Method for decontamination of toxic chemical agents

N,N'-dihalo-2-imidazolidinones are described as decontaminants for toxic chemical agents such as the sulfur mustards. Decontamination is effected by contacting the toxic chemical agent with a decontaminating amount of the N,N'-dihalo-2-imidazolidinone, e.g., 1,3-dichloro-4,4,5,5-tetramethyl-2-imidazolidinone.

CROSS REFERENCE TO RELATED APPLICATIONS 
This application is related to my U.S. application Ser. No. 113,941, filed 
Oct. 28, 1987, U.S. Pat. No. 4,767,542, which is a continuation-in-part of 
my application Ser. No. 15,480, filed Feb. 17, 1987, now abandoned. 
DESCRIPTION OF THE INVENTION 
The use of toxic chemicals in wartime, particularly during World War I, has 
been well documented. Although chemical warfare has not been used on a 
large scale since that time, there is continued interest in the 
development of improved decontamination chemicals to defense against the 
possible use of toxic chemical agents, such as the sulfur mustards and 
nerve agents, e.g., VX. 
Currently, the decontaminant of choice is supertropical bleach (STB), which 
is a white powder containing about 30 percent available chlorine in the 
form of calcium hypochlorite. STB may be used either as a dry mix or as an 
aqueous slurry to decontaminate exterior surfaces and ground that has 
become contaminated with chemical toxic agents. STB deteriorates with time 
and accordingly must be replaced every few years. Further, STB is more 
soluble in aqueous media than in organic media and, therefore, is less 
effective as a decontamination agent against toxic organic chemical 
substances that are disseminated in an aqueous medium. 
It has now been discovered that N,N'-dihalo-2-imidazolidinones may be used 
as a decontaminating chemical reagent against toxic chemical agents such 
as the blister agents, e.g., the sulfur mustards. Alkaline solutions or 
emulsions of the N,N'-dihalo-2-imidazolidinones may also be used as a 
decontaminant for toxic nerve agents, e.g., the VX and the G series of 
nerve agents. The aforedescribed 2-imidazolidinones are relatively stable 
in storage and are significantly more soluble in organic solvents, such as 
tetrachloroethylene, than is STB. Moreover, removal of excess quantities 
of 2-imidazolidinone compounds may be readily accomplished by rinsing with 
water following a successful decontamination operation. Further, they are 
much less corrosive to metal than compounds that liberate free chlorine, 
such as STB, and hence can be used to wash down military equipment made of 
corrodible metals. 
DETAILED DESCRIPTION OF THE INVENTION 
The N,N'-dihalo-2-imidazolidinones described herein are five membered ring 
compounds that may be represented by the following graphic formula I: 
##STR1## 
wherein X and X' are each halogen selected from the group chlorine and 
bromine, provided that at least one of X and X' is chlorine, R.sub.1, 
R.sub.2, R.sub.3 and R.sub.4 are each selected from the group consisting 
of hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, hydroxy and 
substituted phenyl, particularly para-substituted phenyl, wherein said 
phenyl substituents are each selected from the group consisting of C.sub.1 
-C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy and hydroxy; provided, further, 
that not more than one of the substituents R.sub.1 -R.sub.4 is hydrogen. 
The number of phenyl substituents may range from 1 to 2 substituents. 
The alkyl substituents attached to the ring of the 2-imidazolidinone 
compounds or to the phenyl substituent may contain from 1 to 4 carbon 
atoms; namely, methyl, ethyl, propyl, isopropyl and the butyls, e.g., 
n-butyl, isobutyl, and secondary butyl. Similarly, the alkoxy substituents 
attached to the ring or the phenyl substituent may contain from 1 to 4 
carbon atoms; namely, methoxy, ethoxy, propoxy, isopropoxy and butoxy, 
e.g., n-butoxy, isobutoxy, and secondary butoxy. 
N,N'-dihalo-2-imidazolidinones described herein include those in which at 
least 3 of the 4 substituents (namely R.sub.1 -R.sub.4) on the carbon 
atoms at the 4 and 5 positions of the ring are chosen from the described 
alkyl, alkoxy, hydroxy, or substituted phenyl substituents. Preferably, 
all four of the substituents are chosen from said group of substituents. 
