Detailed investigation of the radical-induced destruction of chemical warfare agent simulants in aqueous solution

Article abstract of DOI:10.1021/jp101720j

The persistence of delivered chemical warfare agents (CWAs) in a variety of environmental matrices is of serious concern to both the military and civilian populations. Ultimately understanding all of the degradation pathways of the various CWAs in different environmental matrices is essential for determining whether native processes would offer sufficient decontamination of a particular material or if active chemical decontamination is required. Whereas much work on base-promoted chemical degradation has been reported, additional remediation strategies such as the use of advanced oxidation or reduction process free radical treatments may also be a viable option. We have examined here the primary kinetics and reaction mechanisms for an extensive library of chemical warfare agent simulants with the oxidizing hydroxyl radical and reducing hydrated electrons in water. From these values, it is seen that the reductive destruction occurs primarily through a single mechanism, consisting of hydrated electron capture at the phosphorus group with subsequent elimination, whereas hydroxyl radical oxidation shows two separate reaction mechanisms, dependent on the aqueous pK_a of the leaving group. ? 2010 American Chemical Society.

Full text of DOI:10.1021/jp101720j

J. Phys. Chem. B 2010, 114, 7681–7685
7681
Detailed Investigation of the Radical-Induced Destruction of Chemical Warfare Agent
Simulants in Aqueous Solution
Amberashley Abbott,† Tim Sierakowski,† James J. Kiddle,*,† Kristin K. Clark,‡ and
Stephen P. Mezyk*,‡
Department of Chemistry, Western Michigan UniVersity, 3425 Wood Hall, Kalamazoo, Michigan 49008, and
Department of Chemistry and Biochemistry, California State UniVersity at Long Beach, 1250 Bellflower
BouleVard, Long Beach, California 90840
ReceiVed: February 25, 2010
The persistence of delivered chemical warfare agents (CWAs) in a variety of environmental matrices is of
serious concern to both the military and civilian populations. Ultimately understanding all of the degradation
pathways of the various CWAs in different environmental matrices is essential for determining whether native
processes would offer sufficient decontamination of a particular material or if active chemical decontamination
is required. Whereas much work on base-promoted chemical degradation has been reported, additional
remediation strategies such as the use of advanced oxidation or reduction process free radical treatments may
also be a viable option. We have examined here the primary kinetics and reaction mechanisms for an extensive
library of chemical warfare agent simulants with the oxidizing hydroxyl radical and reducing hydrated electrons
in water. From these values, it is seen that the reductive destruction occurs primarily through a single
mechanism, consisting of hydrated electron capture at the phosphorus group with subsequent elimination,
whereas hydroxyl radical oxidation shows two separate reaction mechanisms, dependent on the aqueous pKa
of the leaving group.
Introduction
One new group of technologies that can also be used for
hazardous chemical removal from waters is advanced oxidation
The persistence of released organophosphorous compounds
such as chemical warfare agents (CWAs) into the environment
remains a worldwide concern. Over the past decade, scientists
have focused their attention on the ability to detect,1 decon-
taminate,2 and destroy CWAs.3 These agents exert their toxic
effects through inhibition of acetylcholinesterase. Because of
their extreme toxicity and restricted use, actual CWAs (Figure
1) such as Tabun (GA), Sarin (GB), Soman (GD), and VX are
not regularly employed in studies at academic laboratories.
Instead, simulants, which mimic the structural and electronic
properties of actual CW agents, are mainly utilized. These
stimulants have the general formula R1R2P(O)X, where X is a
leaving group. Simulant chemicals also have a range of
toxicities, from the hazardous (e.g., paraoxon, LD50 rat: i.p. 0.54
mg/kg)4 to the relatively nontoxic (e.g., diethyl methylphos-
phonate, DEMP LD50 mouse: i.p. 2240 mg/kg,).5
or reduction processes (AO/RPs). These processes are based
on the production of radicals in situ, typically the oxidizing
hydroxyl radical (•OH) and the reducing electron (eaq-). These
generated radicals then react with and degrade the unwanted
contaminant chemicals. However, these radicals will also react
with other water constituents (O2, dissolved organic matter,
bicarbonate) usually present at higher concentrations. Therefore,
for the practical utilization of any AO/RP for CWA removal,
its free radical chemistry (kinetics and reaction mechanisms)
needs to be quantitatively established. Moreover, it is also
important to ensure that no additional hazardous products are
created through these radical-induced degradation mechanisms.
