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IndoleAmine
Dreamreader Deluxe
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| Joined: 09 Feb 2005 |
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18717.10 Points
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Thu Apr 21, 2005 1:10 pm |
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use H2SO4 instead of HCl for having less water for the bromine to dissolve into (water should be excluded as bromine is soluble in it and it is formed in the rxn; see below), and then extract the bromine with DCM instead distilling it.
No stink, good lungs...
And about ratios:
| Quote: |
Example 2:
Same as above, except that 30% H2O2 is used instead of KBrO3. The molar ratio of KBr : H2O2 must consequently be different, that is 2 : 1.
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According to the following equation at least:
2 KBr + H2O2 + H2SO4 ---> Br2 + K2SO4 + 2 H2O |
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anime
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| Joined: 13 Apr 2005 |
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3517.62 Points
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Tue Apr 26, 2005 12:30 am |
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| stratosphere wrote: |
i usually used 1 equiv of HCl, and then distill off the Br2.
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Adding HCl with the H2O2 should oxidize the Cl- and creates Cl2 gas. A chlorinated product may also be formed. Another reason that the H2SO4 should be used. |
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IndoleAmine
Dreamreader Deluxe
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18717.10 Points
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Wed May 04, 2005 12:39 am |
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Good point, although I don't think that elemental chlorine traces in a saturated bromine solution could do any ring chlorination.
Other topic: Does anyone know if 2,5-dimethoxyphenthylamine can also be brominated while in sulfate form?
I don't know, and would guess probably not, but just to be sure.. 
i_a |
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Sandmeyer
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| Joined: 25 Mar 2005 |
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203.32 Points
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Wed May 04, 2005 1:34 am |
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| anime wrote: |
Adding HCl with the H2O2 should oxidize the Cl- and creates Cl2 gas.
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While true that Eo for H2O2 > Eo for Cl2, in practice I never observed any Cl2 evolution, though it worked for Br-, and I- giving Br2 and I2 resp |
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Nicodem
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| Joined: 22 Feb 2005 |
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2584.86 Points
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Wed May 04, 2005 3:21 pm |
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| Quote: |
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Other topic: Does anyone know if 2,5-dimethoxyphenthylamine can also be brominated while in sulfate form?
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PEA salts can be brominated just as the freebases (actually acetates since we are talking about solutions in acetic acid). Hence, it is only a question of sulubility in AcOH. The hydrochloride of the compound I used to test this on was quite soluble in AcOH (but was not 2C-H). I would expect sulphates to be less soluble in acetic acid though.
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While true that E o for H2O2 > E o for Cl2, in practice I never observed any Cl2 evolution, though it worked for Br-, and I- giving Br2 and I2 resp
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Actually H2 O2 can more or less efficiently oxidaze HCl in Cl2 in the presence of Mn cations in catalitic quantities. Thats how I sometimes used to prepare Cl2 . By dripping 30% H2 O2 in conc. HCl where a small quantity of KMnO4 was added. Not an efficient method at all, but at least peroxyde and muriatic acid are cheap and OTC where I live.
Anyway, regarding HCl as acid in the bromine preparation, there is no risk of forming BrCl or Cl2 since their oxidation potential is higher than Br2 and untill there is some Br- present there is no chance of its formation (especially not in water solution). |
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IndoleAmine
Dreamreader Deluxe
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| Joined: 09 Feb 2005 |
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18717.10 Points
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Wed May 04, 2005 4:26 pm |
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"there is no risk of forming BrCl or Cl2 since their oxidation potential is higher than Br2" - but if you use too much H2O2/HCl (or too little KBr) there is a risk..
One more reason to stick to exact ratios.
2 KBr + H2O2 + 2 HCl ---> Br2 + 2 KCl + 2 H2O
(the ratio KBr/HCl/H2O2 must be 2:2:1 molar!!)
Since I don't think (2C-H)2.H2SO4 is soluble in anything else than H2O  , what about the hydrochloride's solubility in plain DCM - anyone familiar with it? Or is the acetic acid essential to the bromination reaction for any reason? GAA doesn't appeal to me as solvent, thats why I'm asking..
