Conformational analysis of the isomers of lewisite

Abstract

Chlorovinyldichloroarsine, also known as lewisite, is a powerful vesicant that has been used in the past as a chemical weapon. Its extreme toxicity makes obtaining experimental data to characterize this notorious chemical system very challenging. In this work, ab initio calculations were carried out on the geminal, cis and trans isomers of lewisite at a variety of levels of theory employing both all-electron and effective-core potential basis sets. The aims were to ascertain the relative stability of these three isomeric forms of lewisite and to characterize their structures, dipole moments and conformational preferences. The trans isomer of lewisite was found to be the most stable and the geminal isomer the least stable. This is consistent with the experimental data available on the compositions of lewisite mixtures.

A Computational Study of Detoxification of Lewisite Warfare Agents by British Anti-lewisite: Catalytic Effects of Water and Ammonia on Reaction Mechanism and Kinetics

“…Another reactant, chlorovinyldichloroarsine, also has three isomeric forms: germinal, cis, and trans. Urban and von Tersch reported that the trans isomer is most favored compared to cis isomer (∼0.6 kcal·mol –1 ) and geminal isomer (∼1 kcal·mol –1 ) at the MP2/6-311+G(2d,p)//MP2/6-31+G(2d,p) level. For this reason, all calculations are carried out on the trans isomer of lewisite.…”

Comprehensive DFT study on molecular structures of Lewisites in support of the Chemical Weapons Convention

“…The agreement between the experimental and calculated data is much satisfactory for bond length. [13]. It is also useful to compare the calculated dipole moment of L 1-1 and cis Lewisite L 1-2…”

“…The protons are located on the periphery of the molecule and therefore are more sensitive to solvent effects. Usually, the agreement between the experimental and calculated data for protons is worse than that of13 C[27,28]. The most mismatch is observed in the 13 C chemical shift of carbon-2 of L 1-1 .…”

“…The LD 50 and LCt 50 of L 1 by inhalation are estimated as 20 mg kg -1 and 1300 mg min m -3 [12]. At the time being, only one structural study of L 1 has been reported by Urban and co-workers [13]. Also experimental data of L 2 and L 3 such as relative stability of their isomers has not been available in the general scientific literature.…”

Kinetic modeling of the thermal destruction of lewisite

“…Smith et al (Smith et al, 1995) identified in mixtures the "geminal" isomer dichloro (1-chlorovinyl) arsine; this third isomer was not observed previously because of its very low amount (<1%). Urban and von Tersch (Urban and von Tersch, 1999) performed a conformational analysis of lewisite isomers using ab-initio calculations and found that the trans isomer has an electronic energy lower than the cis isomer by about 0.6 kcal mol -1 , whereas the geminal isomer, is located at about 1 kcal mol -1 above the trans form. Early works on destruction of lewisite showed that the combustion products include acetylene, acetylene chloride and dichloride, arsenic trichloride AsCl 3 , chlorine, methyl and vinyl chloride (Baronian, 1988).…”