Here are a couple of recent articles by chemist Derek Lowe, author of the classic Sand Won’t Save You This Time

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

January 9, 2013

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”.

http://pipeline.corante.com/azidoazide.png

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.

See link for reader’s comments.

Chlorine Trifluoride: Some Empirical Findings

April 5, 2013

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.

video

Sounds like a fun activity for the next pud!

OCDC said:

Sounds like a fun activity for the next pud!

Perhaps, although I have to confess that my idea of fun doesn’t involve playing with substances that set sand on fire.

:)

pftfweka

I posted this one on the old SSSF, but for those who missed it…

Things I Won’t Work With: Selenophenol

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 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.

……………

I ought to add that the tellurium analogues are allegedly even more stinky than the selenium ones.

I had some fun with pungent odours during chem. Thoroughly (temporarily) damaged some olfactory nerves a couple of times. All good now though.

>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.

A fitter at the coal plant that I used to run many years ago got covered in cresol, which is a mixture of methylated phenols. It gave him nasty burns that turned a bright pink colour over time.

I wonder if there is a small amount of selenium analogues in natural phenols of coal origin. There are certainly sulfur analogues. They accumulated in certain parts of the circuit.

Ketene is an interesting compound. The most pungent stuff I have ever encountered. Almost impossible to seal it in a bottle. I made the mistake of opening up a much wrapped bottle once to see why it was so wrapped. Big mistake.

OCDC said:

I had some fun with pungent odours during chem. Thoroughly (temporarily) damaged some olfactory nerves a couple of times. All good now though.

I got a few whiffs of some interesting sulfur compounds, and I guess I got a bit of olfactory damage from chlorine, bromine, and NO₂.

The halogines are evil chemicals, I’d imagine they are not found free in nature.
I mean you couldnt walk through a pristine forrest and suddenly start gurgling and clawing at your throat because you went ito a pocket of swamp chlorene?

Not in a forest, perhaps, but sulfur and methane and other stuff can be found in the wild.

Peak Warming Man said:

The halogines are evil chemicals, I’d imagine they are not found free in nature.
I mean you couldnt walk through a pristine forrest and suddenly start gurgling and clawing at your throat because you went ito a pocket of swamp chlorene?

Well, halogens are rather reactive, so they don’t tend to persist in large quantities in the free state, but some natural processes can liberate free halogens, and it’s pretty easy to smell free halogens in rather low concentration. IIRC, the decomposition of seaweed can liberate iodine.

Sounds like fun.

We ‘accidentally’ made tear gas in organic chem, my eyes were fnerked for 3 days after. The fume hood, it did not work as described…

OCDC said:

Not in a forest, perhaps, but sulfur and methane and other stuff can be found in the wild.

Lake Nyos is surrounded by forest

PM 2Ring said:

IIRC, the decomposition of seaweed can liberate iodine.

You’d be overpowered by the stench of rotting H2S and other S compounds before any trace amount of iodine hit you…

PM 2Ring said:

Peak Warming Man said:

The halogines are evil chemicals, I’d imagine they are not found free in nature.
I mean you couldnt walk through a pristine forrest and suddenly start gurgling and clawing at your throat because you went ito a pocket of swamp chlorene?

Well, halogens are rather reactive, so they don’t tend to persist in large quantities in the free state, but some natural processes can liberate free halogens, and it’s pretty easy to smell free halogens in rather low concentration. IIRC, the decomposition of seaweed can liberate iodine.

I was reading something recently where someone had discovered free fluorine in micro pores in rocks. They were led to the discovery by the smell of the crushed rock.

I am glad I won’t work near UC again.

Their dioxin disposal was appalling.

http://cheeseburgergothic.com./ckfinder/userfiles/images/france.jpg

morrie said:

Ketene is an interesting compound. The most pungent stuff I have ever encountered. Almost impossible to seal it in a bottle. I made the mistake of opening up a much wrapped bottle once to see why it was so wrapped. Big mistake.

Interesting. What does it smell like? As a super-acetylating agent, I imagine it would smell like vinegar. I have an interest in the relationship between the odour and chemical structure of chemical substances. Not so much about the evil-smelling ones, more about the pleasant-smelling ones, as well as the differences that can occur within a homologous series. I have a hypothesis that the notably more toxic members have a distinctly different odour to their less-toxic relatives. For example, to me (noting that to different people for genetic reasons, the subjective odour of particular compounds may differ), dichloromethane and chloroform have fairly similar odours (though chloroform is “heavier”), but carbon tetrachloride, a particularly toxic member of this series, has a very different odour (also interesting is the fact that carbon tetrachloride is a very much poorer solvent than the other two compounds).

PM 2Ring said:

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.

It was only yesterday before seeing this thread that I had mentioned to someone that according to Wikipedia, nitrogen triiodide is the only known chemical explosive that detonates when exposed to alpha particles and nuclear fission products.

