Drunkguy
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Dry HBr gas
So for a procedure it says the product of the first step was gassed with dry HBr until acidic.
So... im just thinking how to do this procedure (thinking out loud).
I know how to make the HBr, then I guess i pass this through a second chamber containing like either concentrated H2SO4 or CaCl2 or MgSO4.
Alternatively, is it possible to make a stock solution?
E.g. take a known quantity of toluene, gas directly from generator and calculate the weight change. Then say it is 10% HBr by weight, one could just
add some molecular sieves to leech up the H2O. Is this a viable procedure or not?
[Edited on 23-6-2007 by Drunkguy]
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not_important
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Depends on what the reaction is. It may very well be that you can't make a concentrated enough stock, whatever solvent you use will be in too large
of a quantity for the next step.
Concentrated H2SO4 will oxidise HBr to Br2. In the old days it was dried with CaBr2, or P2O5, now P4O10. Mol sieves will dry it, but use 3A or 4A.
H3PO4 absorbed onto pearlite or vermiculite, then heated to 200 C for an hour, can also be used to dry HBr gas. MgSO4 doesn't work well at drying
gases, I've never seen mention of its use that way. Granular CaSO4 will dry gases OK, about as well as H2SO4, but it doesn't have much capacity so
the gas needs to be fairly dry to start with or you need to have enough CaSO4.
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Drunkguy
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Its not super concentrated. The procedure is (hydro)bromination of an enamine, not an alkene.
Im glad of your input though, since the HBr is generated as follows:
NaBr + aqueous HBr (48%) to a slurry. Then drip concentracted H2SO4 and siphon off the gasses.
But if u say bromine is produced then clearly that would give a side reaction.
[Edited on 23-6-2007 by Drunkguy]
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YT2095
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anhydrous Lithium Bromide is a great drying agent for such gases, and it`s not like it can React 
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Drunkguy
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Thanks for the input. In a perfect world, I would be using that then.
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not_important
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For the HBr production, the overall concentration of the H2SO4 is less than if it's used straight as a drying agent. Concentrated H3PO4 is still
better, and you can heat it up to partially dehydrate it to pyrophosphate.
If you've enough hydrobromic acid, you can make your own CaBr2 or LiBr. If you use the chlorides to dry HBr, you'll get some halogen exchange giving
HCl. You can also used dried alumina, but not alumina that has been strongly heated.
Trying to dry it in solution is an ubknown for me. The hydrogen halides hold onto water pretty well, I don't know how well you could dry it. As they
are ionic it seems doubtful you could get a very strong solution in a hydrocarbon. I've got 14 percent in benzene at -4 C, dropping rapidly with
increasing temperature. Saturated solution in CCl4 at STP is 0,8 g per 100 cc. Ethers and other oxygen containing solvents dissolve much more.
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leu
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An old abstract states:
Japan Kokai 73 103,496
Hydrogen Bromide is removed from water by adding lithium or calcium bromide to the aqueous solution and distilling.
Chemistry is our Covalent Bond
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not_important
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| Quote: | Originally posted by leu
An old abstract states:
Japan Kokai 73 103,496
Hydrogen Bromide is removed from water by adding lithium or calcium bromide to the aqueous solution and distilling.
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True for many gases, either add a salt of the gas or one the gas does not react with (NaOH for NH3) and heat.
The gas coming off is fairly wet, though.
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Drunkguy
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The method used in Vogel is somewhat different to the method employed in TSII. This is somewhat concerning since it suggests that the easier method
might be BS.
Is dripping H2SO4 onto NaBr gonna do the job?
I mean it works all right for making a HCl bubbler.
Im not even sure whether to dry it or just use it directly.
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Drunkguy
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Found this also, glad people are being honest and not laying traps 
https://sciencemadness.org/talk/viewthread.php?tid=6133&...
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phj
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H<sub>2</sub>SO<sub>4</sub> cannot be used in the production of HBr.
As quoted before:
| Quote: | Origineel gepost door not_important
Concentrated H2SO4 will oxidise HBr to Br2.
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not_important
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You can use H2SO4 to make HBr, but it can not be very concentrated and it can not be hot. Thus H2SO4 is OK for making somewhat dilute aqueous HBr,
but not gaseous HBr, attempts to do so will give mixtures of HBr and Br2 with the rations depending.
