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Runningbear
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[*] posted on 5-10-2009 at 15:27
Making glacial acetic acid


Hi guys,

Can someone suggest a simple method for making Glacial Acetic Acid. And also spell out any potential sticking points I may run into?

thanks in advance,

Runningbear
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[*] posted on 5-10-2009 at 15:34


NaHSO4 + CH3COONa, that is, sodium acetate and sodium bisulfate, I hear is a good method.
I'd look around. Did you try searching for such a thing on this forum? I know it has been talked about before.




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entropy51
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[*] posted on 5-10-2009 at 15:37


Search, Man! Lots of threads on AcOH.

NaOAc + H2SO4 distilled works fine, but it's not real simple.

So does keten + H2O, but you don't wanna go there.
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[*] posted on 5-10-2009 at 15:58


You caught me at the right time Runningbear as I was just making mention to someone a few minutes ago on the very subject. Good quality Glacial acetic acid cheeply has been a goal of mine for a while. Its easy to make but not so in large enough amounts that make it of much use unless one wanted to run a messload of "micro synthesis" just to get enough to work with.

Every method I have tryed so far needed a second distillation over MgSO4 before it was of good dryness BTW so keep that in mind.

You can use Sodium Acetate and react that with H2SO4 or Sodium Bisulfate. Using H2SO4 contaminates the AcOH with what I think is SO2 pretty easy if you heat it to much and the Bisulfate method is harder to produce decent amounts of AcOH at once because you need a decent amount of heat to push the dry distillation along. I must say though that after performing the following method I must say that all the 'dry' reactions suck and synthesis of an aq solution and extraction from that is just easier then dealing with the issues and expense of the other two.

I have recently been experimenting with the salting out of AcOH from an aq solution using IpOH. I have been making the concentrated AcOH solutions by reacting NaOAc with NaHSO4 and then adding IpOH. After the addition of a large amount of NaCl you will get an upper layer consisting of IpOH+AcOH with small amounts of Isopropyl acetate and H2O. Extract the upperphase and dry with MgSO4, filter this and distill off your IpOH to leave with GAA. The problem is I can not be 100% what I have it GAA because I feel there is some contamination of IpOH preventing it from freezing. Drying agent does not clump even after 48 hours so it is dry... just contaminated. When the AcOH starts to distill the distillate takes on a cloudy color and surface tension starts to present itself in the condenser which was not present during the IpOH prerun.

There is simular methods that use organic solvents which I will attach the references for and out of all the solvents I feel DCM has the best potential for its ease of aquisition. I would love for others to follow these synthesis along with me because I get very little time to play anymore and the anticipation of trying other methods is killing me;) . Also because of the lack of focus I get I would like to hear the results from someone with proper fractioning of the IpOH and AcOH layer.

I got a little bit more data but I have to run at the moment, hear are a few papers someone gave me of interest.

Attachment: Separation_of_isopropanol_from_aqueous_solution_by_salting-out_extraction.pdf (256kB)
This file has been downloaded 1471 times

Attachment: SALT_EFFECT_IN_LIQUID-LIQUID_EQUILIBRIA_OF_ACETIC_ACID-WATER-BENZENE_SYSTEM.pdf (72kB)
This file has been downloaded 696 times


BTW: I have been looking into the oxidation of EtOH to make the AcOH.... Anysuggestions? I seem to be producing a messload of Acetaldahyde and having it bubble out of solution.

[Edited on 6-10-2009 by Sedit]





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entropy51
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[*] posted on 5-10-2009 at 16:33


Old acetic acid references

Suitable for the backyard shed.

A lot of this was worked out over 100 years ago:

http://www.archive.org/details/aceticacidvinega00londrich

http://www.archive.org/details/practicaltreatman00branrich

[Edited on 6-10-2009 by entropy51]
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JohnWW
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[*] posted on 5-10-2009 at 16:56


You can do a lot more, particularly by way of organic acetylations in synthesis, e.g. to protect -OH groups during other synthetic steps, if you prepared acetic anhydride, rather than glacial acetic acid. For most such reactions, which are reversible, the water produced by acetic acid, even with H2SO4 used as a catalyst, would tend to reverse the reaction. Here is the thread on the subject, which runs to 23 pages: http://www.sciencemadness.org/talk/viewthread.php?tid=9 .

