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Author: Subject: A Curious Case of What is This?
Meltonium
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[*] posted on 13-10-2017 at 15:16
A Curious Case of What is This?


Hello, A long while ago I followed NurdRage's procedure for making chloroform and sodium propionate from bleach and methyl ethyl ketone via the haloform reaction.

He refined the sodium propionate into propanoic acid by adding hydrochloric acid to the solution that was separated from the chloroform. This made sodium Chloride and propionic acid.

PrOONa + HCl -> PrOOH + NaCl

Now in solution is a large amount of salt along with water, excess HCl, and propionic acid. The water and propionic acid are distilled off at an azeotrope ~100C. This azeotrope is collected and then sodium bicarbonate is added to produce sodium propionate again. Then, the water is distilled off leaving sodium propionate as well as so residual salt and sodium bicarbonate. Then concentrated sulfuric acid is added to this. The sulfuric acid converts the sodium propionate again to propionic acid which is distilled off without water at 141C.

I preformed this procedure almost a year ago. At the time, I collected the chloroform and left the sodium propionate solution in the bottle and decided to refine it later. Only recently did I attempt to do this and my results are rather confusing.

I did keep a written procedure for the amounts of materials I used. For a 1 gallon bottle of 7%NaOCl, I used 100mL of MEK which shoudl have been an excess. Apparently, I messed up big time on the calculations because when I added HCl to the mixture, copious amounts of Chlorine gas bubbled out. After the gas had subsided, I continued on with the procedure distilling off the azeotrope of water and propionic acid.

The full distillation of 1 gallon took me about 14 hours. The waste was a dark brown liquid with precipitated crystals assumed to be NaCl and the distillate was a clear colorless liquid that fizzed upon the addition of sodium bicarbonate. So far, so good, I thought. (This part was consistent with NurdRage)

Next, I evaporated off the water. I thought that it might be faster to just evaporate off the water instead of distilling it (also, I was running out of ice to keep my condenser cool) so I poured ~600-800mL into a 2L beaker and set it on a hotplate on high. As the evaporation continued, I added more of the sodium propionate solution to replenish what had evaporated. Eventually, I was left with a dark brown liquid that was growing white crystals. I thought this was good enough for the next step and stopped it there.

Finally, I added the sulfuric acid to the mix. Instantly, upon addition of the H2SO4, the solution bubbled and temperature rose. I expected this. What I didn't expect was the distillate.

Literature claims propionic acid is a clear liquid with a strong odor that boils at 141C and has a density of .98g/mL

The liquid that I collected was a clear, colorless liquid that fumes heavily in air, with a sharp odor and a high refractive index. This came over at 103C and the density was calculated to be 1.125g/mL. Very odd, I thought.

I went back to college and came back the next weekend. The product I collected has turned a brown color. Clear to brown indicates some kind of contamination, perhaps oxidation from air or degradation from light.

Can you guys think of what I possibly collected?
I don't think it's propionic acid because of the difference in boiling point and density.
I don't think it's a combination of water and sulfuric acid because of the low bp
I don't think it is excess hydrochloric acid because that was neutralized with bicarb.
I don't think it could be the anhydride because of difference in bp

Any thoughts?




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[*] posted on 13-10-2017 at 17:00


You say you left the reaction for a year - could you clarify at which stage you stopped the work up of the reaction mixture? I'm assuming you stopped after distilling the chloroform off, but you then imply a lot of residual hypochlorite remained?

Edit: Would you be able to perform a melting point test, rough determination of water solubility etc?

[Edited on 14-10-2017 by Lithium]




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[*] posted on 13-10-2017 at 17:24


I have used IPA to make chloroform, sometimes when I have added too much IPA, i get a sweet smelling liquid left over that settles on the top. I thought at first IPA would react to form Acetone in the Sodium Hydroxide and rest of the left overs. But it dosnt smell at all like acetone.

Its a really sweet smell and i only get when lazy and leave the container I have made the chloroform in for a long time, before cleaning. i have always removed the Chloroform straight away, but if i have had an excess of sodium hydroxide and left the waste mixture for a long time I also get a strange product.

I will do this experiment again soon (need chloroform anyway), I always use IPA now because unlike acetone it dosnt need cooling, it isnt anywhere near as exothermic as acetone
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[*] posted on 13-10-2017 at 18:17


Real shot in the dark, and honestly i have no idea how you would of got there. BUT could it be diethyl ketone?

Not sure it could form in your mix though, and I apologize for butting in, but I wanted to have a go at trying to work it out, best advice though is ignore most what i say.

My main reasoning was based on the fact you had propanoic acid, also the boiling point is near the range, but no clue how you would have decarboxylated it (if thats even the right term!)

sorry the density dosnt fit though
[Edited on 14-10-2017 by NEMO-Chemistry]

[Edited on 14-10-2017 by NEMO-Chemistry]
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