Sciencemadness Discussion Board - Beautiful! Al + Br2

Beautiful! Al + Br2

Polverone - 10-8-2004 at 16:58

There's a gorgeous picture in one of my chemistry books of a strip of aluminum burning in bromine. Today, I recreated that image in miniature.

I mixed a small quantity of sodium bromide with an excess of phosphoric acid and an ice cube. I added calcium hypochlorite to this mixture while swirling, giving rise to fumes of bromine above the icy mixture and causing the temperature to rise somewhat. I decided that placing the cooling directly in the jar wasn't the best idea I'd ever had, so I then placed the jar in a bowl of ice water.

I noticed that I could see dark droplets collecting at the bottom of the jar. Ah-ha! Bromine!

Putting on protective gloves for the first time in months, I used a disposable plastic pipet to suck a mL or so of bromine from the bottom of the vessel and place it in a pyrex test tube. Upon nervously adding a twist of aluminum foil to the test tube, I observed a vigorous reaction accompanied by occasional sparks and a thick plume of bromine vapor exiting the test tube. I turned the bathroom fan and shower on and exited the room, closing the door and hoping that the metal in the room wouldn't corrode too much more.

I don't know how soluble water is in bromine. Would it be possible to prepare dry bromine from the crude liquid without distilling it?

Bromine is easier to handle than chlorine, since it is more easily tamed by cold, and someone with more courage than money might be able to produce substantial amounts of anhydrous AlBr3 from homebrewed bromine.

[Edited on 8-12-2004 by Polverone]

vulture - 11-8-2004 at 01:00

I've been tempted to perform this reaction too, but my current lack of bromine and time prevents it.

I wonder what Al + I2 will do? I doubt it's spontaneous, but maybe with some heating?

sylla - 11-8-2004 at 02:40

Al/I2 isn't spontaneus but still very easy to ignite.

Just add a drop of water on the mix ; it will first fume (nice I2 vapors) and then ignite with a bright white color

Esplosivo - 11-8-2004 at 02:43

Vulture, I guess you already know but anyway the rxn between Al and I2 can be started by a drop of water and it then continues reacting on its own. Its quite nice really

Both the Al and I2 should be finely ground fo this to work.

vulture - 11-8-2004 at 02:51

Interesting, I still have a sample of german dark Al laying around...

BromicAcid - 11-8-2004 at 03:20

Quote:

I don't know how soluble water is in bromine. Would it be possible to prepare dry bromine from the crude liquid without distilling it?

When doing my bromine research I found that bromine distilled from a mixture has about 2% water that carries over that is not a 'true' azeotrope. From what I remember bromine is easy to dry but I've never needed dry bromine so I've never tried it.

vulture - 11-8-2004 at 03:37

Bromine can be easily dried by shaking with conc. sulfuric acid. If your bromine contains much water cooling will be necessary ofcourse.

Nick F - 11-8-2004 at 04:20

Is there anything wrong with simply adding crushed fused sodium sulphate, shaking and filtering (using a glass fibre filter)?

vulture - 11-8-2004 at 04:23

That'll work too, but with sulfuric acid you have a much more intimate contact since it's a fluid too. You'll have trouble to get out all the water in one pass with the sodium sulphate or any other solid drying agent (with the exception of P4O10 perhaps).

How about phosphoric acid?

Hang-Man - 11-8-2004 at 06:42

Quote:

I wonder what Al + I2 will do

I wonder what Al + HIO3 will do. Iodic acid is a very powerfull oxidizer if I remember corectly.

German Dark

MadHatter - 11-8-2004 at 19:32

Vulture, you said you still have some German Dark Al powder. Mixed with
finely powdered iodine, that should make for an interesting "flash" powder.

vulture - 12-8-2004 at 03:53

Very possibly, that's why I'll test smallscale first. My primary concern is to fetch the resulting AlI3, as this can be of extraordinary use.

My main problem is that I don't have a good way of drying my iodine without loosing too much, it's expensive as hell.