In previous work on simulants, it was shown that whereas
oxidizing hydroxyl radicals degraded DEMP (Figure 1) and
dimethyl methyl phosphonate (DMMP) in aqueous solution,
reducing hydrated electrons and superoxide anion radicals were
unreactive.6 Although these two compounds have been widely
used as CWA simulants, these phosphonate species show very
low toxicity and do not have a good leaving group like those
found in true CW agents.7 In a preliminary investigation, six
model simulants of the general form (EtO)2P(O)X that are better
mimics of true CWAs were studied, and their rate constants
were established for reaction with hydroxyl radicals and
hydrated electrons.8 Bro¨nsted plots for these model compounds
Whereas base hydrolysis works well to destroy excess
inventory of these types of chemicals, this approach may not
be as readily utilized for real-world decontamination problems.
One major concern would be the CWA contamination of water
supplies. Whereas natural processes will deactivate CWAs
through a variety of processes, active removal may also be
necessary under some circumstances. However, standard water
treatment processes such as activated charcoal absorption or
phase transfer through aeration stripping may not result in
quantitative removal and decontamination.
* To whom correspondence should be addressed. (J.J.K.) Tel: 269-387-
5440; Fax: 269-387-2909; E-mail: james.kiddle@wmich.edu. (S.P.M.) Tel:
562-985-4649; Fax: 562-985-8557; E-mail: smezyk@csulb.edu.
† Western Michigan University.
‡ California State University at Long Beach.
Figure 1. Structure of CW agents and phosphonate simulants.
10.1021/jp101720j  2010 American Chemical Society
Published on Web 05/17/2010

7682 J. Phys. Chem. B, Vol. 114, No. 22, 2010
Abbott et al.
TABLE 1: Rate Constants for the Reaction of CW Agent Simulants
simulant
X
pKaa
ke- (M-1 s-1
)
k•OH (M-1 s-1
)
1
2
3
4
5
6
7
8
Cl
F
OAc
-7
3.2
4.8
9.2
11
12
14
16
16
27b
35
35
35
48
48
3.93 ( 0.24 × 1010
1.83 ( 0.14 × 109
1.11 ( 0.10 × 1010
3.52 ( 0.32 × 109
1.08 ( 0.06 × 109
1.35 ( 0.09 × 109
1.88 ( 0.13 × 1010
9.61 ( 0.05 × 108
5.3 ( 1.4 × 108
6.38 ( 0.52 × 108
2.21 ( 0.13 × 108
7.85 ( 0.59 × 107
3.36 ( 0.91 × 107
7.33 ( 1.16 × 107
1.37 ( 0.10 × 1010
4.73 ( 0.35 × 108
6.63 ( 0.82 × 108
9.04 ( 0.65 × 107
1.40 ( 0.09 × 109
4.13 ( 0.41 × 108
9.88 ( 0.60 × 108
7.19 ( 0.46 × 108
2.35 ( 0.17 × 108
7.66 ( 0.56 × 108
6.02 ( 0.55 × 108
7.87 ( 0.47 × 108
7.63 ( 0.44 × 108
6.20 ( 0.40 × 108
6.34 ( 0.38 × 108
CN
SCH2CH3
OCH2CF3
OH
OCH2CH3
OCD2CD3
CF3
NH2
H
D
CH3
9
10
11
12
13
14
15
CD3
a March, J.; Smith, M. B. AdVanced Organic Chemistry; Wiley: New York, 2001; pp 329-331. pKa values represent the ionization of H-X
in water. b Symons, E. A.; Clermont, M. J. J. Am. Chem. Soc. 1981, 103, 3127.
