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About this Author
DBL%20Hendrix%20small.png College chemistry, 1983

Derek Lowe The 2002 Model

Dbl%20new%20portrait%20B%26W.png After 10 years of blogging. . .

Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases. To contact Derek email him directly: derekb.lowe@gmail.com Twitter: Dereklowe

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March 6, 2013

Safety Warning: Togni's Reagents

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Posted by Derek

togni%27s.pngSome of you may have used the second Togni reagent (shown) as a trifluoromethylating agent. Well, there's a new paper in Organic Process R&D that brings word that it's an explosive hazard. A group at Novasep, in Leverkusen, Germany finds that it has a powerful exothermic decomposition, and (in addition) it's about as combustible as black powder. Sensitivity to impact and friction varied from sample to sample as well, which isn't what you want to hear, either. Their conclusion is that the reagent is "dangerously explosive and may only be transported by approval of the national competent authority." The first Togni reagent (with a dimethyl in place of the carbonyl) wasn't fully evaluated, but it may be just as bad. That one has been available from Aldrich; I imagine that this may change shortly. Too bad - these are useful reagents, but not if you have to suit up to use them safely.

Comments (11) + TrackBacks (0) | Category: Safety Warnings

October 26, 2012

Accident Report, or One Damn Thing After Another

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Posted by Derek

I have this from a lab-accidents-I-have-known discussion over on Reddit. It is, of course, unverified, but it's depressingly plausible. As a chemist, this one is guaranteed to make you bury your head in your hands - it's the second law of thermodynamics come to take vengeance, with the entropy increasing as you go along:

"A graduate student was constructing three solvent stills (dichloromethane, THF and toluene) inside a hood in Room XXXX. As a final step in this process, the student was cutting pieces of sodium metal to add to the stills. Once the sodium had been added, the student began to clean the knife used to cut the sodium. During the cleaning, a small particle of sodium was apparently brushed off the knife. The sodium landed in a drop of water/wet spot on the floor of the hood and reacted immediately making a popping sound. The graduate student was startled by this sound and moved away quickly.

In his haste to get away from the reacting sodium, he discarded the knife into a sink on the bench opposite the hood in which he was working.. Apparently, there was another piece of sodium still adhering to the knife since upon being tossed into the sink, a fire ignited in the sink, catching the attention of another student in the lab. As the flames erupted, the student noticed a wash bottle of acetone sitting on the sink ledge nearby. He immediately grabbed it to get it away from the flames, but in the process, squeezed the bottle, which squirted out some acetone which immediately ignited. The student immediately dropped the bottle and began to evacuate the lab. As he turned to leave, he knocked over a five gallon bucket containing an isopropanol/potassium hydroxide bath which also began to burn. This additional fire caused the sprinklers to activate and the fire alarm to sound which in turn resulted in the evacuation of the building.

When the sprinklers activated, water poured into the bulk sodium-under-mineral-oil storage bottle which had been left uncapped in the hood resulting in a violent reaction which shattered the bottle sending more sodium and mineral oil into the sprinkler water stream. This explosion also cracked the hood safety glass into numerous little pieces although it remained structurally intact. By the time the first-responders arrived on the scene, the fire had been extinguished by the sprinklers, but numerous violent popping sounds were still occurring. The first-responders unplugged the electrical cords feeding the heating mantles, shut off the electricity to the room at the breaker panel and waited until the Fire Department arrived. Eventually the popping noises stopped and sprinklers were turned off. The front part of the lab sustained a moderate amount of water damage The hood where the incident began also suffered moderate damage and two of the three still flasks were destroyed. The student, who was wearing shorts at the time of this accident, sustained second and third-degree burns on his leg as a result of the fire involving the isopropanol base bath.

There were some additional injuries incurred by the first-responders who unexpectedly slipped and fell due to the presence of KOH from the bath in the sprinkler water. These injuries were not serious but they do illustrate the need to communicate hazards to first-responders to protect them from unnecessary injury."

