Righting past wrongs through flow chemistry: the case of chemical warfare agents
Researchers at CiTOS - Center for Integrated Technology and Organic Synthesis – of the University of Liège, led by Jean-Christophe Monbaliu, put their scientific knowledge to use by contributing to the destruction of some of the worst scientific creations produced: chemical warfare agents. Published in the journal Green Chemistry and highlighted as one the most impactful advancements in 2022 (2022 Green Chemistry Hot Articles), this new report provides a positive outlook towards peace.
rganic chemistry has not only contributed to improving our life standards (for example with the development of new medicines), but also the convergence of some of its darkest alleys has led to the creation of new compounds for sinister purposes. A notorious example is chemical warfare agents, optimized and produced with the sole purpose of harming human beings. And even if the word “warfare” suggests their military use, the use of chemical warfare agents has been witnessed both in the context of battle and sadly in attacks against civilians. “In any case, the fact remains that these chemicals have been produced in mass quantities by unscrupulous consciouses, particularly in times of war explains Jean-Christophe Monbaliu, chemist and Director of the Center for Integrated Technology and Organic Synthesis -CiTOS - (MolSys Research unit, Faculty of Science) at the University of Liège. Despite being banned internationally since 1997, the remnants of such chemicals still exist in military inventories or as spoiled ammunitions. Although retreated from public access, they remain an inherent threat to humanity.”
A research team at CiTOS has taken upon itself to develop methods to neutralize one such of these compounds known as mustard gas. Mustard gas is a blistering agent that causes severe damages to eyes, skin, and the respiratory track. Furthermore, contaminated objects such as soil or clothing can prolong its harmful effects on the surrounding victims for weeks, making the environmental persistence of mustard gas particularly long. “Belgium is still very concerned nowadays with mustard gas, adds Jean-Christophe Monbaliu, after World War I, about 10.000 tons of German chemical ammunitions filled with mustard gas were dumped by the Belgian authorities at the Paardenmarkt sandbank, just a few hundred meters from the seashore in Knokke.” Aging of these spoiled ammunitions under in saline water inexorably leads to corrosion and therefore creates a background threat for the environment and surrounding populations.
By using flow chemistry technology, researchers at CiTOS have managed to upgrade common “off-the-shelf” materials such as aqueous bleach and specific alcohols into a highly efficient chemical neutralization system. “This system is based on the production of an alkyl hypochlorite (aka organic bleach), a highly effective yet selective oxidizing agent that, upon contact with mustard gas, produces a non-toxic neutralized species in seconds comments Jean-Christophe Monbaliu. Such organic bleach reagent has however a high intrinsic potency which could itself represent a threat to the user.” Thanks to the use of continuous flow technology, one of the longstanding areas of expertise at CiTOS, the isolation of the alkyl hydrochloride is not necessary through the design of a unique chemical generator. This generator produces the neutralizing agent under controlled and safe conditions, hence avoiding any contact with the operator. It can be used directly for the destruction of sulfur mustards. The complete neutralization system, including the chemical generator, has a very low footprint (the size of a large office printer) and opens up new perspectives for on-board and mobile solutions.
The entire research is conducted using simulants of the chemical warfare agents to reduce the risk of exposure to the research personnel. The methods are then validated in silico using computational chemistry on actual chemical warfare agents, according to an original and robust protocol. Additionally, this study also provides an unprecedented understanding of the mechanism behind this neutralization reaction.
V.-E. H. Kassin, D. V. Silva-Brenes, T. Bernard, J. Legros et J.-C. M. Monbaliu, A continuous flow generator of organic hypochlorites for the neutralization of chemical warfare agent simulants, Green Chemistry, 2022, 24, 3167-3179.
This work was supported by the F.R.S.-FNRS (Incentive grant for scientific research MIS F453020F, JCMM; FRIA PhD Fellowship FC27539, VEK). Computational resources were provided by the “Consortium des Équipements de Calcul Intensif” (CÉCI), funded by the “Fonds de la Recherche Scientifique de Belgique” (F.R.S.-FNRS) under Grant No. 2.5020.11.