TABLE 2: Reaction of Hydrated Electron with
Methylphosphonic Acid
SCHEME 2: Synthesis of Simulant Compounds 5 and 6
species
pH
k(e-) (M-1 s-1
)
16
16
5.08
10.02
1.22 ( 0.04 × 1010
1.62 ( 0.12 × 109
SCHEME 1: Synthesis of Fluorine Containing Chemical
Warfare Agent Simulants
SCHEME 3: Synthesis of Diethyl Phosphonic Acetic
Anhydride
demonstrated that the reduction process followed a single
reaction mechanism, proposed to be initial reduction at the
phosphorus atom, followed by elimination of a leaving group.
In contrast, the hydroxyl radical oxidation showed two distinct
linear regions, indicating more complicated reaction chemistry.
The faster reaction rate constants for hydrated electron reduction
also indicated that active AO/RP treatments that also produced
this radical (e.g., TiO2/hν, electron beam) would be more
efficient options.
Whereas specific degradation rate constants for real CWAs
was attempted based on this small set of data, there were
considerable gaps in the Bro¨nsted plots, resulting in large
uncertainty. To establish quantitative estimates for CWA
reactivities in water further, we have undertaken a more detailed
study here measuring absolute reaction rate constants for both
the hydroxyl radical and hydrated electron with a large library
of organophosphorus CWA simulants in water.
Experimental Section. Eight of the 16 compounds (1, 4, 7,
8, 11, 12, and 14 in Table 1 as well as 16 in Table 2) were
commercially available and used as received. The synthesis of
simulant 2 can be accomplished from diethyl chlorophosphate
(1) in quantitative yield by a solid-phase approach (Scheme 1).9
Subsequent reaction of diethyl fluorophosphate (2) with 2 equiv
of TMSCF3 and a catalytic amount of CsF provides the
trifluoromethylphosphonate analog (10) in pure form after
SCHEME 4: Synthesis of Diethyl D-Phosphonate (13)
chromatography (Scheme 1).10 Compounds 5 and 6 were both
synthesized by substitution reaction using diethyl chlorophos-
phate as the starting material and the appropriate nucleophile
(Scheme 2).11 The diethyl phosphonic acetic anhydride (3) was
synthesized using a modified literature procedure from diethyl
phosphonic acid (7) by the formation of an anhydride with acetyl
chloride in the presence of triethylamine (Scheme 3).12 The
deuterated analog 13 of simulant 12 was synthesized by
refluxing triethylphosphite in D2O, followed by distillation to
obtain the pure product (Scheme 4).13 The required deuterated
analogs of dimethyl methyl phosphonate were each prepared
via a microwave Arbuzov rearrangement of a trialkyl phosphite
and iodomethane precursor appropriately deuterated (Scheme
5).14 All compounds were greater than 98% pure, as character-
ized by 1H, 13C, and 31P NMR spectroscopy as well as GC/MS,
and these data were consistent with those previously reported
in the literature. Reported rate constant errors are a combination
of the measurement precision and compound purity.

Radical-Induced Destruction of CWA Simulants
J. Phys. Chem. B, Vol. 114, No. 22, 2010 7683
e-aq + N O + H O f N + OH- + OH
•
SCHEME 5: Synthesis of Deuterated Analogs of
Dimethyl Methyl Phosphonate
(
)
2
2
2
k2 ) 9.1 × 109 M-1 s-1 (2)
H• + N2O f N2 + OH k3 ) 2.1 × 106 M-1 s-1
•
(3)
However, the reaction of hydroxyl radicals with our CWA
simulants did not generate any significant intermediate species
absorption in the range of 250-800 nm. Therefore, the hydroxyl
radical reaction rate constant for all species of this study was
determined using SCN- competition kinetics, based on the
competing reactions
Kinetic Measurements. The linear accelerator (LINAC)
electron pulse radiolysis system at the Radiation Laboratory,
University of Notre Dame was used for the hydrated electron
and hydroxyl radical reaction rate constant determinations. This
irradiation and transient absorption detection system has been
described in full detail elsewhere.15
•OH + (EtO)2P(O) - X f products
(4)
(5)
•OH + SCN-(+SCN-) f OH- + (SCN)•2-
CWA simulant solutions were made at this laboratory using
water filtered by a Millipore Milli-Q system (>18.2 MΩ). All
solutions were completely sparged with high purity N2O (for
hydroxyl radical experiments) or N2 (for hydrated electron or
hydrogen atom) to remove dissolved oxygen. Stability experi-
ments based on 31P NMR were performed on these solutions to
determine the extent of hydrolysis of simulants 1, 2, and 4. These
experiments demonstrated that 0.010 M solutions of all three
compounds were stable for over 1 week at neutral pH in a 1:1
solution of H2O/D2O, showing no hydrolysis products. This is
in agreement with the literature that indicates that both simulants
and CW agents with F, Cl, or CN substituents only show rapid
hydrolysis at either high or low pH, whereas at neutral pH,
aqueous hydrolysis occurs at a slower rate.16
•-
and monitoring the (SCN)2 absorption at 475 nm. This
hydroxyl radical competition can be analyzed to give the
following analytical expression
Abs(SCN)•2-o
Abs(SCN)•2-
k4[(EtO)2P(O)-X]
k5[SCN-]
) 1 +
(6)
where Abs(SCN)2•-o is the maximum absorbance of the (SCN)2
-
transient measured for only the blank SCN- solution, and
-
Abs(SCN)2 is the reduced yield of this transient when
(EtO)2P(O)-X was added. Typical data are shown in Figure 2a.
