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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: derekb.lowe@gmail.com Twitter: Dereklowe

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In the Pipeline

« The Hydrophobic Effect: I Don't Understand It, Either | Main | Dr. Oz's Problem »

January 28, 2013

Asking the Hard Questions

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Posted by Derek

Well, it is a hard question, and I don't know the answer, either. On Twitter, See Arr Oh wonders:

Know that tangy smell that LAH / NaH give off? Is that oil volatiles, or trace H2 being formed from room moisture?

I'm not sure, but I'd be willing to bet that hydrogen has no smell at all - it would seem too small and too bereft of interactions to see off the nasal receptors. So my guess is mineral oil constituents in the case of sodium hydride, which I usually handle as the dispersion. Now, the lithium aluminum hydride is a dry powder, so in that case, I'd say that I'm smelling the real stuff, which can't be improving my nose very much. That lines up with Chemjobber's explanation: "It's the smell of your nose hairs being deprotonated." Any other guesses?

Comments (20) + TrackBacks (0) | Category: Life in the Drug Labs


COMMENTS

1. Ed on January 28, 2013 1:33 PM writes...

I think it is microscopic airborne particles of reagent reacting with your nasal mucosa.

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2. Victor on January 28, 2013 1:36 PM writes...

some italic tag needs closing

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3. Rich Apodaca on January 28, 2013 1:52 PM writes...

Always wondered the same.

BTW, you can embed tweets in pages:

https://dev.twitter.com/docs/embedded-tweets

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4. katre on January 28, 2013 2:07 PM writes...

I don't know about NaH or LAH, but once while prepping a lab I somehow managed to wave the neat hydrochloric acid the wrong way and got a good smell.

Now I know what it smells like when my mucus membranes turn acidic. Hurt like hell while I was running to the sink.

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5. Hap on January 28, 2013 2:32 PM writes...

NaH/LiH come from the metals - could there be traces of gallium or arsenic in the metals used to make them? For LAH, the aluminum could be a source of those impurities, but for NaH that wouldn't make sense. Alternatively, if they both come from H2, could there be impurities (arsine? phosphine?) in the hydrogen that are incorporated into the hydrides which are released upon hydrolysis? (You would expect that commercial H2 might smell similarly, though, if that were the case.)

What does DBU smell like? If there were airborne base frying your nose, weaker bases than NaH/LAH ought to be required to get the smell.

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6. milkshake on January 28, 2013 2:54 PM writes...

my guess would be phosphine, PH3, originating from trace P impurities in used metals. Very stinky - like rotten garlic

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7. B on January 28, 2013 3:28 PM writes...

@4: I've never minded the smell of neat HCl...breaks up the monotony of making buffers, that's for sure!

NaH I am not as much of a fan of, though I suspect it is something to do with the mineral oil. To me, pure Na (or as close I've come before oxidation) is odorless.

@6: My undergrad had an open drainage system (all drains and sinks went down one pipe). Anyone upstream could make fumes come out of drains in labs downhill, as it were. A graduate student 'accidentally' poured his phosphine reaction down the sink after it was done. The smell was one of the most horrid things I've ever experienced and it lasted for days...

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8. sgcox on January 28, 2013 4:03 PM writes...

It is all in vibrations !
http://www.bbc.co.uk/news/science-environment-21150046

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9. John Wayne on January 28, 2013 4:56 PM writes...

Yeah! What is the BuLi smell? I always guessed it was trace butene from a slow beta elimination, but I never had a GCMS to check my hypothesis.

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10. Oldnuke on January 28, 2013 8:44 PM writes...

I remember asking my late Father what phosgene smelled like (I was working with him at duPont on pesticide development, methomyl to be precise, and phosgene and methyl isocyanate were intermediates). He told me freshly mowed grass and daisies, which I'd be pushing up if there was a leak.

That stuck quote with me for over 40 years... The next summer, I worked somewhere safer -- Fort Detrick.

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11. Broton on January 28, 2013 9:57 PM writes...

Hydrogen is in fact odorless. I base that on an observation I had in high school chem class, when I set up a Hoffman apparatus to make some, and didn't realize part of the collecting widget had a big hole in it.

I stood over the thing for a good few minutes trying to figure out the problem, and never smelled a thing.

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12. Anniechem on January 28, 2013 9:57 PM writes...

We always joke in my lab that it's "the taste of hydride". Although troubling to think about, I think that because dry NaH, CaH2, LAH is such a fine powder that the dust is easily raised, and then unfortunately you inhale a small amount (!).

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13. bones mcghee on January 28, 2013 11:24 PM writes...

I believe it was on an old Org Prep Daily that I first came upon this amazing phosgene image. (thanks milkshake!)

http://thisiswarblog.files.wordpress.com/2012/12/phosgene.jpeg?w=223&h=300

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14. Nosterius on January 29, 2013 7:35 AM writes...

It reminds me of an Angewandte Chemie article on the smell of metals (Angewandte Chemie, Int ed. 2006, vol 45, p 7006). Basically, they say that purified PH3 has no smell at all (seems like they actually tried it).

The odor of coinage originates from aldehydes obtained by reaction of the metal(s) with our skin. I'd expect the reducing power of NaH and LAH dusts to react with our nose mucosa.

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15. MoMo on January 29, 2013 8:55 AM writes...

Just goes to show all the Non-chemists out there that we medicinal chemists are the heroes of Pharma--By constantly exposing ourselves to chemicals that aren't even quantifiable!

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16. PointyHairedBoss on January 29, 2013 12:25 PM writes...

@15 MoMo: "Just goes to show all the Non-chemists out there that we medicinal chemists are the heroes of Pharma--By constantly exposing ourselves to chemicals that aren't even quantifiable!"

Bullfritters. I can quantify ANYTHING.

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17. marklar on January 29, 2013 1:02 PM writes...

How about this one: Every time I used Fe powder for nitro group reductions, there was a definite blood-like smell. You could even sense it when the powder was under an aqueous mixture. Probably has something to do with the chelation with various hemes, albeit at very low concentrations.

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18. eugene on January 29, 2013 4:11 PM writes...

LAH gives off the smell of pain. At least that's what I associate it with. NaH I always used as a suspension so it doesn't tend to fly up, and when I needed it pure, it was stored in a glove box after washing it with hexane. I assume it smells like a similar kind of pain though.

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19. random passerby on January 29, 2013 6:41 PM writes...

Hmmm... while we are talking about smells...

Hydrogen Sulfide: The Next Anti-Aging Agent?

WASHINGTON, DC – January 29, 2013 – Hydrogen sulfide (H2S) may play a wide-ranging role in staving off aging...

(sorry for plaigiarising, ASM!)

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20. ek on January 30, 2013 11:26 AM writes...

Well, I don't think these two guys who recently breathed in H2S will need to worry about staving off aging:

www.ynetnews.com/articles/0,7340,L-4337217,00.html

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