Microsynthesis and electron ionization mass spectral studies of O(S)-alkyl N,N-dimethyl alkylphosphono(thiolo)thionoamidates for Chemical Weapons Convention verification

Article abstract of DOI:10.1002/rcm.6407

RATIONALE The availability of mass spectra and interpretation skills are essential for unambiguous identification of the Chemical Weapons Convention (CWC)-related chemicals. The O(S)-alkyl N,N-dimethyl alkylphosphono(thiolo) thionoamidates are included in the list of scheduled CWC-related compounds, but there are very few spectra from these compounds in the literature. This paper examines these spectra and their mass spectral fragmentation routes. METHODS The title chemicals were prepared through microsynthetic protocols and were analyzed using electron ionization mass spectrometry with gas chromatography as a MS-inlet system. Structures of fragments were confirmed using analysis of fragment ions of deuterated analogs, tandem mass spectrometry and density functional theory (DFT) calculations. RESULTS Mass spectrometric studies revealed some interesting fragmentation pathways during the ionization process, such as alkene and amine elimination and McLafferty-type rearrangements. The most important fragmentation route of the chemicals is the thiono-thiolo rearrangement. DFT calculations are used to support MS results and to reveal relative preference formation of fragment ions. The retention indices (RIs) of all the studied compounds are also reported. CONCLUSIONS Mass spectra of the synthesized compounds were investigated with the aim to enrich the Organization for the Prohibition of Chemical Weapons (OPCW) Central Analytical Database (OCAD) which may be used for detection and identification of CWC-related chemicals during on-site inspection and/or off-site analysis such as OPCW proficiency tests. Copyright

Full text of DOI:10.1002/rcm.6407

Research Article
Received: 13 June 2012
Revised: 26 August 2012
Accepted: 16 September 2012
Published online in Wiley Online Library
Rapid Commun. Mass Spectrom. 2012, 26, 2805–2814
(wileyonlinelibrary.com) DOI: 10.1002/rcm.6407
Microsynthesis and electron ionization mass spectral studies of
O(S)-alkyl N,N-dimethyl alkylphosphono(thiolo)thionoamidates
for Chemical Weapons Convention verification
1
2
1
2
*
Hamdollah Saeidian , Mehran Babri , Morteza Abdoli , Mansour Sarabadani ,
Davood Ashrafi2 and Mohammad Taghi Naseri2
1Department of Science, Payame Noor University (PNU), P.O. Box 19395-4697, Tehran, Iran
2Defense Chemical Research Lab (DCRL), P.O. Box 31585-1461, Karaj, Iran
RATIONALE: The availability of mass spectra and interpretation skills are essential for unambiguous identification of the
Chemical Weapons Convention (CWC)-related chemicals. The O(S)-alkyl N,N-dimethyl alkylphosphono(thiolo)thiono-
amidates are included in the list of scheduled CWC-related compounds, but there are very few spectra from these
compounds in the literature. This paper examines these spectra and their mass spectral fragmentation routes.
METHODS: The title chemicals were prepared through microsynthetic protocols and were analyzed using electron
ionization mass spectrometry with gas chromatography as a MS-inlet system. Structures of fragments were confirmed using
analysis of fragment ions of deuterated analogs, tandem mass spectrometry and density functional theory (DFT) calculations.
RESULTS: Mass spectrometric studies revealed some interesting fragmentation pathways during the ionization process,
such as alkene and amine elimination and McLafferty-type rearrangements. The most important fragmentation route of
the chemicals is the thiono-thiolo rearrangement. DFT calculations are used to support MS results and to reveal relative
preference formation of fragment ions. The retention indices (RIs) of all the studied compounds are also reported.
CONCLUSIONS: Mass spectra of the synthesized compounds were investigated with the aim to enrich the Organization
for the Prohibition of Chemical Weapons (OPCW) Central Analytical Database (OCAD) which may be used for detection
and identification of CWC-related chemicals during on-site inspection and/or off-site analysis such as OPCW proficiency
tests. Copyright © 2012 John Wiley & Sons, Ltd.
