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: Twitter: Dereklowe

Chemistry and Drug Data: Drugbank
Chempedia Lab
Synthetic Pages
Organic Chemistry Portal
Not Voodoo

Chemistry and Pharma Blogs:
Org Prep Daily
The Haystack
A New Merck, Reviewed
Liberal Arts Chemistry
Electron Pusher
All Things Metathesis
C&E News Blogs
Chemiotics II
Chemical Space
Noel O'Blog
In Vivo Blog
Terra Sigilatta
BBSRC/Douglas Kell
Realizations in Biostatistics
ChemSpider Blog
Organic Chem - Education & Industry
Pharma Strategy Blog
No Name No Slogan
Practical Fragments
The Curious Wavefunction
Natural Product Man
Fragment Literature
Chemistry World Blog
Synthetic Nature
Chemistry Blog
Synthesizing Ideas
Eye on FDA
Chemical Forums
Symyx Blog
Sceptical Chymist
Lamentations on Chemistry
Computational Organic Chemistry
Mining Drugs
Henry Rzepa

Science Blogs and News:
Bad Science
The Loom
Uncertain Principles
Fierce Biotech
Blogs for Industry
Omics! Omics!
Young Female Scientist
Notional Slurry
Nobel Intent
SciTech Daily
Science Blog
Gene Expression (I)
Gene Expression (II)
Adventures in Ethics and Science
Transterrestrial Musings
Slashdot Science
Cosmic Variance
Biology News Net

Medical Blogs
DB's Medical Rants
Science-Based Medicine
Respectful Insolence
Diabetes Mine

Economics and Business
Marginal Revolution
The Volokh Conspiracy
Knowledge Problem

Politics / Current Events
Virginia Postrel
Belmont Club
Mickey Kaus

Belles Lettres
Uncouth Reflections
Arts and Letters Daily

In the Pipeline

Category Archives

June 16, 2014

Your Metal Azide Worries Are Over

Email This Entry

Posted by Derek

You may not have felt the need for a better synthesis of metal azides. Personally, my metal azide requirements are minimal, and very easily satisfied. I can get all I need by looking at a structure drawn on a whiteboard from about twenty feet away, thanks, and have no desire to actually prepare any of these things. I do not see this as an irrational reluctance. For example, last year I wrote about mercury azides, a most alarming class of compounds whose synthesis would be much easier if the two solvent layers didn't keep getting disturbed by explosions. I've also covered selenium tetraazide, a cheerful lemon-yellow solid with the annoying habit of blowing up when it gets warmer than about -64C, which would explain why you don't run into it very often.

Ah, but perhaps that's about the change. Thanks to this paper, a collaboration between two groups in Munich (at the TU-München and the Ludwigs-Maximilien-Universität), we now have far easier entry to a wide range of metallic polyazides, oh joy. It turns out that silver azide in liquid ammonia slowly does redox reactions with a variety of other elements, giving a wide variety of otherwise hard-to-obtain compounds. The careful reader will have noted a defect in this scheme: you first have to make a supply of silver azide, which is enough of a show-stopper for me. That Wikipedia article drolly notes that "In its most characteristic reaction, the solid decomposes explosively", and because it's a silver salt, that decomposition can be set off by foolhardy behavior like shining a strong light on it.
So there's your starting material - now let's use it to make something lively. Shown is a corundum crucible before and after heating up a sample of the manganese azide product (as an ammonia complex). Again, the careful reader will note a crucial detail about the post-analysis state of this labware: it has been blown to hell and gone. This will surely happen to everything in which you heat up samples of metal azides, and believe me, many of these items will be less sturdy than a corundum crucible. Before performing this operation, be sure to ask yourself: "Do I want this apparatus to be blown to pieces?"

And before making the metal azide in the first place, naturally, you need to ask "Do I want to blow myself to pieces?" That's because this isn't one of those set-it-and-forget-it Crock-Pot azide reactions. No, you're going to have to hand-craft these things:

". . .The reaction mixtures were intensively stirred using a magnetic stirrer when all AgN3 is dissolved (after approximately one day). As long as there is a residue of AgN3, the vessel only should be shaken very gently to prevent silver azide grains to be ground at the glass wall of the vessel."

