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The Hive => Chemistry Discourse => Topic started by: ning on June 06, 2004, 05:28:00 AM

Title: I think the main idea
Post by: ning on June 06, 2004, 05:28:00 AM: is that it has to be bromine-proof.

One might imagine that since dioxane dibromide is being added, dioxane might be a good solvent to use.

Solubility should be checked. I imagine solvent is not terribly critical.

One would probably do well to choose solvents that can be separated by distillation, since the dioxane is probably homemade. Ether, perhaps? Also, various alkanes like petroleum ether might work, and chloroform would probably also (bp 62).
Title: would dcm be a suitable substitute?
Post by: Bond_DoubleBond on June 06, 2004, 09:46:00 AM: would dcm be a suitable substitute? also, would dcm or chloroform be suitable for an elemental bromine addition to get the bromoketone?
Title: posts with bromine and dcm Post 473493 Post...
Post by: Bond_DoubleBond on June 06, 2004, 10:05:00 AM: posts with bromine and dcm

Post 473493 (https://www.thevespiary.org/talk/index.php?topic=8892.msg47349300#msg47349300)
(Chromic: "Some more questions", Methods Discourse)
Post 442423 (https://www.thevespiary.org/talk/index.php?topic=12542.msg44242300#msg44242300)
(senzualus: "bromination", Serious Chemistry)
Post 434934 (https://www.thevespiary.org/talk/index.php?topic=6898.msg43493400#msg43493400)
(Barium: "Bromination difficulties", Chemistry Discourse)
Post 209004 (missing)
(Osmium: "Re: Liquid Bromine production", Chemistry Discourse)
...many more

the second says that br2 reacts with dcm, but the third states that it works fine.
Title: Bromine does not react with chloroform.
Post by: _mu_ on June 06, 2004, 02:32:00 PM: Bromine does not react with dcm/chloroform.
Title: Alternative bromination solvents
Post by: Kinetic on June 06, 2004, 03:17:00 PM: Bromination of ketones can be carried out in a wide range of solvents; glacial acetic acid is often a solvent of choice, as is DCM. Chloroform, carbon tetrachloride, ethers, alcohols and alkanes (e.g. hexane) can all be used, and I'd only really recommend against using acetone...

The above solvents all work with varying degrees of success depending on the substrate. When brominating propiophenones, DCM is my favourite solvent, as the reaction is over in minutes in almost quantitative yield, and the workup is simple.

If I were you I'd try it in DCM. You may even be able to add the methylamine in the next step without removing the solvent and replacing it with benzene. DCM is a good solvent for the SN₂ swap with methylamine for the bromine of alpha-bromoketones.¹

There is an appreciable difference between the bromination of propiophenones (which my advice is based upon) and that of (O-chlorophenyl)-cyclopentylketone, which is the substrate you're looking to brominate. There may be something which makes DCM unsuitable (solubility, or greatly differing reactivity in different solvents), but it's probably the best bet if you don't want to use CCl₄.

1 For example, see the second step of
Post 475219 (https://www.thevespiary.org/talk/index.php?topic=12065.msg47521900#msg47521900)
(Kinetic: "Benzene -> methaephetamine", Novel Discourse)
Also related:
Post 479479 (missing)
(Kinetic: "Solvent", Newbee Forum)
Title: what the hell is dioxane dibromide
Post by: Sangreal on August 17, 2004, 07:06:00 AM: I actually have problems with all of step 9 of zealot's synth:

9. alpha-Bromo-(o-chlorophenyl)-cyclopentyl ketone

40g ketone is dissolved in 70mls CCl4 and with cooling in snow it is added into a soln of 48g dioxane dibromide in 50mls dioxane, and stirred at RT for 30mins. Then 30mls water are added and the soln is washed with Na2CO3 aq. until neutral. This may lead to some preciptation of the bromoketone, which stays in CCl4. The solvent is removed, giving 47g (85%) of the bromoketone.

Ok, what is dioxane dibromide. Could one just simply add bromine like it mentions in the patent? I believe this may be a mistake in the translation? I tried to search for it on chemfinder.com and could not locate any compound like dioxane dibromide.

I guess my question is, What the hell is dioxane dibromide.
Title: what the hell is dioxane dibromide?
Post by: bbeeasheets on August 17, 2004, 07:43:00 AM: supposedly it makes the bromination step much nicer, than just using br2.
Title: UTFSE
Post by: moo on August 17, 2004, 10:00:00 AM: UTFSE
Title: I have no idea so i plugged it into ...
Post by: ApprenticeCook on August 17, 2004, 03:26:00 PM: I have no idea so i plugged it into chemdraw... this is what it came out with...
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000511502-untitled.jpeg)
As for dibromide.... well it would have to have the number markers.... which isomer? or does it matter?

Right?
-AC
Title: you need to search
Post by: yei on August 17, 2004, 03:41:00 PM: dioxane dibromide, AFAIK is some sort of coordination compound between bromine and dioxane. It is handy because IIRC it is a crystalline solid, and as such is a very handy way to purify and store bromine.

Br2 <- O(Et2)O -> Br2

I think something like this. Each ether function donates electrons to the bromines. Or...the other way around? In any case, the dioxane grips the bromines and hold onto them, and that is why it's used. Very likely one wouldn't need to use dioxane dibromide at all, if one were equipped to handle liquid bromine and had some lying around. Who knows?

Anyhow, all I know about this I learned here, so go searching with TFSE. You will find what you want to know.
Title: dioxane
Post by: bbeeasheets on August 26, 2004, 10:33:00 AM: ok i have synthed dioxane, but have yet to remove the water. since all my other reagants and solvents are lab grade for the ketamine synth, i don't think i want to use the dioxane i made in the first trial. i found dioxane with a froogle search, and the one i wan't to order is 1,4-Dioxane, stabilized 99+% (2.5l). what could it possibly be stabilized with and would the stabilizer affect the reaction ie: (9. alpha-Bromo-(o-chlorophenyl)-cyclopentyl ketone

40g ketone is dissolved in 70mls CCl4 and with cooling in snow it is added into a soln of 48g dioxane dibromide in 50mls dioxane, and stirred at RT for 30mins. Then 30mls water are added and the soln is washed with Na2CO3 aq. until neutral. This may lead to some preciptation of the bromoketone, which stays in CCl4. The solvent is removed, giving 47g (85%) of the bromoketone.) i know i will have to brominate the dioxane, but since it is a bromination step and i have elemental bromine, that doesnt worry me.
Title: apology
Post by: bbeeasheets on August 26, 2004, 01:10:00 PM: i believe i posted this in the wrong forum, so could someone please move this to the chemical and equiptment forum and accept my apology please.
Title: actually, I guess it should be in ...
Post by: yei on August 26, 2004, 10:02:00 PM: actually, I guess it should be in "methods"

try salting that dioxane.

I don't know how watched dioxane is, but good for you to try and replicate scrupulously the experimental conditions.
I doubt the stabilizer will cause much trouble. It will probably be something to prevent peroxide formation. There won't be much. You could always redistill to remove it.
Title: Synthesis of 1,4-Dioxane Dibromide
Post by: Rhodium on August 31, 2004, 12:17:00 PM: Post 255319 (https://www.thevespiary.org/talk/index.php?topic=7334.msg25531900#msg25531900)
(PrimoPyro: "Re: Dioxane dibromide", Chemistry Discourse)