I doubt if the sodium was being added to the dichloromethane still; I've always heard that that's asking for carbene trouble. (Back in my solvent-still days, we used calcium hydride for that one). And it would take a good kick to knock over a KOH/isopropanol bath, but no doubt there was some adrenaline involved. I'm also sorry to hear about the burns sustained by the graduate student involved, but this person should really, really have not been wearing shorts, just as no one should in any sort of organic chemistry lab.

But holy cow. The mental picture I have is of Leslie Neilsen in a lab coat, rehearsing a scene for another "Naked Gun" sequel. This is what happens, though, when things go bad in the lab: we've all got enough trouble on our benches and under our fume hoods to send things down the chute very, very quickly under the wrong conditions. And were these ever the wrong conditions.

Comments (55) + TrackBacks (0) | Category: Graduate School | How Not to Do It | Safety Warnings

August 1, 2012

The Sangji/UCLA/Harran Case: Now Officially a Mess

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Posted by Derek

There have been a number of odd developments in the Sheri Sangji case, the lab fatality at UCLA that led to criminal charges being filed against both Prof. Patrick Harran and the university. The Doing Good Science blog at Scientific American has a thorough round-up of the latest.

Last Friday, charges were dropped against UCLA, and the case against Harran was separated. As part of the deal, UCLA agreed to establish a memorial scholarship and to improve its safety measures. We're still finding out about those, but Chemjobber has more details here and here.

I note that this seems to be a process-heavy, paperwork-heavy system that's going into place. And while that might help, I'm going to remain skeptical, since I've worked under similar conditions, and it did not stop some people from have lab accidents that they shouldn't have had. Now, there's no way of knowing how many accidents these policies prevented, but the ones that got through were just the sorts of things that this safety regime was designed to prevent. So one does have to wonder. It's a natural impulse to think that process improvements are the answer to such situations, though. It's especially going to come out that way when you have lawyers watching who will want to see measurable, quantifiable steps being taken. It's not possible to measure how many people avoided lab hazards as a result of your safety measures - but it is possible to count how many meetings people have to attend, how many standard operating procedures they have to generate and sign off on, and so on.

Now as far as Prof. Harran's case, here's where things get weird. His legal team appears to be attacking the California OSHA report on the lab incident by pointing out that its author was involved in a murder plot as a teenager and lied about it to investigators (falsus in uno. . .). After some confusion about whether this was even the same person, word is now that the investigator has suddenly resigned from his position as a public safety commissioner. So perhaps Harran's lawyers are on to something.

But on to what, exactly? I can understand this as a legal tactic. It's not a very honorable one, but it's been said that lawyers will do anything for you that can be done while wearing a nice suit (that's their ethical boundary). Their job is to exonerate their client, and they will do pretty much anything that leads to that result. Will this? Doubt can be cast on the personal history of the Cal OSHA investigator, for sure, but can it be cast on the report that he wrote? Chemjobber's guess is that this indicates that plea bargaining isn't going well, and that seems quite believable to me.

So that's the state of things now. There will be more, perhaps a lot more, the way this case is going so far. Whether it all will lead to a just outcome depends on what you think justice is, and how it might be served here. And whether any of it will keep someone in the future from being killed by a dangerous reagent that they did not appear ready to use, I have no idea. The longer all this goes on, and the more convoluted it gets, the more I wonder about that.

Comments (20) + TrackBacks (0) | Category: Safety Warnings

February 16, 2012

Imidazole-1-Sulfonyl Azide HCl: Look Out

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Posted by Derek

I don't know how many of you out there like to form azides, but if you do, you've probably used (or thought about using) imidazole-1-sulfonyl azide hydrochloride. This reagent appeared in Organic Letters a few years ago as a safe-to-handle shelf-stable azide transfer reagent, and seems to have found popularity. (I've used it myself).

So it was with some alarm that I noted this new paper on the stability and handling characteristics of the reagent. It's a collaboration between the University of Western Australia (where the reagent was developed, partly by the guy whose lab bench I took over in grad school back in 1983, Bob Stick), the University of British Columbia, and the Klapötke group at Munich. That last bunch is known to readers of "Things I Won't Work With", as experts in energetic materials, and when I saw that name I knew I'd better read the paper pronto.