Glacial acetic acid, in organic synthesis, has little more use than making acetate esters in reactions in which the desired product is immediately removed from the reaction mixture or is otherwise particularly favored, e.g. acetates of certain alcohols, as in industrial cellulose acetate and ethyl acetate manufacture; and, in inorganic chemistry, in preparing soluble acetates of some heavy metals that have few soluble compounds e.g. lead(II) acetate ("sugar of lead", Pb(CH3COO)2.3H2O, used in dyeing and paints), and use as a pH buffer in analytical chemistry as an alkali metal acetate or ammonium acetate.

[Edited on 6-10-09 by JohnWW]
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[*] posted on 5-10-2009 at 17:06


I don't feel theres anything loose about it Entropy. There is so much talk on the internet about these easy ways to GAA such as the standard NaOAc distillations yet I have seen few show results in practice. This should be a well defined area of this forum yet I don't feel it is and you can check this fact by going over the endless threads on this subject. Yes the oxidations of Ethanol have been mentioned a number of times in a variety of forms but since most of ya'll buy your GAA there is not enough practical discussion on the matter.

I know it is well understood processes but pulling it off correctly... and cleanly become another issue all together. I am meerly giving this fellow practical details of what to expect when attempting any of these synthesis other then just saying react Sulfuric with sodium acetate and your good to go.... because thats just not completely true in practice. I recently wanted more then 50ml-100ml or so and began exploring other options with salting out becoming the clear winner.


With all that said and done thanks for the books, I already started reading the first one and it looks like a nice easy to read text with alot of information.
Best regards,
~Sedit


[edit]
HaHa entropy I caught that edit before you had a chance to change it:P


[Edited on 6-10-2009 by Sedit]





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[*] posted on 6-10-2009 at 06:05


Quote:
HaHa entropy I caught that edit before you had a chance to change it


That's because it was intended just for you to see!

I agree about there being too much confusion about making GAA, but the distillation of NaOAc and H2SO4 does work, just as the old books say it does. But the NaOAc does have to be anhydrous if you want strong AcOH. My AcOH comes out > 95%, but not glacial. There are some interesting things in those old books.

If you don't want to buy GAA, buy the indicating stop bath which is >90%. It's cheap and there's nothing suspicious about buying it. You can distill it to get rid of the pH indicator in it. Otherwise it's pure. It can be further dried by azeotropic distillation, and probably by other methods.
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[*] posted on 6-10-2009 at 14:21


It does work and works fine but doing it at a useful scale becomes troublesome.

I like the old style chemistry books like the one you linked to. I grew up reading ones like this from second hand stores and such and they are straight forward and easy to understand without to much technical jargon that some newer text like to jumble up there books with. I still haven't seen a non Pt based oxidation yet but still have more to read there as well.

The indicating stop bath looks like a good idea but I still enjoy the idea of trying to come up with a nice clean GAA synthesis that even the lowest of chemist(Me:D) could make liters of cheeply. Producing liters of it from NaOAc and H2SO4 would not really be cheep or easy but I feel recovery of the AcOH dimmers from an (aq) solution could be done relativly cheep or easy. It that solution was made from the oxidation of EtOH it could be made very cheep.





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[*] posted on 6-10-2009 at 14:58


Quote:
I like the old style chemistry books like the one you linked to

Maybe I misjudged you, Sedit! I'm a 20th century guy, but a 19th century chemist.

Quote:
I still enjoy the idea of trying to come up with a nice clean GAA synthesis that even the lowest of chemist(Me) could make liters of cheeply


I think that would be the ketene method, and you can also go all the way (to Ac2O).
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[*] posted on 6-10-2009 at 16:22


Quote:

Maybe I misjudged you, Sedit! I'm a 20th century guy, but a 19th century chemist.

An old hard back reprint of Antoine Lavoisier's work Elements of Chemistry is one of the things that sparked my interest in chemistry when I was like 9 years old in the first place. After that it was the 25cent used bookstore and antique stores sucking up all kinds of old books. The newer ones where to much for a young kid to grasp even if he is gifted in science but the older ones where well written and to the point performing simple but indispensable chemistry experiments. I have always considered that im a scientist in my mind and an alchemist at heart. Besides.... show me a newer chemistry book that details how to make all your own apparatus. Tinkering is half the fun.

The Ketene method has always drawn me to it but everytime I think I will do so the big flashing warning signes go off. Ketene isn't the most user freindly and heat plus acetone don't sound like a party either. One day I will do it but when that day comes I will know exactly what the hell Im doing and I don't feel I am completely there for that process yet.

Agreed though that is the ultimate in large scale GAA synthesis.





