HBr in GAA

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"

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*

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..

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]

Whoops :)

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

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.