Yes, "grinding" is one of those verbs that you don't want to hear about when azide preps are being discussed, along with "stomping", "whacking", "flinging" and several others to which is only response should be "fleeing". Ah, but once you've dissolved that pesky silver azide, the fun is only just coming over the horizon:

"Crust formation occurring at the fluid level and consisting of silver azide at the beginning of the reaction and the respective metal azide at the end of the reaction have to be carefully scraped off the glass every day with a Teflon spatula. The scraping has to be performed with extreme care. . ."

See, I told you that you didn't want to do this. "Scraping" is yet another one of those verbs that you don't want to hear brought up in this context. If your touch isn't quite delicate enough, someone's going to have to use a larger spatula to scrape you off the ceiling. I note that the experimental section of this paper not only recommends the leather coats that earlier workers in the field have used, but gives suppliers in Berlin and Cologne. And earplugs. And face shields. And helmets. And Kevlar gloves. If scientific meetings were more like fantasy cons, people would be dressing up like this to win prizes.

Comments (27) + TrackBacks (0) | Category: Things I Won't Work With

June 5, 2014

Friendly, Welcoming Triazides. No, Really.

Email This Entry

Posted by Derek

OK, now I'm confused. I can't help but have doubts about this sentence: "Despite their high nitrogen content, the geminal triazides are easy to handle, even when preparative-scale syntheses are performed." It's from a new paper in Ang. Chem., and that just might take these things right out of the "Things I Won't Work With" category. So consider this a marginal entry in the series. I have no "Things That Really Aren't So Bad" category, unfortunately. But I still wondered if these people were pulling my leg. "Easy to handle" compared to what? Cocaine-soaked cobras?

But the authors (from the Kirsch group at the Bergische Universität Wuppertal), mean what they say. And they won my admiration quickly, starting their paper by saying "Over the last decade, the field of organic azides has witnessed a tremendous “boom” (a joke that works just as well in German as it does in English). I also like their summary of previous polyazide literature:

Besides the compounds described herein, only a limited number of polyazidated molecules have been reported with carbon atoms having a similarly high degree of azide substitution. For example, Banert et al. generated the highly explosive tetraazidomethane C(N3)4 in 2007. Hassner et al. described triazidomethane HC(N3)3, the handling of which is also not straightforward. Moreover, several polyazides from higher homologues of Group 14 elements are known, some of which are highly explosive. . .

I've covered some of those very compounds before, and yeah, "not straightforward" is one way to describe their handling. Although looked at from another angle, they're very straightforward indeed: if you make them, they will blow you up.

So anyone who knows anything about azide chemistry would take a look at the current compounds, dive under the desk, and wait for the kaboom. Mystifyingly, it does not come. You can tell that the authors were puzzled, too - I'm sure that they arrived at the proposed structure somewhat reluctantly, because surely these compounds (well, what's left of them) should be accelerating through the newly created skylight by now, right?

It took some analytical work to figure them out, since (as the manuscript points out) there's not too much comparison data out there. I remember the triazidomethane paper having an NMR spectrum, but I always suspected that they ran it in somebody else's magnet down the hall without telling them. But in this case, 15N labeling studies indicated the triazide, and reaction with cyclooctyne to give the (very odd looking) tris-triazole derivative nailed it down for sure. The chemistry to make them seems pretty robust, but looking at the reaction scheme, I still can't shake the sensation, seeing stoichiometric IBX being used to make a geminal triazide, that I'm looking at crater bait. But the products are stable in solution up to 60C, and small amounts could be rota-vapped down without explosion.

The authors advise appropriate caution, of course - these things have to blow up under some sort of provocation, and they'll be bad news when they do. I would not advise scraping them out of a sintered glass funnel with a metal spatula. But the Supplementary Information file describes the prep of two grams of one of these things, which is a convincing demonstration of confidence. If you tried that with any of the previously known organic polyazides, you'd want to get your affairs in order first, hand out earplugs as a courtesy to the crowd, and probably get the cameras running so your descendants can make money off the YouTube ad revenues. No, that's really remarkable stability.

So are these things I won't work with, or not? I'm still not too enthusiastic about trying any of these myself - I most particularly would not have wanted to be the person who made the two-gram batch. (I wonder if they're figured out the structure before the guy did that or not? I hope that's a joke). But under duress, forced to synthesize polyazides at gunpoint, that these are certainly the ones I'd pick. "Most stable triazide" isn't a very reassuring endorsement, but you have to take what you can get.

