kalacrow
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HBr in GAA
Hi folks.
I have been noodling the preparation of HBr in GAA for a bit now, and I wondered if anyone saw a show stopper in the idea of using 48% HBr acid + a
small amount of regular acetic acid in water, and introducing Ketene to it as a way to produce HBR in GAA?
I'm a little rusty.. would there be a competing reaction or byproduct that would prevent this from working? Would there be any reason the HBr would be
liberated from solution in any significant fashion? I don't believe there is, but...
I'm going to work on it, but direction would be appreciated! Thanks!
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kalacrow
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Found one prep for a very weak solution, which simply has you adding Hbr Acid at 48% to GAA. I'm assuming that the GAA is dry enough that it sucks
away the small amount of water involved.
This implies that adding Hbr Acid to acetic anhydride would yield Hbr in GAA, after all the water had been converted.
You could certainly do this in a simple two step process.. I am just concerned that the Ketene would react with the Hbr in solution. In which case, it
would have to be 2 step, namely producing GAA, then bubbling Hbr through it, or using the anhydride procedure.
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MagicJigPipe
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So, what would happen if HBr was bubbled through GAA? If that would work, why not do that?
"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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kalacrow
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Re; Bubbling HBr through GAA
Of course, it would work just fine  But I'm a tinkerer.. and I like to find
processes that are interesting to produce reagents and compounds easily and cheaply. So absolutely, if producing in situ wouldn't work, then that
would be the way to go. It would just require a bit more piping to scavange the excess HBr as it exited the reaction flask, possibly just by sending
it back into solution with very pure dH2O and a very fine bubbler, in a tall column.
But that makes for more steps.. I like the idea of producing it in situ with HBr acid.
There are basically dozens (if not many more) of compounds that are expensive or difficult to get for some people (depending on what country you are
in). I mean.. in the states they SCHEDULED acetic anhydride. MAN. That is just lunacy. Its such a useful thing!
But I digress! So I have had an itch to compile a "formulary" of processes and products that will allow you to get to large numbers of needed
compounds through simple over the counter items. I'm also thinking about including producing various bits and pieces directly from minerals and
natural materials (such as how to get sulfur from iron pyrite, or KNO3 from aged dung, or how to ferment an ethanol mash, or how to get
methanol/ethanol from sawdust, etc) because next thing you know, they'll schedule those too. Plus, sometimes people want to be able to produce these
sorts of things from a "survival" mentality, and so many books on that have been pure BUNK. I would like to put up tested procedures.
I was inspired by finding an old formulary.. but it was so annoying to see that in 1872 you could get so many useful things from "the druggist"
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MagicJigPipe
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Acetic anhydride is NOT scheduled. It is listed. That's very different.
Phenylacetone is scheduled, for example. Basically, you would need a prescription from a doctor to get it and I would be willing to bet that that has
never happened.
I do admire the fact that you wish to find a different route. Good luck!
P.S. Also, in my area (southern US) it is difficult if not impossible to obtain GAA locally, so I know what you mean.
P.S.S. Isn't iron pyrite (fool's gold?) FeS2? If so, wouldn't one be able to easily obtain H2S from this? I just think it would be so awesome to
produce H2S (if you needed it) from something you can buy at just about any gift shop (at least around here) for really cheap.
Wait, FeS2? Isn't that disulfide? Perhaps H2S cannot be produced from this. I am basically a novice when it comes to inorganic chemistry. Could
someone explain this to me, please?
[Edited on 5-24-2008 by MagicJigPipe]
"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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Sauron
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It is easy to purchase anhydrous HBr in cylinders, and bubbling that through GAAgets you the reagent (which is used in peptide work among other
things.)
HBr soln in GAA is also commercially available.
So where are you going to get pure ketene? Ketene generators and lamps produce a mixture of ketene, carbon oxides, unreacted acetone or acetic acid
(feedstocks) etc. Sure you can scrub these out but you have introduced complexities that you say you wanted to avoid. 48% HBr is also not an
inexpensive reagent, or are you going to make your own?