On the topic of azides, I think it is remarkable that hydrazoic acid, perhaps the strongest of all reducing agents (caesium azide decomposes to the elements on heating), can be synthesised from ammonia, a not particularly reactive compound, by an oxidative process.

KJW said:

morrie said:

Ketene is an interesting compound. The most pungent stuff I have ever encountered. Almost impossible to seal it in a bottle. I made the mistake of opening up a much wrapped bottle once to see why it was so wrapped. Big mistake.

Interesting. What does it smell like? As a super-acetylating agent, I imagine it would smell like vinegar. I have an interest in the relationship between the odour and chemical structure of chemical substances. Not so much about the evil-smelling ones, more about the pleasant-smelling ones, as well as the differences that can occur within a homologous series. I have a hypothesis that the notably more toxic members have a distinctly different odour to their less-toxic relatives. For example, to me (noting that to different people for genetic reasons, the subjective odour of particular compounds may differ), dichloromethane and chloroform have fairly similar odours (though chloroform is “heavier”), but carbon tetrachloride, a particularly toxic member of this series, has a very different odour (also interesting is the fact that carbon tetrachloride is a very much poorer solvent than the other two compounds).

It is a long time ago and I can’t recall the smell, apart from the incredible pungency.

I don’t think of chloroform and dichloromethane as being similar. Chloroform has a sweeter smell to me while dichloromethane,which I use as a solvent adhesive is more aggressive. Carbon tetrachloride has a much lesser smell than the other two.

In terms of pungency, perhaps the most pungent thing I have encountered is 1-octene-3-one. It is responsible for the metallic smell of steel. I accidentally made some when I cooked up a big pot of mushrooms.

Another interesting thing I have picked up is that some people describe the smell of benzaldehyde as being like almonds, while other perceive it as a cherry smell. That surprised me. Another smell from mushrooms.

morrie said:

I don’t think of chloroform and dichloromethane as being similar. Chloroform has a sweeter smell to me while dichloromethane,which I use as a solvent adhesive is more aggressive. Carbon tetrachloride has a much lesser smell than the other two.

Dichoromethane and chloroform are easily distinguished by odour, but I do think they have the same type of odour, whereas carbon tetrachloride is very different. However, I could be the odd one out because my collegues at the time had mistaken the odour of carbon tetrachloride for chloroform, whereas to me the odour was similar to cyclohexane and nothing like chloroform (to me, cyclohexane has an odour like carbon tetrachloride and nothing like light petroleum).

morrie said:

Another interesting thing I have picked up is that some people describe the smell of benzaldehyde as being like almonds, while other perceive it as a cherry smell. That surprised me. Another smell from mushrooms.

To me… almonds (although I’m more familiar with benzaldehyde itself). When I first tried Dr Pepper, it reminded me of benzaldehyde. It’s curious to me that both benzaldehyde and hydrogen cyanide are described as having an almond-like odour (I have never smelled HCN). Almonds are said to contain the cyanohydrin of benzaldehyde, and therefore produce both benzaldehyde and hydrogen cyanide on hydrolysis, but this would not explain any similarity between the odours of these two compounds.

KJW said:

morrie said:

Another interesting thing I have picked up is that some people describe the smell of benzaldehyde as being like almonds, while other perceive it as a cherry smell. That surprised me. Another smell from mushrooms.

To me… almonds (although I’m more familiar with benzaldehyde itself). When I first tried Dr Pepper, it reminded me of benzaldehyde. It’s curious to me that both benzaldehyde and hydrogen cyanide are described as having an almond-like odour (I have never smelled HCN). Almonds are said to contain the cyanohydrin of benzaldehyde, and therefore produce both benzaldehyde and hydrogen cyanide on hydrolysis, but this would not explain any similarity between the odours of these two compounds.

Yes, it is interesting that both components are reported to have an almond smell.

http://lateralscience.co.uk/Fluorine/Fluorine.html

My own experience with fluorine has been solely with its compounds. In particular, natural calcium fluoride crystals (fluorite or fluorspar). Also hydrofluoric acid, during a highly ill-advised “experiment” I witnessed being conducted in the clean room of a semiconductor manufacturer. The glass and quartz-ware used in diffusion furnaces must be kept scrupulously clean to avoid contamination of the silicon wafers being processed. Consequently it is periodically bathed in a mixture of hydrofluoric and nitric acids. Full protection clothing was donned over normal clean room eyes-only-exposed garb, and a large silicon wafer (complete with defective 4Mb DRAMs) was “carefully” thrown into the acid bath. Nothing happened for about twenty seconds, as the HF attacked the silicon, heating up the wafer until a runaway reaction started. The acid bath then erupted into a frightening boiling maelstrom, with the violent evolution of copious amounts of red and brown fumes of nitrogen oxides. The complete destruction of high technology by the tiger of chemistry. Splendid. Note – Acid ready for disposal was used, production was not compromised, and no animals were endangered. I stood well back!

http://theodoregray.com/PeriodicTable/Stories/011.2/index.html