Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1224800
This invention relates to a novel simulator of a chemical warfare agent.
~ ore particularly, this invention relates to a chemical which may be used
to simulatè nerve aas in an improved manner durin~ decontamination procedures.
Difficulties of a technical and administrative nature prevent the use of
nerve nas in research, development, and testing procedures due to the hazards
involved. ~urrent safety and security re~ulations which govern the use of
toxic chemical warfare agents preclude most research, development, and testing
of nerve aas such dS VX in ~ost la~oratories. For exa~ple, no outdDor testing
may be done ~ith the actual nerve aas itsel f. Thus, in order to facilitate
che~ical defense research, develop~ent, testin~ and evaluation, it is vital to
have an inventory of che~ical simulants for such nerve gas for s~ecific
purposes. It can be seen where simulants are vital to sustained progress ;n
the improvement of our defensive posture relative chemical warfare. As one
can see, simulants are use~ in every major area of the research operation of
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chem~cal warfare agents. They are necessary in everp stage of the life cycle
of a system from conception through basic research, development, testing,
evaluation an~ training.
To date, the only compound used to mimic the chemical behavior of VX is
O-ethyl S-ethyl methylDhosphonothiolate. Howe~er, the solubility and
reactivity of this compound preclude the valid performance study of VX at
varying pH levels.
It is known that each of the areas of study in testing and evaluation set
their own parameters relative the experimental or operating stages. These
parameters dictate what properties are essential for an effective slmulant in
the areas under study. In the past, experimenters had to use their individual
judgement in selecting simulants and, many times, a simulator was a material
which was used because it was readily available or because of prior use in
another stage of the cycle. Many times, the material used for one specific
purpose was not altogether satisfactory for a second speclfic purpose because
of its properties.
There has been a long standing need in the research cnmmunity of chemical
defense for a catalog of co~pnunds which might be used as simulants for
specific chemical agents under specific conditions particular decomposition or
decontamination. In particular, a search for a slmulant of VX under
decontamination studies is extremely important.
It is therefore an object of this in~ention to provide a simulant for VX
nerve gas for use in research, development, evaluation and testing of
chemically active liguid decontaminants.
Another object is to provide a simulator of YX which is safe to use hut
mimics the physical and chemical properties of the cited dangerous tnxic agent
itself.
Other objects and many of the attendant advantages of this invention will
become rore apparent to thos~ skilled ;n the art from a reading of the
detailed specification which follows.
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~2Z4800
In general, the simulator of VX must be liquid, should have a solubil~ty
similar to YX, and in solut~on should be destroyed by ox~datlon and hydrolysis
in a manner and rate si~ilar to VX. Thus the three main properties of a
simulant are state, solubility, and reactivity. However, a fourth requirement
of a decreased amount of toxicity when compared to VX is highly important.
We have found that the chemical 2-(diisopropylam~no)ethyl
dimethylthiocarbamate is the preferred stimulant for use ln place of VX nerve
gas in decontamination studies.
The formula for this simulator is, viz.
lo ~CH3~ \ / CH3
2 _, N-CH -CH -S-C-N
~ 3~2 2 2 ~ CH3
The table I which follows sets forth a comparison of the physical and
chemical properties of this simulator as compared to YX.
TABLE I
Cited
YX Simulator
For ula267.4 232.4
Point 298C 320
Dens;ty-25C 1.008qlCm3 0.978g/Cm3Yiscosity-25C 9.96 cP 9.75 cP
SolubiliOty in 0.11M/liter O.nl5M/liter
Hydrolysis 40 hours @ pH10 60 hours @ pH10
ToxicitY 500,0nO M~lsec~l 17M~lsec~l
.
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As seen in Table 1, the properties of a necessary si~ulant in place of YX
are shown. It has been found that a8 a result of this comparison, the
simulant of thls invention could replace YX in various studies which have to
be ~ade. In particular, the simulant besides havin~ properties, which are
substantially e~uivalent to that;of VX, is less tox~c th~n the nerve gas and
could be used to study decontam~nation procedures. As shown, the s~ulant has
no significant anti-cholinesterate properties which make it less dangerous.
Thus, a low tox kity substltute has been found for YX.
PREPARATIO~I
The simulant 2-(diisopropylaminol ethyl dimethylthiocarbamate is prepared
from equimolar a~ounts of dimethylcarbamayl chloride and 2-
- [diisopropylamino)ethanethiol hydrochlorid~. The latter two chemicals are
refluxed for about 2D hours ~n a five-fold molar excess of pyridine. The
pyridine is evaporated, and the residue dissolved in chloroform. Th~s
solution ls washed with dilute sodium hydroxide solution, dried o~Yer magnesium
sulfate, and the chloroform is evaporated under vacuum. The product is then
purified by vacuum distillation, and ~s collected at 118 - 120C at .55
torr. The distillate, a colorless liquid, was confirmed as a pure compound by
nmr spectroscopy, elemental analysis, and gas chromatography.
COMPARISnN
REACTIQN TO AQUEO~S HYPOCHLORlTE
In separate experiments, the simulant of this ~nvention and VX nerve gas
were reacted with a five-fold ~olar excess of sodiu~ N, N-dichloroisocyanurate
in water. At intervals of two to ten ~inutes, al~quots of each of the
materials were re~oved and analyzed iodi~etrically for active ch~orine
concentration.
VX nerve gas un~er the above reaction conditions, consumed chlorine in
two ki~etically distinct processes. In the first f~lY minutes, there was a
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rapid consumption of ahout 1.5 mole equivalent of hypochlorite per mol of VX
ner~e gas. This was followed by a slower but nearly l~near consumption of
chlorine over a substantially two hour period.
The chlorine consumption of the simulant of this ~nvention followed a
similar two-stage pattern when compared to VX. During the period of 15
minutes to 60 minutes after miKing, their re~ative chlorine consumptions are
within lQ percent of each other.
In comparison, VX is a liquid, so is the si~ulant of this invention. V~
could never be ~imicked by a solid. VX and the cited si~ulant of this
invention have similar solubilities in water and both are pH dependent in
similar ways. Once in solution, VX nerve gas may be destroyed by oxidation or
hydrolysis, and such is the chemical reactivity of the s~mulant of this
invention.
There has been a long-standing need in the chemical defense research
community for a simulant which would satisfactDrily m1mlc the physical and
chemical properties of YX. The slmulant of this invention has been prepared
and its physical properties, slow hydrolysis, and behavior toward hypochlorite
make this a suitable simulant for VX. The homologues of the simulant of this
invention do rot exhibit the desired propert~es. The cited simulant of this
invention may be added to a catlog of compounds which may be used as si~ulants
for specific agents under specific conditions. For exa~ple, the simlllant o~
this invention may be used in the testing of che~ically active liguid
decontaminants in place of YX for research, development, test, and evaluation
of new systems.
~YPOCHLnRITE OXIDATION
Sodium N, N-dichloroisocyanurate (Fichlor reagent) was used in the
comparison of the hypochtorite oxidation reaction. When YX was added to an
unbuffered solution of the Fichlor reagent in water at a S molar excess
relative VX, there was an i~m~diate reactiDn. h'ithin I minute, the YX was
destroyed. The data for the simulant in Fichlor exhibited a similar
12248~)0
pattern. There was an initial rapid burst of chloring consumption ~y the
simulant wh~ch was followed by a slower steady-state consumption. The
correlation of VX and simulant relative Kinetics is highly satisfactory for
the lntended purpose of test~ng and eva~uatlon of the decontam~natlon
procedure.
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