Interaction of vapor-phase and liquid organophosphonates with inorganic surfaces

Chemical warfare agents (CWAs) pose a threat to humanity, which motivates research focused on their destruction. Often, research deals with non-toxic simulants of CWAs, such as dimethyl methyl phosphonate (DMMP) and diisopropyl methyl phosphonate (DIMP). These compounds, like CWAs, are liquids at room temperature and boil just below 200 °C. In different scenarios, their interactions with inorganic solids may initially involve either liquid or vapor phases. This paper reviews published experimental data describing how the initial phase (vapor or liquid) of DMMP or DIMP influences the properties of their residues adsorbed to different inorganic surfaces. To facilitate comparisons between different sets of experiments, the focus is on the commonly reported shift and possible split of the PO peak assigned to the phosphoryl group, sensitive to molecular interactions in organophosphorus liquids and detected by Fourier Transform Infrared (FTIR) spectroscopy. Data sets for multiple metal oxides and salts are compared to one another. Systematic and distinct trends are found for the PO peak behavior for residues of evaporated and liquid DMMP and DIMP left on different surfaces. The literature data offer compelling evidence that the properties of residues left by organophosphonates on inorganic surfaces vary depending on the initial phase of the organophosphonate.