Midey Anthony J, Miller Thomas M, Viggiano A A
Air Force Research Laboratory, Space Vehicles Directorate, 29 Randolph Road, Hanscom AFB, Massachusetts 01731-3010, USA.
J Phys Chem A. 2009 Apr 30;113(17):4982-9. doi: 10.1021/jp900614a.
Kinetics studies of a variety of positive and negative ions reacting with the GX surrogate, dimethyl methylphosphonate (DMMP), were performed. All protonated species reacted rapidly, that is, at the collision limit. The protonated reactant ions created from neutrals with proton affinities (PAs) less than or equal to the PA for ammonia reacted exclusively by nondissociative proton transfer. Hydrated H(3)O(+) ions also reacted rapidly by proton transfer, with 25% of the products from the second hydrate, H(3)O(+)(H(2)O)(2), forming the hydrated form of protonated DMMP. Both methylamine and triethylamine reacted exclusively by clustering. NO(+) also clustered with DMMP at about 70% of the collision rate constant. O(+) and O(2)(+) formed a variety of products in reactions with DMMP, with O(2)(+) forming the nondissociative charge transfer product about 50% of the time. On the other hand, many negative ions were less reactive, particularly, SF(5)(-), SF(6)(-), CO(3)(-), and NO(3)(-). However, F(-), O(-), and O(2)(-) all reacted rapidly to generate m/z = 109 amu anions (PO(3)C(2)H(6)(-)). In addition, product ions with m/z = 122 amu from H(2)(+) loss to form H(2)O were the dominant ions produced in the O(-) reaction. NO(2)(-) underwent a slow association reaction with DMMP at 0.4 Torr. G3(MP2) calculations of the ion energetics properties of DMMP, sarin, and soman were also performed. The calculated ionization potentials, proton affinities, and fluoride affinities were consistent with the trends in the measured kinetics and product ion branching ratios. The experimental results coupled with the calculated ion energetics helped to predict which ion chemistry would be most useful for trace detection of the actual chemical agents.
开展了多种正离子和负离子与模拟物GX（甲基膦酸二甲酯，DMMP）反应的动力学研究。所有质子化物种反应迅速，即在碰撞极限下反应。由质子亲和力（PA）小于或等于氨的质子亲和力的中性物质产生的质子化反应物离子仅通过非解离质子转移进行反应。水合H₃O⁺离子也通过质子转移迅速反应，来自第二水合物H₃O⁺(H₂O)₂的产物中有25%形成质子化DMMP的水合形式。甲胺和三乙胺均仅通过聚集反应。NO⁺也以约70%的碰撞速率常数与DMMP聚集。O⁺和O₂⁺与DMMP反应形成多种产物，O₂⁺约50%的时间形成非解离电荷转移产物。另一方面，许多负离子反应性较低，特别是SF₅⁻、SF₆⁻、CO₃⁻和NO₃⁻。然而，F⁻、O⁻和O₂⁻均迅速反应生成m/z = 109 amu的阴离子（PO₃C₂H₆⁻）。此外，O⁻反应中产生的主要离子是失去H₂形成H₂O的m/z = 122 amu的产物离子。NO₂⁻在0.4 Torr下与DMMP发生缓慢的缔合反应。还进行了DMMP、沙林和梭曼离子能量性质的G3(MP2)计算。计算得到的电离势、质子亲和力和氟亲和力与测得的动力学和产物离子分支比趋势一致。实验结果与计算得到的离子能量相结合，有助于预测哪种离子化学对实际化学战剂的痕量检测最有用。
