The most important chemical reactions of phosphoryl halides is the
hydrolysis of the bond between phosphorus and the fluoride. This P-F bond is easily broken by nucleophilic agents, such as water and
hydroxide. At high
pH, sarin decomposes rapidly to nontoxic
phosphonic acid derivatives.
[12][13]
Sarin degrades after a period of several weeks to several months. The shelf life can be shortened by impurities in precursor materials. According to the
CIA, some Iraqi sarin had a shelf life of only a few weeks, owing mostly to impure precursors.
[14]
Its otherwise-short shelf life can be extended by increasing the purity of the precursor and intermediates and incorporating
stabilizers such as
tributylamine. In some formulations, tributylamine is replaced by
diisopropylcarbodiimide (DIC), allowing sarin to be stored in
aluminium casings. In
binary chemical weapons, the two precursors are stored separately in the same
shell and mixed to form the agent immediately before or when the shell is in flight. This approach has the dual benefit of solving the stability issue and increasing the safety of sarin munitions.
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