Oxidative Neutralization of Mustard‐Gas Simulants in an On‐Board Flow Device with In‐Line NMR Monitoring

Abstract

The fast and effective neutralization of the mustard-gas simulant 2-chloroethyl ethyl sulfide (CEES) using a simple and portable continuous flow device is reported. Neutralization takes place through a fully selective sulfoxidation by a stable source of hydrogen peroxide (alcoholic solution of urea-H O adduct/MeSO H freshly prepared). The reaction progress can be monitored with an in-line benchtop NMR spectrometer, allowing a real-time adjustment of reaction conditions. Inherent features of millireactors, that is, perfect control of mixing, heat and reaction time, allowed the neutralization of 25 g of pure CEES within 46 minutes in a 21.5 mL millireactor (t =3.9 minutes). This device, which relies on affordable and nontoxic reagents, fits into a suitcase, and can be deployed by police/military forces directly on the attack site.

Catalytic Processes for the Neutralization of Sulfur Mustard

“…Of note, i)the oxidanti ne xcess was quenched in the collection vial to prevent over-oxidation, and ii)a benchtop NMR spectrometer was used for real-time and in-flow monitoringo f the reaction progress. [52] The ideal process for the oxidative neutralization of sulfur mustard should involve molecular oxygen, however, the direct oxidation of sulfides by O 2 classically requires elevated temperature andp ressure [53] and HD decontamination by this method would requires pecific instrumental setups. Yet, milder conditions can be reachedb ya ctivating oxygen with suitable catalysts (see section3).…”

“…The technology permitted the conversion of 25 g of CEES to the corresponding sulfoxide in 46 min, with a flow rate of 5 mL min −1 and 3.9 min residence time. Of note, i ) the oxidant in excess was quenched in the collection vial to prevent over‐oxidation, and ii ) a benchtop NMR spectrometer was used for real‐time and in‐flow monitoring of the reaction progress [52] …”

Continuous Flow Organic Chemistry: Successes and Pitfalls at the Interface with Current Societal Challenges

“…Compact and mobile continuous flow reactors are therefore very useful for rapid deployment and safe on‐site operation. For instance, Legros and colleagues reported a continuous process for the neutralization of mustard gas {1‐chloro‐2‐[(2‐chloroethyl)sulfanyl]ethane, 263 } (Figure ) . The authors selected an oxidation reaction as the most suitable way to neutralize model compound 264 structurally related to 263 .…”

Merging Gradient‐Based Methods to Improve Benchtop NMR Spectroscopy: A New Tool for Flow Reaction Optimization

“…Towards this aim, gradient-based solvent elimination schemes have been compared on a benchtop spectrometer [7] and applied to reaction monitoring. [8,9] These developments have shown that benchtop NMR could be made more efficient by capitalizing on methodological developments made at high field. But while such proof-of-concept studies have shown the potential of gradient-based pulse sequences to improve the performance of benchtop spectroscopy, such potential could be pushed even further by combining tailored pulse sequence blocks to optimize the detection of signals of interest in a complex mixture.…”