Comments (22) + TrackBacks (0) | Category: Things I Won't Work With

August 28, 2013

Mercury Azides. I'll Get Right On Those For You.

Email This Entry

Posted by Derek

Azides have featured several times in the Things I Won't Work With series, starting with simple little things like, say, fluorine azide and going up to all kinds of ridiculous, gibbering, nitrogen-stuffed detonation bait. But for simplicity, it's hard to beat a good old metal azide compound, although if you're foolhardy enough to actually beat one of them it'll simply blow you up.

There's a new paper in Angewandte Chemie that illustrates this point in great detail. It provides the world with the preparation of all kinds of mercury azides, and any decent chemist will be wincing already. In general, the bigger and fluffier the metal counterions, the worse off you are with the explosive salts (perchlorates, fulminates, and the others in the sweaty-eyebrows category). Lithium perchlorate, for example, is no particular problem. Sodium azide can be scooped out with a spatula. Something like copper perchlorate, though, would be cause for grave concern, and a phrase like "mercury azide" is the last thing you want to hear, and it just might be the last thing you do.

As fate would have it, though, none of this chemistry is simple. You can get several crystalline forms of mercuric azide, for one thing. The paper tells you how to make small crystals of the alpha form, which is not too bad, as long as you keep it moist and in the dark, and never, ever, do anything with it. You can make larger crystals, too, by a different procedure, but heed the authors when they say: "This procedure is only recommended on a small scale, since crystalline α-Hg(N3)2 is very sensitive to impact and friction even if it is wet. Heavy detonations occur frequently if crystalline α-Hg(N3)2 is handled in dry state".

Ah, but now we come to the beta form. This, by contrast, is the unstable kind of mercury azide, as opposed to that spackle we were just discussing. These crystals are not as laid-back, and tend to blow up even if they're handled wet. Or even if they're not handled at all. Here, see if you've ever seen an experimental procedure quite like this one:

After a few minutes, the deposition of needle-like crystals starts at the interface between the nitrate and the azide layer (β-Hg(N3)2). After some time,
larger crystals tend to sink down, during this period explosions frequently occur which leads to a mixing of the layers, resulting in the acceleration of crystal formation and the growth of a mat of fine needle-like crystals. . .

Hard to keep a good smooth liquid interface going when things keep blowing up in there, that's for sure. Explosions are definitely underappreciated as a mixing technique, but in this case, they are keeping you from forming any larger crystals, a development which the paper says, with feeling, "should be avoided by all means". But it's time to reveal something about this paper: all this mercury azide stuff is just the preparation of the starting material for the real synthesis. What the paper is really focused on is the azide salt of Millon's base [Hg2N+].

Now that is a crazy compound. Millon's base is a rather obscure species, unless you're really into mercury chemistry or really into blowing things up (and there's a substantial overlap between those two groups). A lot of the literature on it is rather old (it was discovered in the early 1800s), and is complicated by the fact that it usually comes along as part of a mixture of umpteen mercury species. But it really is a dimercury-nitrogen beast, and what it's been lacking all these years - apparently - is an azide counterion.

There are two crystalline forms of that one, too, and both preparations have their little idiosyncracies. Both forms, needless to say, are hideously sensitive to friction, shock, and so on - there's no relief there. For the beta form, you take some of that mercuric diazide and concentrated aqueous ammonia, and heat them in an autoclave at 180C for three weeks. No, I didn't just have some sort of fit at the keyboard; that's what it says in the paper. I have to say, putting that stuff in an autoclave has roughly the same priority, for me, as putting it under my armpits, but that's why I don't do this kind of chemistry.

But the alpha form of the Millon's azide, now that one takes some patience. Read this procedure and see what it does for you:

Nitridodimercury bromide [Hg2N]Br (0.396g, 0.8mmol) is suspended in a saturated aqueous solution of sodium azide NaN3 (dest. ca. 3mL) at ambient temperature, resulting in an orange suspension which was stirred for ten minutes. The solution is stored at ambient temperature without stirring under exclusion of light. After one week, the colourless supernatant was removed by decantation or centrifugation and the orange residue was again suspended in a saturated aqueous solution of sodium azide NaN3. This procedure was repeated for 200 to 300 days, while the completion of the reaction was periodically monitored by PXRD, IR and Raman spectroscopy. . .

