clearly_not_atara
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Finally, OTC dihalomethane (dibromomethane)
The ban on DCM sent everyone reeling, but worst hit were those using it as a reagent. OrgSyn famously uses sodium arsenite to reduce the haloforms,
but arsenic is not a nice thing to work with nor is it easily acquired.
Now, surprisingly, the whole prep is found in a public abstract.
https://onlinelibrary.wiley.com/doi/abs/10.1002/047084289X.r...
| Quote: | Preparative Methods: to a stirred suspension of sym-trithiane (0.73 mol) in water was added Br2 (7.1 mol) dropwise to maintain a reaction temperature
of 35–40 °C. Cooling by ice bath may be required. After the addition of Br2 is complete, the reaction is stirred for an additional 15 min. The
product is extracted into CH2Cl2, washed with 5% sodium bisulfite solution, and dried. Concentration and distillation yields bromomethanesulfonyl
bromide in 42–48% yield as a pale yellow liquid.1, 2
Handling, Storage, and Precautions: reactive sulfonylating agent: avoid contact with skin and mucous membranes. Stable at 25 °C for at least 2
weeks. Decomposes forming CH2Br2 and SO2. Use in a fume hood. |
S-trithiane is produced readily by the rxn of formaldehyde with H2S as expected.
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Keras
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What ban?
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bnull
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What about this bit
| Quote: | | The product is extracted into CH2Cl2 |
You still need DCM for that, right?
Edit: @Keras, DCM was banned in the US last year.
[Edited on 30-9-2025 by bnull]
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clearly_not_atara
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Quote: Originally posted by bnull  | What about this bit
| Quote: | | The product is extracted into CH2Cl2 |
You still need DCM for that, right?
Edit: @Keras, DCM was banned in the US last year. |
I think this is a case where chloroform or DCE would be acceptable. I am pretty sure that bromine does not oxidize chloroform. For this product you
definitely want a heavier-than-water solvent.
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chempyre235
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Not exactly a full ban, just eliminated from OTC sources like paint stripper and brake cleaner. There are still several uses the EPA has recognized
its continued use under this ban.
| Quote: |
Uses that will continue under the Workplace Chemical Protection Program are highly industrialized and important to national security and the economy.
These are uses for which EPA received data and other information that shows workplace safety measures to fully address the unreasonable risk could be
achieved. These uses include:
Use in the production of other chemicals, including refrigerant chemicals that are important in efforts to phase down climate-damaging
hydrofluorocarbons under the bipartisan American Innovation and Manufacturing Act.
Production of battery separators for electric vehicles.
Use as a processing aid in a closed system.
Use as a laboratory chemical.
Use in plastic and rubber manufacturing, including polycarbonate production.
Use in solvent welding.
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Even under this ruling, DCM is still available for the lab from several online suppliers. Still, this synthesis is interesting. Is the trithiane
necessary, or can DCM be produced from other formaldehyde sources, like trioxane, or POM resin?
https://www.epa.gov/newsreleases/biden-harris-administration...
[Edited on 9/30/2025 by chempyre235]
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
"I weep at the sight of flaming acetic anhydride." -@Madscientist
"...the elements shall melt with fervent heat..." -2 Peter 3:10
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Deathunter88
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| Quote: Originally posted by chempyre235 |
Not exactly a full ban, just eliminated from OTC sources like paint stripper and brake cleaner. There are still several uses the EPA has recognized
its continued use under this ban.
| Quote: |
Uses that will continue under the Workplace Chemical Protection Program are highly industrialized and important to national security and the economy.
These are uses for which EPA received data and other information that shows workplace safety measures to fully address the unreasonable risk could be
achieved. These uses include:
Use in the production of other chemicals, including refrigerant chemicals that are important in efforts to phase down climate-damaging
hydrofluorocarbons under the bipartisan American Innovation and Manufacturing Act.
Production of battery separators for electric vehicles.
Use as a processing aid in a closed system.
Use as a laboratory chemical.
Use in plastic and rubber manufacturing, including polycarbonate production.
Use in solvent welding.
|
Even under this ruling, DCM is still available for the lab from several online suppliers. Still, this synthesis is interesting. Is the trithiane
necessary, or can DCM be produced from other formaldehyde sources, like trioxane, or POM resin?
https://www.epa.gov/newsreleases/biden-harris-administration...
[Edited on 9/30/2025 by chempyre235] |
Technically, yes, it's not a full ban. Practically speaking, it might as well be. I work in a research lab at a T20 university and the EHS department
has told everyone to stop using it except for the most critical of experiments, and the bar to satisfy their judgement of what "critical" means is
very high.
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clearly_not_atara
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^yeah I've just seen people treating it like DCM is gone, apparently there are a few sources but it's harder to get and that means it can also be an
"interesting" purchase which nobody wants
Trithiane is apparently produced in the reaction of aqueous
formaldehyde with thiosulfate in the presence of acid, which sounds an awful lot nicer than the hydrogen sulfide method described on Orgsyn. See:
https://www.tandfonline.com/doi/abs/10.1080/0308664850807336...
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Keras
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Oh well then it might be time to stock it over here in Europe, lest the EU follow suit. :/
[EDIT: Seriously, are there cases where chloroform cannot be used as a substitute to DCM when acting as solvent?]
[Edited on 1-10-2025 by Keras]
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Texium
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| Quote: Originally posted by Keras | | [EDIT: Seriously, are there cases where chloroform cannot be used as a substitute to DCM when acting as solvent?] |
Yes. Any reaction that is run under even moderately basic conditions. Chloroform’s pKa is 15.7 which means even hydroxide can
deprotonate it. The resulting anion ejects chloride to form dichlorocarbene, which you generally don’t want in your reaction unless you’re making
a dichlorocyclopropane or something.
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bariumbromate
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buy it from this seller https://ozcanium.com/products/dichloromethane he ships to the usa
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Keras
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| Quote: Originally posted by Texium | | Quote: Originally posted by Keras | | [EDIT: Seriously, are there cases where chloroform cannot be used as a substitute to DCM when acting as solvent?] |
Yes. Any reaction that is run under even moderately basic conditions. Chloroform’s pKa is 15.7 which means even hydroxide can
deprotonate it. […] |
Fair enough. I hadn't in mind the acidic property of the hydrogen atom. That makes me think I ought to try the synthesis of salicylaldehyde this way
again. It’s a nice reaction.
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Fery
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I tried that and got just pure sulfur. Maybe I did something wrong (temperature/ratio/???). Na2S2O3 + 2 HCl -> 2 NaCl + S + SO2 + H2O.
https://www.sciencemadness.org/whisper/viewthread.php?tid=11...
In the article you posted they used very cold solutions at -25 C and then warmed to 42 C. I did the mixing of reagent at room temperature and the
reaction at 85 C. I used slight 5% excess of Na2S2O3, in the article they wrote not to use any excess
https://sci-hub.se/10.1080/03086648508073367
Attachment: meyer1985.pdf (463kB)
This file has been downloaded 60 times
I synthesized trithiane via H2S route here:
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
The problem was that the most of H2S just did not react and escaped. You should generate large amounts of H2S cheaper by heating S + paraffin
(wax/oil). Another problem trithiane is insoluble in aqeuous environment and the delivery tube clogs (you should use wide tube), impossible to
increase efficiency of gas dissolution and reaction by decreasing bubbles size by using a capillary or even sintered bubbler (they would clog very
quickly).
[Edited on 3-10-2025 by Fery]
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