I'd advise keeping it simple. Anhydrous HBr, purchased or prepared, and glacial acetic acid. Dissolve the former in the latter to the appropriate
molarity (6 M comes to mind, but it's been a while since I read about this.)
Sic gorgeamus a los subjectatus nunc.
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MagicJigPipe
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Surely one must have a business to purchase anhydrous HBr. But, I don't know for sure. I DO know that I was basically told to "fuck off" when I
inquired about buying HCl and then later Cl2 from Airgas.
Why must people be SO rude? It's as if they just assumed I was either fucking with them or trying to make some sort of
WMD-mass-chemical-dirty-nuke-poison-salt-chlorine-mustard bomb.
Honestly, if I were trying to cause harm with Cl2 or HCl, I would certainly not buy it to where it could be traced back to me. Duh!!!! You don't
even have to know what chemistry is to "make" Cl2 or HCl. "Rant" over.
All that aside, I agree with Sauron that, by far, the easiest way would be to bubble HBr through GAA. Even if you were making HBr yourself. Related
but OT question: In older texts (and possibly some new ones) what is meant by "ethanolic HCl"? I always assumed it was HCl dissolved in EtOH but now
that I think about it, HCl reacts with EtOH. So, what does it mean?
"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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Sauron
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Here they will sell me HCl and HBr tanks but no Cl2 or SO2.
The regs come from the MOD.
The gases are in general cheap. The regulators are expensive and must be purchased, and there is drayage on the cylinders but it is trivial. They do
not sell lecture bottles, but will fill them if you have your own. Cylinders come in half and third sizes as well as the normal size.
Sic gorgeamus a los subjectatus nunc.
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kalacrow
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Thanks for the replies
Thanks very much for the replies!
Well of course I could BUY the HBr in acetic acid (33%). Its a commonly used reagent and not at all restricted.
I could also buy GAA and bubble HBr through it, which I also purchased, or prepared.
But how would that be FUN?
I think the unreacted acetone is an acceptable impurity for these purposes, since anyone who would do this is probably not trying to use it for
biochemistry (just rudimentary organic chem) and little of it will remain in solution in the final product. Likely you can distill the crude product
to get rid of it, but I'm not certain if HBr forms an azeotrope with Acetic Acid.. can't seem to find a reference. If it does, you could just do
simple distilliation to get most of it over.
I'm not too sure about the carbon oxides as far as impurities.. perhaps if I used N2? That would be going beyond the "simple" idea though. I suppose a
calcium scrubber could be put in place in the vapor path, since quick lime is.. well.. pretty common! That would at least deal with CO2.
Acetic Acid isn't an issue since the Ketene reacts with it to form the anhydride (or such is the idea) Also we're not worrying too much about
optimizing purity or yield... this is more like "advanced backyard chemistry" And apologies.. I meant "listed"!
Hmm. This IS sounding a lot more complicated than I expected... but it still sounds nifty, at least as an experiment to see what happens!
Re: Iron Pyrite - yes it is indeed FeS2.. here is an anarchist who explains how to derive sulfur from it using an ancient chinese method:
http://individ.blogspot.com/2005/09/gunpowder-raw-materials....
..and to answer any future questions of "why would you want to go through that trouble?" the answer is in the name of this board!
I'm MAD I tell you.. MAD!!!!!! Muhahahaha!
*ahem*
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not_important
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You'll want to fully condense the acetone out of the ketene before reacting the ketene with the aq HBr, acetone slowly polymerises in strong acids.
The carbon oxides are no problem, nor is the methane, but the ethylene is likely to add HBr; how important that would be depends on how good your
ketene generator is - too hot or too long in the heated portion leads to more ethylene.
Ketene itself reacts with protonic acids, with halogen acids to give CH3COX. As the acetyl halide will quickly react with water, this isn't a problem
for what you want to do.
You'll find you're trying to balance the rate of reaction between ketene and water, and the loss of the HBr as gas. Cool the solution too much and
the ketene reacts slowly, although the strong acid should keep reaction rates up; too warm and a lot of the HBr will swept away by the inert gases
from making the ketene.
MJP - in the cold and absence of catalysts such as ZnCl2, HCl and EtOH are pretty slow to react. Not a reagent you leave sitting on the shelf, but it
can be prepared.
