June 26, 2009

The Taming Of White Phosphorus

A research team headed by Dr. Jonathan R. Nitschke at the University of Cambridge (UK) and Academy Professor Kari Rissanen at the University of Jyväskylä (Finland) has made a breakthrough in rendering white phosphorus table to air, as reported in the latest issue of Science.
White phosphorus, a molecular solid consisting of discrete P4 tetrahedra, is ordinarily pyrophoric (and thus stored under water) - it bursts spontaneously into flame upon contact with atmospheric oxygen (when taken out from under water).

The joint research groups were able to show unambiguously that white phosphorus, viz. P4 molecules were encapsulated within the container molecules prepared by the Cambridge team and structurally characterized in Jyväskylä. Within these capsules, the phosphorus becomes air stable for months. A view of the encapsulated P4 inside the container molecule can be seen here http://users.jyu.fi/~krissane/P4_full.html
(manipulate the molecule by selecting it by mouse and clicking).

Even being tightly bound it is possible to release the encapsulated P4 by the addition of a competing guest, benzene. Once removed, the white phosphorus regains its air-sensitivity, rapidly reacting with oxygen if present.

This work thus provides a novel way to handle white phosphorus safely, and a potentially new means of stabilizing similar very sensitive and reactive chemicals from the environment, and conversely, protecting the environment from hazardous substances.


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