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Author: Subject: Acetic acid synthesis, unknown sideproduct
Emlingur
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sad.gif posted on 10-4-2016 at 04:49
Acetic acid synthesis, unknown sideproduct


I made acetic acid by bubbling ethenone through water, but my weight calculations seem off, so i think i have some sideproduct. I know for sure that no diketene got through as the apparatus was shielded from all light, and the ethenone was run through two condensers, before being bubbled through the water. Somone I asked suggested ethyl acetate might be my culprit, or maybe that tiny amounts of acetic anhydride was made, but I would like more suggestions, or even a solid answer gotten from experience with the same problem.

[Edited on 10-4-2016 by Emlingur]
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CharlieA
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[*] posted on 10-4-2016 at 08:28


What is the molecular formula of ethenone, please?
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hissingnoise
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[*] posted on 10-4-2016 at 09:29


It's CH2=C=O, as a quick google would've shown you . . . ?

Quote:
Somone I asked suggested ethyl acetate might be my culprit, or maybe that tiny amounts of acetic anhydride was made.

It seems likely that some dimer came over to form acetoacetic acid . . .

Oh, and welcome to scimad!

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Emlingur
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[*] posted on 10-4-2016 at 09:34


Thanks, I will check that out.
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Chemist_Cup_Noodles
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[*] posted on 18-4-2016 at 05:43


I'm kind of curious as to why you're using this route to make acetic acid. I mentioned I was trying to get some high concentration acetic acid in another thread (everyday chemistry on the general chemistry board) and I got some good and simple suggestions there. Several people said they had used oven dried sodium acetate and concentrated sulfuric acid to produce acetic acid and then distilled the product. This should produce glacial acetic acid, which you could just use as a stock solution if you don't need it to be so strong. I think I've seen a youtube video, maybe on Nile Red's channel, detailing this method also.




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hissingnoise
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[*] posted on 18-4-2016 at 07:10


Quote:
I'm kind of curious as to why you're using this route to make acetic acid.

Well, the fact that ethenone reacts with AcOH to form the anhydride makes the route particularly interesting? ;)

[typo edit]



[Edited on 18-4-2016 by hissingnoise]
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clearly_not_atara
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[*] posted on 18-4-2016 at 09:08


If you have a working setup for ketene and you can't manage acetic acid, I just wonder what wormhole you came through and how long have you been living in this Universe? Also, seriously, that shit's dangerous as fuck, if you just want AA use the nitrogen dioxide route or the zinc/silver acetate pyrolysis.
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Chemist_Cup_Noodles
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[*] posted on 21-4-2016 at 06:14


Quote: Originally posted by clearly_not_atara  
If you have a working setup for ketene and you can't manage acetic acid, I just wonder what wormhole you came through and how long have you been living in this Universe? Also, seriously, that shit's dangerous as fuck, if you just want AA use the nitrogen dioxide route or the zinc/silver acetate pyrolysis.


There are honestly so many different ways to make acetic acid. I just saw another method that NeonPulse posted in the Everyday Chemistry topic over on the Gen Chem board. All he said he used was dry anhydrous sodium acetate and sodium sulfate. Low yield, but also low cost. He didn't go into detail but he posted a picture of his distillation apparatus with it so I'm assuming that he just distilled off his product.

But you know, sometimes the purpose of doing a reaction really isn't the end, but rather the means. Surely the fun can lie in the doing. So I'm not trying to knock anyone's methods, I was just trying to point out a theoretically simpler method. Actually, forming the anhydride does sound fairly interesting though. The whole route seems fairly interesting, albeit rather labor intensive it seems between running the ethenone (or ketene, I suppose) through two condensers and shielding the whole thing from all light.

Sorry for helping so little on your original issue @Emlingur, but I'm curious by how much your original weight calculations were off. Did you keep the water you bubbled the ethenone through chilled to make the ethenone more soluble? But that would probably mean you would get a weight under what you expected, which could just be attributed to low yield. So I'm going to guess that maybe you got a weight over what you were expecting, which I would think would be more attributable to sideproducts. I'm not very familiar with the reaction you are doing so I'm trying to build an understanding as I go. Forgive me, but as I'm not in college quite yet I'm having to work on studying organic chemistry in my own time. Knowing my own limitations, hopefully I some of my questions can lead this discussion in a good direction. Some pictures of your setup would also be helpful for getting a better understanding of what might have gone wrong. Also, what is the heat of reaction for ethenone and water versus ethenone reacting with AcOH? Maybe if you could keep it cold enough and determine a catalyst that favors one reaction over the other that could help prevent the formation of the anhydride. How reactive is the anhydride as opposed to just normal AcOH? Namely, is it as good of a chelating agent?

