We present hybrid density functional theory (DFT) calculations of gas-phase hydrolysis of dimethyl methylphosphonate (DMMP) by the cyclic tetramer of zirconium hydroxide. Various binding configurations of DMMP and its hydrolysis products to the tetramer as well as transition structures connecting them were explored using structure optimizations based on multiple, randomly selected initial structures. Consistent with previously reported adsorption of DMMP on hydroxylated surfaces of metal oxides, we find that DMMP initially binds to the tetramer by forming a hydrogen bond between the phosphoryl O and a bridging hydroxyl. DMMP can further interconvert to a more stable Lewis adduct with the phosphoryl O coordinated to a Zr atom. We also find that the addition of a terminal hydroxyl to DMMP followed by methanol elimination from the resulting trigonal bipyramidal intermediate is thermodynamically and kinetically favored over other possible hydrolysis mechanisms. We present a detailed reaction path diagram for the addition-elimination mechanism. These calculations support recent observations of the reactivity of amorphous zirconium hydroxide toward organophosphorus compounds including chemical warfare agents.

Gas-phase hydrolysis of dimethyl methylphosphonate by the cyclic tetramer of zirconium hydroxide

254th National Meeting (2017)

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