AplotofAbs(SCN)2•-o/Abs(SCN)2•- againsttheratio[(EtO)2P(O)-
X]/[SCN-] gives a straight line of slope k4/k5 and based on the
established rate constant for hydroxyl radical reaction with
During the irradiation process, the solution vessels were
bubbled with only the minimum amount of gas necessary to
prevent air ingress to prevent loss of chemical. Dosimetry was
performed using N2O-saturated, 1.00 × 10-2 M SCN- solutions
at λ ) 475 nm, (Gε ) 5.09 × 104) with average doses of 3-5
Gy per 2 to 3 ns pulse.17 All kinetic measurements were
performed at room temperature, which varied across the range
18 ( 2 °C, although individual measurements were constant to
(0.3 °C.
SCN-, k5 ) 1.05 × 1010 M-1 s-1 19
,
the k4 rate constant can
then readily be calculated. (See Figure 2b.) The simulant
oxidation rate constants obtained are summarized in Table 1
and shown in a Bro¨nsted plot in Figure 3a.
The Bro¨nsted plot shows a distinct break in the leaving group
dependence, clearly indicating a change in mechanism between
the simulants with good and poor leaving groups. These new
data show excellent consistency with previous measurements.8
In addition, the new data for simulants with leaving group pKa
values in the range of 12-16 show no rate constant variation
and are in very good agreement with the higher pKa values
previously measured. This is not a surprise because the net
atomic charge on phosphorus will be greater in those compounds
with deactivating groups (1-4), which will favor the initial
reaction of the hydroxyl radical directly at the phosphorus atom.
Alternatively, simulants 5-8, 10-12, and 14 have less atomic
charge on the P atom, which would promote the initial oxidation
to be a hydrogen atom abstraction from the methylene carbon
to produce a carbon-centered radical. Verification of this
mechanism has been established by study of the deuterated
analog 9, of triethylphosphate (8) that resulted in a primary
kinetic isotope effect of kH/kD ) 3.06. These data confirmed
the hydrogen-atom abstraction by the hydroxyl radical at the
methylene carbon consistent with the proposed change in
mechanism.
Upon completion of experiments, waste samples were mixed
with bleach solution to neutralize the residual CWA simulants.18
Results and Discussion
The electron pulse radiolysis of water produces hydroxyl
radicals, hydrated electrons, hydrogen atoms, and other species
according to the stoichiometry19
H2O -/\/\/\/\/\/\ f 0.28•OH + 0.27 ea-q + 0.06•H +
0.05 H2 + 0.07 H2O2 + 0.27 H+ (1)
where the numbers in this equation are the G values (yields) of
production for each species in units of µmol Gy1-. Typical total
radical concentrations generated were ∼3-5 µM, thus ensuring
that pseudo-first-order kinetics were always maintained.
