a stir bar and let the mixture stir overnight to remove most of the water and polar impurities.
This will also give it time to destroy the halogenated impurities as well.
You might be wondering if you can use sodium hydroxide,
you can certainly use it but i prefer potassium hydroxide because when it absorbs enough water
it actually phase separates out of the ether into a seperate layer.
You can actually see that layer if you look closely.
Sodium hydroxide also separates, but it forms a thick goo which doesn't stir very easily.
An easily stirred layer tends to work faster than a thick goo.
Anyway, I'm going to let this stir overnight.
I forgot to film it here but i also stoppered the flask with a glass stopper to prevent ether evaporation.
So here we are the next day.
You can see most of the impurities have been pulled out by the potassium hydroxide
and some of it has turned brown due to various condensation reactions initiated by the potassium hydroxide.
Good thing it's all separated into another layer.
We now simply decant our ether into a new container.
Now for some very easy grignard reactions, this ether is pure enough and dry enough as is.
But to improve reliability i'm going to go a step further and destroy the remaining impurities with sodium metal.
Just get about 10g of sodium metal and cut it up into small pieces.
Then add them directly to the ether.
You can see it start to bubble as the sodium reacts with any remaining water and impurities and generates hydrogen gas.
i'm going to loosely stopper the flask with a plastic stopper so the hydrogen can still squeeze out
and escape but keep most of the ether vapor in.
You might wondering why I didn't add sodium the first time around and went with potassium hydroxide at the beginning.
Two reasons actually, one is cost.
Potassium hydroxide is cheaper than sodium metal and for an amatuere chemist like me using less sodium is always preferable.
The second and bigger reason is safety.
This is a lot of water.
If this amount had reacted directly with the sodium then it would likely have exploded.
Ether is extremely flammable and igniting it with a sodium explosion would have likely started an ever bigger fireball of burning ether.
In the past, there have been cases of scientists being killed after being engulfed by fireballs of burning ether.
So to avoid that i removed most of the water first with potassium hydroxide before going on to using sodium to finish it off.
Anyway, i let this sit overnight to react.
Here we are the next day.
The bubbling has stopped and the sodium is becoming discolored as it starts destroying other impurities.
At this point to help it along i'm going to drop in a stir bar and let the mixture stir on my magnetic hotplate stirrer.
Looking back, there was no point in letting it sit until the bubbling stopped,
so you can just add the sodium metal and begin stirring right away unless it's boiling too much.
Anyway, i left mine stirring for another day.
And here we are the next day.
The flask has become cloudy as the sodium destroys more impurities causing them to precipitate out.
The stir bar knocking around the sodium is also chipping off whatever impurities reacted with the sodium and solidified.
I'm now going to replace the plastic stopper with a greased glass stopper and completely seal the flask from air.
We want it sealed now so air and moisture doesn't get in and waste the sodium before it has a chance to destroy the remaining impurities.
A plastic keck clip should be applied so on the off chance it's still bubbling
and the pressure does become great enough to pop off the stopper,
it won't go flying away and possibly smash something else of value.
Keep stirring it now for as long as needed to destroy all the impurities.
You might be wondering how to tell and for professional chemists they add in an indicator which is benzophenone.
Benzophenone reacts with sodium to form a green, blue, red or even purple solution
once all the water and reactive impurities are destroyed.
The color is dependent on the solvent.
Benzophenone in ether tends to form red or purplish colors.
Unfortunately for us amateur chemists getting benzophenone is not easy so we're going to need another indicator.
Interestingly enough we can use the sodium metal itself.
Right now it's all covered in sodium oxides, hydroxides and other impurities and everytime it gets hit by the stir bar some of these are knocked off.
The sodium metal then quickly reacts with more impurities and becomes covered again.
But once all the impurities are destroyed the sodium will no longer react.
After that point, rather than getting dirtier as time progresses, the sodium will actually get cleaner as it gets knocked around.
And then something fun happens.
And here we are after a week.
The sodium cleaned up to the point that it started cold welding together into this nice shiny sphere.
It's at this point that we can say all the reactive impurities have been destroyed.
If they hadn't then the sodium would quickly tarnish again.
Now we setup a simple distillation apparatus and gently distill off the diethyl ether.
Remember to use thoroughly dried apparatus so we don't reintroduce water contamination into our ether.
Now i know spending over a week to purify diethyl ether seems excessive but as said before this batch was highly contaminated.
Ether usually only takes a couple of days to purify.
By the way you might be wondering how this sodium sphere is so large, as I only started with a small amount of sodium.
I found out later that this sphere was hollow.
It was filled with ether as well as particles of the impurities that had been knocked off earlier.
Once i squeezed out all the ether the lump left over was much closer to the original quantity of sodium i used.
You may also be wondering why i didn't use my favourite drying agent, molecular sieves, and used sodium instead.
Molecular sieves only remove water, but all the reactive impurities are still there and would still kill our grignard reaction.
Sodium drying is still the best way to purify grossly impure diethyl ether.
Anyway, after all the ether is distilled we now have a batch of fresh, purified, and dried ether which is perfect for use in grignard reactions.
I'm going to use this right away, but if you're going to store it then i reccomend storing it over molecular sieves
or sodium metal to destroy any peroxides that may form or any moisture it absorbs from the air.
Anyway, as said before, I'll be using this for grignard reactions.
Thanks for watching.
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