What's this about Chemical-Warfare?! Nerve agents?! What's the difference between VX and Sarin?

Question

In light of the bizarre murder/assasination of N. Korean dictator's 1/2 bro at a Malaysian airport, the world's "deadliest weapon of mass destruction" has been herald as VX in all the news headlines. I haven't heard of it... and apparently not very many others have as well?

VX is part of a group of nerve-agents (organophosphates) that have been created and used as chemical warfare as "weapons of mass deconstruction." It can be diseminated via liquid or vapor that has neither scent nor taste, which makes it so terrifying. Watch and learn more about the history of VX on the History Channel clip.

But I don't understand how VX differs from Sarin (another nerve-agent used for Chemical Warfare but possibly in Syria and Iraq)? I don't understand how they differ in their symptoms and manifesting themselves.

Why is VX so much more potent?

Answer 1

Both are organo-phosphorous/phosphate compounds, and both act by inhibiting acetylcholinesterase, leading to sustained muscle contraction and usually death by asphyxiation.

Sarin however is much less stable due to the phosphorus-fluorine bond being easily broken by water or basic/nucleophilic materials. The products of this hydrolysis are relatively non-toxic phosphonic acids. Not all of the VX hydrolysis products appear to be fully non-toxic, which likely adds to it's designation as "deadliest".

Additionally, there's the measured LD50 of the two, with Sarin being 172 μg/kg (rat, intravenous) and VX being only 7 µg/kg. I don't know the exact chemical reasons for this, but one could assume the differences in structure lead to different and possibly more efficient binding affinity for VX or some other "advantageous" feature that makes it so deadly.

And finally, the two agents have different levels of volatility. Sarin is much more volatile, and so can be "cleared" much more easily. VX is likely to stick around in contaminated materials since it doesn't evaporate out of them as easily, and this could arguably make it more "deadly" over time.

Useful and in depth reference here