Chemical warfare agents (CWAs) are toxic chemicals used as
weapons of war. CWAs, mainly mustard gas, were used on a
large scale in World War I. In addition to mustard gas,
nerve agents such as sarin and tabun were employed for the
first time in the Iran–Iraq war. Sarin also was used in some
terrorist attacks in Japan.[1] The Chemical Weapons Conven-
tion (CWC) prohibits the production, development, storage
and use of CWAs. Chemicals regarded as potential risk and
toxicity are listed in an annex to CWC in three distinct
schedules (scheduled chemicals). The Organization for the
Prohibition of Chemical Weapons (OPCW) is responsible
for implementation of the CWC. In order to detect and
identify CWC-related chemicals in different matrices, the
OPCW maintains a network of designated laboratories. The
analytical performance of designated laboratories and labora-
tories seeking designation is regularly evaluated by the
OPCW through official proficiency tests (PTs).[2] The monitor-
ing and analysis of CWAs, their precursors and degradation/
reaction products is an important part of verification activities
in support of the CWC.[3] For unambiguous identification
of CWC-related chemicals in environmental samples, the
availability of mass spectra, interpretation skills and rapid
microsynthesis of suspected chemicals are essential require-
ments. Mass spectrometry coupled with gas chromatography
(GC/MS) provides a key analytical technique for the unam-
biguous identification of scheduled chemicals during PTs
and off- and/or on-site analyses.[4] With respect to the
number of scheduled compounds, it is impossible to have a
complete collection of mass spectral data for all CWC-related
chemicals. In recent years, some studies have been reported
which include microsynthesis and interpretation of mass
spectra of such chemicals.[5–12] Except the other scheduled
compounds, chemicals with at least one phosphorus atom
bonded to methyl, ethyl, isopropyl, or propyl moieties are
included in schedule 2.B.4 of the CWC. They are precursors,
reaction or degradation products of nerve agents such as
sarin, soman, and VX. Their presence in environmental
matrices may show non-compliance with the CWC. O-Alkyl
N,N-dimethyl alkylphosphonothionoamidates and S-alkyl
N,N-dimethyl alkylphosphonothiolothionoamidates (general
structure shown below) are also included in schedule 2.B.4.
* Correspondence to: H. Saeidian, Department of Science, Payame
Noor University (PNU), P.O. Box 19395-4697, Tehran, Iran.
E-mail: dcrl@isiran-net.com
Rapid Commun. Mass Spectrom. 2012, 26, 2805–2814
Copyright © 2012 John Wiley & Sons, Ltd.

H. Saeidian et al.
were kept at 230 and 150 ꢀC, respectively. The scan range was
35–500 m/z. GC/MS/MS analyses were performed with an
Agilent 7890N gas chromatograph interfaced to a 7000A triple
quadruple mass spectrometer. The GC conditions were as
noted above. The MS/MS analyses were carried out using
nitrogen as collision gas, at collision energy of 10 eVand source
temperature of 180 ꢀC. Automated mass spectral deconvolution
and identification system (AMDIS) software was used to calcu-
late retention indices (RIs) of the synthesized compounds. An
alkane mixture [from octane (C8) to tetracosane (C24)] was used
for calculations of RIs.
To the best of our knowledge, no detailed investigation on the
mass spectral fragmentation process of these chemicals is
available in the literature.
S
H3C
N
P
O(S)R
H3C
R'
R ¼ alkylð≤ C6; incl: ArÞ; R0 ¼ CH3; C2H5
Computational details
All geometry optimizations and frequency calculations of all
species were carried out using the Gaussian 03 program.[15] Den-
sity functional theory with the Becke three parameters hybrid
functional (DFT-B3LYP) calculations were performed with a 6–
311 ++G (2d, 2p) basis set for all atoms. Vibrational frequencies
were calculated at the same level to ensure that each stationary
point is a real minimum. Harmonic-oscillator approximation
was also used for the thermodynamic partition functions.
After geometry optimization and frequency calculations, zero-
point energies (ZPEs) and thermal corrections are obtained at
298 K. Bond dissociation enthalpies (BDEs) of P–O and P–S
bonds were extracted from enthalpies as calculated by Gaussian
03. The difference between enthalpies for reactants and
products was used for calculation of BDEs.[16–18] Thus the BDE
A general microsynthesis protocol for the O(S)-alkyl N,N-
dimethyl alkylphosphono(thiolo)thionoamidates (Scheme 1)
was developed. Electron ionization (EI) mass spectra of these
chemicals with possible fragmentation routes are also investi-
gated through the analysis of fragment ions of deuterated
analogs, MS/MS experiments and energy calculations. Density
functional theory (DFT) calculations were performed in order to
find relative preference formation of fragment ions. The study is
also focused on the differentiation of isomeric compounds.
