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How Not to Do It

How Not to Do It: Hydrogen Bromide

I’ve written before about all the fun you can have in a lab with compressed gas cylinders. We use the things all the time in chemistry, but as pieces of apparatus, they can only be pushed so far. The problem is that they demonstrate their unhappiness by venting great quantities of stuff that you’d rather not breathe (if you’re lucky), or by taking off like an unguided missile and punching holes in the walls and ceilings (if you’re not). That latter behavior is flat-out guaranteed to show up if you abuse them – for one of the more spectacular examples, see here.
I’ve never had one take off on me, fortunately, but I haven’t always stuck to the straight and narrow with the things, either. My worst behavior has usually been with lecture bottles, the dilettante-sized gas cylinders that bench chemists often use. Most chemistry departments have a few of these sitting around, generally charged with foul reagents that are needed every three or four years or so. Sulfur dioxide, boron trifluoride, phosphine – that’s the sort of thing. They’re low-use almost by definition. If there’s a regular need for a gaseous reagent, you buy larger cylinders of it, because lecture bottles are by far the most expensive way to go.
In graduate school, I was setting up some Prins reactions, which take some sort of acid component to make them run. If you use an aqueous one, you generally get an alcohol out of them (from water picking up the final cation), but if you go anhydrous you can get all sorts of other compounds. I needed a bromide, so anhydrous hydrogen bromide it was.
We had a fairly crusty lecture bottle of it around, and I eventually located some dubious-looking small regulator valves. I picked the least-corroded looking one and screwed it on. Lecture bottles have a main metal-faucet style valve up at the top, like all gas cylinders, and once you open that it’s up to the regulator valve to stop things down to manageable flows. I had my reaction set up, so I worked some tubing onto the thing and had a go at opening it up.
No dice. Boy, was that thing tight. I reached into the hood and wrestled around with it, to no avail. I took it out and got a better grip in another part of my hood, away from my reaction setup. Tighter than two quarts of fresh frogs in a half-pint pickle pot, as Walt Kelly once put it – the valve wouldn’t budge.
I’ll skip over a couple of intermediate stages and cut right to the final scene, which is me clutching the darn lecture bottle to my chest, hopping around the lab grunting and cursing as I put all my strength into trying to force the stupid valve open. You won’t see a pictograph of that method in the instruction booklet, I’m pretty sure. A recording of what happened next would have gone something like this: “Urk! Unk! Ark! WHOA!”
The valve opened, finally responding to my Conan-the-Barbarian technique, and the cheap regulator then hissed out an orange cloud of gaseous HBr right into my shirt pocket. Not a good storage compartment, actually. I whooped, shut the valve, laid the gas cylinder down fast and stripped off my shirt where I stood. You haven’t really lived in a lab until you’ve taken off your clothes in it, I always say. I staked my claim to this one by standing in it shirtless, splashing saturated sodium bicarbonate on my chest, and glaring at the remains of what used to be one of my favorite shirts.

23 comments on “How Not to Do It: Hydrogen Bromide”

  1. Eric M says:


  2. milkshake says:

    I had a regulator failure on a full tank of HCl gas. The lecture bottle being so small and expensive and we planed to use HCl gas a lot – so I bought a full tank and a expensive spiffy regulator made of Monel alloy. In the middle of the night I thought I would put the tank to use in my experiment – I attached the new regulator and opened the main ventil and “whooosh” – the tank erupted into the lab through the leak in the poorly asembled regulator around the pressure reduction stage. It was in humid time of summer in southern Arizona, the mosoon season, so the HCl produced a thick caustic fog. I shut my eyes, then the tank and blind I run out through the emergency door just in front of puzzled cops eating their donuts on the parking lot. Then I had to explain why was being pursued by white cloud and why I was undressing on the run.
    (The fancy “corrosion-resistant” regulator got tested in the incident alright – you could exactly tell where the leak was by the metal etching.)

  3. eugene says:

    Did that incident have something to do with the paper version of Chemical Abstracts? Nowadays, if I see a procedure that calls for for anhydrous HCl or phenyl mercury, I usually spend an extra hour or two on SciFinder after checking the March book first (sometimes going to the library) for an alternative procedure. If I had to deal with Chemical Abstracts though, that wouldn’t bee too fun and I’d rather just do the first synthesis I could find.
    Congratulations on surviving and sorry about the shirt. I know how it feels to have acid eat your favorite shirt. It’s been five years but it’s still hard to forget that shirt. And it was eaten by (relatively) harmless aqueous acid too.

  4. psi*psi says:

    Something similar happened at my university–except I think it was a full-size tank of HCl. The valve was stuck, and a few people had the tank on the ground trying to open it…suddenly, the building was evacuated, the street it was on got closed down, and a friend of mine, who was unfortunately in the room at the time, ended up in the hospital. He’s OK now, though.

  5. Wavefunction says:

    Once I dropped a one liter glass bottle of conc. HCl on the floor and all the floor tiles came loose. It’s hard to forget the sounding I got for that.

  6. DLIB says:

    The average lifespan of a bench organic chemist–higher ( due to good diet and medical insurance ) or lower ( due to exposure to who knows what )? BTW, the people that weld oil rig pipes on the bottom of the ocean get extra pay for every foot they go deeper into the pipe ( extra hazard pay ).
    It’s a way human life is valued ( by some economists I know ) — how much extra would I have to pay you if there was a 0.00XX% greater chance you’d die. My guess is you guys aren’t paid enough!!