[Edited on 12-8-2004 by vulture]

thunderfvck - 12-8-2004 at 12:04

Can AlBr3/AlI3 be used to replace AlCl3?

Esplosivo - 12-8-2004 at 12:35

Quote:

Originally posted by thunderfvck
Can AlBr3/AlI3 be used to replace AlCl3?

In which procedure/reaction? I suppose that AlCl3 possess some different chemical properties when compared to AlBr3 and AlI3.

Hang-Man - 12-8-2004 at 13:02

AlCl3 is used as a deliquescent and as a catylst in cracking oils and other organic reactions, specifically the Friedel-Crafts rxn (acylation of aromatic compounds)

Seing as the latter isn't usefull to many home chemists, I assume he means as a deliquescent.

thunderfvck - 13-8-2004 at 09:40

Actually I was wondering if they could be used to replace AlCl3 in Friedel Crafts akylations.

C6H6 + R-X --AlCl3--> C6H5-R + HX

R=alkyl group
X=halogen

I've also seen it mentioned in other reactions as well, although I can't remember which...Anyways, I was just wondering if I could substitute this with AlBr3/AlI3?

[Edited on 13-8-2004 by thunderfvck]

BromicAcid - 26-3-2005 at 14:55

I did aluminum turnings (which were oxidized on one side) with bromine dried under H2SO4 today and took pictures every 10 seconds or so, attached is the series of pictures I ended up with. I had to use a stir rod as the aluminum turnings reacted that got smaller and smaller and sunk to the bottom forming a lump. When I pulled out the stirring rod it was covered in a black slime, the tube was mildly hot. When I put the stirring rod in Xylene it crackeled like it was red hot and the AlBr3 started to flake off and colored the Xylene greyish/redish. Overall it looked neat but I didn't get any sparks or anything, I think the aluminum was too thick. Might have to try it again as I did it for my book project and wanted a near picture, I guess I'll just do chlorine and sodium, always a crowd pleaser

Edit: Just some notes, when I was drying my Br2 with H2SO4 white choking fumes kept coming off, a mixture of HBr and SO2 I would guess. This could come from any of a number of sources, NaBr dissolved in my Br2 (although the solubility of NaBr in Br2 is incredibly low). KBrO3 in my Br2, and any of a number of impurities in my drain cleaner H2SO4 or maybe just bromines action on the dyes present or any of a number of things. There was inital quick gas evolution then it slacked off, it looks like less Br2 vapor comes off the mixture then just bromine stored under H2O so I might have to try this and just store my bromine under H2SO4, should really distill it all first considering it appears to react with it though, might be a good way to get rid of whatever is in there that is reacting. Oh well, back on topic.

[Edited on 3/26/2005 by BromicAcid]

albr3.jpg - 20kB

Aluminium & Iodine

kryss - 27-3-2005 at 05:48

This is impressive too, we did it at school years ago - you can grind them up together then nothing happens until you add a couple of drops of water which starts a vigourous reaction - I'd do this outside unless you have a fume hood! You get I2 vapour and AlI3 vapour coming off - loads of corrosive smoke!! :cool:

BromicAcid - 19-6-2005 at 19:18

Being that anhydrous aluminum bromide is so useful I decided to make a quantity of it today. I added 6 or 7 grams of aluminum turnings to a large Pyrex test tube and added 20 ml or so of bromine to a sepretory funnel along with 30 ml concentrated H2SO4 and shook it up to dry the bromine. After drying I took the stem of the sepretory funnel and put it into the test tube, using some duct tape around the opening. I turned the stopcock to allow a drop to fall in every few seconds.

Each drop was accompanied by some white/yellow fumes, I'm assuming they were Al2Br6 vapors mixed with some HBr and Al2O3 and such. The reaction continued and after a while I had a deep black liquid at the bottom of the test tube. I figured this was unreacted bromine but I couldn't figure out why the aluminum left inside wasn't reacting so I ruled that out, I later found out the melting point of aluminum bromide is <100C so due to the heat of reaction this was probably mostly molten aluminum bromide. Anyway, the reaction continued and ever once in a while the aluminum would catch on fire, it would burn like a strip of magnesium, melting onto itself and sending deep red fumes out of the cracks in the duct tape. Eventually the bottom portion of the test tube solidified and the top was in a puddle of Br2/AlBr3 and was reacting away merrily. And finally the whole thing was solidified, looking similar to metal where the crystals were in contact with the side of the test tube, the mass was very heavy.