Furthermore, the retention indices (RIs) of all the studied
compounds are reported.
EXPERIMENTAL
+
•
for P–O bond in dissociation of [CH3P(S)(N(CH3)2)OCH3]
+
•
! CH3P(S)(N(CH3)2) + OCH3 is determined by:
Reagents and chemicals
ꢀ
ꢁ
All chemicals required for the microsynthesis of O(S)-alkyl
N,N-dimethyl alkylphosphono(thiolo)thionoamidates 4 were
purchased from Sigma-Aldrich (St. Louis, MO, USA), Fluka
(Neu-Ulm, Germany) and Merck (Darmstadt, Germany),
and were used as received. Alkylthiophosphonic dichlorides
1 were synthesized in-house by the existing method.[13,14]
ꢁ
þ
BDEP-O
¼
H
þ HOCH
3
CH PðSÞðNðCH Þ2
ð
Þ
3
3
ꢁþ
ꢂH CH PðSÞðNðCH Þ ÞOCH
½
3ꢃ
3
3
2
Procedure for the microsynthesis of O(S)-alkyl N,N-dimethyl
alkylphosphono(thiolo)thionoamidates 4
To a solution of dimethylamine hydrochloride (2) (0.2 mmol)
and alkylthiophosphonic dichloride 1 (0.2 mmol) in CH2Cl2
(300 mL), triethylamine (0.4 mmol) in CH2Cl2 (300 mL) was
added dropwise, while stirring. The reaction mixture was
stirred at ambient temperature for 10 min. The triethylamine
hydrochloride salt was filtered off and the resulting solution
was added dropwise to a solution of sodium alkoxy and/or
thiolate in 300 mL CH2Cl2. The mixture was stirred for 10 min
at ambient temperature. The resulting precipitate was
filtered off and the solution was analyzed using GC/MS
and GC/MS/MS as required.
GC/MS and GC/MS/MS analyses
The GC/MS analyses were performed using an Agilent 6890N
gas chromatograph equipped with a 5973 mass-selective detec-
tor. An HP-5MS capillary column (length 30 m, 320 mm i.d. and
0.25 mm film thickness) and helium as carrier gas at constant
flow of 1ꢀ.8 mL min–1 were used. The oven temperature was
ꢀ
set at 40 C for 3 min and then was increased to 280 C with
ramp of 10 ꢀC/min and held at 280 ꢀC for 6 min. The samples
were injected in splitless mode at an injection temperature of
250 ꢀC. The temperatures of the EI source and analyzer
Scheme 1. Microsynthesis route of O(S)-alkyl N,N-dimethyl alkylphosphono(thiolo)-
thionoamidates 4.
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ESI-MS studies of alkylphosphonothionoamidates
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H. Saeidian et al.
RESULTS AND DISCUSSION
Synthesis
The microsynthesis of the O(S)-alkyl N,N-dimethyl alkyl-
phosphono(thiolo)thionoamidates 4 generally involves five
steps: (1) alkylation of phosphorous trichloride, with alkyl iodide;
(2) oxidation of alkylphosphine dichloride; (3) thionation of
alkylphosphonic dichloride; (4) addition of dimethylamine
hydrochloride to alkylthiophosphonic dichloride 1 in the
presence of triethylamine as a base to form N,N-dimethyl
alkylthiophosphoramidic chloride 3; and (5) subsequent
reaction with sodium alkoxy and/or thiolates to yield desired
products 4 (Scheme 1). Dropwise addition of triethylamine
to dimethylamine hydrochloride (2) gently produced dimethy-
lamine in dichloromethane solution which then reacted
with alkylthiophosphonic dichloride 1 to form N,N-dimethyl
alkylthiophosphoramidic chloride 3 The GC/MS analysis of
the mixture in the initial step clearly indicated the formation
of 3 with high yield (up to 85%) as indicated by the GC/MS
results. Subsequently, conversion of 3 into the corresponding
O(S)-alkyl N,N-dimethyl alkylphosphono(thiolo)thionoami-
dates 4 was observed with moderate to good yields within
10 min. The main feature of this microsynthetic protocol is the
immediate synthesis of the desired chemicals under mild condi-
tions. In this study we have synthesized and analyzed 24 O(S)-
alkyl N,N-dimethyl alkylphosphono(thiolo)thionoamidates 4
using the above mentioned method.
Mass spectral analyses
Major EI fragment ions of these compounds are given in Table 1.
