Theoretical proton affinity and fluoride affinity of nerve agent VX

Area of Science:

• Computational Chemistry
• Chemical Reactivity
• Toxicology

Background:

• Nerve agent VX is a highly toxic organophosphorus compound.
• Understanding VX's reactivity is crucial for developing effective countermeasures and decontamination strategies.

Purpose of the Study:

• To computationally investigate the proton and fluoride affinities of VX at all potential reactive sites.
• To elucidate the preferred reaction pathways and products upon protonation and fluoridation of VX.

Main Methods:

• Density Functional Theory (DFT) calculations using B3LYP functional with 6-31G* and 6-31+G* basis sets.
• Second-order Møller–Plesset perturbation theory (RI-MP2) with cc-pVTZ and aug-cc-pVTZ basis sets for energy calculations.
• Analysis of protonation sites, dissociation channels, and fluoride ion interactions.

Main Results:

• Protonation preferentially occurs at the nitrogen atom, with a high proton affinity (-ΔE ∼ 251 kcal/mol).
• CH4 dissociation and molecular destruction channels were identified as energetically accessible.
• The most favorable fluoride reaction pathway involves S-P bond cleavage, yielding a fluorinated product and a dealkylated fragment (-ΔE ∼ 44 kcal).
• F- ion-molecule complexes were also observed, indicating diverse interaction modes.

Conclusions:

• VX exhibits unique reactivity patterns distinct from surrogate compounds.
• The calculated affinities and reaction pathways provide critical insights into VX's chemical behavior.
• These findings can inform the design of agents for VX detection, neutralization, and medical treatment.