Bromine handling?

transistor child · gnome

Never had any first hand experience with bromine, and is curious on exactly how dangerous it is. Safety data doesn't look good, but a lot of those things are often exagurated. How bad are the vapors, and is it impossible to handle in a small lab without real fumehoods? Does bromine dissolved in GAA fume a lot? How fast does frozen bromine thaw in roomtemp? Smile

Maybe a good solution is producing bromine by KBR/etc and leading it directly into GAA, is this a viable route for lets say 10g bromine?

I appreciate any information you can give me. Many thanks.

Vitriodor · Sun Jun 19, 2005 6:39 am

Bromine is not a very nice gas to work with but with some precautions it can be handled safely. Don´t forget that it vaporizes rapidly so so keep the temperature as low as possible, and be aware that bromine is much heavier than air, it will collect at the bottom of your "fume"hood.

PROCEDURE
Preparation of the source of free bromine
Dissolve 1 gram of potassium bromide, KBr, in 10 mL of water.
Add 5 drops HCl (28% muriatic acid) and then add liquid bleach dropwise until no further color change occurs This brown liquid will be the source of free bromine.

DISCUSSION
Free chlorine is formed by the reaction between the hypochlorite ion from the bleach and the hydrochloric acid. The released chlorine oxidizes the bromide ion in solution to free bromine.
ClO-(aq) + H+(aq) + Cl-(aq) OH-(aq) + Cl2(g)
Cl2(g) + 2 Br-(aq) Br2(aq) + 2Cl-(aq)

http://www.woodrow.org/teachers/ci/1986/exp33.html

stratosphere · Sun Jun 19, 2005 10:19 am

i have managed to work with liquid bromine under less then ideal circumstances without injury or discomfort.
generated it by heating in the following molar proporations: 2mol KBr in eneough water to dissolve it , 1mol H202 (17%) and slowly adding 2mol HCl (30%), there is not significant fuming at room temperture , install condensor and keep reicever on ice bath and heat soltn, preferably with only a small hole on reciever side for pressure equalization, for ventalation the setup was placed by a window with a fan going outward.

even at ice temperatures the stuff fumes pretty good so best to keep it stoppered but if only opened briefly keeping face well away ,wearing rubber gloves and doing so near fan/window is adequate.
im sure dry ice would be even better, probobly get very little fuming.

when Br2 was dissolved in DCM there was no fuming so id assume that the same would be true with GAA.
having the GAA already in the reciever flask might eliminate fumes altogether, of course there would be some water introduced from aquous soltn.
you could always do a small run to insure eveything works and if it doesn't then no big disaster.

transistor child · gnome

Thanks for the help!
Seems as nasty as I thought.
Posionous stuff really scare the shit out of me. Very Happy

Found some interesting old post from the Hive when Vauugh claimed to have brominated 2,4-dimethoxyphenethylamine successfully with NBS with a 70% yield (and he only ran the reaction for half an hour). As it releases bromine and HBr (if I understood it correctly) it should work perfectly, with almost as good yields. It would be great if it was true.

Star-light · Blacklight bulb

Bromine is indeed not pleasant to work with.

But it is perfectly possible without a fume hood if you are careful....:

The following has worked very well:

1. Half face respirator with filters for bromine
2. Goggles
3. Lots of ventilation
4. Cool the bromine and your pipette in the fridge before use.

This resulted in no discomfort at all, and easy working.

You will find that pipetting bromine is difficult due to its density (wants to run out the bottom of the pipette).

Above all be extremely careful not to drop or knock over the bottle or you will have an emergency on your hands. If carrying a bottle of bromine across a hard floor, it is best to put it inside a plastic container with padding, and hold this with both hands, whilst watching where you are going so that you do not trip over something!

You will also want to make sure that you have some damage limitation in place.

Water and soap to wash spills off with.
Sand to contain a spill
Water/hose for use in case of spill
Sodium Thiosulfate / Sodium Bicarbonate to neutralize spills

Bromine is fine to work with, but don't do it without taking precautions.

icecool · Insistent Chemist

If I would do something like this I would put DCM and NaBr (or any other Br salt) and IIRC also a drop of H2SO4 have all in a seperatory funnel and then dropwise add H2O2 30% to this for more information about this have a look at the bromine topic in general chemistry or essential chemistry.
There is good information about this so bromine will dissolve in DCM and you can add the standard solution of DCM+Br to the phenetylamine.

PolyAlchemia · Tue Jun 21, 2005 10:10 pm

A glance at a MSDS (material saftey data sheet) for bromine might also be usefull for evaluating the handeling concerns. google bromine msds.