  7. kmd says:

    The back of my hood is still stained orange from my experience with an HBr tank a few years ago…
    As a sidenote, I’ve found that Oxone is really good for ruining shirts as well. First the shirt changes colors, then it fall apart…

  8. MikeEast says:

    I still shudder at the remembrance of being tasked to dispose of two old and crusty bottles. One of MeSH and the other, anhydrous HF. I refused and still managed to graduate…

  9. Dennis says:

    I (an undergraduate) am currently running a reaction that requires anhydrous HCl (and DCl) but we bought solutions of them already dissolved in ether. Is this not common? Or just not suited to larger scale operations? Is it just that no one in their right mind would trust an undergraduate with a bottle of gaseous HCl?

  10. Rich Apodaca says:

    I’m with Eugene (#3). Any procedure calling for corrosive/explosive gasses or flammable solids gets a thorough double-check for alternatives. You’d be amazed at how many literature procedures call for these dangerous, yet largely optional, reagents.
    You may live to tell the tale if you go with the HBr lecture bottle, but think of all the disposal issues and the impact on the environment, if nothing else.

  11. petr says:

    i remember myself preparing anhydrous hbr from bromine and tetraline when i was undergrad. now, when i need anhydrous hcl, i ask our technician to prepare defined solution of it in ether 🙂

  12. TNC says:

    To continue on DLIB’s point, is there a credible study of the lifespans and mortality of bench chemists? While we all hear the horror stories of terrible accidents, I’m more interested to hear about bizarre cancers and the like.
    I’d guess our livers are workhorses, but it’s hard to tease that away from the beer drinking.

  13. CMC guy says:

    I was Chemical Safety Officer and we moved a lab and collected like 39 lecture bottles of all sorts of things- many nasty, most years old, mostly just a little material left, several with valves as Derek experienced. A few we where able to empty ourselves (i.e. bubble thru to capture and neutralize) and return empty to Aldrich or otherwise properly dispose but we also spent several thousand to get others removed.
    For large scale HCl tanks (size of cyro N2) are common- although with any gas precautions needed but often better set up, plumbing and valves to deal with.
    I have also used the Br2/tetraline procedure to generate HBr cited petra and easy/works great.
    I worked where management wanted PhD to wear ties even at bench- after eating away or staining the tips of a couple I just keep a tie at my cubicle to put on if any Visitors were to come thru

  14. Handles says:

    Yes, TNC, my old boss seemed to think there was such a study, but I never saw it. He used to say chemists lived longer than the general public, but not as long as physicists.

  15. Handles says:

    Heres a couple I found on PubMed, but all I can read is abstracts:
    PMID: 7252610
    PMID: 7252611
    PMID: 16174663
    The last one, a study of employees at Dow, says:
    “Employees experienced lower mortality and cancer incidence rates than the general population for several major causes of death, including heart disease, respiratory cancer and many other cancers.”

  16. TNC says:

    Thanks, Handles. Gee, that first study makes it look kinda bad, but the second study (which is a followup of the 1st) kinda negates it. I like the comment about “…a slight excess was seen of absences due to mental disorders.” Of course, these are chemists from 1959, so God knows what they were doing. Washing hands in benzene while smoking, to be sure.
    I’d be interested to see what would happen if you studied a modern pharma company. Who’s healthier, the desk-bound managers or the chemical-exposed bench types?

  17. Kim says:

    I never tire of reading these stories. =)

  18. Bunsen Honeydew says:

    I have found that a great way to generate small to modest quantities of HX (X = Cl, Br, I, and I guess F would work too, but special precautions would be required because of the reaction between HF and glass) is to add neat H2SO4 to solid NaX. The gas bubbles out and you can bubble it from one flask directly into your reaction. It’s safe, simple, and cheap. I wouldn’t want to use a kilo of NaCl though.

  19. Lab Rat says:

    I had a similar experience with HCl as Derek descibes (including the jumping around lol). But I wanted to mention to #18 that a modification of his procedure gives (adding conc H2SO4 dropwise to a chilled Toluene suspension of NaN3) give a nice anhydrous titratable solution of HN3 (Yes, we did have bottles of the solution in the freezer).
    Looking back, it doesn’t seem like such a good idea but it was the only thing that work for some of the tough mitsunobu rxns and it made purification MUCH easier on large scale.

  20. daniel says:

    Can someone send me on my e-mail the synthesis of HBr gas and the preparation. Also it will be nice if you send me the quantity of the ingredients. Thanks.

  21. CMC guy says:

    daniel- no e-mail…
    I can suggest you look for a Br2/Tetralin procedure as pretty simple and effective if you can’t just get a lecture bottle (Vogel shows reaction but no citation and also not seen in Org Syn online)-I think I had an old lab text book with the procedure-unfortunately most my books and files are boxed at home these days. Perhaps someone else has handy.

  22. Chem Grad says:

    In response to lab rat #19. This procedure would make explosive Hydrogen Azide and not NH3 so please do yon add Sulfuric acid to Sodium Azide.

  23. JohnC says:

    The reference for Br2/Tetralin is Inorganic Syn, 1939, 1, 149. It can also be found on TCI America webstie.

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