Chemistry Blog

Halogen Bonding

Some of you may be familiar with the term “halogen bonding”. In analogy to hydrogen bonding, this weak interaction occurs between an electron donor, such as nitrogen, and a halogen (Cl, Br, I). The halogen acts as an electrophile.

This is possible because the halogen has a region of positive partial charge at its tip, the so-called sigma-hole, as shown by calculations (doi:10.1007/s00894-006-0130-2). The group of Resnati and Metrangolo in Milan have used this interaction to construct a variety of polymeric chains and networks for crystal engineering. As they discuss in their current Science paper (doi:10.1126/science.1162215), it also plays an important role for drug design, which I am particularly interested in. Many drugs on the market are halogenated aromatics. The exact role of the halogen for binding is not always known, since often it was introduced in order to tune the hydrophobicity of the compound. I suspect that in many instances, halogen bonding to a backbone carbonyl oxygen could be of importance.

Clearly, more work is required to further investigate halogen bonding in a biological context. If people want to incorporate this kind of interaction into rational drug design or crystal engineering, good quantitative models will be needed.

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Thermite Bullets

In the most recent issue of X-men, issue #193 Jan. 2007, there is an interesting new bullet used to fight one of the main villains in the current story arc. The bullets are fired by Mystique and lob into the water-based bad-guy. See image below.

Technically Hydrogen is neither a product of the reaction nor is it a by-product produced when the reaction is ran in the presence of water. But, if enough heat is radiated from the reaction in a short enough time in the presence of water, then yes, any surrounding water will probably decompose to it’s constituent parts of hydrogen and oxygen gas. You can click the picture above to see the whole comic page to better appreciate the chemical implications of Thermite Bullets.

Thermite Chemical Equation
Fe₂O₃(S) + 2Al(s) –> Al₂O₃(s) + 2Fe(s)

For more thermite action check out the Brainiac special below. Just keep in mind, Brainiac has been known to fake its science videos (to popularize science) to the grave dis-service of the actual science.

Finally, you can blame excimer of the coronene bloggers for this, but after navigating Jim Tour’s website a bit more thoroughly I’ve discovered an interesting audio file of Tour explaining his adventures of collecting Porn magazines from gas stations and the pervertedness of homosexuality. Link to file: The True Meaning of Manhood
How the hell can professors keep making these derogatory comments with impunity?

Note 1: Thermite does not detonate! Maybe HMX can cover the process of detonation and what it really involves as a guest blogger one day.

Mitch

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