Thus, N,N'-dihalo-2-imidazolidinone derivatives contemplated herein are 
tri- and tetra-substituted N,N'-dihalo-2-imidazolidinones. More 
preferably, the R.sub.1 -R.sub.4 substituents and the phenyl substituents 
are C.sub.1 -C.sub.4 alkyl groups, i.e., methyl and ethyl groups. Still 
more preferably, R.sub.1 -R.sub.4 are methyl groups. 
Examples of the aforedescribed dihalo-2-imidazolidinone compounds include, 
but are not limited to: 
1-bromo-3-chloro-4,4,5,5-tetramethyl-2-imidazolidinone; 
1,3-dichloro-4,5,5-trimethyl-2-imidazolidinone; 
1,3-dichloro-4,4,5,5-tetramethyl-2-imidazolidinone; 
1,3-dichloro-4-methoxy-4,5,5-trimethyl-2-imidazolidinone; 
1,3-dichloro-4-hydroxy-4,5,5-trimethyl-2-imidazolidinone; 
1,3-dichloro-4-ethyl-4,5,5-trimethyl-2-imidazolidinone; 
1,3-dichloro-4,4-diethyl-5,5-dimethyl-2-imidazolidinone; and 
1,3-dichloro-4,4,5,5-tetraethyl-2-imidazolidinone. 
By substituting other described substituents for one or more of the named 
R.sub.1 -R.sub.4 substituents, i.e., methyl, ethyl, methoxy, hydroxy, 
etc., other corresponding named N,N'-dichloro-, dibromo- or 
bromochloro-2-imidazolidinone derivatives may be named. 
N,N'-dihalo-2-imidazolidinone derivatives of the present invention may be 
prepared by reacting the corresponding unhalogenated 2-imidazolidinone 
with a source of chlorine, or, in the case of N-bromo-N'-chloro 
derivatives, first a source of chlorine and then a source of bromine. 
While elemental chlorine and bromine may be utilized, milder 
chlorinating/brominating agents may be used. Examples thereof include: 
N-chlorosuccinimide, N-bromosuccinimide, calcium hypochlorite, sodium 
hypochlorite, tertiary butyl hypochlorite, trichloroisocyanuric acid, 
N-chloroacetamide, N-chloro- or bromo-amines, etc. Halogenation of the 
unhalogenated 2-imidazolidinones may be accomplished in mixtures of water 
and common inert organic solvents, e.g., methylene chloride, chloroform 
and carbon tetrachloride, at room temperatures. Inert organic solvents may 
be used along with N-halamine halogenating reagents. 
Unhalogenating tetraalkyl substituted 2-imidazolidinones may be prepared by 
first reducing the corresponding 2,3-dialkyl-2,3-dinitrobutane, e.g., 
2,3-dimethyl-2,3-dinitrobutane, to the 2,3-dialkyl-2,3-diaminobutane, 
e.g., 2,3-dimethyl-2,3-diaminobutane, and then forming the 
2-imidazolidinone by reacting the 2,3-dialkyl-2,3-diaminobutane with 
phosgene in basic solution. Such reduction step may be accomplished by the 
method described by J. Bewad, in the article, "Concerning Symmetrical 
Tertiary alpha Dinitroparrafin", Ber., 39, 1231-1238 (1906). The 
2-imidazolidinone may be synthesized by the method described by R. Seyre 
in the article, "The Identity of Heilpern's `Pinacolylthiourea` and the 
Preparation of Authentic 2-Thiono-4,4,5,5-tetramethylimidazolidinone", J. 
Am. Chem. Soc. 77, 6689-6690 (1955). It is contemplated that other 
described 2-imidazolidinone derivatives may be prepared from the 
corresponding 1,2-substituted-1,2-diaminoethane, or by other organic 
synthetic routes known to those skilled in the art. For example, it is 
contemplated that 
1,3-dichloro-4-methoxy-4,5,5-trimethyl-2-imidazolidinones may be prepared 
by cyclizing 2-methyl-3-methoxy-2,3-diaminobutane and chlorinating the 
resulting 4-methoxy-4,5,5-trimethyl-2-imidazolidinone. Similarly, it is 
contemplated that 1,3-dichloro-4-hydroxy-4,5,5-trimethyl-2-imidazolidinone 
may be prepared by cyclizing 2-methyl-3-hydroxy-2,3-diaminobutane and 
chlorinating the resulting 4-hydroxy-4,5,5-trimethyl-2-imidazolidinone. 