When using H2SO4 to make HBr (aq), you need to keep the solution cold and have an excess of the bromide salt. After separation of the
sulfate/bisulfate formed, HBr is distilled as the constant boiling mixture; use a spray trap to prevent salt solution from being carried over.
Because of the salts remaining in solution you can't recover all the HBr.
That works best if you have CaBr2, such as used in dense fluids for oil well drilling, because the precipitation of CaSO4 helps drive the reaction and
remove most of the calcium and sulfate from solution. You still can't run it very concentrate, as both oxidation of HBr will occur and the CaSO4
becomes more soluble in strong acid.
So H2SO4 is a somewhat roundabout way to get to HBr gas - make a lot of HBr(aq), distill to constant boiling, add dry CaBr2 (not the hydrate) and heat
to force some of the HBr out of solution, dry the HBr with more dry CaBr2.
Yields are not wonderful, your mileage may vary. but because you weight the CaBr2 before adding it to the hydrobromic acid you can trun around and
diute it to use for making the next batch of hydrobromic acid.
Or ask, does it really need to be HBr?
[Edited on 26-6-2007 by not_important]
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Drunkguy
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I think anhydrous p-toluenesulfonic acid can also be used to trap the enamine for reaction with the organometallic in the next step..
[Edited on 26-6-2007 by Drunkguy]
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MagicJigPipe
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One time a long time ago I attempted to create a small amount Br2 by NaBr and concentrated H2SO4 because I heard that it would oxidize the HBr.
First I mixed them together (didn't measure... just did "half and half") and no visible reaction. So, I heated it strongly. At first a smokey vapor
started to come through and out of my vacuum tube. I thought it was SO2 but I couldn't smell any. Then very small amounts of Br2 started to condense
and at the same time, HBr started to come out of the vacuum tube.
So, I got a mixture of Br2 and HBr.
Maybe my H2SO4 wasn't fully concentrated (can't remember because it was so long ago). I never figured out why this happened and haven't tried it
again since.
Seems like if it was more effecient it would be a good way to make both substances at once. Although there seemed to be much more HBr than Br2.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Klute
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| Quote: | Originally posted by Drunkguy
I think anhydrous p-toluenesulfonic acid can also be used to trap the enamine for reaction with the organometallic in the next step..
[Edited on 26-6-2007 by Drunkguy] |
In that case, you might better be off using p-TsOH... Looks like less of a hasssle IMHO. If you can't buy the hydrate, react toluene with conc.
sulfuric acid, see Vogels for this, there alot of info around on this subject... You might need to recrysatllize from conc. HCl to get mostly the p
isomer, although small amount of isomeres won't be a problem I think... Then reflux with a Dean STark with toluene until no more water comes along.
You can use a simple distn setup if you haven't got a Dean Stark, just add dry toluene now and then to maintain level. You will then have a solution
of anhydrous p-TsOH in toluene. Then add it dropwise to your enamine in dry solvant, or the other way round, I don't remember, and you've got your
iminium salt.
But i suppose you've already read about all this.
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turd
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Oh, someone is trying to make PCP?
Self-made tosic acid works great (expect >50% in an amateur setting). A dean-stark is easily improvised. At first it's quite scary that the thing
turns dark red, but so does lab-grade tosic acid.
And don't forget a sitter or don't do it in public.
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MagicJigPipe
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Why bring that up? Whether he's making PCP with it or not let's not bring it out in the open. Let's not draw attention to this board by drug speak.
Especially encouraging it's use!
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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turd
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I bring it up because it is relevant to the question at hand - only for this system I know that self-made TsOH (all reagents dirt cheap!) works very
well.
I don't think that in this day and age of terrorism paranoia a forum with an "Energetic Materials" sefction would get any more attention from big
brother just because someone is trying to do some small scale synthesis of regulated compounds (or probably some legal analog). To anyone in the know
it's darn obvious what this thread is about anyway, so no point in beating around the bush (which I hate).
And btw: I definitely do not encourage the intake of PCP. Yes, doing it once is an interesting experience but there are better substances to spend
your time on.
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Drunkguy
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Did I say that's what I was planning to do (searches thread). Didn't think so. My interest was in the principles. If I wanted to make anhydrous HBr
i'd me following the method in Vogel that drops liquid bromine onto tetralin. I've learnt from bitter experience that taking short-cuts is taking
pit-falls. Not necessarily in every possible case, but as a general rule of thumb.
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pantone159
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| Quote: | Originally posted by turd
To anyone in the know it's darn obvious what this thread is about anyway |
I had no idea this might be the case until your comment, actually.
