mr_bovinejony - 20-11-2020 at 10:14
Let me preface this by saying like most preparations in my lab, this one was done half assed and half drunk because I didn't expect it to work, and
although the results are inconclusive I strongly believe that we are on the right track for an oxalyl chloride synthesis.
So this idea was stolen from chemplayer who prepared acetyl chloride by bubbling dry hcl gas into Acetonitrile and glacial acetic acid. Im not sure
the stochiometry that was used for that, but for my synthesis I used a 4 times molar equivalent of Acetonitrile to anhydrous oxalic acid. Theres a
paper thats on the oxalyl chloride thread that explains this Acetonitrile and acid synthesis, i think on the second page
Anhydrous oxalic acid was prepared by reflux in toluene with a dean stark, it turned a dark gray color over the past 3 weeks as well.
A 500 ml rbf was loaded halfway with salt, preferred to be anhydrous but mine wasn't, and on top of a two way adapter was loaded a pressure equalizing
addition funnel with 200 mls of drain cleaner sulfuric acid, probably between 90 and 93 %. To the other neck of the two way adapter a drying tube
with calcium chloride was led by a hose and glass tube into the reaction flask. The reaction flask contained 100 mls of Acetonitrile and 40 grams of
anhydrous oxalic acid.
The first note here, the acid did not dissolve at all into the Acetonitrile. I heated it up to around 60c and a clear mixture was had, but as it
cooled in the ice bath the acid crashed back out. Maybe a cosolvent should be used to keep it dissolved.
The reaction flask was put in an ice bath, and the sulfuric was dripped onto the salt. Hcl gas was generated and bubbled into the reaction flask for
about an hour. This was all done in the fume hood, at no time did I smell hcl gas or see it escape from the reaction flask.
Second note. Chemplayer bubbled hcl gas until no more dissolved into the reaction flask. Mine was still able to dissolve some gas since at the end of
the addition and upon heating the gas generation flask even still there was no smell or noticed vapor of hcl gas.
The apparatus was disassembled and the reaction flask, now a slushy of oxalic acid and Acetonitrile, was stoppered and left overnight. The next day a
distillation apparatus was assembled. It should also be noted that when I unstoppered the reaction flask, no smell of hcl was notice. Maybe this was
because I had set up the apparatus quickly, but usually with hcl I always get a whiff. Anyways the distillation was started and to my surprise a small
amount of liquid came over from 59 to 64c. A whopping 4 mls of some slightly viscous clear liquid was collected. After the head temp rose above 70c
the distillation was stopped and taken apart. The smell of hcl gas was very overwhelming at this point.
The 4 mls of liquid that had collected had a very sharp hcl odor, but not exactly like hcl if that makes sense. This liquid was pipetted into an
amount of water and white vapors were observed coming off along with more hcl stank.
So was oxalyl chloride made? I don't know. I've never seen it before so I don't know if its viscous. Never smelled it either so I can't compare the
smell. But judging by the boiling point and reaction with water, id say a small amount was made even if the 4mls wasn't entirely oxalyl chloride.
In my opinion I think as far as otc acyl chlorides go, this procedure is our best bet. If there is a way to keep the oxalic acid in solution I would
think the yield would be much better, and of course taking more care to keep everything anhydrous.
[Edited on 20-11-2020 by mr_bovinejony]
njl - 20-11-2020 at 10:36
Good stuff. Maybe DMSO as a cosolvent? It's high boiling too so maybe you could squeeze out a bit more during distillation. Not sure if the product of
DMSO + HCl would be too electrophilic though.
edit: DMSO and oxalyl chloride are the reagents for a swern oxidation, and a side product of that reaction is HCl so maybe it's worth a try.
[Edited on 11-20-2020 by njl]
mr_bovinejony - 20-11-2020 at 10:58
Oxalic acid is soluble in dmso? I'll try a few tests with it and Acetonitrile
karlos³ - 20-11-2020 at 11:02
DMSO and oxalyl chloride? Prepare for THE STINK 
mr_bovinejony - 20-11-2020 at 11:18
I've only had bad experiences with halogens and dmso, my wife could smell the shit 3 days after it happened!
Pumukli - 20-11-2020 at 12:01
Then it's time to reach new dimensions in your relationship! :-) Maybe DMSO and oxalyl-chloride is not that bad, after all...
clearly_not_atara - 20-11-2020 at 13:50
DMSO reacts with oxalyl chloride at ambient temperature, as karlos alluded. Not recommended.
Dr.Bob - 21-11-2020 at 05:22
I agree that DMSO is not a good cosolvent due to reactions with oxalyl chloride. As long as some of the oxalic acid is in solution that should
react, and the oxalyl chloride will be more soluable, so that should slowly bring the acid into solution, so not sure that you need a cosolvent. If
you think that you have made oxalyl chloride, best way to test it to mix it with an acid in DCM or CHCl3 and see if you get the acid chloride. You
can always react with an amine to make an amide to test it.
mr_bovinejony - 21-11-2020 at 06:53
The problem is that the amount of oxalic acid that was not in solution was overwhelming, if there was any in solution it was very minimal. Maybe this
reaction needs to be run at 50 or 60c to keep it all in solution so it can react?
Tsjerk - 21-11-2020 at 07:11
You stated there was no HCl leaving the reaction right? If that is the case there is at least enough of the acid in solution.
mr_bovinejony - 21-11-2020 at 07:17
Oh I meant oxalic acid, I would think that because its barely soluble in the Acetonitrile it didn't get a chance to react all the way with the hcl
that was dissolved. I'll have to look at the paper again, and see if the reaction takes place while the hcl is being bubbled in or if it can be heated
so the oxalic acid while go into solution and react
Tsjerk - 21-11-2020 at 09:23
Ah, I meant oxalic acid as well. If HCl isn't coming out of solution it has to either dissolve in acetonitrile or react with the oxalic acid that is
in solution. As long as some oxalic is solution and the reaction is fast enough it should be fine.
mr_bovinejony - 21-11-2020 at 12:18
Well I know for next time I need to use way more hcl gas, and probably keep the heat on a bit so it all stays in solution. At least with during the
distillation it should finish reacting what it can once its heated again