To this I added some benzene cautiously, hoping there wasn't much unreacted Br2 in the mix, and hoping that there wasn't copious amounts of some complex like AlBr4+Br- present in large amounts. There was some bubbling but nothing major so I added more, the mixture became black from the AlBr3 dissolving and the bubbling ceased. Hopefully most will dissolve and I can filter and evaporate my benzene to get my product.

Some neat things about AlBr3:

1) Technically it could furnish anhydrous HBr gas:

AlBr3 + 3H2O ---> Al(OH)3 + 3HBr

Water would be a contaminate but one could simply use a drying tube of AlBr3 to convert excess water to HBr. Unlike organic methods of producing HBr, all the bromine used to make the AlBr3 would be recovered as HBr.

2) Electroplating Aluminum:

I found a few articles on electroplating aluminum from toluene. Turns out that over 25g of AlBr3 will dissolve in 100 ml toluene and this can be used as a bath to electroplate shiny aluminum on objects. Aluminum powder would not be much of a stretch from here.

3) Of course it can be a catalyst in alkylations and other organic reactions.

4) Drying agent

5) Produce the alkali metals though non-aqueous electrolysis of fused AlBr3 with an alkali halide in nitrobenzene.

Never the less, the reaction of bromine with aluminum is indeed beautiful, just be wary it heats up very hot rapidly if there is lots of aluminum present, there is a sort of induction period with dry Br2 at room temp so don't over do it.

a123x - 19-6-2005 at 20:32

I've recently been experimenting with making alkoxides by the electrolysis of solutions of NaBr in methanol or ethanol. In one chamber of the electrolytic cell the alkoxide is formed and in the other, a solution of bromine in alcohol is formed. This solution of bromine in alcohol reacts readily enough with iron powder to produce FeBr3. The reaction isn't very reapid with Fe but does get fairly warm. I figure aluminum should react well enough with such a bromine solution. The alcohol can then be distilled off to leave the anhydrous AlBr3.

tom haggen - 19-6-2005 at 21:48

Just out of curiosity, would the manufacture of bromine go something like this.

3NaBr + H3PO4 <====> 3HBr + Na3PO4

2HBr + NaOCl <====> 2Br + NaCl + H2O

Lambda - 19-6-2005 at 23:05

Quote:

Originally posted by sylla
Al/I2 isn't spontaneus but still very easy to ignite.

Just add a drop of water on the mix ; it will first fume (nice I2 vapors) and then ignite with a bright white color

Quit a few decades ago, a teacher wanted to demonstrate to his students, the redox reaction between aluminium powder and silver nitrate.

He demonstrated this experiment on a hot summer day. It was so warm that day that sweat-drops accumulated on his forehead. While mixing these two ingredients together in a pestill, a drop of sweat fell into it. The bright flash that resulted from this catalytic induced reaction, blinded this poor old chump for more than two weeks.

During this periode he was hospitalized.

Quote:

We can't live without water, but it shoure can make life short sometimes !

[Edited on 20-6-2005 by Lambda]

Madandcrazy - 20-6-2005 at 06:31

Tell the teacher too, redox composites with Al are hard to ignite and a few nitrates being qualified for this.
When the powder

fine, the reaction can be ignited with a electric arc or carbon arc.

Polverone, i wondering about the tread of the sticky production of AlBr3

by sodium bromide in a homebrewed process.

blip - 20-6-2005 at 13:54

Quote:

Originally posetd by a123x
I've recently been experimenting with making alkoxides by the electrolysis of solutions of NaBr in methanol or ethanol. In one chamber of the electrolytic cell the alkoxide is formed and in the other, a solution of bromine in alcohol is formed. This solution of bromine in alcohol reacts readily enough with iron powder to produce FeBr3. The reaction isn't very reapid with Fe but does get fairly warm. I figure aluminum should react well enough with such a bromine solution. The alcohol can then be distilled off to leave the anhydrous AlBr3.