As it turns out, the hydrochloride isn't quite as optimal as thought. It's impact-sensitive, for one thing, and not shelf-stable. The new paper mentions that it decomposes with an odor of hydrazoic acid on storage - you don't want odors of hydrazoic acid, believe me - and I thought while reading that, "Hmm. My bottle of the stuff is white crystalline powder; that's strange." But then I realized that I hadn't looked at my bottle for a few months. And as if by magic, there it was, turning dark and gooey. I had the irrational thought that the act of reading this paper had suddenly turned my reagent into hazardous waste, but no, it's been doing that slowly on its own.

So if you have some of this reagent around, take care. The latest work suggests that the hydrogensulfate salt, and especially the fluoroborate, are less sensitive and more stable alternatives to the hydrochloride, and I guess I'll have to make some at some point. (They also made the perchlorate - just for the sake of science, y'know - and report, to no one's surprise, that it "should not be prepared by those without expertise in handling energetic materials"). But it needs no ghost come from the grave to tell us this.

So, back to my lab and my waste-disposal problem! And here's a note on the literature. We have the original prep of the reagent, a follow-up note on stability problems, and this latest paper on alternatives. But when you go back to the original paper, there is no mention of the later hazard information. Shouldn't there be a note, a link, or something? Why isn't there? Anyone at Organic Letters or the ACS care to comment on that?

Update: I've successfully opened my bottle, with tongs and behind a blast shield, just to be on the safe side, and defanged the stuff off by dilution.

Comments (17) + TrackBacks (0) | Category: Chemical News | Safety Warnings | The Scientific Literature

February 1, 2012

Potassium Hydride Is Not Your Friend

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Posted by Derek

Noted chem-blogger Milkshake seems to have had a close call with a fire started by a tiny potassium hydride residue. It looks like he made it through without serious injury, but that sort of thing will definitely shake a person up.

I hate potassium hydride. Its relative sodium hydride is a common reagent, but it's much tamer (and even so, can cause interesting fires - I knew someone who ignited a heap of it on the pan of a balance while he was weighing it out, which slowed things down a bit). Sodium hydride is usually sold as a 60% dispersion, a dark grey powder soaked with mineral oil to keep it from deteriorating too quickly (and to keep it from setting everything on fire). You can buy 95% sodium hydride, the dry stuff, and there are people who swear by it, but I tend to sweat at it. You never know if it's been stored properly; you may be adding a slug of sodium hydroxide to your reaction without knowing it. And there's the fire part. You'll want to move briskly if you're using the 95%, and I'd pick a day when the humidity is low.

But potassium hydride, that's another beast entirely. It makes the sodium compound look like corn meal, in terms of how forgiving it is. You can't get away with the clumpy oily powder form at all - traditionally, KH is sold as a gooey dispersion of grey powder sitting under a few inches of mineral oil. If it's well dispersed, it's supposed to be 35%. You shake the stuff up until you think it's even mixed, then pipet out the amount of gunk that corresponded to the KH contained therein. Sure you do. What actually happens is that you pipet out the stuff, noticing while you do that it's already settling out inside the pipet, thereby to clog it up when you try to transfer it. No fun.

It's becoming available now dispersed in a block of wax, which is not such a bad idea at all. Wax isn't any harder to get out of your reaction than oil is, and you can carve off chunks and weigh them without so many what-am-I-doing moments. But Milkshake worries that this ease of use will lead to more fires during workups (which is where his reaction ran into trouble), and he may well be right. If you're going to use KH, don't let your guard down.

Comments (47) + TrackBacks (0) | Category: Chemical News | Life in the Drug Labs | Safety Warnings

December 28, 2011

The UCLA Lab Fatality: Criminal Charges Filed

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Posted by Derek

Most readers here will remember the fatal lab accident at UCLA in 2009 involving t-butyllithium, which took the life of graduate student Sheri Sangji. Well, there's a new sequel to that: the professor involved, Patrick Harran, has been charged along with UCLA with a felony: "willfully violating occupational health and safety standards". A warrant has been issued for his arrest; he plans to turn himself in when he returns from out of town this season. The University could face fines of up to $1.5 million per charge; Harran faces possible jail time.