So you're looking at eight months of this, handling the damn stuff every Monday morning. The authors describe this procedure as "slightly less hazardous" than the other one, and I guess you have to take what you can get in this area. But the procedure goes on to say, rather unexpectedly, that "longer reaction times lead to partial decomposition", so don't go thinking that you're going to get a higher yield on the one-year anniversary or anything. What way to spend the seasons! What might occur to a person, after months of azidomercurial grunt work . . .surely some alternate career would have been better? Farm hand at the wild animal ranch, maybe? Get up when the chickens would be getting up, if they'd made it. . .head out to the barn and slop the wolverines. . .hmm, forsythia's starting to bloom, time to neuter the hyenas soon. . .

No, no such luck. The hyenas will have to remain unspayed, because it's time to add fresh azide to the horrible mercury prep. Only three more months to go! Sheesh.

Comments (42) + TrackBacks (0) | Category: Things I Won't Work With

May 8, 2013

Things I Won't Work With: Dimethylcadmium

Email This Entry

Posted by Derek

Cadmium is bad news. Lead and mercury get all the press, but cadmium is just as foul, even if far fewer people encounter it. Never in my career have I had any occasion to use any, and I like it that way. There was an organocadmium reaction in my textbook when I took sophomore organic chemistry, but it was already becoming obsolete, and good riddance, because this one of those metals that's best avoided for life. It has acute toxic effects, chronic toxic effects, and if there are any effects in between those it probably has them, too.

Fortunately, cadmium is not well absorbed from the gut, and even more fortunately, no one eats it. But breathing it, now that's another matter, and if you're a nonchemist wondering how someone can breath metallic elements, then read on. One rather direct way is if someone is careless enough to floof fine powders of them around you. That's how cadmium's toxicity was discovered in the first place, from miners dealing with the dust. But that's only the start. There's a bottom of the list for breathable cadmium, too, which is quite a thought. The general rule is, if you're looking for the worst organic derivatives of any metal, you should hop right on down to the methyl compounds. That's where the most choking vapors, the brightest flames, and the most panicked shouts and heartfelt curses are to be found. Methyl organometallics tend to be small, reactive, volatile, and ready to party.

Dimethyl cadmium, then, represents the demon plunked in the middle of the lowest circle as far as this element is concerned. I'll say only one thing in its favor: it's not quite as reactive as dimethyl zinc, its cousin one row up in the periodic table. No one ever has to worry about inhaling dimethyl zinc; since it bursts into ravenous flames as soon as it hits the air, the topic just never comes up. Then again, when organozincs burn, they turn into zinc oxide, which is inert enough to be used in cosmetics. But slathering your nose with cadmium oxide is not recommended.

Even though dimethylcadmium does not instantly turn into a wall of flame, it can still liven the place up. If you just leave the liquid standing around, hoping it'll go away, there are two outcomes. If you have a nice wide spill of it, with a lot of surface area, you fool, it'll probably still ignite on its own, giving off plenty of poisonous cadmium oxide smoke. If for some reason it doesn't do that, you will still regret your decision: the compound will react with oxygen anyway and form a crust of dimethyl cadmium peroxide, a poorly characterized compound (go figure) which is a friction-sensitive explosive. I've no idea how you get out of that tight spot; any attempts are likely to suddenly distribute the rest of the dimethylcadmium as a fine mist. Water is not the answer. One old literature report says that "When thrown into water, (dimethylcadmium) sinks to the bottom in large drops, which decompose in a series of sudden explosive jerks, with crackling sounds", and you could not ask for a clearer picture of the devil finding work for idle hands. Or idle heads.

Even without all this excitement, the liquid has an alarmingly high vapor pressure, and that vapor is alarmingly well absorbed on inhalation. a few micrograms (yep, millionths of a gram) of it per cubic meter of air hits the legal limits, and I'd prefer to be surrounded by far less. It's toxic to the lungs, naturally, but since it gets into the blood stream so well, it's also toxic to the liver, and to the kidneys (basically, the organs that are on the front lines when it's time to excrete the stuff), and to the brain and nervous system. Cadmium compounds in general have also been confirmed as carcinogenic, should you survive the initial exposure.

