We'll be preparing acetic anhydride the .

classic way using acetyl chloride and sodium acetate the single most important .

thing in this reaction is that your sodium acetate must be anhydrous and .

completely dry we've baked ours in an oven at 200 degrees C for four hours in .

total occasionally stirring the powder the textbook process is to actually melt .

the solid prior to performing the reaction however we wanted to see if we .

could get a reasonable yield through just oven drying weigh out 80 grams of .

anhydrous sodium acetate and place this into a dry 500 ml flask we've added a .

thermometer to track the temperature now stopper the flask and place it into an .

ice bath and get the contents as cool as you can measure out 60 grams of chilled .

acetyl chloride .

about 55 mils of liquid as you can see you'll need ventilation here now slowly .

add a small amount of the chilled acetyl chloride to the sodium acetate in the .

ice bath .

give the mixture a stir and allow the acetyl chloride to absorb and react this .

produces quite a lot of heat so go slowly and don't allow the temperature .

to rise above about 60 degrees C otherwise you'll risk losing acetyl .

chloride it's easy to overshoot we added a little too much and quickly hit .

70 degrees so go slow and allow the mixture to cool between additions once .

the acetyl chloride is completely added swirl the flask and you'll notice some .

more heat generated the contents of the flask turns into a liquid slurry now set .

up for simple distillation .

liquid so a thermometer in the still head isn't necessary we've used a .

calcium chloride drying tube to protect the distillate the first sign of liquid .

boiling is around 110 degrees C since our sodium acetate is unlikely to be .

100% dry there will almost certainly be some acetic acid present in our mixture .

pretty soon a strong distillation starts and a solvent front creeps up the .

adapter tube it's always very satisfying to watch this distillation is pretty .

rapid to begin with and slowly tails off but keeps going for quite a while as .

distillation proceeds the slurry in the flask turns more and more solid .

quite a lot of liquid distal off so don't stop the heat too early .

it took a good hour and a half before the distillation died down to a very low .

level in the contents of the flask turned the yellow burnt color .

here's our final distillate it has a slight yellow color as you can see .

definitely contains a city can hydrate but also smaller impurities such as .

acetic acid and maybe some ketone .

as well. To purify our crude product, we'll fractionally distill it. We're using a 40 .

centimeters Vigro Cologne as you can see here. We've chosen to fractionally distill because .

acetic acid and acetic anhydride have boiling points which are around 30 degrees apart.

You could possibly use a simple distillation on a strong heat source such as an oil bath, .

but you'd need to go very slowly and carefully. Soon after heating strongly the liquid in the .

flask boils and we get another nice solvent front climbing up the column. We used aluminum foil to .

insulate the column to make the distillation more efficient. When the vapor reached the top of the .

column, we initially got a temperature of about 100 degrees C and slowly cooled.

At this point we got a slow distillation of a small amount of initial product. This had a faint .

yellow color and an acetic acid aroma and ultimately we discarded this. Once the temperature .

rose in the still head to above 130 degrees C, we switched the receiving flask and then began to .

collect the distillate as our main product. Use ventilation because of the high temperature .

and we noticed that even the tiniest amount of anhydride vapor in the air is quite irritating .

to the eyes even if you can't smell it. Note that we performed the initial reaction twice and then .

combined the products for this distillation so the volumes you can see here are double.

Complete distillation took around two and a half hours in total and the boiling point .

was very consistent throughout.

At the end the boiling flask contained some tar-like residue.

Here's our final product, 130 grams of pure colorless acetic anhydride. Given that we .

used doubled the first reaction, this corresponds to an average yield on our first reaction .

of 83% based on acetyl chloride used. The product doesn't smell strongly of acetic acid.

In fact, you initially think it has no aroma at all and then suddenly it hits you, a very .

pungent and irritating aroma. Another common question is how it mixes and reacts with water.

Let's add a little bit and find out. You can see at the bottom of the beaker that there is a .

separate bubble of acetic anhydride with a small bubble of air trapped on top. This is cold water .

and the reaction is slow. We can see something happening, but it's a slow process.

Stay tuned for some interesting experiments which make use of our acetic anhydride.

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