08-23-02 10:54
No 348051
Recently Rhodium posted about para Clorinations with NaCl and Oxone i believe. Will oxone Convert NaBr into Br2 or is it nescesary to first produce HBr Like with an I2 extraction with HCl/H2O2.. would it be wise to try a 2 phase bromination by dissolving 2CH freebase in DCM and addin (aq) Oxone to an (Aq) solution of NaBr??? or even better collect Br2 In DCm wash with Bicarb the combine with 2CH.???
So much game I could sell a hooker some pussy
Vl_
(Synaptic Self-Mutilator)
08-23-02 16:09
No 348105
The best way to brominate aromatic rings with KBr (or an equivilant of NaBr) as the source is via a reference that Osmium gave to brominate vanillin. What are you planning to brominate?
Here's the general idea:
Prepare 120ml of GAA, 40ml H2O, 11.8g H2SO4 (120mmol), 14.3g KBr (120mmol) and 5.8g 35% H2O2 (60mmol) in a container. Stir and watch as the solution turns orange-red as the bromine is formed, and it starts to smell like bleach.
Dissolve 100mmol of freebase (or hydrochloride, shouldn't matter either way) into 50ml GAA in a flask. Cool this in an icebath. Then drip in the Br2 solution from the container. Once this is done, slowly drip in 5.8g 35% H2O2 (60mmol). Basify the whole thing, extract and work up as usual.
The overall reaction goes as follows:
A + H2O2 + KBr + H+ ==> Br-A + 2 H2O + K+
Of course, there's a few separate reactions going on:
in the container:
1) H2O2 + 2 KBr + H+ ==> Br2 + H2O + K+
in the flask:
2) A + Br2 ==> Br-A + Br-
3) H2O2 + 2 Br- + H+ ==> Br2 + H2O (then back to rxn 2 with the Br2, until most all the Br- is used up)
I've done this on PMA, and I'm unsure if it works exactly as stated as the Br-PMA seemed to have pretty much the same effect as the starting material, so caveat emptor.
(Hive Addict)
08-23-02 22:42
No 348212
2CH
So much game I could sell a hooker some pussy
Vl_
(Synaptic Self-Mutilator)
08-23-02 23:55
No 348221
Yeah, I read that.
The above procedure is for 100mmol of aromatic you want to brominate. DMMDA-2, PMA, MDA, 2C-H, vanillin, whatever... it will work for any of it, and making bromine in situ is a blessing compared to handling liquid bromine.
Good luck!
(Newbee)
08-24-02 02:20
No 348265
(Rated as: excellent)
Recently Rhodium posted about para Clorinations with NaCl and Oxone i believe. Will oxone Convert NaBr into Br2 or is it nescesary to first produce HBr Like with an I2 extraction with HCl/H2O2.. would it be wise to try a 2 phase bromination by dissolving 2CH freebase in DCM and addin (aq) Oxone to an (Aq) solution of NaBr??? or even better collect Br2 In DCm wash with Bicarb the combine with 2CH.???
SYNTHETIC COMMUNICATIONS
Vol.32,No.15,pp.2313 –2318,2002
AN EFFICIENT AND REGIOSELECTIVE
OXYBROMINATION OF AROMATIC
COMPOUNDS USING POTASSIUM
BROMIDE AND OXONE
General Procedure for the Bromination of Aromatic Compounds:
Oxone (2.2 mmol) was added to a well stirred solution of KBr
(2.2 mmol) and substrate (2.0 mmol) in methanol (10 mL) and the reaction
mixture was allowed to stir at room temperature. The reaction was
monitored by thin layer chromatography (TLC).After the completion of
the reaction.The mixture was filtered and solvent evaporated under reduced
pressure.The products were puri fied by column chromatography over silica
gel and confirmed by HNMR and Mass spectra.
Parasubsts are dominating and generally > 70 %
//Tyrone Slothrop
(Stranger)
08-24-02 03:26
No 348284
This is the greatest thing since sliced bread
(Synaptic Self-Mutilator)
08-24-02 03:39
No 348289
Why is oxone better than H2O2/H2SO4? But... if the above reference is correct, there's no need for brominations to be done in acetic acid, and methanol will suffice. (that's good news!)
Any opinions?
(Hive Addict)
08-24-02 11:05
No 348444
I bet this will also work with KCl And KI too. We will call this the easy analog maker.
VL_
So much game I could sell a hooker some pussy
Vl_
(Hive Bee)
08-26-02 14:27
No 349161
It cill work for KCl, but not for KI.
H2SO4 can not form HI when reacting with KI, but will form HCl when reacted with NaCl. H2O2 will produce free I2 from HI and free Cl2 from HCl, but getting to HI from NaI or KI is the problem.
Rather use NIS for your Iodinations, elemental I2 will not work anyway.
(Stoni's sexual toy)
08-26-02 18:26
No 349216
> H2SO4 can not form HI when reacting with KI
It should work as long as the concentrations aren't too high.
I'm not fat just horizontally disproportionate.
(Hive Bee)
08-26-02 20:15
No 349237
What has HI got to do with the subject? Isn't the H2SO4 supposed to catalyze the oxidation (H2O2 + 2H+ + 2e- --> 2H2O)? Furthermore, there are many examples of I2 + oxidising agent aromatic iodinations, including H2O2, peracetic acid, HNO3 and its salts, NO2 and KMnO4. (Goddamn, if there were no subscript tags it would take a lot less time to write a post!
)
(Stranger)
08-27-02 01:35
No 349326
../rhodium /doisynt
(Moderator)
08-31-02 23:55
No 351083
I bet this will also work with KCl And KI too. We will call this the easy analog maker.
Since the following paper the paper cited by slothrop by the Narender group is on iodination using KI and oxone, you are definitely correct
(Chief Bee)
09-03-02 00:37
No 351978
And here it is: ../rhodium /oxone.a
(Chief Bee)
10-05-04 03:52
No 534473
(Rated as: good read)
Mild and regioselective oxidative bromination of aromatic compounds using ammonium bromide and oxone
N. Narender, K.V.V. Krishna Mohan, S.J. Kulkarni and K.V. Raghavan
J. Chem. Research (S), 597-598 (2003) (../rhodium/pdf /aromatic.bro
Abstract
The selective mono-bromination of various activated aromatic compounds is reported using in situ generated bromine from NH4Br as a bromine source and oxone as an oxidant for the first time.
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