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kalacrow
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Thanks muchly NI. I did a bit of looking about and ended up nodding vigorously
Well, acetone scavenging is not a big deal, I don't think. A cold trap should suffice. I'll be working this up for real over the next week or two (on
paper) and getting the numbers down to make sure I have things reasonably solid.
I -just- came across the acetic anhydride thread on the OChem section..silly me! It seems that the only real objection to this method is the nastiness
of Ketene, and I smiled when a poster talked about ganging several reaction vessels so as to not lose any ketene to the environment. It was exactly
what I had in mind.
Of course, there will probably be some HBr coming over as well, which is fine for these purposes. The first vessel should be tall and thin to maximize
the reagent contact. The next in series could be smaller and through experimentation with heat control and vacuum I am sure I could balance things out
relatively qiuckly.
The carbon is just a nuisance.. in the classic case you use a nichrome grid that gets gunked up by carbon, but in this case I'm using a tube furnace
so if it was really necessary I could design it with stop cocks on either side of the furnace, turn down the reaction and swap out, then replace and
turn it back up. Scraping the carbon out with a mild acid and a bottle brush shouldn't be a problem!
Of course before I set anything big up I'll be doing it on a small scale to see if it is even practicable. If not, I'll just generate busloads of
glacial acetic first, then setup a gas reaction setup for bubbling HBr through it. Hmm. Well, I'll likely do the glacial acetic reaction first in any
event, just to get familiar with it, before I go messing about with HBr acid conversion. Thanks as well for the tip on ethylene. Rigid temperature
control required... I'll need a good sensor. Which, by the way, is the thing which is making me think that this might be much, much better in a 2 part
setup. However, it depends on how easy it is to control the reaction conditions in practice.
I suppose I just -like- the equipment! It appears most just want the simplest reaction with the most standard lab apparatus, but I love the mad
scientist setup with valves, tubing, and the requisite van de graaf sphere! I need to setup a neon sign transformer and bent coat hangers to get that
climbing spark gap thingie as well..
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MagicJigPipe
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A Jacob's Ladder is what you mean. I've always wanted to have one of those, as well, in the "lab". As soon as someone sees that, though, they might
think you are the next Dr. Frankenstein (or worse, some kind of mad scientific terrorist. You know, like a supervillan except not super).
Speaking of "sensors". This is going to sound strange but, believe it or not, there are these, "thermocouple" thermometers at Wal-Mart that go up to
~500*F (I think). Surprisingly, they work very well for many lab applications. They have a pointed metal rod sticking out that can be easily wrapped
in teflon tape. I picked one up a few weeks ago just to play around with it but soon learned that it was an indespensible piece of lab equipment.
They're only $8, too.
"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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kalacrow
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Nice tip about the cheap thermocouple.. thanks! It can't be used in this one tho, unless it goes over 700..  But I'll be checking them out.
Jacob's Ladder! Thanks! I couldn't remember the term. Regardless of the Frankenstein shades surrounding you when you have it on, it definitely is
going to make you feel more creative, I think. That is, until some dope ignores your warning not to touch it while in operation. . . .
Looking farther into the ketene lamp process, it appears that condensing out the acetone from the stream is a no brainer.. just use a big or multiple
condensers and a trap flask to recover. Apparently ethylene is still a problem, but we'll see what we can do about that. Orgsyn has a great article
about this, although they are using the ketene for something other than making GAA:
http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1...
But, the setup is a nice place to start from. The main issue is disposing of any unreacted ketene. I mentioned before that I thought the best way
would be to have multiple reaction vessels, as well as to have the main vessel be tall and thin, leading the inlet pipe to the very bottom, and having
finely divided glass (aka, take a hammer to a pyrex measuring cup) to diffuse.. I still think that is true, but the reaction is so slow even with a
gang setup you might not get it all. It will definitely require drip rate addition tweaking, and aspirator tweaking. But now.. it seems like it's not
only doable, it's pretty spot on. I may have to lead the aspirator into a drain, but that doesn't bother me since it will become almost entirely
acetic acid anyway, immediately biodegrade when it hits the waste stream.. and I'll get a free drain cleaning out of it as well.