The study of only hydroxyl radical reactions was achieved
by presaturating the simulant solutions with N2O, which
quantitatively converts the produced hydrated electrons and
some hydrogen atoms to hydroxyl radicals
Hydrated Electron Reaction. The hydrated electron rate
constant with these simulants was determined by directly
following its near-infrared absorption at 700 nm.20 These values

7684 J. Phys. Chem. B, Vol. 114, No. 22, 2010
Abbott et al.
-•
Figure 4. (a) Pseudo-first-order decay kinetics of hydrated electron at
700 nm and natural pH in the presence of 25.0 (0), 51.6 (O), 80.2 (4),
and 144.7 (3) µM (EtO)2P(O)OAc. Solid lines correspond to fitted
exponential decays. (b) Second-order rate constant determination for
(EtO)2P(O)OAc. Solid line corresponds to rate constant of k ) 1.10 ×
Figure 2. (a) Measured (SCN)2 absorbance at 475 nm in N2O-
saturated 136.1 µM KSCN with 0 (0), 264 (O), and 728 (4) µM
(EtO)3PdO at 19 °C and natural pH. (b) Transformed competition
kinetics plot for this compound using maximum absorbance intensities
of part a. Line corresponds to weighted linear fit, with: slope ) 0.0686
( 0.0035, intercept ) 1.001 ( 0.014, R2 ) 1.000, corresponding to
1010 M-1 s-1
.
reaction rate constant of 7.19 × 108 M-1 s-1
.
The Bro¨nsted plot for the series of CW simulants reacting
with the hydrated electron is presented in Figure 3b. This plot
highlights the previous excellent linearity for the majority of
our simulants over the entire range of leaving group pKa values.
The linearity suggests a single mechanism for reaction of the
hydrated electron with all simulant compounds. This mechanism
appears to be consistent with initial electron capture at phos-
phorus, followed by loss of a leaving group. The measured rate
constants are faster for compounds 1-4, which have good
leaving groups in water, where it is reasonable that the reduced
X- is released into solution. However, compounds with poor
leaving groups (5-8, 10-12, and 14) undergo much slower
reduction, and by analogy to the loss of hydrogen atoms from
the reaction of hydrated electrons with phosphate (H2PO4-, k
) 1.5 × 107 M-1 s-1) may instead be eliminating radical
fragments (X•, C2H5 ).22 Again, the mechanism is consistent with
•
data from primary kinetic isotope effect measurements between
the non deuterated species 12 and its deuterated analogue 13
(kH/kD ) 3.17). In addition, compounds 14 and 15 show a
secondary isotope effect (kH/kD ≈ 2.2) again confirming the
capture of the electron at the phosphorus atom.
Also, transient spectral data obtained for the reduction of
simulant 1 showed the loss of the absorption for the hydrated
electron (700 nm) directly correlated with the growth of a new
transient at 340 nm. This new transient is attributed to the
phosphinoyl radical, formed by the loss of chloride; however,
it is not clear which of the two tautomeric structures is
responsible for the absorption.23
Three simulant reduction measurements were found to deviate
from the overall linearity shown in Figure 3b. The fluoride-
substituted simulant reaction rate constant was slower than
expected; however, our measured value can only be considered
a lower limit because of the slight material loss observed as
vapor upon the injection of this simulant. However, compound
7, the diethyl phosphonic acid, showed a significantly higher
than expected rate constant, on the same order of magnitude as
the diethyl chlorophosphate (1). At neutral pH, the phosphonic
acid will be ionized (pKa ) 1.42), and it is unlikely that a
charged oxygen atom (O2-•) would act as a leaving group in
Figure 3. Bro¨nsted plot for reaction of CWA simulants with (a)
hydroxyl radical and (b) hydrated electron from values given in Table
1. Also shown are predicted rate constants for GA (O), GB (3), GD
(]), and VX (4) reaction with both radicals.
were determined by fitting exponential decays to the pseudo-
first-order kinetics of this species in pulse-electron irradiated,
nitrogen-saturated, solutions at natural pH. (See Figure 4a.)
