Gas Chromatography-Mass Spectrometric Studies of O -Alkyl O -2-( N,N -Dialkylamino) Ethyl Alkylphosphonites(Phosphonates) for Chemical Weapons Convention Verification

The electron ionization (EI) mass spectra of a series of O-alkyl O-2-(N,N-dialkylamino)ethyl alkylphosphonites(phosphonates), which are precursors of nerve agents, were studied for Chemical Weapons Convention (CWC) verification. General EI fragmentation pathways were constructed and discussed. Proposed fragment structures were confirmed through analyzing fragment ions of deuterated analogs and density functional theory (DFT) calculations. The observed fragment ions are due to different fragmentation pathways such as hydrogen and McLafferty+1 rearrangements, alkene, amine and alkoxy elimination by α- or β-cleavage process. Fragment ions distinctly allow unequivocal identification of the interested compounds including those of isomeric compounds. The presence and abundance of fragment ions were found to depend on the size and structure of the alkyl group attached to nitrogen, phosphorus and oxygen atoms.