Microsynthesis and mass spectral study of Chemical Weapons Convention related 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides

Abstract

Chemical Weapons Convention (CWC)-related compounds where the phosphorus atom is part of a ring have very limited representation in mass spectral libraries and the open literature. Here we report electron ionization (EI), chemical ionization (CI) and electrospray ionization tandem mass spectrometry (ESI-MS n ) spectra and retention indices for 2-alkyl-1,3,6,2-dioxathiaphosphocane-2-oxides (alkyl C 1 to C 3 ) which are new cyclic chemicals covered under the CWC. The EI mass spectra show a pattern of ion fragmentation that is similar to that of other cyclic phosphonates in that loss of the alkylphosphonic acid as a neutral loss is more important than the presence of the protonated alkylphosphonic acid. In contrast to other cyclic phosphonates, the 2-alkyl-1,3,6,2-dioxathiaphosphocane-2-oxides show almost no protonated alkylphosphonic acid and as a result the spectra do not carry the same distinctive signature of the phosphorus-carbon bond that is required for the chemical to be covered under the CWC.

Mass spectral characterization of the CWC‐related isomeric dialkyl alkylphosphonothiolates/alkylphosphonothionates under gas chromatography/mass spectrometry conditions

“…In the present study, the EI spectra of all the phosphonothionates (19)(20)(21)(22)(23)(24)(25)(26)(27) show the expected • OR radical loss from the molecular ion; however, the spectra also include the ion due to the loss of • SR radical from the molecular ion, [M-SR] + , which is always of lower abundance (<5%, except for 24) than the [M-OR] + ion. Formation of the [M-SR] + ion can be explained by a thiono-thiolo rearrangement.…”

“…Although the studied compounds undergo thiono-thiolo or thiolo-thiono Scheme 6. Plausible CI fragmentation pathways of (i) dialkyl alkylphosphonothiolates (1-18) and (ii) dialkyl alkylphosphonothionates (19)(20)(21)(22)(23)(24)(25)(26)(27) rearrangement, the resulting fragment ions from the rearranged products are found to be of low abundance. Consequently, this process does not affect the regular fragmentation pathways of the studied compounds that provide structural information.…”

“…In O,O'-dialkyl alkylphosphonothionates (19)(20)(21)(22)(23)(24)(25)(26)(27), alkyl groups are attached to both the oxygen and the phosphorus atom, and the other heteroatom (S) exists as P = S. Thus, in this case, it is important to determine the size of the alkyl group attached to oxygen and phosphorus (Scheme 4).…”

“…[25,26] Most of the precursor/degradation products of nerve agents such as phosphonofluoridates, phosphonic acids, cyclic and acylic phosphonates have been studied extensively for their unambiguous identification. [27][28][29] Dialkyl alkylphosphonothiolates and the corresponding phosphonothionates (schedule 2.B.4), which are precursors of the nerve agents and/or are by-products during the synthesis of the nerve agents, [30] are less toxic and are stable in normal environmental samples. Thus, they are often used as the spiking chemicals in the samples of the official PTs conducted by the OPCW.…”

Mass spectrometric study on O(S)-alkyl N,N-dimethylamino alkylphosphonates (alkylphosphonothiolates) for Chemical Weapons Convention verification purposes

“…mass spectra of the CW agents, their precursors and degradation products such as N,N-dialkylaminoethanols, alkylphosphonates, N,N-dialkylphosphoramidates, sulfur and nitrogen mustard, methylphosphonites, N,N-dialkylaminoethane-2-sulfonic acids, Noxides of aminoethanols, N,N-dialkylaminoethane-2-thiols, alkyl methylphosphoric acids [4][5][6][7][8][9][10][11][12][13][14]. One of the CWC-related chemicals is O(S)-alkyl N,N-dimethylamino alkylphosphonates (alkylphosphonothiolates).…”