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[*] posted on 6-10-2009 at 21:00


Sedit, thanks for the comprehensive post. I like the salting out method. i can find or make all the required chems. I'm going to give it a go. Can you tell me the starting percentages for combining NaOAc with NaHSO4 and how much IpOH should I add to this? And when you say a large amount of NaCl, how much are you talking about?

Also, I'm interested in the DCM method as I think it might keep a bit of water out. Can you elaborate a bit further on this method?

Runningbear
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[*] posted on 7-10-2009 at 07:03


JohnWW - Acetates is the obvious use you may think of for glacial acetic acid, but in synthesis I would say its use as a solvent is much more prevailent.
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[*] posted on 7-10-2009 at 11:43


Quote: Originally posted by Runningbear  
Sedit, thanks for the comprehensive post. I like the salting out method. i can find or make all the required chems. I'm going to give it a go. Can you tell me the starting percentages for combining NaOAc with NaHSO4 and how much IpOH should I add to this? And when you say a large amount of NaCl, how much are you talking about?

Also, I'm interested in the DCM method as I think it might keep a bit of water out. Can you elaborate a bit further on this method?

Runningbear


The paper attached talks about the equilibrium data you are looking for that pertains to the use of DCM and quite a few other organic solvents. DCM is not the best one to use at all but for me is the easiest and cheepest to obtain. The fact that it could be recovered so quickly and cleanly also makes the process much more attractive.

If you read thru it you will see it stated that the AcOH exsist in its dimmeric state(AKA glacial) in the organic solvant. I do not really believe this to be so when using IpOH but drying agents and the azeotrop between H2O and IpOH clears up the excess water. Also the IpOH salting out paper that I included in the first post talk about the use of potassium carbonate instead of NaCl which means that there would be less water in the mixture to begin with.

No word though on the concentrations of the AcOH solution at first though because I only added H2O to aid in dissolving all the reagents. This really didn't work well and In future works I am going to add the water and distill it to push any equilibrium in the direction of AcOH. The distillate will be salted out with various salts after that into DCM. I feel multiple portions of DCM should be used then combined before distillation for the highest recovery percentage.

Attachment: Mechanism_of_acetic_acid_transfer_from_aqueous_sodium_chloride_solutions_to_some_organic_solvents.pdf (388kB)
This file has been downloaded 706 times





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[*] posted on 7-10-2009 at 12:12


Quote:
When the AcOH starts to distill the distillate takes on a cloudy color and surface tension starts to present itself in the condenser which was not present during the IpOH prerun.

Sedit, what is the head temperature when the AcOH starts to distill? Thanks.

This is interesting, but it looks as messy as all the other methods! Still, if it works.....
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[*] posted on 7-10-2009 at 13:29


I dunno as did not have a thermometer on it when the AcOH started to come over. I was forced into a short path retort style distillation. The rubber stopper that held my thermometer in place shriveled and shrunk because of the Isopropylacetate(I assume) and screwed me up for finding the temperature before any AcOH came over. I just switched to something else and continued. Will not be hard for me to set something back up to get the temperature but I just haven't done it yet.

It will be a few days because im going out of town either tommorow afternoon or friday but I want to get right back on it as soon as I get back.

You are right though, it is a bit messy, but I have not streamlined it yet either. I was going to wait till I got everything simplified as possible before posting about it publicly but seeing as how Runningbear brought this up I thought I would make mention of it and possibly have a helping hand at trying various salts and solvents in the process as well as discuss some possible EtOH oxidations.(BTW the link you gave me says that they even have the same problem Im having where so much is lost in the formation of Acetaldahyde cutting yeilds down dramaticly)

You got them little trolls in the back of my head yelling Ketene in my ear once again. I keep telling them "No!, its to dangerous" but then they call me a vulgar name for a womans private area and egg me on even more.... Maybe I should try it... or get some medication to stop the voices:P





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[*] posted on 7-10-2009 at 14:47


Stay away from ketene. Easier & safer to buy that stop bath and concentrate it if you have to.

I would try something that will separate from H2O better than iPrOH, like DCM, EtOAc? Just a hunch.

[Edited on 7-10-2009 by entropy51]

[Edited on 8-10-2009 by entropy51]
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[*] posted on 28-10-2009 at 01:51


If I was going to purify indicator stop bath (85% acetic acid), what is the simplest method?

Is it worth making a dilute solution of ethyl acetate from a portion of the stop bath solution then fractionally distilling the ethyl acetate / water azotrope off?

Should I dry the indicator stop bath with sodium bisulfate or some other drying agent first?


