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Author: Subject: HVZ bromination with S instead of P?
clearly_not_atara
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[*] posted on 15-9-2019 at 12:24
HVZ bromination with S instead of P?


It’s well-known that S + Br2 converts many acids to their anhydrides. The rxn byproduct HBr can react again to convert anhydrides to acyl bromides which are enolizable. Overall, this resembles the HVZ reaction:

http://en.wikipedia.org/wiki/Hell-Volhard-Zelinsky_halogenat...

S is much more available than P which is the usual catalyst for this reaction (forming PBr3 in situ). P has the practical advantage of not producing SO2 efflux, but S is much cheaper in practice. So is this a possible poor man’s HVZ?

Another possibility: could succinic or phthalic anhydrides be used?

[Edited on 15-9-2019 by clearly_not_atara]

[Edited on 15-9-2019 by clearly_not_atara]




[Edited on 04-20-1969 by clearly_not_atara]
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Pumukli
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[*] posted on 16-9-2019 at 09:40


I heard about S for chlorinating acetic acid but never got to the experimental phase. :-)
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DavidJR
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[*] posted on 16-9-2019 at 09:48


No idea but I bet if you use sulphur it will absolutely stink...
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12thealchemist
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[*] posted on 17-9-2019 at 06:20


Quote: Originally posted by DavidJR  
No idea but I bet if you use sulphur it will absolutely stink...


You wouldn't suffer from organosulphur byproducts unless a very unlikely reaction mechanism took place - at no point is a P-C bond formed in the mechanism, so no S-C bond would form. You would have to watch out for sulphur oxides though




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Loptr
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[*] posted on 17-9-2019 at 06:24


Quote: Originally posted by 12thealchemist  
Quote: Originally posted by DavidJR  
No idea but I bet if you use sulphur it will absolutely stink...


You wouldn't suffer from organosulphur byproducts unless a very unlikely reaction mechanism took place - at no point is a P-C bond formed in the mechanism, so no S-C bond would form. You would have to watch out for sulphur oxides though


I believe the thought is that H2S would be formed during the course of the reactions and also most likely during any quench with water. That is pretty smelly.

[Edited on 17-9-2019 by Loptr]




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