I don't think your side product would be ethyl acetate though. In order for that to form, you would need to not only reduce the ethene group to an ethyl group, and seeing as AcOH only tends to lose the one hydrogen, the stoic for it would be quite messy, and the bond energies you would need to break and then form just don't seem as theoretically favorable as opposed to the acetic anhydride.

I hope I haven't said anything too wrong and or moronic. Please call me out and correct me if I have.





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clearly_not_atara
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[*] posted on 21-4-2016 at 11:40


Everything you said sounds right -- except for making acetic acid from sodium acetate and sodium sulfate. I'm guessing you mean the synthesis or acetic anhydride from sodium acetate and sodium pyrosulfate.

Anyway, if you want to make pure (or pure enough) acetic acid, going through the anhydride isn't a bad idea -- but making a ketene generator is just really dangerous and I don't think it should be attempted by someone inexperienced. Obviously he survived, so I could be wrong.
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Chemist_Cup_Noodles
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[*] posted on 21-4-2016 at 13:55


Quote: Originally posted by clearly_not_atara  
Everything you said sounds right -- except for making acetic acid from sodium acetate and sodium sulfate. I'm guessing you mean the synthesis or acetic anhydride from sodium acetate and sodium pyrosulfate.


Y'know, I was thinking that his reagents were rather odd. NeonPulse actually did say sodium bisulphate in his post here though, so I transcribed that incorrectly. But you can see though that he claimed to be making glacial acetic acid, even though idk how.

Quote: Originally posted by clearly_not_atara  

but making a ketene generator is just really dangerous and I don't think it should be attempted by someone inexperienced.

Wow I just saw a video showing just how dangerous this stuff is... 5ppm IDLH value, holy shit. That's fucking crazy.

By the way he made another thread that I've linked here in case anyone else wants to check it out.

Edit reason: I made a joke that was too dark for some people's tastes. Whoops. Sorry to those offended.

[Edited on 22-4-2016 by Chemist_Cup_Noodles]

[Edited on 22-4-2016 by Chemist_Cup_Noodles]




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hissingnoise
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[*] posted on 22-4-2016 at 00:47


Quote:
I wouldn't be so quick to say he survived. In his last post here, six days ago, he did mention that ketene (happy now) gas escaped quite often during bubbling :o RIP @Emlingur, though your time on sciencemadness was brief, you will be dearly missed.
I would say his family should make vinegar and then pickles, out of the acetic acid he gave his life to make, but considering that it might have unknown contaminants, quite possibly being acetic anhydride, maybe that wouldn't be such a good idea. Sorry that your valiant efforts were in vain, comrade.

Why would anyone post stupid, nasty shite like this, Noodles ─ do you think you're being funny, is that it???

Oh, and "ethenone" is the correct name for the simplest ketene . . .

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[*] posted on 22-4-2016 at 01:31


This thread is like making CO2 from phosgene and water ;) .
I know a beautiful synthetic way of making CO2:
- bubble phosgene through a dilute solution of NaOH in water
- add some acid to the solution, after all of the phosgene has dissolved
Your CO2 nicely bubbles out of solution.

You still want to make something mundane like acetic acid from ketene?

[Edited on 22-4-16 by woelen]




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Chemist_Cup_Noodles
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[*] posted on 27-4-2016 at 07:30


It certainly makes more sense to make the acetic anhydride from this process than just plain acetic acid. If you have a good setup for handling your ethenone gas though, what other possible experiments could you do with it? Anything more exotic than just acetic anhydride or acid?



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hissingnoise
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[*] posted on 27-4-2016 at 08:14


Quote:
Edit reason: I made a joke that was too dark for some people's tastes.

I just think a "joke" without so much as a smidgin of humour isn't exactly a barrell of laughs!
Quote:
If you have a good setup for handling your ethenone gas though, what other possible experiments could you do with it? Anything more exotic than just acetic anhydride or acid?

Any compound with such great reactivity obviously has many and varied uses . . . ?

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