After all this, if you still feel the urge to experience dimethylcadmium - stay out of my lab - you can make this fine compound quite easily from cadmium chloride, which I've no particular urge to handle, either, and methyllithium or methyl Grignard reagent. Purifying it away from the ethereal solvents after that route, though, looks like extremely tedious work, which allows you the rare experience of being bored silly by something that's trying to kill you. It is safe to assume that the compound will swiftly penetrate latex gloves, just like deadly and hideous dimethylmercury, so you'll want to devote some time to thinking about how you'll handle the fruits of your labor.

I'm saddened to report that the chemical literature contains descriptions of dimethylcadmium's smell. Whoever provided these reports was surely exposed to far more of the vapor than common sense would allow, because common sense would tell you to stay about a half mile upwind at all times. At any rate, its odor is variously described as "foul", "unpleasant", "metallic", "disagreeable", and (wait for it) "characteristic", which is an adjective that shows up often in the literature with regard to smells, and almost always makes a person want to punch whoever thought it was useful. We can assume that dimethylcadmium is not easily confused with beaujolais in the blindfolded sniff test, but not much more. So if you're working with organocadmium derivatives and smell something nasty, but nasty in a new, exciting way that you've never quite smelled before, then you can probably assume the worst.

Now, as opposed to some of the compounds on my list, you can find people who've handled dimethylcadmium, or even prepared it, worse luck, although it is an (expensive) article of commerce. As mentioned above, it used to be in all the textbooks as a reliable way to form methyl ketones from acid chlorides, but there are far less evil reagents that can do that for you now. It's still used (on a research scale) to make exotic photosensitive and semiconducting materials, but even those hardy folk would love to find an alternative. No, this compound appears to have no fan club whatsoever. Start one at your own risk.

Comments (53) + TrackBacks (0) | Category: Things I Won't Work With

April 5, 2013

Chlorine Trifluoride: Some Empirical Findings

Email This Entry

Posted by Derek

Over the years, I've probably had more hits on my "Sand Won't Save You This Time" post than on any other single one on the site. That details the fun you can have with chloride trifluoride, and believe me, it continues (along with its neighbor, bromine trifluoride) to be on the "Things I Won't Work With" list. The only time I see either of them in the synthetic chemistry literature is when a paper by Shlomo Rozen pops up (for example), but despite his efforts on its behalf, I still won't touch the stuff.

And if anyone needs any more proof as to why, I present this video, made at some point by some French lunatics. You may observe the mild reactivity of this gentle substance as it encounters various common laboratory materials, and draw your own conclusions. We have Plexiglas, a rubber glove, clean leather, not-so-clean leather, a gas mask, a piece of wood, and a wet glove. Some of this, under ordinary circumstances, might be considered protective equipment. But not here.

Comments (42) + TrackBacks (0) | Category: Chemical News | Things I Won't Work With

January 9, 2013

Things I Won't Work With: Azidoazide Azides, More Or Less

Email This Entry

Posted by Derek

When we last checked in with the Klapötke lab at Munich, it was to highlight their accomplishments in the field of nitrotetrazole oxides. Never forget, the biggest accomplishment in such work is not blowing out the lab windows. We're talking high-nitrogen compounds here (a specialty of Klapötke's group), and the question is not whether such things are going to be explosive hazards. (That's been settled by their empirical formulas, which generally look like typographical errors). The question is whether you're going to be able to get a long enough look at the material before it realizes its dream of turning into an expanding cloud of hot nitrogen gas.

It's time for another dispatch from the land of spiderweb-cracked blast shields and "Oh well, I never liked that fume hood, anyway". Today we have a fine compound from this line of work, part of a series derived from N-amino azidotetrazole. The reasonable response to that statement is "Now hold it right there", because most chemists will take one look at that name and start making get-it-away-from-me gestures. I'm one of them. To me, that structure is a flashing red warning sign on a dead-end road, but then, I suffer from a lack of vision in these matters.