These solutions also contained 0.10 M methanol to scavenge
the hydroxyl radicals and hydrogen atoms, converting them into
relatively inert methanol radicals.19 The pseudo-first-order rate
constants were plotted against the simulant concentrations
(Figure 4b), and from these kinetic data (Table 1), it is evident
that simulants that more precisely resemble CW agents in their
structure have reduction rate constants 20-40 times faster than
those for their oxidation. This suggests that treatments that
generate both oxidizing and reducing species in water, for
example, heterogeneous catalysis by TiO2, sonolysis, or the
electron beam irradiation processes, would be the most efficient
approach for the destruction of these types of agents.21

Radical-Induced Destruction of CWA Simulants
J. Phys. Chem. B, Vol. 114, No. 22, 2010 7685
TABLE 3: Estimated Rate Constants for the Reaction of
CWAs in Water Based on Bro¨nsted Plot values of this Study
(See Figure 3)
kinetic evidence also suggests that alkyl phosphonates such as
diethyl methylphosphonate, although easy to handle, may
undergo different oxidation and reduction chemistry. Therefore,
caution should be exercised when suggesting that these latter,
nontoxic, compounds are automatically reasonable models for
chemical warfare agents.
CW agenta leaving group ∼pKab k(e-) M-1 s-1 k(HO•) M-1 s-1
Tabun, GA CN
Sarin, GB
Soman, GD F
VX
9.2
3.2
3.2
3.6 × 109
6.8 × 109
6.8 × 109
3.2 × 109
8.0 × 107
8.8 × 108
8.8 × 108
8.8 × 108
F
S(CH2)2N(iPr)2 10.6c
Acknowledgment. We would like to thank the Radiation
Laboratory, University of Notre Dame, for use of their accelera-
tor facilities. We would also like to thank Ms. Casandra Cox
for help with some of these kinetic measurements, and A.A.
would like to acknowledge the ACS Project SEED for support.
a Complete structures shown in Figure 1. b March, J.; Smith,
M. B. AdVanced Organic Chemistry; Wiley: New York, 2001; pp
329-331. pKa values represent the ionization of H-X in water.
c Value for CH3CH2SH. Silva, C. O.; da Silva, E. C.; Nascimento,
M. A. C. J. Phys. Chem. A 2000, 104, 2402.
References and Notes
(1) Yang, Y.; Ji, H.-F.; Thundat, T. J. Am. Chem. Soc. 2003, 125, 1124.
(2) Yang, Y.-C.; Baker, J. A.; Ward, J. R. Chem. ReV. 1992, 92, 1729.
(3) Wagner, G. W.; Yang, Y.-C. Ind. Eng. Chem. Res. 2002, 41, 1925.
(4) Benschop, H. P.; Van den Berg, G. R.; Van Hooidonk, V.; De Jong,
L. P. A.; Kientz, C. E. J. Med. Chem. 1979, 22, 1306.
(5) Munro, N. B.; Talmage, S. S.; Griffin, G. D.; Waters, L. C.; Watson,
A. P.; King, J. F.; Hauschild, V. EnViron. Health Perspect. 1999, 107, 933.
(6) Aguila, A.; O’Shea, K. E.; Tobien, T.; Asmus, K.-D. J. Phys. Chem.
2001, 105, 7834.
water. Therefore, we believe that the dominant operating
mechanism for this compound is direct electron capture to form
a phosphoranyl radical. We posit that this fast rate constant is
due to enhanced resonance stabilization available within the
delocalized π-system of the phosphoryl anion, which assists the
radical formation occurring at the phosphorus atom. The direct
electron capture at phosphorus has been shown by electron spin
resonance to produce these phosphoranyl radicals.24
(7) A search of Scifinder Scholar (CAS RN 756-79-6) [dimethyl
methylphosphonate] retrieved 2795 references, of which 256 contained the
word “simulant”.
However, because of its low pKa values, we could not directly
determine the rate constant for the nonionized form of the diethyl
phosphonic acid (7) with the hydrated electron. Therefore, to
gain further insight into this particular reduction process, reaction
rate constants for the analogous species methylphosphonic acid
(16) were determined with the hydrated electron at pH 5.08
and 10.02 (Table 2). The rate constant of k ) (1.22 ( 0.04) ×
1010 M-1 s-1 determined at pH 5.08 for the monoionized form
of 16 is similar to the value obtained for the diethyl phosphonic
acid of k ) (1.88 ( 0.04) × 1010 M-1 s-1, indicating a consistent
reaction mechanism. Moreover, at pH 10.02, the reaction rate
constant for the doubly ionized methylphosphonic acid with the
hydrated electron is only an order of magnitude slower (k )
(1.62 ( 0.12) × 109 M-1 s-1), a difference that can be attributed
to ionic strength effects. These rate constants are all significantly
faster than that reported for the dissociative reduction occurring
(8) Kiddle, J. J.; Mezyk, S. P. J. Phys. Chem. B 2004, 108, 9568.
