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Jor
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I just ordered the 100g metaphosphoric acid from Aldrich before posting the link. Otherwise it would be gone in a few minutes 
According to item description, it is 33,5-36,5% metaphosphoric acid, stabilized with >65% sodium metaphosphate. Why do they stabilize it? Does it
still have the powerfull dehydrating properties then?
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LSD25
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Yeah, they were - unfortunately as of this time they are no longer offering ANY items for sale, which is kind of a change from what they had on offer
for the last couple of weeks
Whhhoooppps, that sure didn't work
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Fluorite
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How does sulfuric monochloride react with phosphoric acid? Can it be used to dehydrate it at room temperature?
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njl
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You're gonna have to elaborate on "sulfuric monochloride". Do you mean chlorosulfuric acid? Or disulfur dichloride?
Reflux condenser?? I barely know her!
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Fluorite
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Sorry I meant disulfur dichloride
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njl
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Alright, well I really doubt anyone here can answer from experience. In all likelihood the answer is yes, but what the phosphoric acid is dehydrated
to I couldn't say. Probably won't work exactly how the dehydration of acetate does. Something will be dehydrated but perhaps not in the way that you
want.
edit: I just realized how old this thread is. Also, would there even be an advantage to dehydrate with S2Cl2?
[Edited on 5-1-2021 by njl]
Reflux condenser?? I barely know her!
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chloric1
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https://cdnsciencepub.com/doi/pdf/10.1139/v56-102
This is an interesting and informative 13 page article regarding “the strong phosphoric acid‘s “their synthesis in their properties.
Interesting to note that no cyclic phosphoric acids detected. They made them by heating the required amount of P2O5 with 85% orthophosphoric acid to
350 Celsius. They s process is a lower temperature method so they are able to stop reaction right when the acids start to attack the Pyrex container
Fellow molecular manipulator
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chornedsnorkack
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And no branched acids.
They suggest, reference to link 40 (van Wazer, Holst 1950) that branched acids should promptly decompose in "all solvents".
On what grounds?
Decomposition of a branched acid is still breaking a P-O-P bond. It may be easier than in a straight or cyclic acid but it is sluggish even in cold
water.
Their solvents do contain water - something which favours hydrolysis, sluggish as it is. And the rest is alcohol (isopropanol) - also capable of
forming phosphate esters and in the process releasing water and breaking P-O-P bonds.
Could you dissolve phosphoric acids in a solvent which has no mobile hydrogens, no way to free water on reaction and difficulties attacking bonds?
Like triethylamine?
Looks like a convenient solvent. Boils at +89 C. Freezes at -115 C.
Is triethylamine a good solvent for its salts?
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clearly_not_atara
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When an article from 50 years ago disagrees with ideas that are still held today, it is possible that we have been mistaken for decades, but it is
also possible that the article is itself mistaken. In this case, it seems to be the latter; the cyclic structure was detected by Chakarawet et al via
crystallization and protonation of salts with bis(triphenylphosphanyl)iminium:
"Crystalline Metaphosphate Acid Salts: Synthesis in Organic Media,
Structures, Hydrogen-Bonding Capability, and Implication of
Superacidity": https://drive.google.com/file/d/1joJWfWU_YhE-VWbGISAi0S7Jvva...
Notably, one inference derived in the above publication is that H3P3O9 is of comparable strength, and possibly stronger, than TfOH (!). This gives
some clarity to the question of why it is so noxiously corrosive to its containers.
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chornedsnorkack
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Quote: Originally posted by clearly_not_atara  |
When an article from 50 years ago disagrees with ideas that are still held today, it is possible that we have been mistaken for decades, but it is
also possible that the article is itself mistaken. In this case, it seems to be the latter; the cyclic structure was detected by Chakarawet et al via
crystallization and protonation of salts with bis(triphenylphosphanyl)iminium:
"Crystalline Metaphosphate Acid Salts: Synthesis in Organic Media,
Structures, Hydrogen-Bonding Capability, and Implication of
Superacidity": https://drive.google.com/file/d/1joJWfWU_YhE-VWbGISAi0S7Jvva...
Notably, one inference derived in the above publication is that H3P3O9 is of comparable strength, and possibly stronger, than TfOH (!). This gives
some clarity to the question of why it is so noxiously corrosive to its containers. |
This is an interesting and novel claim.
The systems of P2O5-hygroscopic superacid should be well known because they form a standard synthetic route to the oxides/anhydrides. Has anyone
previously noted what form metaphosphoric acids take in, for example, H2S2O7/P2O5 solution?
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