But remember, N-amino azidotetrazole (I can't even type that name without wincing) is the starting material for the work I'm talking about today. It's a base camp, familiar territory, merely a jumping-off point in the quest for still more energetic compounds. The most alarming of them has two carbons, fourteen nitrogens, and no hydrogens at all, a formula that even Klapötke himself, who clearly has refined sensibilities when it comes to hellishly unstable chemicals, calls "exciting". Trust me, you don't want to be around when someone who works with azidotetrazoles comes across something "exciting".
It's a beast, all right. The compound is wildly, ridiculously endothermic, with a heat of formation of 357 kcal/mole, all of which energy is ready to come right back out at the first provocation (see below). To add to the fun, the X-ray crystal structure shows some rather strange bond distances, which indicate that there's a lot of charge separation - the azides are somewhat positive, and the tetrazole ring somewhat negative, which is a further sign that the whole thing is trembling on the verge of not existing at all.

And if you are minded to make some yourself, then you are on the verge of not existing at all, either. Both the initial communication and the follow-up publication go out of their way to emphasize that the compound just cannot be handled:

Due to their behavior during the process of synthesis, it was obvious that the sensitivities (of these compounds) will be not less than extreme. . .

The sensitivity of C2N14 is beyond our capabilities of measurement. The smallest possible loadings in shock and friction tests led to explosive decomposition. . .

Yep, below the detection limits of a lab that specializes in the nastiest, most energetic stuff they can think up. When you read through both papers, you find that the group was lucky to get whatever data they could - the X-ray crystal structure, for example, must have come as a huge relief, because it meant that they didn't have to ever see a crystal again. The compound exploded in solution, it exploded on any attempts to touch or move the solid, and (most interestingly) it exploded when they were trying to get an infrared spectrum of it. The papers mention several detonations inside the Raman spectrometer as soon as the laser source was turned on, which must have helped the time pass more quickly. This shows a really commendable level of persistence, when you think about it - I don't know about you, but one exploding spectrometer is generally enough to make recognize a motion to adjourn for the day. But these folks are a different breed. They ended up having to use a much weaker light source, and consequently got a rather ugly Raman spectrum even after a lot of scanning, but if you think you can get better data, then step right up.

No, only tiny amounts of this stuff have ever been made, or ever will be. If this is its last appearance in the chemical literature, I won't be surprised. There are no conceivable uses for it - well, other than blowing up Raman spectrometers, which is a small market - and the number of research groups who would even contemplate a resynthesis can probably be counted on one well-armored hand.

Comments (58) + TrackBacks (0) | Category: Things I Won't Work With

May 15, 2012

Things I Won't Work With: Selenophenol

Email This Entry

Posted by Derek

This fine reagent was mentioned here (disparagingly) in the comments the other day, and I knew that it was time to add it to the list. I've had some other selenium entries before, and they're all here for the same reason: their unsupportable stenches. Everyone, even people who've never had a chemistry class in their lives, knows that sulfur compounds are stinky, of course, but it's a problem that continues as you move down Group XVI of the periodic table.

And it's not like plain phenol itself has no odor. It's strong, penetrating, and completely unmistakable. As soon as I get a whiff of the stuff, I'm immediately transported back to the Verser Clinic, the small hospital in the town I grew up in back in Arkansas. Phenol smells like an old-fashioned medical office; it was used for many years as a disinfectant (and was, in fact, introduced as such by Joseph Lister himself). If you move it down a notch to sulfur, you get thiophenol, which is easy to describe: burning rubber - the pure, potent, platonic ideal of burning rubber, bottled up and daring you to open the cap. I can't say that I won't work with thiophenol, since I have (very much to my regret, at times), but I've used it most reluctantly, and probably haven't touched it in at least fifteen years.

Ah, but move down one more element and you have selenophenol, and that's a more exotic reagent. I've never seen any, and after reading the descriptions, I never want to. Actually, let me take that back: I'd look at some from the other end of the lab. What I never want to do is open any of it up. The chemical literature has numerous examples of people who are at a loss for words when it comes to describing its smell, but their attempts are eloquent all the same. A few years ago, Gaussling at the Lamentations on Chemistry blog referred to it as "The biggest stinker I have run across. . .Imagine 6 skunks wrapped in rubber innertubes and the whole thing is set ablaze. That might approach the metaphysical stench of this material." So we'll start with that.

I believe that this lovely compound is commercially available (if you're anywhere close to anyone making it, you'll know about it). But should you wish to prepare it with your own hands, do violence to your own schnozz, and drape yourself out of your own window while you throw up into your own rhododendrons, feel free to use this reliable preparation from Organic Syntheses, circa 1944. This features the note that "it is frequently advisable to work with [selenium compounds] on alternate days", which I suppose is to give them time to work their way out of your nasal passages.