This is the first time I've heard of such a case going to criminal prosecution, and I'm still not sure what I think about it. It's true that the lab was found to have several safety violations in an inspection before the accident - but, on the other hand, many working labs do, depending on what sort of standards are being applied. But it would also appear that Sangji herself was not properly prepared for handing t-butyllithium, which (as all organic chemists should know) bursts into flames spontaneously on exposure to air. She was wearing flammable clothing and no lab coat; no one should be allowed to start working with t-BuLi under those conditions. Being inexperienced, she should have been warned much more thoroughly than she appears to have been.

So something most definitely went wrong here, and the LA County DA's office has decided to treat it as a criminal matter. Well, negligence can rise to that level, under the law, so perhaps they have a point. Thoughts?

Update: here's a post that rounds up the responses to this across the blogging world.

Comments (97) + TrackBacks (0) | Category: Chemical News | Graduate School | Safety Warnings

September 27, 2010

Charges in the TMS Diazomethane Case

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Posted by Derek

Readers may remember the case of Ronald Daigle, who died of exposure to TMS diazomethane a couple of years ago in Nova Scotia.

Sepracor, the company who owned the facility at the time, has now pleaded not guilty to five charges related to this accident. (Many more details at C&E News). This case appears (slowly) to be going to trial, so it'll be something to keep an eye on. . .

Comments (8) + TrackBacks (0) | Category: Safety Warnings

August 27, 2010

How Much is the PI To Blame?

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Posted by Derek

Chemjobber has a post up on the responsibility of the professor in the Texas Tech explosion case. I have to agree with him: if you're going to get grant money to have your group work on energetic materials, you have to keep a close eye on things. And the C&E News piece on the whole affair doesn't make it sound like that was happening. It's easy for me to sit here, ex post facto, and say something like this, but I'll say it anyway: from what I can see, this research group wasn't being run the way it should be.

At the same time, there's no amount of training that will keep a real idiot from doing something stupid (thus the German quote that led off my previous post on the subject). Believers in seminars and checkboxes always have to come up against that fact, and against the people that exemplify it. But here's what you have to do with such people: get rid of them. Get them off the dangerous projects at the very least, and try to get them out of your group, out of the building, out of chemistry as a career. Anyone who would scale up a known sensitive, energetic material by a factor of 100 over the recommended amount and then put it in a mortar and pestle does not belong in a chemistry lab.

But that takes us back around to the professor again. Anyone running a research group should know when there's someone in it with a reputation as a wild-eyed cowboy. And when your group is concentrating on hazardous materials, well. . .

So sure, there should have been more training, and it sure sounds as if this lab could have used a better culture in general. But the first thing it could have used was this guy's rear end being kicked down the stairs. And Chemjobber's right: all of these are the responsibility of the PI.

Comments (40) + TrackBacks (0) | Category: Graduate School | Safety Warnings

August 24, 2010

Gegen die Dummheit . . .Well, Guess Who Wins, Again

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Posted by Derek

If you haven't heard about the explosion at Texas Tech earlier this year, this piece is the place to learn about it. (More from Chemjobber and the newly re-blogging Paul Bracher). In short, two graduate students were preparing a nickel hydrazine perchlorate complex, on far more than the recommended scale, and one of them was severely injured while trying to break up the substance in a mortar and pestle.

This is, as any experienced chemist could tell you, not a surprise. Call me when something like that doesn't blow up. But these weren't experience chemists. They were grad students, and I'm just glad that they didn't pay an even higher price for not realizing what they were getting themselves into.

At the same time, I find myself lining up more with Bracher's post, although I won't express myself quite as vigorously. The entire point of this research program was to look at hazardous energetic materials. The professor involved specifically told the students not to make more than 100 mg of material; they made ten grams. The injured student then ground up this material - yep, I did say "mortar and pestle" for real back there - with no blast shield, and gave the stuff one last poke after having taken off his goggles. He now gets to learn to write with his other hand. I can't figure out how he's still alive.

It's cruel, but one thing I actually respect about the physical sciences is that they have no regard for humanity. No exceptions are made; they respect no laws save their own. In a chemistry lab, we are dealing with the world as it really is, not as we'd like it to be. And if you want to believe that you can scale up the synthesis of a violent explosive by a factor of 100, despite warnings, and poke at the material without protection - well, you'd be just as well off doing it to a tiger. Perchlorates don't care what you think you can get away with, or how invulnerable you think you are.

