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Author: Subject: Sulfur and oil reaction
Adas
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[*] posted on 10-3-2013 at 10:52
Sulfur and oil reaction


Hello, it's me again. :P

A while ago, I performed an experiment in which I heated sulfur under sunflower oil. The sulfur melted and colored the oil red-black. Then I cooled it down and poured the oil (very viscous liquid) out, the solid sulfur remained at the bottom of the test tube.

I think that the sulfur made disulfide bonds on double bonds in the oil (like vulcanizing rubber), am I correct?

P.S.: You can imagine the TERRIBLE smell. :D I may do some more experiments with it.




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AndersHoveland
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[*] posted on 10-3-2013 at 12:09


It is also possible that traces of thiols may have been formed.
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platedish29
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[*] posted on 10-3-2013 at 12:32


TRy adding caustic soda to it, you should reverse the process and get the oil clear again.
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Adas
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[*] posted on 10-3-2013 at 12:57


Quote: Originally posted by AndersHoveland  
It is also possible that traces of thiols may have been formed.


I don't think so, or they were thiols with high molecular weight, so they might have smelled different.




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blogfast25
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[*] posted on 10-3-2013 at 13:24


Quote: Originally posted by Adas  

I think that the sulfur made disulfide bonds on double bonds in the oil (like vulcanizing rubber), am I correct?

P.S.: You can imagine the TERRIBLE smell. :D I may do some more experiments with it.


It's possible. Normal vulcanisation reactions do require also accelerators, otherwise the formation of -S- and -S-S- bonds is very slow.




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[*] posted on 10-3-2013 at 13:38


Probably a dealkylation, making dimethyl sulfide or diethyl sulfide gases.



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Adas
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[*] posted on 11-3-2013 at 12:26


Quote: Originally posted by Eddygp  
Probably a dealkylation, making dimethyl sulfide or diethyl sulfide gases.


I would have noticed that! I know roughly how DMS and DES smell, and they would have caused VERY intense smell. The smell I observed was not so intense, probably a small amount of H2S, and maybe some SO2 and something else.

I tried heating that red oil with NaOH, but it didn't seem to get its original color back.

[Edited on 11-3-2013 by Adas]




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[*] posted on 11-3-2013 at 16:24


I suspect there are -S-S-S-S-S- sulfur chains in the oil. I am not sure where the red color is coming from, but it molten sulfur also has a dark red color, and there might be a connection.

Quote: Originally posted by Eddygp  
Probably a dealkylation, making dimethyl sulfide or diethyl sulfide gases.

I doubt that. The hydrogens would come off first before that.
There are hydrocarbon cracking reactions, but those usually only happen at much higher temperatures, which I doubt is the case here.

But even for the hydrogens in alkane groups to be oxidized, that still typically requires combustion temperatures. Unless perhaps the heat is enough to break the weak sulfur-sulfur bonds, which could then act like radicals to attack the alkane. This is the case with chlorine in the presence of light, for example.

I think most likely the unsaturated double bonds in the oil are being oxidized by the sulfur, like Adas originally guessed.

[Edited on 12-3-2013 by AndersHoveland]
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[*] posted on 11-3-2013 at 23:56


Reducing sulfur by heating it with hydrocarbons (like paraffin oil, for example) gives hydrogen sulfide at high enough temperature. Check the literature. This is one of the laboratory methods at producing hydrogen sulfide.
Triglicerides are likely to behave similarly.




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