In this video we prepare benzyl cyanide using the cold netrile synthesis you'll

need a 500 ml flask set up with stirring.

This reaction is a nucleophilic attack of a cyanide ion onto benzyl chloride to give

us our product.

So you will first need to prepare an aqueous solution of alkali cyanide, either sodium

or potassium cyanide will work.

We prepared our solution using the method we demonstrate in another video, we created

a solution of around 140 ml.

containing, around 30 grams of mixed sodium potassium cyanide.

Check out our other video for details of how we, do this by heating potassium, ferrocyanide

and sodium metal together, to form a melt.

Place the cyanide solution into the 500 ml flask, be, careful when handling cyanides

as they really are extremely toxic, and be sure to dispose of them safely.

Now set up an addition funnel on top of the, flask, if possible have this close to the atmosphere

in, order to avoid toxic fumes.

Now weigh out 40 grams of benzyl chloride, as a, warning, this substance is extremely

nasty and although it might, not seem like it burns your eyes, it absorbs into, your

body and quite literally, leaves a nasty taste in, the mouth.

Make sure that the benzyl chloride you use for that, is in the right amount of quantity,

and that it is in the right amount of quantity, and that it is in the right amount of quantity.

This, reaction is free from hydrochloric acid or hydrogen chloride gas.

If these are present they could cause dangerous cyanide gas, to be produced.

Add the benzyl chloride to the addition funnel and be, sure that the tap is closed, use ventilation

here in, order to minimize your exposure.

Then measure out 40 milliliters of ethanol, we've used absolute ethanol, but a little

won't turn here.

Add this to the benzyl chloride in the addition funnel.

Now heat the flask on a hot plate to around 50, degrees C and slowly begin addition of

the alcoholic benzyl, chloride to the flask drop wise with stirring.

The mixture will turn slightly cloudy but you won't see, much happen at this point.

Complete addition, should take around 30 minutes.

Once done, turn off the stopcock and replace the addition, funnel with reflux condenser.

Take extra care when washing, out the funnel because you don't want to breath in, the piercing

and toxic fumes of benzyl chloride.

Turn up the heat and start to reflux the mixture, in the flask.

You'll start to see a yellow and then perhaps orange, color appear.

Keep refluxing.

Going for a good three hours in total.

An hour or so and you'll see the color becoming, darker, and an orange colored oil, starting

to appear on, the top of the liquid in the flask.

This is now two hours in, and we've turned the, stirring off just for a moment to show

you the, layer of orange oil.

Keep going and after three hours, turn off the heat, and allow the reaction mixture to

cool with stirring continuing.

Here's the flask after three hours, now set up for, simple distillation in order to distill

as much of the, ethanol off as possible.

Distillation occurs fairly rapidly.

When you have collected around 35 mils of distillate, you, can switch off the heat and

allow the flask to, cool down to room temperature.

You may notice an unpleasant smell like burning rubber, this, is benzyl isocyanide, a minor

side product of the reaction, we'll need to get rid of this.

Pour the contents of the reaction flask into a separating, funnel.

Allow the layers to separate well, then drain off the, bottom aqueous layer, remember this

still contains cyanide.

So dispose of carefully.

It is important to, clean the flask after three hours.

Now measure out 20 mils of concentrated sulfuric acid, in 40 mils of water.

Add the acid slowly to the water, this will give off a lot of heat and may boil, so be

careful.

Add half of this still hot acid and water mixture, to the product in the funnel.

Given it a good shake for a few minutes then, allow to separate, some of the dark color

into the bottom acid layer.

Separate the bottom acid layer, then add the remaining acid

to the funnel and repeat the process, shaking again for

a few minutes.

This should now have removed most of the unpleasant aroma,

leaving you with an aromatic smelling product.

Now prepare 40 ml of a saturated sodium bicarbonate solution.

Add this to the product in the separating funnel

well to neutralize any remaining acid.

Once again, separate off and discard the bottom aqueous layer.

We're nearly there now.

Finally we wash the product with 40 ml of a

saturated sodium chloride solution.

The last bit of separating may take a while to complete.

So be patient with the last drops of water to separate.

Here's our crude product poured into a storage container.

32 grams of benzyl cyanide, which corresponds to a crude yield

of 86% based on starting benzyl chloride.

It's still dark and contains some impurities.

To purify you, can vacuum distill this.

However the vacuum is essential to stop the product decomposing

at its high boiling point.

We will do some experiments and see if we can use this product.

Check this is for further reactions.