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[*] posted on 28-10-2009 at 06:40


Runningbear, you can distill the stop bath just to get rid of the indicator it contains, which remains behind in the pot. The stop bath I get is often > 90% AcOH. I find 90% AcOH works for many purposes, but not for everything of course.

You can azeotrope off the water with EtOAc, but it requires a fair amount of ester to remove the water. I believe butyl acetate is supposed to work better than EtOAc, but I haven't tried it yet. I haven't found drying agents to be very useful, other than distilling from over CaCl2 which increases the concentration but the effect is not huge.

Those ancient books I posted above give some of the old methods for concentration that might be worth a look.

If you haven't already, set up a titration method so you can follow the progress of any concentration method you try.
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[*] posted on 29-10-2009 at 04:09


Entrophy, there were some great methods in that doc. I'm going to test a few of them.

I also found the following patent, which if it works as started, sounds like a really good simple method for final purification.

ACETIC ACID RECOVERY FROM AQUEOUS SOLUTION BY DISTILLATION AND CRYSTALLIZATION

Primary Examiner:
Yudkoff, Norman
Assistant Examiner:
Foster R. T.
Claims:

1.A process of dehydrating acetic acid containing up to about 20 weight percent water comprising cooling the acetic-water mixture sufficiently to crystallize a substantial portion of the acetic acid present, and vaporizing under vacuum the remaining mother liquor, said vaporization to occur at temperatures between the freezing point of acetic acid and the eutectic temperature.

EXAMPLE 1

100 ml. of acetic acid containing 6.07 weight percent of water was placed in a heat-insulated glass flask at 10°C. in liquid form. Agitation in the form of stirring was begun, and a vacuum pulled, thereby reducing the pressure so that crystallization was observed. At the end of 50 minutes, 76 percent of the material remained in the flask, being in the form of dry acetic acid crystals containing 0.36 weight percent water.

To compare conventional crystallization, 100 ml. of the same crude acetic acid was cooled in a flask to 0°C. with agitation. The crude crystals which resulted were centrifuged for 10 minutes. The product contained 2.4 weight percent water, with a yield of 62 percent acetic acid.

EXAMPLE 2

100 ml. of the same crude as above was cooled to 0°C. with an ice bath with agitation. After crystal formation, a vacuum was pulled, resulting in a pressure of about 10 mm. Hg, under isothermal conditions (0°C.). At the end of 60 minutes, 82 percent of dry acid crystals were recovered containing 0.54 weight percent water.


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[*] posted on 29-10-2009 at 06:55


What is the number of that patent, and preferably a link, please?
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[*] posted on 29-10-2009 at 07:05


Quote: Originally posted by JohnWW  
What is the number of that patent, and preferably a link, please?


http://www.freepatentsonline.com/3677023.html

gsd
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[*] posted on 29-10-2009 at 13:35


Runningbear, SC Wack posted that patent a couple of months ago. I gave it a shot with an aspirator and cold trap, not wanting to pump AcOH vapor into my pump oil. It didn't work under those conditions (15 mm Hg), but presumably would go better on pump vacuum. Let us know if you can make it work, it would be nice if it did!
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[*] posted on 5-11-2009 at 06:05


I find these methods that people are trying to adapt rather well tricky and fancy and unnecessary. Just buy vinegar, convert it to the acetate, evaporate off the water. Dry it at 150 for several hours, it does not decompose, combine this with NaHSO4 in a 'dry' blender to intimately mix the salts, pour salts in to a 'dry' round bottom, tap in some conc sulphuric and distill. It has to be glacial, there is no water in the system.
Patience and thoroughness is simply the key here, not tricks.
A very simple test for glacial acetic acid is a few ml in a 'dry' test, a spatula end of calcium carbonate will only form a slurry with glacial whereas wet acetic will give off CO2. Add a drop of water to the slurry and whoosh, sort of, more like a slow whoosh.




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[*] posted on 5-11-2009 at 06:38


Quote:
It has to be glacial, there is no water in the system.


Sounds so good in theory don't it? But reality does not always run according to theory. Never once was I able to achieve glacial statues on the first run and MgSO4 was always added to remove the traces of H2O and the distillation had to be run again. We are talking countless times here not once or twice. Not to mention.... Have you ever tried it? Its a pain in the ass letting SO2 into the product to often, H2SO4 does the same. This is good for a few ml but after that it starts to become a real pain with localized over heating and incomplete reactions.

[Edited on 5-11-2009 by Sedit]





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