We are going to do the classic benzoin condensation reaction.

This is done in schools using thiamine, vitamin B1. But this is a bit woozy, so we .

decided to try it the proper old-school way using cyanide as the catalyst.

The first thing you'll need is one gram of an alkali cyanide salt. We've used our .

mixed sodium potassium cyanide and it's from an impure batch so it's a yellow .

color. But it should work fine.

As always be very careful when handling cyanides as they are very toxic. This .

little bit of powder is enough to kill you, probably five times over. Dispose of .

any waste solutions using hypochlorite bleach which oxidizes the cyanide into .

much less toxic cyanate before disposing. I'll measure out three mils of water.

Add this to the cyanide and stir to make a solution. It should all dissolve.

Here we go. Now measure out 10 grams of benzaldehyde. Ours is slightly yellow .

colored and it's from the reaction we did in a previous video which used .

benzyl alcohol and manganese dioxide. Check it out at the link here. Now measure .

out 20 mils of ethanol. It doesn't matter if this isn't dry. Add the ethanol to the .

benzaldehyde solution in the flask. And now add the aqueous cyanide solution to .

the flask containing the ethanol and benzaldehyde. To begin with you won't .

see much happen. The solution is just a slight yellow color at this stage. Set up .

for reflux with the flask on a hot plate and very gently refluxing the solution.

It doesn't need to be too fast. Just a slow and steady reflux. If you are doing .

the reaction using only a few grams of benzaldehyde, you can get away with .

heating in a conical flask and using only a few grams of benzaldehyde.

We are going to leave this refluxing now for a total of two hours.

Throughout this period you will notice the color of the reaction mixture slowly .

turn a darker orange color. Here we are after two hours. At this point we removed .

the condenser and allowed some of the alcohol to evaporate off the reaction.

Once we saw solid forming on the side of the flask, we removed the flask from the .

heat. Here's the flask cooling down. The contents get down to just above room .

temperature but are still quite liquidous. You can see here it's fun to .

make our product crystallize on demand. We scratched the flask with a glass rod.

Very quickly crystals start to form. And then suddenly the whole mass .

crystallizes. The contents of the flask are pretty solid as you can see. We tip .

the contents into a cinter and filter them off.

Wash the flask out with a little cold water. Then use this to wash the solid in .

the filter. This will remove any cyanide salts left. Then finally wash with 10 .

mils of ice-cold ethanol. Dry the solids well on the pump to create a fine .

powder. And here's a portion of our product. We got 7.2 grams of benzoin .

which is a 72% yield on starting benzaldehyde.

We could recrystallize this but the product seems pretty pure as it is.

It has quite a delicate faint aromatic aroma and no almond like benzaldehyde .

smell remaining. We'll use this for some future experiments.