In order to enrich the OPCW central analytical database
(OCAD),[19] the GC retention indices were also calculated
according to the Van Den Dool method and AMDIS software.[20]
The plausible fragmentation routes of 4 are also illustrated
in Fig. 1. The mass spectra of the title chemicals exhibit
some isobaric ions (hence indistinguishable), as listed in Table 1,
for example, fragment ions [B] and [I] are isobaric ions
for O-methyl N,N-dimethyl methylphosphonothionoamidate
(entry 1, Table 1). The presence of these ions in the spectra of
other homologs indicates operation of different mechanisms.
Mass spectral appearance of these compounds is influenced
by the alkyl group on oxygen and/or sulfur (Fig. 2). The
most important fragmentations in mass spectra of 4 were the
McLafferty, McLafferty+1 and thiono-thiolo rearrangements
which led to ions [A], [D] and [E], respectively.
In the McLafferty-type rearrangement, the alkyl on oxygen
and/or sulfur (XR) is left as an alkene, as represented by
Scheme 2. For O-methyl and O-phenyl analogs formation of
an allylic or vinylic group is not possible. Consequently,
spectra for these chemicals are distinct. It is important to note
that the relative intensity of ion [A] is higher in the n-alkyl
analogs than in the sec-alkyl analogs. This difference may be
considered as unambiguous identification of isomeric chemi-
cals. On the other hand, the McLafferty-type rearrangement
in phosphonothiolothionoamidates occurs better than in
phosphonothionoamidates, as shown in Table 1.
Formation of ion [B] from 4 is through loss of the alkyl radical
on oxygen and/or sulfur. It should be mentioned that the
absence of [B], but generation of [C] via P–O bond cleavage in
the O-aryl analogs, indicates that the C–O bond is stronger than
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ESI-MS studies of alkylphosphonothionoamidates
Figure 1. Proposed fragmentation routes for O(S)-alkyl N,N-dimethyl alkylphosphono(thiolo)thionoamidates 4.
6
2
18
5
Figure 2. Representative EI mass spectra of 4.
It is noteworthy that the base peak for the phosphono-
thiolothionoamidates is ion [C] (entries 16–20, Table 1) but
its relative abundances for phosphonothionoamidates are
moderate. The bond dissociation enthalpy (BDE) of the P–O
bond in O-propyl N,N-dimethylmethylphosphonothiono-
amidate (entry 5, Table 1) was calculated to be higher by 91
kJmol–1 than the BDE of the P–S bond in S-propyl N,N-
dimethyl methylphosphonothiolothionoamidate (entry 17,
Table 1). The higher relative intensity of ion [C] for phospho-
Scheme 2. McLafferty-type rearrangement on chemical 4.
the P–O bond in such compounds (Scheme 3). The stability of
leaving radicals is also important for P–O bond cleavage in such
cases. This fact could be used for aryl/alkyl group distinction in
such chemicals.
nothiolothionoamidates than phosphonothionoamidates and
BDE calculations show that P–S bond cleavage in phospho-
nothiolothionoamidates requires less energy than P–O bond
cleavage in phosphonothionoamidates. The fragment [D]
Rapid Commun. Mass Spectrom. 2012, 26, 2805–2814
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H. Saeidian et al.
Scheme 3. Proposed route for formation of ions [B] and [C].
Scheme 4. Proposed mechanism for formation of ion [D].
R'
S
S
P
R'''
+
RO
P-O bond cleavage
P
(H3C)2N
R'
N(CH3)2
O
H
R''
C
R = -CHR''R'''
Thiono-thiolo rearrangement
R'
S
R'''
O
P
R'''
O
R'
H
-RS
(H3C)2N
P
O
H
P
S
R''
R'
N(CH3)2
(H3C)2N
R''
E
Scheme 5. The thiono–thiolo rearrangement for formation of ion [E].
+
•
can be formed from the molecular ion (M ) with double
hydrogen transfer. The relative intensity of ion [D] for
4 depends on the size of the alkyl group on the oxygen
and/or sulfur atom in the molecule. The larger alkyl group
(≥ C4) leads to an intense peak for ion [D]. In O-alkyl analogs,
this ion abundance is the largest or the second largest peak in
the mass spectra. The ion [D] can be postulated to arise via a
McLafferty+1 rearrangement[21,22] that involves an initial
hydrogen migration (1,5 C-S H shift) to the sulfur-bearing
radical cation site, leading to a distonic species (Scheme 4).
