[wildfyr]

Hi all,
I have a bottle of glacial acetic acid. At least, it was glacial when it was shipped to me, now that I've opened it a couple times I assume its got a couple tenths of a % of water in it. What is the most straightforward way to remove this? Add some acetic anhydride? Use activated molecules sieves? Both?

I've seen what the handbook suggests tetraacetylborate, or by adding acetic anhydride and heating over CrO3. I only care about the water, so it seems like the only important bit is the acetic anhydride. Am I missing anything?

[OrganicDan96]

I would be a little concerned about acetic anhydrous in your acetic acid, do you plan to distill it?

[wildfyr]

Let's pretend I'm a regular poster and want to be as lazy as possible  .

I will if I have to.

[Enthalpy]

Could the conductivity tell how little water was absorbed, and spare the drying altogether?

[rolnor]

I wonder if not the acid can react with molecular sieves?

[pgk]

1). You add a little amount of acetic anhydride and wait a little bit until crystallization below 15oC. If not, you add a little more acetic anhydride.
Don’t worry about a little excess of acetic anhydride because it will soon be transformed to glacial acetic acid, as being highly hygroscopic.
2). Yes, molecular sieves are aluminum silicate and alkali/alkali earth aluminosilicate complex salts and thus, they can react even, with weak acids.

[hollytara]

acetic acid BP 118, acetic anhydride BP 139  - so disitillation will leave the acetic anhydride behind. 

Mol sieves are often problematic for carbonyls - not good for acetone for example, will slowly catalyze aldol reactions.  I can see something similar for the acetic acid and especially for any acetic acid solutions with acetic anhydride!

[pgk]

Distillation of organic acids is not very convenient, acetic acid included.

[wildfyr]

If there is, say, 0.2% water in there, then adding acetic anhydride and distilling it all seems pretty painful. Its 500 mL I think.

I guess I could add a little acetic anhydride then just distill a small amount of acetic acid as I need it.

I wonder if I could do the trick where I reflux it with the setup is rbf under open addition funnel containing of sieves with a condenser on top of that. The reaction to adsorb most of the water is pretty fast, but aldol condensation on the sieves takes some time. After letting it reflux under the sieves for a while, I can then reduce the temperature and run a reaction in the rbf on the bottom.