Comments (41) + TrackBacks (0) | Category: Graduate School | Safety Warnings

June 30, 2010

How Not To Do It: Hydrogen Gas Mixtures

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Posted by Derek

Culturing bacteria is usually a pretty quiet affair. Bacteria aren't too noisy, and the equipment used to keep them happy isn't too dangerous. But there are exceptions. If you're going to culture anaerobes, you need somewhat more advanced technique, what with all that oxygen-is-deadly business. A professional-grade culture chamber for those beasts is usually filled with a mixture of about 80% nitrogen, 10% carbon dioxide, and 10% hydrogen. And those you'll be getting from three compressed gas cylinders, which is how they were doing it in a lab at the University of Missouri until Monday afternoon. . .

Well, regular readers will be expecting this to be a story of someone who did not remember to Treat Compressed Gases With Respect, but that's not the case. No, this is what happens when you don't Treat Hydrogen With Respect - and everyone in the audience who's had a hydrogenation reaction get frisky on them will be nodding their head in agreement at that thought. Somehow, enough hydrogen and enough oxygen got together around an anaerobic culture hood, and the mixture found an ignition source, and well. . .
062810_InsideExplosion_2_t_w600_h1200.jpg
Problem is, just about any hydrogen/air mixture will do. Anything from about 4% hydrogen in air to about 75% will ignite, and everything except the two ends of that range will go ahead and explode if given the chance. (Only acetylene is worse in that regard). And it doesn't take much to set it off, either, which is the other nasty thing about working with hydrogen. A static-electricity spark is plenty, as are the sparks generated by electrical switch contacts and the like.
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As you can see, the lab was not improved by the resulting explosion. The latest report I have is that four people were injured, one seriously enough to still be in the hospital, although their condition has been upgraded to "good".

Initial reports were that this was due to human error, although everyone seems to be backing off that judgment until an official investigation is finished. At any rate, the local fire department stated Monday night that the problem was one or more people in the lab "not being familiar with the warning systems designed to alert them when the hydrogen level was approaching explosive limits (and) the gas was left on". If that was the case, then. . .you ignore a hydrogen level alarm at your peril. And here are seventeen blown-out windows, four people who are lucky not to have been killed, and one demolished lab as evidence.

Update: I had a link up to a commercial anaerobic culture chamber for illustration, but (as the manufacturer points out) these use cylinders of premixed gas with only 5% hydrogen which obviates this very problem. I thought it best to take down the link so that no confusion results - after all, it wasn't the model that was being used in this incident (and in fact would have avoided it completely). I should add that the email I received about this out was exactly the sort of courteous and informative request I have no problem responding to, as opposed to some others that have come in over the years.

(Photos are courtesy of the Missourian and the Columbia Fire Department).
Missou%20explosion%20exterior%2Cjpg.jpg

Comments (19) + TrackBacks (0) | Category: How Not to Do It | Safety Warnings

September 21, 2009

More on T2, and Degrees

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Posted by Derek

Friday's article on the T2 explosion has had a lot of readers, thanks to links from various outside sources. One line from it has attracted a disproportionate amount of comment - the one where I mentioned that the two owners of the company had only undergraduate degrees. This needs some clearing up; I should have explained myself more clearly in the original post.

First off, there are two things I most definitely didn't mean. I do not, of course, mean to imply that anyone without a graduate degree is incapable of running a complex or hazardous chemical process. Nor am I assuming that there's some sort of magic in a graduate degree program that turns a person into someone who actually can run such things. I've seen enough smart people who didn't go to grad school (and enough fools with PhDs) not to believe either of those.

The key thing here (besides intelligence, which is necessary, but not sufficient) is experience. And what experience gives you, among other things, is a sense of knowing what needs to be worried about. That's what the T2 people seem to have lacked. It's no exaggeration that every time I've described this accident to an experienced scale-up or process chemist, their response has been outrage and incredulity. De mortuis nil nisi bonum, and my apologies in advance to any relatives or colleagues of the deceased, but these people were conducting a very hazardous chemical process, and the lack of care they showed while doing so is stunning. No calorimetry to look for exothermic reactions, a totally inadequate rupture disk for venting that large a reactor, no attempt to set up the process as a flow or feed (which also would have given you built-in temperature control), and no backup for the absolutely crucial cooling system.