I think AlBr3 would react with the alcohol to produce the aluminum alkoxide and HBr since alcohol is protic, similar to the reaction with water.

verode - 2-8-2005 at 20:16

Quote:

Originally posted by blip

Quote:

I think AlBr3 would react with the alcohol to produce the aluminum alkoxide and HBr since alcohol is protic, similar to the reaction with water.

`Try with dry NH4Cl + Al + heating

Fleaker - 2-8-2005 at 20:28

As far as lighting a redox composition, (standard iron oxide/aluminum thermite) a sparkler or magnesium ribbon will work if it is finely ground.

An even more interesting reaction with bromine is to try it with magnesium powder rather than aluminum powder. A big difference in terms of the speed. It takes about 15 to 30 seconds for bromine to get going on aluminum foil (time for it to heat up) but with magnesium, it's almost instantaneous. Obviously, make sure to do any reaction with bromine (or any of the halogens) outdoors.

Question: Has anyone noticed that after you do a large Br and Al reaction and go to clean out the flask, massive volumes of HBr is ejected in to the air? Happened to me some months ago, and I was glad I got in under the hood quick.

praseodym - 3-8-2005 at 06:17

Do you mean using a Mg fuse to start off the reaction? Is it something like the thermit reaction?

neutrino - 3-8-2005 at 11:25

I think he was just talking about mixing magnesium and bromine instead of aluminum and bromine.

ChemicalBlackArts - 17-8-2005 at 23:13

As far as storing bromine(l) goes, vermiculite is excellent in extending reagent grade bromine's shelf life. FLINN Scientific ships any liquid bromine orders with about a pound of vermiculite.
And regarding chlorine, it really isn't that dangerous to handle, given a fume hood, and proper synthesis. I normally produce aqueous chlorine using equal volumes of normal bleach (NaOCl) and 12M HCl, and displace the other halogens from there.

ayumichen - 21-8-2006 at 07:58

who can explain the mechanism that Al reacts with I2 by water as the catalyst?
Why use water?What's the mechanism?

[Edited on 21-8-2006 by ayumichen]

hodges - 21-8-2006 at 14:13

Quote:

Originally posted by ayumichen
who can explain the mechanism that Al reacts with I2 by water as the catalyst?
Why use water?What's the mechanism?

Someone who knows more about this than I do can confirm and/or invalidate this, but I'm guessing that the iodine forms some hypoiodous acid with water. This acid dissolves the oxide coating that is always present on the surface of aluminum, allowing the iodine to come in contact with the aluminum metal that was previously protected by the oxide.

Hodges

12AX7 - 21-8-2006 at 18:29

Should be something like I2 + H2O > HI + HOI, where the HI dissolves Al2O3 more or less as rapidly as HCl does.

Tim

ayumichen - 21-8-2006 at 23:17

Thank u!

In fact , I'm from China.We are discussing this problem in our bbs,too.
I found this bbs on Yahoo,accidentally.
PS:where r u from?

lys_134 - 22-8-2006 at 02:12

In my opinion,HI produced by I2 resolving is very little.Though the reaction one(AlI3+H2O->Al(OH)3+HI)is great,acid is not needed at first.If the oxide membrance is very thick,then the acid won't destroy it easily besaides I- likes Cl-.So I think H2O is exactly as a diffuse phase at first,then the reaction two(Al+I2->AlI3) change into liquid-solid pattern.As H2O->I2 arising,the bond of I-I is impaired,the reaction will become easier.At this time,AlI3 is protected by the oxide membrance,the reaction one is in incentive period.With time going on,H+ become more and more,the oxide membrance is destroyed.Then lots of AlI3 react with H2O,arising great heat.So I2 and H2O change into gas.The reaction two change into gas-solid with the heat of H2O pattern.

[Edited on 22-8-2006 by lys_134]