[Edited on 25-5-2008 by kalacrow]
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Vogelzang
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Use NaBr and H3PO4
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kalacrow
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| Quote: | Originally posted by Vogelzang
Use NaBr and H3PO4 |
Well sure.. 3 NaBr + H3PO4 = 3 HBr + Na3PO4
Assuming you are only using this as a gas generator, of course.. its totally OTC. Just have to keep in mind flammability.
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Jor
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No, it won't go as far as sodium phosphate!
NaBr + H3PO4 <<-->> HBr + NaH2PO4
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Vogelzang
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| Quote: | Originally posted by Jor
No, it won't go as far as sodium phosphate!
NaBr + H3PO4 <<-->> HBr + NaH2PO4 |
I found these links by Googling "sodium bromide" and phosphoric
http://www.chemtopics.com/unit03/ppu3.pdf
http://blog.modernmechanix.com/2008/05/20/fun-with-the-halog...
http://www.pierce.ctc.edu/chemistry/r100/100c8ho.htm
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kalacrow
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Whoops :)
Wow.. how did i make that mistake? That's the last time I use an online chem balancer and not pay as close attention to my typing!
It's a good thing when I actually DO reactions I triple check them in the real world.
Thanks muchly.
[Edited on 27-5-2008 by kalacrow]
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kalacrow
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Additional noodling and searching yields the expected result.. Hbr/GAA generated in situ usingHBr acid and ketene is a difficult reaction to control.
So, I'll just be playing about with GAA generation using a ketene setup to begin with. There is, thankfully, a large amount of information on this
topic, and HBr can be liberated from any number of OTC sources.
Methane = boom, so rigorously tested gas tight apparatus will be used, and a gentle aspirator to apply a small amount of vacuum at the tail end will
allow the reaction gases to be sent down the drain. Heat source placement and length will be important, since we don't want additional by products
from ketene reacting with itself. Also, instead of boiling acetone, it is probably better to use flash vaporization by adding the acetone dropwise to
a hot flask.. you can control the reaction rate easily then and minimize ketene losses by slowing it down until very little is seen to escape. TLC
used throughout to check reaction progress.
Time to start building
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kalacrow
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Musings and discoveries
I'm amazed I didn't find the 'keten lamp' post before this.. although the characters asking the questions seem to be a bit ridiculous, the information
is fantastic. I know you guys get frustrated dealing with some folks, but I wanted to thank you for the references you made in that thread. They have
helped a lot with my design.
I can also see this has been done before, and I've greedily sucked down posts that have good details. Apologies that I wasn't more thorough with the SE.
I'm gratified that my initial design was almost identical in concept to a number of others that are proven, and the fact that the reaction conditions
for acetone should be terribly brief with vigorous recycling back to the boiler is just what I had in mind as well. I was not shocked, but happy to
note, that the less acetone converted to ketene, the purer the yield of ketene, which jibed with my initial thoughts on it. I'm guessing the point of
diminishing returns is around 10% or so, as mentioned by various studies and papers.
I was considering using a bubbler.. but I wouldn't think of doing that without using a bit of N2 pressure to eliminate back pressure. I also was going
to cool the reaction flask somewhat (given how gases work), which also seems to be borne out. Once I work out all the properties involved, I'll have a
much better idea of temperatures. And finally, in the absence of a bubbler I am noodling ganging up a few reaction vessels instead, which has also
been discussed. I've been considering using a BAC (Big Ass Column for the
reaction flask so that if I do indeed use a bubbler, its actual throughput will not cause back pressure to any great degree. As for the furnace, that
is still up for grabs.. obviously electrical heating is easier to implement and insulate, and control. It will not, however, be very inexpensive, even
considering the price of various flammable gases having gone up. I'll have to decide if I want to make up a simple, ceramic "furnace" setup, and then
of course be incredibly anal about vapor leakage, or just deal with the energy cost. The thing is, with a furnace setup I can use anything gaseous
that will burn for the process. We'll see.. I've done producer gas before, and played about with other things.
So, a big confidence builder! Thanks to all, and I'll probably babble here from time to time about my progress.
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