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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

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March 3, 2005

Things I Won't Work With: Carbon Diselenide

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Posted by Derek

Column VI of the periodic table doesn't start out smelly, but that's probably just because we run on its first element, oxygen. Animal ancestors of ours who felt woozy all the time from the stench of oxygen didn't leave much of a legacy, so we're all pretty positive about it. But when you start moving down into the next rows, everything changes.

Sulfur's next, and its fame as a reeking element is well deserved. Skunks, rotten eggs, burning tires - they all have delightful sulfurous tang, and we have sulfur compounds in the lab that are worse yet. But most people don't think about the elements to come.

The next heavier element in the series is selenium, which most people will have heard of primarily from its presence in health food stores. It is indeed an essential trace element, although I'd think that if your cuisine includes a reasonable amount of garlic (as it should!) then you're getting all the selenium you need. You don't want to overdo it, because this essential dietary factor is also a pretty efficient poison, which is a useful First Lesson in Toxicology right there. (And no, I don't think it's possible to get selenium poisoning from eating too much garlic; I think many other effects would kick in before you noticed any selenium-related problems.)

Selenium compounds are, if anything, more intrinsically noxious than sulfur ones. Imagine a sort of hyperskunk, scattering its enemies before it and making them carom off trees and dive into ponds. The heavier selenium atoms tend to make the compounds less volatile, though, so you don't always get their full bouquet. The smaller compounds get in their licks, though. One of the simpler selenium-rich compounds, for example, is carbon diselenide, an exact homolog of the carbon dioxide in your breath and in your glass of soda. Instead of a gas, the selenide is an oily liquid with a higher boiling point than water. Most of us organic chemists have never seen it.

Which is just fine. The first report of the compound in the chemical literature is from a German university group from 1936, and it was a memorable debut. A colleague of mine had a copy of this paper in his files, and he treasured a footnote from the experimental section which related how the vapors had unfortunately escaped the laboratory and forced the evacuation of a nearby village. The authors stressed the point that its aroma was like nothing that they'd ever encountered.

The compound made a few appearances over the next couple of decades, but one of the next synthetic papers dates from 1963. (That's Journal of Organic Chemistry 28, 1642, for you curious chemists.) The authors are forthright:

"It has been our experience that redistilled carbon diselenide has an odor very similar to that of carbon disulfide. However, when (it is) mixed with air, extremely repulsive stenches are gradually formed. Many of the reaction residues gave foul odors which were rather persistent (and) it should be noted that some of the volatile selenium compounds produced may be extremely toxic as well as foul."

Something for everyone! At least it lets you know when it's coming. Interestingly, in recent years, the compound has actually made a comeback, with more references to it in the past twenty years than in the fifty before. It's been used to prepare a number of odd compounds that have shown promise as organic semi- and superconductors, and there's actually a commercial source for the disgusting stuff (which may be a first.) I'd like to see what they ship it in.

Comments (14) + TrackBacks (0) | Category: Things I Won't Work With


1. The Novice Chemist on March 3, 2005 10:10 PM writes...

So is there anything that will kill the smell? I'm always a fan of using bleach to kill sulfur smells, but I don't know how easy or difficult it is to oxidize the selenium.

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2. mike on March 4, 2005 8:00 AM writes...

Bleach works reasonably well to remove the smell from solutions of organoselenium compounds. I used volatile selenium compounds as a graduate student, and rinsing all glassware with bleach before removing them from the hood was essential in order to keep my labmates from complaining.

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3. jeff bonwick on March 4, 2005 9:51 AM writes...

You neglected to mention the granddaddy of them all,
one row down: tellurium. Inhalation of even trace amounts causes "tellurium breath", which is worse than garlic breath and lasts for months.

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4. Derek Lowe on March 4, 2005 10:15 AM writes...

Hah! As is typical of the blogging world, I'm saving that one for another post. You're right about the breath - I've heard of people who basically had to take leaves of absence to get over tellurium exposure.

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5. otey on March 4, 2005 12:30 PM writes...

Your post today is one reason I visit this site so frequently. Delightful and well done.

A non-chemist.

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6. Harry on March 5, 2005 8:00 PM writes...

I have a lot of experience with organoselenium compounds. When I first started my own custom manufacturing laboratory, selenium chemistry was a hot ticket item.