Now, it's quite possible that if the people who set up the T2 reactor had been through a graduate program that they would have gone on to do the exact same thing. But it might have helped a bit, which might have been enough to keep four people from being killed. Graduate work is supposed to involve research, experiments that haven't been run before. If you get a degree that's worth anything, you've had the experience of having to figure experimental setups out on your own, and that means that you should have had some chances to think about what might go wrong with them. And the larger the scale of your chemistry, the more you should think about that last point.

Having a couple of reactions take off and spray the inside of your fume hood brings home the problems of heat transfer and pressure relief in a way that no textbook can quite match, and that's not something that you'll experience as an undergraduate in most colleges. Now, it's true that you can experience that at work, too, where the lessons will be even more vivid. That's why in an industrial setting an experienced chemist without a doctorate is almost always much more worth listening to than a freshly arrived PhD - if they're any good, they've seen a lot and they've learned from it.

The people running T2 not only did not take proper precautions, they had been told that they needed to bring in a consultant to look over their process. In other words, "get someone in here who can see things that you're overlooking". But they didn't do that. It's also possible that they might have brought someone in and ignored their recommendations, too, and there's no degree program that can keep you from acting like that, either. They'd run this thing over and over just the way it was, and they probably thought that everything was under control. But it wasn't. And they had no idea.

Comments (30) + TrackBacks (0) | Category: Chemical News | Safety Warnings

September 18, 2009

175 Times. And Then the Catastrophe.

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Posted by Derek

I noted this item over at C&E News today, a report on a terrible chemical accident at T2 Laboratories in Florida back in 2007. I missed even hearing about this incident at the time, but it appears to have been one of the more violent explosions investigated by the federal Chemical Safety and Hazard Board (CSB). Debris ended up over a mile from the site, and killed four employees, including one of the co-owners, who was fifty feet away from the reactor at the time. (The other co-owner made it through the blast behind a shipping container and suffered a heart attack immediately afterwards, but survived). Here's the full report as a PDF.
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The company was preparing a gasoline additive, methylcyclopentadienyl manganese tricarbonyl (MCMT). To readers outside the field, that sounds like an awful mouthful of a name, but organic chemists will look it over and say "OK, halfway like ferrocene, manganese instead of iron, methyl group on the ring, three CO groups on the other side of the metal. Hmmm. What went wrong with that one?"

Well, the same sort of thing that can go wrong with a lot of reactions, large and small: a thermal runaway. That's always a possibility when a reaction gives off waste heat while it's running (that's called an exothermic reaction, and some are, some aren't - it depends on the energy balance of the bonds being broken versus the bonds being made, among other things). Heating chemical reactions almost invariably speeds them up, naturally, so the heat given off by such a reaction can make it go faster, which makes it give off even more heat, which makes it. . .well,, now you know why it's called a runaway reaction.

On the small scales where I've spent my career, the usual consequence of this is that whatever's fitted on the top of the flask blows off, and the contents geyser out all over the fume hood. One generally doesn't tightly seal the top of a reaction flask, not unless one knows exactly what one is doing, so there's usually a stopper or rubber seal that gives way. I've walked back into my lab, looked at the floor in front of my hood, and wondered "Who on earth left a glass condenser on my floor?", until I walked over to have a look and realized where it came from (and, um, who left it there).