You surely can't mean that an interest in dry HBr must mean PCP? That would be preposterous.
I'm certainly not 'in the know', I have never had the slightest interest in trying this compound, but I did look some stuff up once when I was trying
to figure out what piperidine was and why it was on DEA List I, so I at least know what pieces are put together to make PCP, I figure I must know far
far more about it than your average LE, but I had no idea this applied until you said something.
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Drunkguy
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Piperidine is not even mentioned at all, at least not by me. If people got some concrete knowledge of medicinal chemistry they would appreciate that
the principles of organic synthesis can be used to make lots of interesting compounds not merely ones that are from the illicit genre. It's like in
Vogel a method is given for making P2P. Is that to say that the author explicitly was catering for meth cooks when he decided to include that in his
book? That's an open question.
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Drunkguy
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At the time of writing this thread (several months ago), I had recently purchased some NaBr and was interested what possible uses it might have. I
only have 100g btw and after some serious consideration I decided that maing HBr was not a suitable use for it.
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Mush
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Preparation of hydrogen bromide
US 2705670 A
sulfuric acid, sodium bromide
Parts are by weight unless otherwise specified.
Example 1
A mixture containing 88 parts of water, 98 parts of 100% sulfuric acid, and 206 parts of sodium bromide is heated to 100-110 C. The sulfuric acid and
a part of the sodium bromide react to form hydrogen bromide which immediately dissolves in the water without liberation of hydrogen bromide gas.
While maintaining the temperature within the same range, an additional 98 parts of 98% sulfuric acid is slowly added. During the addition of the acid,
gaseous hydrogen bromide is continuously evolved. The free bromine content of the evolved gas is approximately 0.035% and the moisture content is
about 0.5%. The yield of gaseous hydrogen bromide is about 96% of the theoretical yield.
Example 2
A mixture containing 11 parts of water, 12 parts of sulfuric acid, and 206 parts of sodium bromide is heated to 100-110 C. The sulfuric acid and part
of the sodium bromide react as in Example 1 to form a mixture in the nature of a slurrycontaining water, hydrogen bromide, sodium bromide and sodium
acid sulfate. The water to total bromine ratio in the mixture is approximately 1 to 15.
While maintaining the temperature in the range of 100l10 C., 186 parts of 98% sulfuric acid is slowly introduced while agitating the mixture. During
the addition of the acid gaseous hydrogen bromide having a free bromine content of about 1% is continuously evolved in quantitative yield.
When it is attempted to use less water than employed in this example, the mixture is difficult to stir uniformly and erratic results are obtained.
Example 3
A mixture containing 20 parts of sodium bromide and 9.6 parts of water is heated to 100-104 C. To the mixture there is gradually and simultaneously
added 71.4 parts of 96.6% sulfuric acid and 52.1 parts of sodium bromide. Shortly after the initial introduction of the sulfuric acid, hydrogen
bromide gas begins to evolve and the evolution continues throughout the introduction of the acid. The evolved hydrogen bromide gas is analyzed by
passage through a weighed drying tube followed by absorption in water for the purpose of titration. Excellent yield of gaseous hydrogen bromide,
having a moisture content of about 1.1% and a very low bromine content, is obtained.
Example 4
A mixture of 20 parts of sodium bromide and 1.9.6 parts of water is heated to a temperature of 100 C. in a vessel equipped with a reflex condenser.
To the mixture there is gradually and simultaneously added 71.4 parts of 96.6% sulfuric acid and 52.1 parts of sodium bromide while gradually raising
the temperature to 150 C., but at no time does the temperature of the escaping gases exceed C. During the addition of the sulfuric acid and the sodium
bromide, both gaseous hydrogen bromide and an azeotropic mixture of hydrogen bromide and water are evolved. The reflux condenser effects condensation
of the hydrogen-bromide water azeotrope and returns it to the reaction vessel. The hydrogen bromide gas escapes in excellent yield. Analysis of the
gas shows about 1% water and about 1% bromine.
Example 5
A mixture containing 100 parts of water and 130 parts of hydrogen bromide is heated at 100 C. To this mixture is added gradually and simultaneously
103 parts by weight of sodium bromide and 100 parts of 98% sulfuric acid, the addition of the sodium bromide being made at a rate slightly faster than
the addition of acid so as to insure the presence of sodium bromide in the reaction mixture at all times.