In fact there was even an organoselenium compound called Ebselen

that was being clinically tested as an NSAID.

We made a number of selenium compounds (Diphenyl diselenide, Selenophene, Benzene seleninic acid, Selenomethionine, etc) almost every one of those compounds reeked to a greater or lesser extent.

Phenyl Selenol, which was the precursor to the Diphenyl Diselenide was the worst, even a small whiff of it was enough to set off cold-like symptoms for about 8 hours, and the smell was abominable!

We did get inquiries from time to time for Carbon diselenide. We declined after reading this statement (paraphrased ) by Gunter in his massive book on Selenium chemistry. "Carbon diselenide has by far the worst odor this author has experienced in his lifetime of working with selnium compounds". Knowing what the ones we already worked with smelled like- we had no desire to try one that was even worse.

Fortunately our business had grown away from those compounds, and they no longer appear to be hot ticket items. Thanks for bringing back some old memories

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7. nonesuch on March 6, 2005 4:35 AM writes...

"And no, I don't think it's possible to get selenium poisoning from eating too much garlic"

Damn. And here I thought that it might be possible to give vampires selenium poisoning.

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8. Stu Savory on March 6, 2005 1:23 PM writes...

Our chem-lecturer at university used "tellurium-breath!" as a verbal insult to people he intensly disliked ;-)

Stu Savory

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9. Silyld on March 7, 2005 4:12 AM writes...

Ha - good post. As someone who used to have make multigram lots of the stuff for semiconucdtor research on at least a montly basis i cannot disagree with you. Its a pig to make - passing boiling DCM over elemental selenium at 400 degrees is not fun - and the clean up operation was even worse. We used to store it in the freezer at -20 for quite a long period of time (and then chcuk the freezer after a couple of years !). Its an excellent way of inserting CSe2 into carbamates BTW !

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10. Fletch on March 7, 2005 12:27 PM writes...

Those of us who are old enough and who have worked with electronics prior to the modern semiconductor age are sure to remember the lovely odor of roasted selenium rectifiers. They used to be a component in virtually every inexpensive TV, radio, and low power device. Drawing excessive current through one of these devices produced an immediate cloud of vile smelling vapor and an immediate evacuation of the area. I can still smell the stuff in my memory and it has been a good forty or more years since I had the misfortune to toast one!

Having grown up in a house with an organic chemistry lab in the basement, I find your writings remind me of the special things I took for granted. Oysters and Urine were the two major odiferous components in my dad’s lab (he was a biochemist). On the other hand, my grandfather’s lab was more oriented to tanning leather odors. I was twelve before I realized that not all kids had that neat stuff in their basements.

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11. The Novice Chemist on March 7, 2005 3:15 PM writes...

What, might I ask, was your father doing in the downstairs lab? This brings to mind a whole other thing: are we losing amateur scientists? It's one thing to build a cruise missile in your backyard (home electronics and aviation enthusiasts are common), but home chemistry (especially the non-amphetamine syntheses) would seem to be rather difficult.l

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12. Douglas on March 7, 2005 9:14 PM writes...

Anecdotally, yes, we are losing amateur chemists. When using too much electricity is probably cause for a search warrant, when buying glassware runs the risk of a visit from the DEA... Doing things is the offical, legal domain of business only, not consumers.

In short, *I'm* too scared to be an amateur chemist, despite a deep fascination.

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13. Fletch on March 8, 2005 6:31 AM writes...

Downstairs lab was used for consulting work and research. For a long time, dad was one of the few chemists around who did estrogen determinations - it paid a lot more than Georgetown and the U of MD where he taught. My grandfather was chief chemist for the Dept of Agriculture, and he was a plain old workaholic.

Thnking about basement labs reminds me that if either of those labs were in existance today, they would have been in violation of every environmental and drug law in existance. Not that the labs were dangerous, they were spotless and neat, but "OMG - he has CHEMICALS in his house! He is a druggie or terrorist and is polluting the neighborhood". And you wonder why there is a decline in home science?

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14. Eric Jablow on March 9, 2005 11:14 PM writes...

Does anybody make and sell real chemistry sets for children any more? Is there a worthy successor to the A. C. Gilbert Chemistry set? My niece's tenth birthday is coming up.

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