Star-light · Blacklight bulb

icecool · Insistent Chemist

Example 1:
In a 50ml addition funnel there was added 4ml methylenechloride, 15ml water, 8ml of 35% sulphuric acid and 1.2g of KBr (9.5mmol). When the solid dissolved and the mixture cooled to the room temperature I slowly added 1.07g of KBrO3 (1.9mmol) in 10ml of warm water. The precipitated bromine was extracted in the lower organic phase by shaking. This dark red Br2/DCM phase was then added to the reaction mixture containing 4.95mmol of a certain methoxyamphetamine hydrochloride in acetic acid. This must be done carefully in order to stop the addition before the upper water phase comes into the reaction mixture. Then a further 3ml of DCM was added, the funnel shaken and the addition repeated. A third 2ml DCM portion might be needed if you want to fully extract the Br2 from the water phase, but not really necessary. The yield of the product was 84%.

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.

Example 3, 4..:
Instead of KBr, you can of course also use NaBr, NH4Br, CaBr2 etc.

_________________________________
edit
Additional information:

Other suitable oxidants are KMnO4, MnO2, (NH4)2SO5 and NaBO3×4H2O just to name a few OTC ones. I never used any other than KBrO3 or H2O2 though, but this was only a matter of convenience, not because it would only work with these others. Don’t forget to change the molar ratio appropriately to the relevant redox equation though. The ratio must always be exactly the one you need to oxidize the bromide into bromine. Not enough will result in excess of bromide therefore some bromine will remain in the water phase (Br2 is soluble in KBr solution as it forms the KBr3 complex). Too much oxidant will result in some bromine getting oxidized into hypobromous acid or higher oxo-acids (HBrO, HBrO3). If this is taken strictly into account then you can suppose an almost quantitative formation of Br2 (I usually calculate for a 5 to 10% excess of Br2 in relation to the PEA×HCl being brominated, just to make sure there is enough of it even if the extraction is not quantitative).
Also there is no need whatsoever to make the freebase of the PEA substrate as it is described in PiHKAL and on the Rhodium’s pages. The bromination works just as good on hydrochlorides themselves, except that just slightly more solvent might be necessary to fully dissolve the salt. The difference is also in the work-up as you need to strip off the acetic acid solvent and do an acid-base extraction instead of filtering the less soluble hydrobromides from the acetic acid solution. The good thing is that the yields are good, and that you get a purer product at the end due to the acid-base extraction (I make the hydrochlorides at the end).

This above piece of text is the piece that helped me a lot....

bio · Working Bee

..........Bromine is fine to work with, but don't do it without taking precautions........

Here is one I suggest so this doesn't happen to you! Check the bottle closures and wrap tight with teflon tape.

Had a few large bottles of Bromine which came in a heavy wooden crate and the bottles sealed in cans. Curious me just had to "inspect" the goods which came from a major supplier. Extra heavy amber bottles with 28/400 white poly something closures (caps). These aren't the reagant bottle deep threads, like 33/430.

Anyway used a little out of one bottle and put the others away in the outdoor storage shed (good thing). A couple months later went to check on a few things and the bromine bottles were neatly lined up and EMPTY. The precious bromine vapor had eaten the liners and wafted away.

riggie · Sat Jun 25, 2005 7:06 am

I bought brom in germany for about 100 dm a liter, that was in the nineties. It came in sealed Can, containing "glimmer" and a seald plasicwrapped galssbottle.
And yes it is quite nast stuff.
Where I live now, I can get this stuff in glass ampullettas 250 g each, only thin glass, not sealed or wrapped.
This is the thirld world buddy!

Chris The Great · Mon Jun 27, 2005 5:41 am

I've made bromine once before, by bubbling Cl2 gas through a solution of NaBr. As has already been said, ventilation is essential.

However, what hasn't been mentioned is the danger that bromine poses to your skin. If liquid bromine contacts the skin, it will immediatly soak in. Once it has, it will sting and literally burn a hole in your skin. A drop somehow found it's way to my pantleg and then my leg, and left a bright yellow spot. This turned the a brown-yellow colour of rotting flesh half an hour later, and peeled off leaving me with a second degree burn which is still healing 2 weeks later.

Because of this, I would highly recommend wearing rubber gloves when handling bromine.

PSY420 · Fri Jul 01, 2005 5:41 pm

You might all find this old hive topic quite intresting :

https://www.synthetikal.com/hiveboard/chemistrydiscourse/000508433.html

--PSY420--