During the addition of the sodium bromide and the sulfuric acid, substantially anhydrous hydrogen bromide, containing a negligible amount of free
bromine, is evolved in nearly quantitative yield.
Example 6
A reaction mixture comprising water, sodium bromide and hydrogen bromide having a water to total bromine ratio of about 1:1.8 is prepared in the
following manner: 206 parts of sodium bromide and 188 parts of 52% sulfuric acid are introduced into a reaction vessel provided with a mechanical
stirrer, a reflux condenser and means for the gradual introduction of sulfuric acid and alkali metal bromide. This mixture is heated with continuous
stirring nearly to the boiling point and maintained there until reaction is complete. To the thus formed reaction mixture concentrated sulfuric acid
is introduced very gradually while maintaining the vapor temperature above the surface of the reacting mixture at a high point, but not above 100 C.
Hydrogen bromide gas escapes from the top of the reflux condenser and is obtained in excellent yield substantially free from bromine.
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Mush
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High yield co-production of anhydrous hydrogen bromide and sodium bisulfate
US 7045111 B1
EXAMPLE 1
Aqueous slurry with NaBr and water: A slurry of 258 gm sodium bromide and 58 gm water was prepared and added to a 500 ml round bottom flask. To this
was added 238 gm of concentrated sulfuric acid over a period of 1.5 hours at a temperature of approximately 120° C. Upon addition of 15% of the
sulfuric acid, hydrogen bromide gas began to off gas and was collected in a water trap. The reaction bottoms were then heated to 145° C. once all the
sulfuric acid was added to drive off additional HBr.
The reaction effluents were as follows:
205 gm of HBr was collected and consisted of 90% HBr and 10% water.
334.3 gm of sodium bisulfate was collected and contained 4.0% Br—.
EXAMPLE 2
An aqueous slurry of NaBr in 48% HBr: A slurry of 600 gm sodium bromide and 110 gm of 48% aqueous hydrogen bromide was prepared and added to a 1000 ml
round bottom flask. To this was added 637 gm of concentrated sulfuric acid over a period of 1.5 hours. The initial temperature at the beginning of the
acid addition was 70° C. and was ramped up to 140° C. at the end of the acid addition. Hydrogen bromide was generated immediately upon the addition
of sulfuric acid and was collected in a water trap.
The reaction effluents were as follows:
526 gm of HBr was collected and consisted of 90% HBr and 10% water.
820 gm of sodium bisulfate was collected and contained 3.9% Br—.
EXAMPLE 3
An aqueous mixture of NaBr and NaHSO4—H2O: A slurry of 600 gm sodium bromide with 62 gm of 48% aqueous hydrogen bromide 59 gm NaHSO4 and 8 gm water
was prepared and added to a 1000 ml round bottom flask. To this was added 638 gm of concentrated sulfuric acid over a period of 45 minutes. The
temperature was held at 120° C. Hydrogen bromide was generated almost immediately upon the addition of sulfuric acid and was collected in a water
trap.
The reaction effluents were as follows:
487 gm of HBr was collected and consisted of 98% HBr and 2% water.
887 gm of sodium bisulfate was collected.
EXAMPLE 4
Bromide reduction in NaHSO4: The sodium bisulfate-hydrate bottoms stream from example 2 was held at 140° C. and 10″ of vacuum was applied for 10
minutes. The bromide level was reduced from 3.9% to 0.36%. The sodium bisulfate-hydrate melt began to solidify due to reduction in concentration of
the hydrate (the hydrate melts at 58° C. and the non-hydrated sodium bisulfate melts at greater than 315° C.). 50 gm of water was added to rehydrate
the mixture and 20″ of vacuum was again applied for 10 minutes. The bromide concentration was reduced from 0.36% to 0.061%.
EXAMPLE 5
Water Balance and Recycling NaHSO4 Consisting of Reactions 5A and 5B:
Reaction 5A
A slurry of 800.0 gm sodium bromide and 128.0 gm water was prepared and added to a 1000 ml round bottom flask. To this was added 840 gm of
concentrated sulfuric acid over a period of 70 minutes at a temperature of approximately 130° C. Upon addition of 15% of the sulfuric acid hydrogen
bromide gas was generated and passed through a water condenser. The aqueous 48% HBr condensate was collected and the non-condensable HBr was collected
in a water trap. The reaction bottoms were then heated to 145° C. after all the sulfuric acid was added to drive off additional HBr.
