chornedsnorkack
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Best conditions for sulphur iodide
Sulphur does not react with iodine.
Sulphur iodide is known but unstable because it decays:
4S2I2->S8+4I2
Sulphur iodide is stable below -30 degrees.
Standard way to synthesize sulphur iodide is metathesis:
S2Cl2+2HI->S2I2+2HCl.
S2Cl2 is a perfectly well characterized substance that freezes at -80 degrees and boils at +137 degrees without decomposition.
HI is a perfectly well characterized substance that freezes at -51 degrees and boils at -35 degrees without decomposition.
HCl boils at -85 degrees. Its volatility may drive metathesis.
Which conditions would you pick to get sulphur iodide with minimum decomposition? E. g. would you add HI to excess of S2Cl2, or
vice versa? Which are good solvents for S2I2, to handle it without decomposition and then separate it?
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Sulaiman
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Quote: Originally posted by chornedsnorkack  |
S2Cl2 is a perfectly well characterized substance that freezes at -80 degrees and boils at +137 degrees without decomposition.
HI is a perfectly well characterized substance that freezes at -51 degrees and boils at -35 degrees without decomposition.
HCl boils at -85 degrees. Its volatility may drive metathesis.
Which conditions would you pick to get sulphur iodide with minimum decomposition? E. g. would you add HI to excess of S2Cl2, or
vice versa?
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First, realise that I'm guessing here based on no direct knowledge,
... by analogy with 'add acid to water not vice versa',
and assuming that the reaction is exothermic,
I would add the higher b.p. liquid to the lower b.p. liquid,
as vice versa would be more likely to cause the lower b.p. liquid to boil.
CAUTION : Hobby Chemist, not Professional or even Amateur
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AJKOER
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Here is a 1940 paper claiming a stable composition in CCl4 at https://link.springer.com/article/10.1007/BF03046545 . However, I believe this has been challenged.
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Per this 2016 reference https://pubs.rsc.org/en/content/articlehtml/2016/sc/c6sc0024... , to quote:
"trisulfur radical anion (S3˙−) 4c gained less attention for their few applications in organic reactions. 4 S3˙− can be easily formed by the
reaction of elemental sulfur with KOH in DMF at room temperature. 5 Although S3˙− species has been known for more than 40 years,5 applications for
the synthesis of organosulfur compounds have been very limited. 6 The development of new reactions involving S3˙− and its further applications are
still great challenges"
So, if there is any path to a Sulfur iodide, I would speculate possibly via its reaction with I2˙- (yet another radical anion), but it will likely
be some time in the future.
[Edited on 23-11-2019 by AJKOER]
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chornedsnorkack
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| Quote: Originally posted by Sulaiman | | Quote: Originally posted by chornedsnorkack |
S2Cl2 is a perfectly well characterized substance that freezes at -80 degrees and boils at +137 degrees without decomposition.
HI is a perfectly well characterized substance that freezes at -51 degrees and boils at -35 degrees without decomposition.
HCl boils at -85 degrees. Its volatility may drive metathesis.
Which conditions would you pick to get sulphur iodide with minimum decomposition? E. g. would you add HI to excess of S2Cl2, or
vice versa?
|
First, realise that I'm guessing here based on no direct knowledge,
... by analogy with 'add acid to water not vice versa',
and assuming that the reaction is exothermic,
I would add the higher b.p. liquid to the lower b.p. liquid,
as vice versa would be more likely to cause the lower b.p. liquid to boil. |
I would not be worried about assuming the reaction is exothermic.
I would rather be worried about reaction being reversible and incomplete.
For that reason, I would prefer adding higher bp sulphur chloride to lower bp hydrogen iodide excess - that reaction should go to completion.
Unreacted excess HI can easily be distilled off at -35, but unreacted sulphur chloride is harder to separate from sulphur iodide without decomposition
of sulphur iodide.
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fusso
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I wonder if finkelstein works on S—Cl?
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chornedsnorkack
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NaI for metathesis and acetone for solvent? But separation from products may get difficult. NaI is not volatile, and acetone boils at +56 Celsius.
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AJKOER
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I would start by working with the 1940 process (I cited above) and potentially improve upon it by working with naturally occurring charged
nano-particles centered at 100 nm (see general discussion at https://www.sciencedirect.com/topics/engineering/particle-su... ). This may involve, as is known in the art, using a surfactant additive, for
example.
My guess is that Sulfur and Iodine nano-particles of opposite charge will attract each other and possibly further create an unstable S2I2 product to
some degree. The use of light as a starting catalyst may be of assistance.
[Edited on 12-12-2019 by AJKOER]
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chornedsnorkack
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In 1940 process, note that CCl4 freezes at -23 degrees and boils at +77. My first suggestion was improve the process by choosing a
different solvent, one of lower melting and boiling point. One I proposed was a reagent, liquid HI that boils at -35 degrees, but there are other
options.
| Quote: Originally posted by AJKOER | by working with naturally occurring charged nano-particles centered at 100 nm (see general discussion at https://www.sciencedirect.com/topics/engineering/particle-su... ). This may involve, as is known in the art, using a surfactant additive, for
example.
My guess is that Sulfur and Iodine nano-particles of opposite charge will attract each other and possibly further create an unstable S2I2 product to
some degree. The use of light as a starting catalyst may be of assistance.
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My guess is that S2I2 is endothermic towards decomposition to S8 and I2, and therefore catalysis would
just promote decay of S2I2. Instead, the approach should be to not create good conditions for the unwanted reactions of sulphur
iodide decay, while promoting sulphur iodide formation.
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