The N,N'-dihalo-2-imidazolidinones described herein may be used to 
decontaminate toxic chemical agents such as blister agents, e.g., the 
sulfur mustards, and other toxic agents that are susceptible to oxidation 
by halogen. Alkaline aqueous solutions or emulsions of the 
N,N'-dihalo-2-imidazolidinones may also be used as decontaminant for toxic 
nerve agents, e.g., the VX and the G series. 
The nerve agent VX is reported to have the following chemical graphic 
formula, 
##STR2## 
The G series of nerve agents include Tabun (GA), i.e., ethyl 
phosphorodimethylamidocyanidate, 
EQU [((CH.sub.3).sub.2 N)--P(O)(CN)OC.sub.2 H.sub.5 ]; 
Sarin (GB), isopropyl methyl phosphonofluoridate 
EQU [CH.sub.3 P(O)(F)OCH(CH.sub.3).sub.2 ]; 
Soman (GD), pinacolyl methylphosphonofluoridate 
EQU [CH.sub.3 P(O)(F)OCH(CH.sub.3)C(CH.sub.3).sub.3 ] 
The sulfur mustards include the compounds; bis(2-chloroethyl) sulfide (HD), 
EQU [ClCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 Cl]; 
1,2-bis(2-chloroethylthio)ethane (Q) 
EQU [ClCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 Cl]; 
bis(2-chloroethylthioethyl)ether (T), 
EQU [ClCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 SCH.sub.2 
CH.sub.2 Cl]; 
mixtures of compounds HD and Q, i.e., mustard and 1,2-bis(2-chloroethyl 
thio)ethane; and mixtures of mustard (HD) and T, i.e., mixtures of 
bis(2-chloroethyl) sulfide and bis(chloroethyl thioethyl) ether. 
Decontamination of toxic chemical agents susceptible to oxidation by 
halogen may be accomplished by contacting the toxic chemical with a 
decontaminating amount of the described N,N'-dihalo-2-imidazolidinone. 
Commonly, the imidazolidinone decontaminating compound will be used in 
amounts such that at least one mole of the imidazolidinone compound is 
used for each mole of toxic chemical agent, i.e., at least an equal molar 
amount. In order to insure total detoxification, it is common to utilize a 
large excess of the decontaminating chemical compound i.e., the 
imidazolidinone, vis-a-vis the toxic chemical agent. 
Decontamination may be accomplished by applying an aqueous solution or 
emulsion (hereinafter collectively referred to as an "emulsion") of the 
imidazolidinone in water or dissolved in an organic solvent that is part 
of an aqueous emulsion. Preferably, the emulsion of the imidazolidinone 
will have an alkaline pH, e.g, have a pH of between about 9 and about 11, 
e.g., about 10. More particularly, the aqueous emulsion (sans 
decontaminant) may comprise from about 25 to about 65 weight percent 
water, from about 5 to 45 weight percent organic solvent, e.g., 
chlorinated organic solvents, and from about 10 to about 30 weight percent 
of one or more surfactants, e.g., cationic emulsifiers. The aforedescribed 
formulations are representative only and solely for purposes of example. 
Depending on the organic solvent used and the amount of 2-imidazolidinone 
compound incorporated into the solvent, different amounts of water and 
surfactant may be required. Such amounts may be readily found without 
undue trial and error experimentation by one skilled in the art. 
By way of further example, a common aqueous emulsion utilized for calcium 
hypochlorite or sodium dichloroisocyanurate is an emulsion comprising 
about 63 weight percent water, 7.4 weight percent tetrachloroethylene, 1,4 
weight percent trimethyl C.sub.8 -C.sub.10 quaternary ammonium chloride, 
16.5 weight percent cetyl trimethyl ammonium chloride and 11.7 tetrabutyl 
ammonium hydroxide. This type of emulsion composition may be used with the 
imidazolidinones described herein. 
