Fragmentation mechanisms in mass spectrometry of Chemical Weapons Convention related spiro alkylphosphonates and alkyldioxaphosphinane oxides

• Microsynthesis and NMR, EI-MS and ESI-MS analyses of some spiro alkylphosphonates I and alkyldioxaphosphinane oxides II, which are covered under schedule 2.B.4 of Chemical Weapons Convention (CWC) annex of chemicals, are reported.
• Electron ionization (EI) and electrospray ionization (ESI) mass spectra of these chemicals, with possible fragmentation routes, were investigated via analysis of fragment ions of deuterated analogs and MS–MS experiments.
• The proposed fragmentation pathways include some new ionization processes, such as isomerization of cations to stabilized carbocations and oxocarbocations, and elimination of formaldehyde and alkoxy through concerted retro [2 + 2] cycloaddition reaction and 1,2 PO alkyl shift.
• These data could be useful for the successful detection and identification of CWC-related chemicals in on-site inspection and OPCW proficiency tests.

The availability of mass spectra and interpretation skills are essential for unambiguous identification of the Chemical Weapons Convention (CWC)-related compounds. This paper examines electron ionization (EI) and electrospray ionization (ESI) mass spectral fragmentation routes of spiro alkylphosphonates I and 5,5-bis(chloromethyl)-2-alkyl-1,3,2-dioxaphosphinane 2-oxides II as compounds which are covered under CWC schedule 2.B.4. Mass spectrometric studies revealed some fragmentation pathways, such as elimination of alkyl(oxo)phosphane oxide (RPO2), chlorine, chloromethylene, alkene, HCl, and H2O, α-cleavage and McLafferty-type and hydrogen rearrangements. The proposed fragmentation processes include some new fragmentation patterns, such as isomerization of cations to stabilized carbocations and oxocarbocations, and elimination of formaldehyde and alkoxy through concerted retro [2 + 2] cycloaddition reaction and 1,2 PO alkyl shift. Structures of fragments were confirmed using EI-MS and MS/MS analysis of the deuterated analogs. The results will make a contribution to the Organization for the Prohibition of Chemical Weapons (OPCW) Central Analytical Database (OCAD) which may be used for the detection and identification of CWC-related compounds during on-site inspection and OPCW proficiency tests.

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