D. K. Rohrbaugh

Trifluoromethylthiolation of Trimethylsilyl Enol Ethers

The treatment of bis-(1,2-trimethylsilyloxy)-1-cyclobutene, 1-(1-trimethylsilyloxy)cyclpentene and 1-(1-trimethylsilyloxy)cyclohexene with trifluoromethylsulfenyl chloride has been found to furnish trifluoromethylthiolated carbonyl derivatives.

Characterization of equimolar VX–water reaction product by gas chromatography–mass spectrometry

Abstract One method proposed for the destruction of the chemical warfare nerve agent VX, O -ethyl S -2-(diisopropylamino)ethyl methylphosphonothiolate, is hydrolysis by the addition of an equimolar amount of water. To better understand this reaction, a method was developed for characterization of the resulting product and for monitoring product stability. Conditions for derivatization of the acidic products to their trimethylsilyl esters, with subsequent analysis by gas chromatography–mass spectrometry using electron (EI) and methane chemical ionization (CI) were optimized to allow nonchromatographable acids and organic products to be detected in a single analysis, without loss of volatile products, and with minimal side reaction. EI and methane CI mass spectra of 23 identified degradation products are provided. Results indicate that the product is relatively stable at ambient temperatures in a closed container with only a minimal amount of thiol secondary reaction being observed.

Detection of alkyl methylphosphonic acids in complex matrices by gas chromatography–tandem mass spectrometry

Abstract A method was developed to detect alkyl methylphosphonic acids in complex matrices using gas chromatography–tandem mass spectrometry. By converting the acids to their trimethylsilyl derivatives and monitoring the collision-induced dissociation of m/z 153 to m/z 75 under electron ionization or methane chemical ionization (CI) conditions, five members of this series (alkyl=ethyl, isopropyl, isobutyl, pinacolyl and cyclohexyl) were selectively detected against backgrounds of diesel fuel and soil extracts containing base–neutral–acid polynuclear aromatic hydrocarbons and pesticides without interference. Detection limits were 200–500 pg injected. Ammonia CI was successfully employed for molecular mass confirmation.

Methanol chemical ionization quadrupole ion trap mass spectrometry of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its degradation products

Mass spectrometric analysis of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) degradation products by electron ionization produces extensive fragmentation with little or no molecular ion information making product identification difficult. Milder chemical ionization (CI) is commonly used to provide molecular mass and structure confirmation. In this study, methanol was used as a CI reagent in combination with an ion trap detector for detection and identification of over 30 compounds present in a thermally degraded sample of VX. The use of methanol provides superior results for this class of compounds with less fragmentation than commonly observed with gas reagents and offers logistical advantages for on-site analysis by being easier to transport and safer to use than gas cylinders.

Microwave Induced Reaction of H-Dimethylphosphonate with Styrene Oxide

Microwave catalyzed reaction of a neat mixture of styrene oxide and H-dimethylphosphonate furnished dimethyl methylphosphonate, trimethylphosphate, phenylacetaldehyde, 1-methoxy-2-phenylethanol, 1-phenylethleneglycol, cis- and trans-1,3-diphenylcyclobutanes, hydrogen 1-(2-phenylethyl)methylphosphinate, (1-phenylethyl)dimethylphosphonate, and (1-phenylethyl)dimethylphosphonate via free radical processes.

Identification of degradation products of 2-chloroethyl ethyl sulfide by gas chromatography-mass spectrometry

Gas chromatography-mass spectrometry under both electron impact and methane chemical ionization conditions has been used to detect impurities and degradation products present in the mustard simulant 2-chloroethyl ethyl sulfide, with a detection limit of 0.05 area percent. After one and two years of storage at ambient temperatures, the primary degradation product was 1,4-dithiane formed from the degradation of dimeric sulfonium ions. Oxidation and hydrolysis products were not detected.

Trifluoromethylthiolation of masked carbonyl precursors: Reaction of trifluoromethylsulfenyl chloride with enol acetates

Incorporation of fluorine and fluorine containing groups such as trifluoromethyl and trifluoromethylthio moieties considerably enhances the biological property and potency of the parent products. This communication describes the results of trifluoromethylthiolation of masked carbonyl precursors such as enol acetates, the mechanism of formation and mass spectral characterization of the compounds formed.

THERMAL DEGRADATION OF BIS (2-CHLOROETHYL) SULFIDE (MUSTARD GAS)

Abstract The thermal degradation of mustard gas (ClCH2CH2SCH2CH2Cl, “HD”), with and without 5% added water, is examined. GC/MS, LC/MS and NMR were employed to comprehensively analyze the products. After 75 days at 90°C, 91% HD remains (80% with 5% water). After 40 days at 140°C, 30% HD remains (24% with 5% water) and black “tar” precipitates form. The apparent Ea is 22.4 kcal/mol. Major products include Q (ClCH2CH2SCH2CH2SCH2Cl), 1,2-dichloroethane, polysulfides and 1,4-dithiane. With 5% water, oxygenates such as 1,4-thioxane and 2-chloroethanol are produced as are numerous sulfonium ions, including S-(2-chlorethyl)-1,4-dithianium, a major component of “mustard heels.” The decomposition does not go to completion due to the equilibrium nature of the reaction at these temperatures.

Trifluoromethylthiolation of 1,3-Dithiane

With a view to synthesize 2-(trifluoromethylthio)-1,3-dithiane (1), 1,3-dithiane (2) was reacted in dry pentane at −78°C under dry N2 with trifluoromethylsulfenyl chloride (3) and was found to furnish the desired compound in poor yields along with ten other compounds. Under similar conditions, 2-lithio-1,3-dithiane on treatment with 2 and bis-(trifluoromethyl)disulfide (4) gave 8.0% and 10.0% yields of 1, respectively. In connection with this study, (cholromethyl) propyl sulfide and bis-(propylthio)methane were synthesized. The reaction of the latter with 3 was also investigated. The characterization of the primary compound formed in the reaction of 2 with 3 using the ‘INAPT ’-NMR and GC-MS, the probable mechanism of the formation of the various compounds and their mass spectral identification are presented in this article.

Reactions of Trifluoromethylsulfenyl Chloride and Trifluoromethylthiocopper with 2-(Trimethylsilyl)thiazole

The treatment of 2-(trimethylsilyl)thiazole with trifluoromethylsulfenyl chloride furnishes the expected 2-(trifluoromethylthio)thiazole in satisfactory yields along with the ring contraction product of the azirine-type. However, the reaction of 2-bromothiazol with trifluoromethylthiocopper gives poor yields of the above compound. The mechanism of formation and the mass spectral characterization of the products are presented in this article.