The aqueous emulsion is commonly buffered with conventional buffering 
agents to a pH of from about 9 to about 11, e.g., about 10. An example of 
such a buffering agent is the sodium carbonate-sodium bicarbonate system. 
Any conventional organic solvent that solubilizes the 
N,N'-dihalo-2-imidazolidinone, e.g., the common hydrocarbon (aromatic and 
paraffinic) solvents or halogenated hydrocarbon solvents may be used as 
the organic medium carrier for the imidazolidinone compound. In choosing a 
suitable organic solvent, the volatility, flammability and toxicity of the 
solvent should be considered, i.e., relatively non-volatile, non-flammable 
and non-toxic solvents should be selected. For example, there can be 
mentioned, tetrachloroethylene, trichloroethylene, tetrachloroethane, 
pentachloroethane, xylene, cyclohexanone or mixtures of organic solvents. 
The N,N'-dihalo-2-imidazolidinone may be dissolved in the organic solvent 
to the extent of its solubility therein or to levels less than saturation. 
It is expected that the 2-imidazolidinone may be used in amounts 
sufficient to form about a 0.1 to about a 0.4 molar solution in the 
organic solvent. 
In addition, it is contemplated that the N,N'-dihalo-2-imidazolidinone may 
be used as a decontaminant in the neat solid form or blended with a solid 
inert filler such as alumina, silica, etc.

The present invention is more particularly described in the following 
examples which are intended as illustrative only since numerous 
modifications and variations therein will be apparent to those skilled in 
the art. 
EXAMPLE 1 
Approximately 0.1 gram (4.74.times.10.sup.-4 moles) of 
1,3-dichloro-4,4,5,5-tetramethyl-2-imidazolidinone was placed in a 5 
millimeter (OD) NMR tube. Enough deuterochloroform (CDCl.sub.3) was added 
to the NMR tube to a height of about 3 centimeters. All of the 
imidazolidinone dissolved readily. To a second identical NMR tube was 
charged several drops of the mustard simulant 2-chloroethyl sulfide to a 
height of about 0.5 centimeters (approximately 5.40.times.10.sup.-4 
moles). The mustard simulant was diluted to a height of 3 centimeters with 
deuterochloroform. A drop of tetramethylsilane, which werved as an NMR 
standard, was added to each tube. A proton NMR spectrum was recorded for 
each sample tube using a Varian EM 300 Spectrometer. The contents of the 
two NMR tubes were then mixed by adding the imidazolidinone solution to 
the mustard simulant solution at ambient temperature. A white suspension 
at the interface of the mixing was immediately observed, indicating that a 
chemical reaction had occurred. The resulting mixture was shaken 
thoroughly and a proton NMR spectrum of the reacting mixture recorded 
between the time of mixing and 6 minutes elapsed time. The NMR spectrum of 
the mixture differed markedly from that of the original spectra for the 
imidazolidinone and mustard simulant (new NMR bands occurred at .delta. 
1.89 (doublet), .delta. 4.02 (doublet), .delta. 5.24 (multiplet), and 
.delta. 7.03 (broad unresolved). From such changes in the spectra, it was 
concluded that a rapid chemical reaction occurred which should also occur 
for the mustard agent, bis(2-chloroethyl) sulfide, since the art 
recognizes that 2-chloroethyl sulfide simulates well the reactions of 
bis(2-chloroethyl) sulfide. 
The white suspension that occurred at the mixing interface was determined 
to be the unhalogenated 2-imidazolidinone precursor, i.e., 
4,4,5,5-tetramethyl-2-imidazolidinone. It was concluded that the 
2-imidazolidinone functions as a mild oxidizing agent in converting the 
sulfide simulant to sulfoxides and possible sulfones. 
Although the present invention has been described with reference to 
specific details of certain embodiments thereof, it is not intended that 
such detail should be regarded as limitations upon the scope of the 
invention except as and to the extent that they are included in the 
accompanying claims.