Water acts as catalyst for explosions

March 21st, 2009 - 12:51 pm ICT by IANS  

London, March 21 (IANS) Water, the most abundant liquid on earth, exhibits some unusual chemical properties when placed under extreme conditions. It can even trigger explosions.
Scientists at the Lawrence Livermore National Lab (LLNL) in California have shown that water, in hot dense environments, plays an unexpected role in catalysing complex explosive reactions.

A catalyst is a compound that speeds chemical reactions without being consumed. Platinum and enzymes are common catalysts but water rarely, if ever, acts as a catalyst under ordinary conditions.

Detonations of high explosives made up of oxygen and hydrogen produce water at thousands of degrees Kelvin and up to 100,000 atmospheres of pressure, similar to conditions in the interiors of giant planets.

While the properties of pure water at high pressures and temperatures have been studied for years, this extreme water in a reactive environment has never been studied until now.

Using first-principle atomistic simulations of the detonation of the high explosive PETN (pentaerythritol tetranitrate), the team discovered that in water, when one hydrogen atom serves as a reducer and the hydroxide (OH) serves as an oxidiser, the atoms act as a dynamic team that transports oxygen between reaction centres.

“This was news to us,” said lead researcher Christine Wu. “This suggests that water also may catalyse reactions in other explosives and in planetary interiors.”

This finding is contrary to the current view that water is simply a stable detonation product, according to a Lawrence Lab release.

“Under extreme conditions, water is chemically peculiar because of its frequent dissociations,” Wu said. “As you compress it to the conditions you’d find in the interior of a planet, the hydrogen of a water molecule starts to move around very fast.”

These findings are slated for publication in the April issue of the new journal Nature Chemistry.

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