I'm not so sure. When I was a teaching assistant in grad school, I taught three labs a week one semester, and one of those labs, damn it all, was the phenyl Grignard reagent. We had them making it in diethyl ether, outside of the small and inadequate fume hoods, and the solvent fumes were fit to strip paint. By the end of the Monday lab, I was well saturated with ether and had a terrible headache, which returned as soon as I caught my first whiff of the stuff on Tuesday afternoon. I barely made it through that lab, mostly by holding my breath and using a lot of hand gestures, and I took the opportunity on Wednesday to get as much fresh air as I could. But when I came back for the Thursday session, the first first wave of ether vapor washed over me and nearly stretched me out on the tiles. I taught the entire lab from the hallway, shouting and waving like Monty Python's "Semaphore Version of Wuthering Heights". So in my mind, the choice between getting these things over with and stretching them out is still not settled.

That Org Syn prep also notes that it can produce small amounts of hydrogen selenide, which is very toxic indeed (and will give you a sore throat, too, apparently, before it kills you). This luckless graduate student from the 1920s got to experience both of these bracing selenium room fresheners in the course of his work:

Berzelius described the poisonous effect of hydrogen selenide quite impressively; "In order ta get acquainted with the smell of this gas I allowed a bubble not larger than a pea to pass into my nostril ; in consequence of its smell I so completely loss my sense of smell for several hours that I could not distinguish the odor of strong ammonia even when held under my nose. My sense of smell returned after five or six hours, but severe irritation of the mucous membrane set in and persisted for a fortnight' The writer has been working on the gas for some time and was also quite seriously affected once, the injury persisting for many days. That it is more poisonous than the hydrogen sulphide is well known."

So you have that to look forward to on your way to selenophenol. And at your destination? Assuming your nose is still attached to your face, you'll experience what few chemists ever have. I'll let this 1908 report from Wisconsin take over:

When benzeneselenonic acid in solution is treated with reducing agents such as hydrogen sulphide, sulphur dioxide, or, best, with zinc and hydrochloric, acid selenophenol is obtained as a yellow oil with an overpowering and most nauseating odor. . .The odor of diphenyl diselenide is extremely disagreeable but is not nearly so bad as that of selenophenol.

. . .The effect of selenophenol on the skin is very similar to that of thiophenol, forming blisters which itch intensely. After a time, these dry up, the skin scales off, and there appears to be a deposit of red selenium beneath it. The odor of selenophenol is very penetrating, and is nauseating beyond description.

Gloves, man, gloves. Unless, of course, you wish to be tattooed with elemental selenium while being nauseated beyond description. Should this be your idea of a fun Saturday night, I will not stand in your way.

Comments (47) + TrackBacks (0) | Category: Things I Won't Work With

November 11, 2011

Things I Won't Work With: Hexanitrohexaazaisowurtzitane

Email This Entry

Posted by Derek

Let's start with the name. Quite a mouthful, isn't it? Believe me, that one's pretty chewy even for experienced organic chemists. We see lots of more complicated nomenclature, of course, but this one some features some speed bumps, that make you go back to make sure that you're reading it correctly. I'll take you through my own thoughts as an example.

You skip to the end in chemical names - Mark Twain would have felt about them the same way he felt about the German language. But this brings me up short, because very few chemists could walk up to the board and draw an isowurtzitane. And I am not among their number. I have a vague picture of these "wurtz" compounds being funky three-dimensional cage structures, and that much only from having probably read too many photochemistry papers over the years. So the only thing that "isowurtzitane" calls to mind is some complicated framework of fused rings, looking like one of those wire sculptures that unexpectedly fold up flat when you pull on them.

Moving on out, as you do in a systematic name, I see that this is a hexaaza variation, which makes the picture a bit fuzzier. That's a lot of nitrogens substituted for carbons, and the first thought is that this must be some weirdo condensation product of ammonia, some aldehyde, and who knows what. You can get some pretty funny-looking structures that way, like hexamethylenetetramine (which I've actually used a couple of times). I don't know where those nitrogens are, I think to myself, but I'll bet that's how they got there, because any other pattern would be a synthetic nightmare. So far, so good. But now comes the u