Could one for example also brominate 2C-H base dissolved in DCM with Br2/DCM soln. - or is it essential to have just ANY salt form of the PEA, and one would need to use the carbonate/acetate/hydrochloride in DCM?
thx
i_a |
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IndoleAmine
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18717.10 Points
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Fri May 06, 2005 12:48 am |
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-g-
Last edited by IndoleAmine on Mon May 30, 2005 4:58 pm; edited 1 time in total |
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icecool
Insistent Chemist
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| Joined: 16 Feb 2005 |
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8466.84 Points
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Wed May 11, 2005 3:15 am |
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| IndoleAmine wrote: |
The HBr is obviously not very soluble in DCM.. 
(for brominating 033.871 mmol of a certain phenethylamine acetate dissolved in a little DCM, continuous extraction of the bromine creating mixture over 1 1/2 hours was necessary  , using at least 400ml DCM instead of the expected <200ml...)
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What do you mean by the continous extraction?
Your idea seems good, exept for the frozen Br.
You would need dry ice and acetone for that...which is not that OTC. |
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icecool
Insistent Chemist
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8466.84 Points
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Wed May 11, 2005 3:16 am |
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| IndoleAmine wrote: |
The HBr is obviously not very soluble in DCM..
(for brominating 033.871 mmol of a certain phenethylamine acetate dissolved in a little DCM, continuous extraction of the bromine creating mixture over 1 1/2 hours was necessary , using at least 400ml DCM instead of the expected <200ml...)
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What do you mean by the continous extraction? |
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IndoleAmine
Dreamreader Deluxe
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18717.10 Points
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: Bromine help
Wed May 11, 2005 3:52 am |
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-g-
Last edited by IndoleAmine on Mon May 30, 2005 4:58 pm; edited 2 times in total |
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Sandmeyer
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| Joined: 25 Mar 2005 |
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203.32 Points
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IndoleAmine
Dreamreader Deluxe
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18717.10 Points
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: Bromine help
Wed May 11, 2005 6:13 pm |
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SANDMEYER:
Nicodems post is about brominating amounts of 2.5mmol (!), come back when you have successfully accomplished bromination of larger amounts with this variation, then we maybe can discuss this topic, but unless you've done so, you should keep in mind that:
1) You have no right to decide for others whats garbage and what not
2) You apparently have no experience whatsoever with brominating larger amounts of phenethylamines in DCM, else you wouldn't redirect to nicodem's post for brominating >30mmol amounts..
3) therefore: please shut up, unless you have anything useful to add..
The information content of your post approximates zero and contains only the remark that my preceeding post(s) were/are garbage, along with a link to a already mentioned and discussed procedure (which I already tried btw- its good for small amounts of substrate only) - such behaviour really doesn't help anyone and further is insultive, subjective and also your rantings are simply not true (sorry)..
What do you wanna accomplish with posts like this, besides bringing bad mood? |
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icecool
Insistent Chemist
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8466.84 Points
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re: Bromine help
Wed May 11, 2005 7:20 pm |
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Sandmeyer before I ask questions I read the whole topic.
Like I did this time too, and I think indole amine did a good job, by doing this reaction and posting his results with this procedure.
I just had a question about it.
Anyway if you would have added more DCM at once insted of too little.
And also dry IIRC your DCM wasn't dry.
You would get crystals too immediatelly without an acid base extraction or am I getting this wrong?
It isn't that big of a problem for SWIM to do an acid base extraction but do you mean with Me2CO acetone?
And if I get it right your 2C-B.HCl fell out as an oil because there wasn't enough DCM present? |
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loki
guinea pig
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| Joined: 09 Mar 2005 |
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14167.88 Points
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re: Bromine help
Wed May 11, 2005 7:37 pm |
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| wouldn't plain old lye solution remove the stain too? works perfectly for iodine stains at least... oh that's right i keep forgetting how flighty iodine is... |
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IndoleAmine
Dreamreader Deluxe
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| Posts: 681 |
| Location: Bahamas |
18717.10 Points
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: Bromine help
Wed May 11, 2005 8:05 pm |
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-g-
Last edited by IndoleAmine on Mon May 30, 2005 4:58 pm; edited 1 time in total |
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