But on a large scale, well, things are always different. For one thing, it's just plain larger. There's more energy involved. And heat transfer is a major concern on scale, because while it's easy to cool off a 25-milliliter flask, where none of the contents are more than a centimeter from the outside wall, cooling off a 2500-gallon reactor is something else again. Needless to say, you're not going to be able to pick it up quickly and stick it into 25,000 gallons of ice water, and even that wouldn't do nearly as much good as you might think. The center of that reactor is a long way from the walls, and cooling those walls down can only do so much - stirring is a major concern on these scales, too.
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What's worth emphasizing is that this explosion occurred on the one hundred seventy-fifth time that T2 had run this reaction. No doubt they thought they had everything well under control - have any of you ever run the same reaction a hundred and seventy-five times in a row? But what they didn't know was crucial: the operators had only undergraduate degrees (Update: here's another post on that issue), and the CSB report concludes that the didn't realize that they were walking on the edge of disaster the whole time. As it turns out, the MCMT chemistry was mildly exothermic. But if the reaction got above the normal production temperature (177C), a very exothermic side reaction kicked in. Have I mentioned that the chemistry involved was a stirred molten-sodium reaction? Yep, methylcyclopentadiene dimer, cracking to monomer, metallating with the sodium and releasing hydrogen gas. This was run in diglyme, and if the temperature went up above 199C, the sodium would start reacting energetically with the solvent. Update: corrected these temperature values

Experienced chemists and engineers will recognize that setup for what it is: a black-bordered invitation to disaster. Apparently the T2 chemists had experienced a few close calls in the past, without fully realizing the extent of the problem. On the morning of the explosion, the water cooling line experienced some sort of blockage, and there was (fatally) no backup cooling system in place. Ten minutes later, everything went up. In retrospect, the only thing to do when the cooling went out would have been to run for it and cover as much ground as possible in the ten minutes left, but that's not a decision that anyone usually makes.
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Here you see part of the company's reactor vessel, which ended up on some train tracks 400 feet away. The 4-inch-wide shaft of the agitator traveled nearly as far, imbedding itself into the sidewalk like a javelin. My condolences go out to the families of those killed and injured in this terribly preventable accident. The laws of thermodynamics, unfortunately, have no regard for human life at all. They cannot be brushed off or bargained with, and if you do not pay attention to them they can cut you down.

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May 26, 2009

On the Uselessness of the MSDS

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Posted by Derek

With all the recent discussions around here about safety, I think that there's one thing that all of us working chemists can agree on: MSDSs are often the next thing to useless.

They're not supposed to be, at least in theory. The idea is that a materials safety data sheet collects all the relevant toxicity, handling, and disposal information for a given chemical so it can be referenced by users, emergency responders, and so on. But somewhere along the line, things have gone well off track. I refer interested readers to the famous example of the MSDS for sand. Sea sand.

The first thing we find is that it is a cancer hazard. Then we note that "Prolonged exposure to respirable crystalline quartz may cause delayed lung injury/fibrosis (silicosis)". Which is true, but (of course), we have no idea of what "prolonged" means in this context, and we may not realize that sand, in its commonly encountered forms, is not easy to inhale. One should " Wear appropriate protective clothing to prevent skin exposure", but if we were to contact this substance through our own carelessness? We should "Immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes.". We should take care at all times: "Do not let this chemical enter the environment." But that should go without saying, since we've been enjoined to "Use only in a chemical fume hood".

Now, what this thing is trying to tell us is that extensive exposure to finely ground silica dust is bad for the lungs. This is absolutely true, even if lawyers have been trying to make dubious fortunes off of it. A person should take care not to inhale sand dust, and should take particular care if exposure to such dust is a regular feature of one's job.

But there needs to be a way to get this information across without making a bag of sand sound like a weapon of mass destruction. I don't know how many times I've heard of chemical spills being treated like high-level radioactive waste because emergency responders (or local news reporters) read the MSDS and hit the panic button. (A famous example was the closure of the Bay Bridge in California once by a few bags of iron oxide (keep in mind that this happened before the current environment of worries about terrorist incidents). The responders knew what the chemical was: they read the MSDS, which (naturally) told them to wear full protective equipment, avoid exposure, wash copiously and seek medical attention, etc. For a few bags of rust.

There has to be a better way - you'd think, at any rate. But the MSDS is lawyer language, when you get right down to it, and there's the problem. Trying to insulate everyone from liability is not something that can be done simultaneously with trying to inform people in case of an emergency. Very few chemists, in my experience, spend much time with these forms at all, preferring to get their information from almost any other source. There has to be a better way.