The reaction effluents were as follows:
478 gm of non-condensable HBr was collected and consisted of: 82% HBr, less than 300 ppm bromine and 18% water.
230 gm of condensed aqueous HBr was collected and consisted of: 58.6% HBr, 0.201% bromine, and 41.2% water.
1056 gm of sodium bisulfate (hydrate) was collected and contained 4.0% Br—.
Reaction 5B
857.2 gm of sodium bisulfate were removed from the reaction flask leaving 198.8 gm of sodium bisulfate (hydrate). To this were added 800 gm sodium
bromide and the 230 gm of aqueous hydrogen bromide collected above. To this slurry was added 840 gm of concentrated sulfuric acid over a period of 60
minutes at a temperature of approximately 130° C. Hydrogen bromide gas was generated immediately upon the addition of the acid. The hydrogen bromide
gas was passed through a water condenser and the aqueous hydrogen bromide condensate was collected. The non-condensable HBr was collected in a water
trap. The reaction bottoms were then heated to 145° C. to drive off additional HBr.
The reaction effluents were as follows:
689 gm of non-condensable HBr was collected and consisted of: 99.9% HBr, less than 300 ppm bromides, and 0.1% water.
73 gm of condensed aqueous HBr was collected consisting of: 59.5% HBr, 0.352% bromides, and 40.1% water.
1303 gm of sodium bisulfate was collected and contained 4.0% Br—.
From this series of reactions it is evident that reacting NaBr in a slurry will allow for complete conversion of NaBr to HBr without a build up of the
aqueous azeotropic hydrogen bromide. This is evident since the first reaction collected 230 gm of aqueous hydrogen bromide and the second collected
only 73 gm.
It also shows that the reaction can successfully be carried out in a slurry of NaBr formed from the sodium bisulfate hydrate and aqueous hydrogen
bromide. This will allow for the process to be carried out in an alternating batch reaction scheme which operates continuously, where one reactor will
be used for acidification and a second for carrying out the steam distillation. Cycling between the two reactors will allow for a very efficient
process.
EXAMPLE 6
Bromide Reduction in sodium bisulfate with water: To the 1303 gm of sodium bisulfate above was added 130 gm water and the mixture was distilled under
a maximum of 14″ of vacuum at a temperature of 141° C. (well above the HBr azeotrope temperature of 124° C. at atmospheric pressure). After
removing 100 ml of water the bromides were reduced from 4.0% to 0.37%.
An additional 100 ml of water was added and the distillation above was repeated but under a maximum of 18.5″ of vacuum at a temperature of 134° C.
After removing an additional 100 ml of water the bromides were reduced from 0.37 to 0.12%.
An additional 50 ml of water was added and the distillation above was repeated but under a maximum of 20″ of vacuum at 130° C. After removing an
additional 90 ml of water, 50 mls that were added and 40 ml of water of hydration, the bromides were reduced from 0.12% to 0.03%.
Therefore, the use of water to remove bromides from sodium bisulfate is very effective. The process can be carried out as indicated above using liquid
water. Once skilled in the art can adapt such a procedure to a continuous process using a column or using steam in place of water.
EXAMPLE 7
Bromide removal via spray drying: To simulate spray drying a 28.9 gm of crude NaHSO4 was added to a 500 ml vacuum flask and heated to 125° C. The
NaHSO4 formed a thin film on the bottom of the flask. Quickly applying vacuum to this will simulate a spray dryer. 28″ of vacuum was applied and
held for 1 minute. The flask was then vented to the atmosphere and this application of 28″ vacuum and venting were repeated two additional times.
This process reduced the bromide concentration from 9.2% to 0.95%.
To these spray dried solids was added 3 ml water to re-hydrate the mixture. It was heated to 125° C. and all the solids were allowed to
dissolve/melt. Vacuum was again applied as above. The bromides were reduced from 0.95% to 0.13%.
To the dried bottoms above were added 3 additional mls of water and the solids were allowed to dissolve/melt. Vacuum was applied as in the first step
and the bromides were reduced to 0.0028%.
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clearly_not_atara
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Use toluenesulfonic acid. If you have concentrated H2SO4, and you are trying to dissolve something in toluene, you can make toluenesulfonic acid. If
you're using benzene or xylene, a similar situation exists.
Heating TsOH with dry NaBr should produce a stream of pure HBr, which can be dried further over MgSO4.
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Texium
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