A radical cation and a neutral species are produced after
single bond cleavage. Then a hydrogen atom transfers from
the neutral molecule to the radical cation, yielding a cation
and a stable radical fragment. Another interpretation is also
possible: in the distonic species second hydrogen is abstracted
in a concerted manner, with simultaneous hydrogen migration
(1,4 C-X H shift) and single bond cleavage involving a five-
membered state. This may explain why these mechanisms are
favorable with larger alkyl groups (≥ C4). Indeed, in such cases,
leaving of the stable allylic radical is the major driving force for
this rearrangement (Scheme 4). The absence of ion [D] from the
O-methyl and O-phenyl analogs supports this proposed
fragmentation.
The high intensity ion [E] for phosphonothionoamidates
+
•
•
was generated through loss of the -SR group from M .
Fragmentation of ion [E] in the mass spectrum of O-methyl-d3
N,N-dimethyl methylphosphonothionoamidate (m/z 106, entry
2, Table 1) produces a base peak at m/z 63 corresponding to
loss of the N,N-dimethylamino group involving hydrogen
transfer to the P = O group. Observation of ion [E] is due to
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ESI-MS studies of alkylphosphonothionoamidates
Scheme 6. Proposed fragmentation pathway of ion [G] for the O-methyl N,N-dimethyl
methylphosphonothionoamidate.
the thiono-thiolo rearrangement (Scheme 5). Such an intramo-
lecular rearrangement can be regarded as a case of the
Pishchimuka reaction,[23] where S = P–OR rearranges to an
O = P–SR group. The thiono–thiolo rearrangement in the gas
phase has been reported.[24] In phosphonothionoamidates
the sulfur atom, as a soft base, has higher affinity for the
carbon atom of the alkoxy group. On the other hand, the
electron-donating N,N-dimethylamino substituent in phos-
phonothionoamidates increases the nucleophilicity of the
sulfur atom and accelerates intraconversion. It is interesting
to note that the relative intensity of ion [E] in the n-alkyl
analogs is higher than in the sec-alkyl analogs (Table 1). This
shows that the thiono–thiolo rearrangement was facilitated
in the presence of n-alkyl groups. Thus the thiono–thiolo rear-
rangement ([E]) in n-alkyl derivatives predominates P–O
bond cleavage ([C]). Energy calculations also confirmed this
conclusion. It shows that the formation energies of ions [C]
and [E] in O-propyl N,N-dimethyl methylphosphonothiono-
amidate (entry 5, Table 1) are 207 and 138 kJmol–1, respectively.
In the sec-alkyl derivatives, operation of both mechanisms has
almost the same possibility to occur (Table 1). Therefore, such
structural isomers could be distinguished by characteristic
ions [C] and [E].
also observed. The product ion spectrum of the ion at m/z
112 from O-methyl-d3 N,N-dimethyl methylphosphonothio-
noamidate (Fig. 3(b)) supports the structural assignments
shown in Scheme 6.
Loss of the N,N-dimethylamino group and the alkyl on the
oxygen and/or sulfur from M + were seen in the formation of
•
ion [H], which was observed for the most of the studied chemi-
+
•
cals. M was also fragmented to ion [I] via cleavage of the P–R0
bond. It is interesting to note that ion [I] could be related to three
possible structures (Fig. 4), which are resonance forms.
However, the free energy of structure (a) in the case of
XR= OCH3 was calculated to be 44 and 43 kJ mol–1 higher than
structures (b) and (c), respectively. This revealed that cleavage
of the P–R0 bond initiated from phosphorus (a) was not
preferred over that initiated from nitrogen (b) or oxygen (c).
It should be noted that in the case of R0 = CH3 elimination of
the methyl moiety on nitrogen resulted in an isobaric fragment
with [I]. However, the product ion scan of ion [I] in the mass
spectrum of O-methyl-d3 (m/z 141) revealed that it further
fragmented to ions m/z 42, 43 and 44 corresponding to loss of
the N,N-dimethylamino group.
The interesting fragment [J]/[J0] can be formed through two
possible fragmentation pathways. (1) Elimination of sulfur
from [I]/[I0] or (2) 1,2 P-S alkyl(R0) shift then elimination
Loss of sulfur and an XR group from M + leads to fragment
•
+
of the R S radical from M (Scheme 7).[24] The spectra of
deuterated analogs clearly show the corresponding ion to this
fragment (entries 2, 4, 22 and 24, Table 1). On the other hand,
the free energy of [J0] was found to be higher by 3 kJ mol–1
than that of [J], indicating [J] as the preferred structure.