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May 22, 2009

Blowups Happen

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Posted by Derek

There's an article up at Slate on the UCLA lab accident death. It finishes up by saying:

If Sheri Sangji's death is to mean anything, it must be that no lab chief—and certainly no federal agency—claiming to further human welfare ever again tolerates the risk of harm to lab workers. That means that university administrators from the provost on down must make safety a serious concern and a requirement for career advancement and hiring, and tenure and promotion committees must hold faculty members responsible for seeing that everyone in their labs has the training, skills, and equipment needed to work safely. Funding agencies must make a good safety record and evidence of safety awareness real conditions for getting and keeping grants. Never again should academic research needlessly claim the life of a researcher.

Brave words, but I feel pretty sure that academic research will, in fact, needlessly claim more lives every so often. You've got a lot of people at widely varying levels of experience (and widely varying levels of sense), working all hours of the day and night, often under pressure to produce results. Accidents will happen.

Now, I think that academic labs could be a lot safer than they are, and that they should be. It's worth taking steps to try to realize that. But if you set the standard as "never again should anything bad happen", you will fail. I've worked in an industrial environment that implemented the fiercest, most draconian safety policy I've ever experienced. Multiple, overlapping layers of safety meetings, with an extensive standardized list of topics that had to be covered every time. Incident reports, discussed in detail, every time. Attendance mandatory, and logged on a signup sheet, and tied to bonus payouts. Multiple, overlapping layers of documentation, countersignatures, standard operating procedures, etc. And we still had explosions, due to varying amounts of cluelessness, stupidity, and just plain bad luck.

They will happen. They should be minimized, prepared for, and guarded against. But acting as if there's a policy which will prevent them is foolish, and risks making the perfect the enemy of the good.

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May 19, 2009

TMS Reagents: Handle With Care!

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Posted by Derek

Some emails and discussions with colleagues have raised an important point to be learned from the recent TMS-diazomethane tragedies. Many people are probably taking some of these reagents less seriously than they should.

As organic chemists know, the trimethylsilyl group is a strange beast, and can often substitute for a proton in small reagents. That often gives such compounds new and useful properties along the way – for example, hydrazoic acid (hydrogen azide) is an extremely dangerous substance because of its unpredictable explosive qualities. It should never be generated except in very dilute solution (that is, unless you’re prepared at every moment for a serious detonation, and not many people are). But the corresponding trimethylsilyl azide is an article of commerce – you can pick up the phone and order a bottle. No one in the history of the fine chemical industry, as far as I know, has been crazed enough to offer hydrazoic acid for sale. How could it be delivered - by trained hummingbirds?

But the two reagents can do many of the same transformations, since the TMS group is often just about as easy to lose at the end of the reaction as a proton is. The exact same situation obtains with trimethylsilyldiazomethane: no one’s ever tried to sell or ship the parent compound, but solutions of the TMS derivative are ready to be ordered at your convenience.

But that's only because they're less explosive. All the TMS reagents are just as poisonous as their proton counterparts. And that's where I think some chemists aren't making the connection. We treat diazomethane gingerly because we don't want it to explode, but we should also be handling it like the volatile toxin it is. The same goes for hydrazoic acid. If you have to deal with the stuff, you're mostly thinking every second about how it could go off on you. But you should also be thinking about how it's a potent, poisonous vasodilator. It doesn't have to blow up: a good deep gust of it will relax your arterial walls permanently by killing you, and TMS azide will do the exact same thing.

These compounds are intrinsically toxic, and they're also toxic because they'll hydrolyze back to the parent compounds in a warm, wet environment - like the inside of your lungs. I think that people treat another one of the series, trimethylsilyl cyanide, with more respect. That's because HCN gets a lot of respect for its inhalation toxicity (and with damned good reason), and opening an ampoule of TMS-CN is (or should be) a reminder that it's just as nasty. And since it doesn't explode, that's the main thing that you think about.

So spread the word: these reagents, though extremely useful, are not to be handled lightly. They're volatile and they're just as poisonous as their parents. The ease of ordering and handling them, in fact, may make them even more of a potential hazard. Treat 'em with respect.

Note: for those looking for a thorough reference work on the subject, this seems like an up-to-date choice.

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