(9) Sierakowski, T.; Kiddle, J. J. Tetrahedron Lett. 2005, 46, 2215.
(10) Tworowska, I.; Dabkowski, W.; Michalski, J. Angew. Chem., Int.
Ed. 2001, 40, 2898.
(11) Quin, L. D. A Guide to Organophosphorus Chemistry; Wiley-
Interscience: New York, 2000; Chapter 5.
(12) Mizrakh, L. I.; Evdakov, V. P.; Sandalova, L. Y. Zh. Obshch. Khim.
1965, 35, 1871.
(13) Clement, J.-L.; Finet, J.-P.; Frejaville, C.; Tordo, P. Org. Biomol.
Chem. 2003, 1, 1591.
(14) Kiddle, J. J.; Gurley, A. F. Phosphorus, Sulfur Silicon Relat. Elem.
2000, 160, 195.
(15) Whitman, K.; Lyons, S.; Miller, R.; Nett, D.; Treas, P.; Zante, A.;
Fessenden, R. W.; Thomas, M. D.; Wang, Y. In Proceedings of the ′95
Particle Accelerator Conference and International Conference on High
Energy Accelerators; IEEE No. 95CH35843, Dallas, TX, 1996.
(16) Black, R. M.; Harrison, J. M. In The Chemistry of Organophos-
phorus Compounds; Hartley, F. R., Ed.; John Wiley: New York, 1996; Vol.
4, pp 781.
(17) Buxton, G. V.; Stuart, C. R. J. Chem. Soc., Faraday Trans. 1995,
91, 279.
(18) Groenewold, G. S.; Williams, J. M.; Appelhans, A. D.; Gresham,
G. L.; Olson, J. E.; Jeffery, M. T.; Rowland, R. EnViron. Sci. Technol.
2002, 36, 4790.
for HPO4 over the pH range of 9-12.3 (k ) 1.4 × 105 M-1
2-
s-1).19 This indicates that the same reaction mechanism is
occurring for both the mono- and di-ionized species.
On the basis of our data in our Bro¨nsted plots, we can readily
extrapolate hydrated electron and hydroxyl radical rate constants
for actual CW agents in water based on the pKa values for their
leaving groups. These rate constant values are given in Table 3
and are also indicated in Figure 3a,b.
(19) Buxton, G. V.; Greenstock, C. L.; Helman, W. P.; Ross, A. B. J.
Phys. Chem. Ref. Data 1988, 17, 513.
(20) Hug, G. L. Optical Spectra of Nonmetallic Inorganic Transient
Species in Aqueous Solution; National Standard Reference Data Series, US
Government Printing Office: Washington, NSRDS-NBS 69, 1981.
(21) Treatment Technologies for the RemoVal of Methyl Tertiary Butyl
Ether (MTBE) from Drinking Water, 2nd ed.; Melin, G., Hogan, T., Eds.;
NWRI-99-06; National Water Research Institute: Fountain Valley, CA,
2000.
Conclusions
(22) Christensen, H.; Sehested, K.; Logager, T. Radiat. Phys. Chem.
1994, 43, 527.
(23) Bentrude, W. G. In Free Radicals; Kochi, J. K., Ed.; John Wiley
& Sons: New York, 1973; Vol. II, p 616.
(24) Nelson, D.; Symons, M. C. R. J. Chem. Soc., Perkin Trans. 2 1977,
286.
The reaction of chemical simulants containing leaving groups
that mimic those in actual agents are better representatives for
the development of methods for the detection, decontamination,
and destruction of CW agents. The predicted rate constants for
the true CW agents demonstrate that reductive-based radical
destruction would be more efficient than oxidative species. The
JP101720J