Sciencemadness Discussion Board

methyl acetate

thereelstory - 8-5-2010 at 20:50

i know what wiki says, but anyone here have any success synth this?

not_important - 8-5-2010 at 21:19

Yes.

SeaDonkey - 20-6-2010 at 11:42

I'm interesting in synthesizing simple esters too. Methanol and acetic acid aren't hard to get your hands on so I may give this a shot one of these days.

Rich_Insane - 27-6-2010 at 12:04

Err, you also need sulfuric acid as a catalyst, I believe.

DJF90 - 27-6-2010 at 12:36

Nope, just an acid catalyst. Sulfuric acid is a common example, but not the only one applicable. I have an excellent paper using Iron (III) sulfate, with great yields.

numos - 19-3-2014 at 13:55

could HCl be used as a catalyst?

Where could I find a method using HCl?

HgDinis25 - 19-3-2014 at 14:03

This is a simple esterification reaction. The following equilibrium happens, when you add acetic acid to methanol:
CH3OH(l) + CH3COOH(l) --><-- CH3COOCH3(l) + H2O(l)

Now, methyl acetate forms an azeotrope with water, boiling at 56.1 ºC, with 95% methyl acetate. Methanol doesn't form an azeotrope with water and boils at 64.7. If you find a way of carefully, in a distillation apparatus, heat this reaction to 56.1, you would remove the methyl acetate as 95% methyl acetate and 5% water, and drive the equilibrium to the right, producing even more methyl acetate.

About the catalyst, sulfuric acid is usually prefered because it's the most common acid with almost no water in it. So, it serves as a dehidration agent, removing some water and driving the equilibrium to the right.

[Edited on 19-3-2014 by HgDinis25]

Ozone - 19-3-2014 at 18:56

I prefer to use strong acid cation resin (essentially sulfuric acid in solid phase) as a catalyst. But, then again, I'm frequently making higher boiling esters, so it's handy to be able to filter the catalyst out. For low boilers, like methyl acetate, just use the cheapest (clean) thing (any non-volatile acid should do), and concentrate the product. A Dean-Stark trap or Claisen arm should allow you to pull off the water and return the ester to the pot. Once the evolution of water ceases, distill off your product, and go from there.

O3

numos - 19-3-2014 at 19:36

I have little to no experience in O-chem, so forgive me if I'm slow here, I searched "methyl acetate" here and no decent results appeared.

I think this is a great way to start, seeing how no explosive/toxic substances are involved (relatively).

So let me get this right:
I add methanol and acetic acid [is 5% distilled vinegar ok?, or should I use acetic anhydride, I much prefer vinegar] to a boiling flask, stoichiometric amounts? Then add a catalyst, 98% H2SO4, how much?

Then what? Is this a reflux reaction?
Where can I find temp, time, and apparatus setup data?
I'm not after high yield or intense purity.

I have a 24/40 organic chem glassware setup, no hotplate :( yet, so I'm stuck with a blowtorch and an oil-bath. Blowtorch + methanol = disaster?

I realize this is a lot of questions, is there a pdf with detailed methods?

DraconicAcid - 19-3-2014 at 19:37

Vinegar won't work, you need nearly pure acetic acid. Acetic anhydride will also work.

numos - 19-3-2014 at 20:58

Is everything else correct? what about synth data?

Metacelsus - 20-3-2014 at 08:21

Quote: Originally posted by numos  
Blowtorch + methanol = disaster?


Quite possibly, especially with the oil bath. You could try using a water bath instead, as the product's boiling point is low enough.

subsecret - 24-3-2014 at 16:43

HCl can be used as a catalyst, but it needs to be introduced in anhydrous form, preferably dissolved in the methanol, as introducing an aqueous HCl solution would drive the equilibrium the wrong way. I've heard that sulfuric acid is used because the sulfate group (or bisulfate, depending on how many protons have been taken) is not very nucleophilic, so it tends not to interfere. I know that HCl can be used as an acid catalyst, but why doesn't the more nucleophilic chloride ion interfere with the reaction?

You can basically use as much catalyst as you want, as it is only regenerated throughout the reaction. On a small scale such as this, several milliliters should be enough. You may want to find a published procedure that included volumes and reflux time.

BromicAcid - 24-3-2014 at 17:52

Sulfuric would be preferred because is is not very volatile, if you try to distill methyl acetate with HCl catalyst then you will likely bring some of your hydrogen chloride over.

subsecret - 29-3-2014 at 18:51

Didn't think of that, Bromic. Thanks.