Ion [K] was generated by the loss of the CH2=NCH3 group
0
•
•
[F], as observed in the spectra of most compounds 4. Ion [G]
is formed through cleavage of the N,N-dimethylamino group
+
•
from M . Support for these routes is provided by analysis of
mass spectra of deuterated analogs (entries 2 and 4, Table 1).
The product ion scan of ion [G] for the O-methyl N,N-
dimethyl methylphosphonothionoamidate, m/z 109, revealed
that it further fragmented to ions m/z 94, 79, 77 and 63, 62,
61 and 47 (Scheme 6 and Fig. 3(a)).
+
0•
•
•
from M . Elimination of -SH and –R radicals from the ion
[K] resulted in ions [L] and [M], respectively. These proposals
are supported by deuterium-labeling studies, which show
the formation of corresponding ions to these fragments.
Additional support for these routes was provided by the
The thiono–thiolo rearrangement and 1,2 P-S methyl
migration[24] in the fragmentation process of ion [G] for O-
methyl N,N-dimethyl methylphosphonothionoamidate are
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H. Saeidian et al.
(a)
(b)
Figure 3. (a) MS/MS of the O-methyl N,N-dimethyl methylphosphonothionoamidate,
m/z 109; (b) MS/MS of the O-methyl-d3 N,N-dimethyl methylphosphonothionoamidate,
m/z 112.
is formed by the loss of the N,N-dimethylamino group and
alkyl on oxygen and/or sulfur from M + involving hydrogen
•
transfer to the P=S group. It is worth noting that loss of a
neutral ethylene is possible from O-alkyl N,N-dimethyl
ethylphosphonothionoamidates (entry 21–24, Table 1). The
corresponding m/z values for these processes are shown in Fig. 1.
Finally, ion [P]/[P0] for 4 was formed through loss of
aldehyde and/or thioaldehyde from M•+.[25] The spectra of
the deuterated analogs showed the corresponding ion to
this fragment. It is interesting to note that the fragment
ion [P]/[P0] was ascribed to two possible structures shown
in Scheme 8. Formation of ion [P]/[P0] can be explained
by hydrogen migration involving sulfur and/or phos-
Figure 4. Three possible resonance structures of ion [I].
precursor ion scan of ions m/z 113, 80 and 98 in mass
spectrum of O-methyl-d3 N,N-dimethyl methylphospho-
nothionoamidate (Fig. 5 and Supporting Information).
The intense ion [N] was produced from the N,N-dimethyl-
amino group which fragmented to ion m/z 42 by the loss of a
hydrogen molecule and m/z 43 by the loss of a hydrogen
radical. The presence of these fragments in mass spectra is
an indication of an N,N-dimethylamino moiety in 4. Ion [O]
+
•
phorus atoms. The free energy of the [CH3-PS(N(CH3)2)H]
ion was found to be higher by 33 kJmol–1 than that
+
•
of [CH3-P(N(CH3)2)SH] , indicating the latter as the preferred
structure.
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ESI-MS studies of alkylphosphonothionoamidates
Scheme 7. Proposed mechanism for formation of ion [J]/[J0].
[L]+
[M]+
[K]
Figure 5. MS/MS of the O-methyl-d3 N,N-dimethyl methylphosphonothionoamidate,
m/z 113.
Acknowledgements
We would like to thank three anonymous reviewers for
providing helpful feedback that improved the manuscript.
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Scheme 8. Proposed mechanism for formation of ion [P]/[P0].
CONCLUSIONS
An improved process for microsynthesis of O(S)-alkyl N,N-
dimethyl alkylphosphono(thiolo)thionoamidates is reported
in this paper. The chemicals were synthesized under mild
conditions. EI-MS and MS/MS of the title compounds were
also investigated with the aim to enrich OCAD, which may
be used in OPCW verification activities and during OPCW
PTs. The most important fragmentation route in mass spectro-
metric analysis of the chemicals is the thiono–thiolo rearran-
gement. Energy calculations of fragment ions revealed their
relative preference of formation during ionization.
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SUPPORTING INFORMATION
Additional supporting information may be found in the
online version of this article.
Rapid Commun. Mass Spectrom. 2012, 26, 2805–2814
Copyright © 2012 John Wiley & Sons, Ltd.
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H. Saeidian et al.
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