IT is ON again: Na Promoted Aerobic Oxidation of Alcohols to Ketones, Tet. Lett., 2009, in press. [tx mt and Excimer][1]

  I’m not quite in a position yet to judge English (but shouldn’t there be a hyphen in the title?) In fact, what pissed me off is the negligence that led to a blatant (in my view) typo in the abstract. It is not nickel (III) chloride that should be there, but nickel (II) chloride. Because nickel (III) chloride does not exist in the hands of people who manage to pull this shit off. It immediately gets oxidized to Ni (MMXII).

  I don’t have problems with believing the chemistry. Shit happens, you know. Nickel and sodium metals under nitrogen will oxidize your mom. The reviewers have obviously had better things to do than paying attention. Or writing blog rants. Then, the confused reader is wondering: “Maybe it happened on quenching? Maybe their nitrogen was not pure?” and directs his attention to supplementary information. Which is? Bingo! Not there, ’cause it’s TetLett. I understand that you can’t tell everything there is in a four-page communication, and I’m sure that the authors are working on a follow-up, working so hard that they can’t even double-check what’s in the abstract of their fucking paper. They know it will attract attention, this is why they decided to work on it. Yet — they don’t give a fuck.

  Just fucking shoot me. I just can’t express my concern with the fact that this kind of thing happens all the fucking time, everywhere. I’m telling you, twenty years from now, when the internet kids will raise their kids, the last grammar nazis will be prosecuted the same way as the actual nazis are. Then y’all be crying like spanked bitches. I really hope that fucking neutrinos become microwaves way before this, so that we build giant floating buckets of hope and go adrift off the shores of Himalayas.

  No big deal? The consequences of chronic, ubiquitous neglect extend well beyond scientific publishing and writing. As it could’ve been put in Soviet Russia, today you neglect to notice a typo in the abstract of your paper, tomorrow you’ll sell the Motherland. In Soviet Russia, which might have suffered from neglect (among other things) more than any country in the world. I’m willing to go as far as blaming the failure of the cute little idea of communism on the fact that people don’t give a fuck, not because they’re evil or greedy as a society. Ok, I’d better wrap up now.

  I kind of feel miserable sitting here and spewing shit for no apparent reason. Why did I spend an hour writing about it, and fifteen more minutes editing it, why do I give a fuck? What if I don’t? Will you?

  [1] If the link doesn’t work, don’t blame me. I’m not the one who can’t make DOIs work for articles in press and publishes ISHTAR.

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Given my fascination with singlet oxygen, I absolutely have to direct you to this post on Khymos. Chemists who are also into homebrew should definitely check this out!

It’s been a while since I looked at anything oxygen-related. Maybe soon I’ll branch out from materials just a little and put something up on photodynamic therapy.

Back to something I started a while ago and didn’t finish: how to generate singlet oxygen. Probably the best-known means is photosensitization–use a dye (Rose Bengal, Methylene Blue, etc.) and a lamp. The dye is photoexcited and transfers its energy to oxygen, giving the singlet.[1] While this can involve some pretty cool-looking lamps (see left), it doesn’t have to–you can do it Dylan’s way with a lamp from Home Depot. (This group has even managed to do it without solvent!) Photochemical reactions can have some scale-up issues, though, despite being super-cool.

Alternatively, you can use peroxide and things involving metals (ew, metals, ick). Molybdates, peroxotungstates and La(OH)₃ seem to work alright.[2] CaO₂ appears to be the most popular, but it sounds kinda tricky to make. (Anyone done this?)

And then there’s a fun little reaction I did a while ago.[3] Uses a weird little hypervalent iodine compound–[Bis(trifluoroacetoxy)iodo]benzene, oft-abbreviated as “PIFA”–and catalytic H₂O₂ to generate singlet oxygen.

I mentioned singlet oxygen a while back in the context of solar cell materials. However, I didn’t get to go into specifics, and unlike solid-state chemistry (which is too close to solid-state physics for my tastes), photochemistry is among my current obsessions. While I can’t quite put this in completely plain non-chemist English, I think I can make it manageable for chemists who can’t do quantum.

Oxygen in its ground state is a triplet. Spectroscopic notation: ³Σg- This is a consequence of its degenerate HOMO energy levels. (Nice diagram from Wikipedia, but why isn’t it in the article about oxygen?) Focus on the two electrons in the pi-antibonding orbitals, OK? Their spins are parallel. This makes oxygen paramagnetic. I know SOMEONE has to have seen this demonstration, since the Physics department at Brown University has such a good picture of it.

You know, the one where you pour liquid oxygen over the poles of a really strong magnet…and it sticks? Looks like a little donut? (By contrast, if you do the same thing with liquid nitrogen, nothing this exciting happens.)

Back to the orbital diagram. Look at the pi-antibonding electrons. Imagine “flipping” one of them so that the spins points the other way. This is the ¹Σg+ state. While it is a singlet state (note the “1″ multiplicity instead of the “3″ for the ground state), it’s actually the second excited state. This one actually doesn’t get much consideration, because it decays so quickly to the first excited state that there isn’t time enough for it to do anything interesting.

So what are the electrons doing in the first excited state? Back to the pi-antibonding electrons in the diagram. Now visualize putting both of them into the same orbital and making the spins antiparallel. This is ¹Δg oxygen. It is what’s commonly referred to as singlet oxygen.

Why does this matter? Think of most organic compounds in their ground state. Absorbing a little light in the UV or visible range will immediately kick them up into an excited state. Of course, most organic compounds (radicals and triplet weirdos excluded!) are ground-state singlets, so their electrons have paired spins in the first place. And the excited state they reach when you add light is also a singlet. This is not accidental. It’s also something oxygen can’t do. This is because there are NO SPIN FLIPS DURING EXCITATION! As a consequence, triplet oxygen cannot be directly excited to the singlet state. (This is good news for us, since reactive oxygen species are not beneficial to our continued living.)

Next: how is singlet oxygen produced?

In order to explain why organic solar cells don’t last so long, a little chemistry background is in order. As I said in Part One, most carbon-based semiconductors are p-type materials.[1] These can be polymers or smaller molecules. P3HT, MEH-PPV, MDMO-PPV …the list goes on.