ESI formation of a Meisenheimer complex from tetryl and its unusual dissociation

The reactivity of the explosive tetryl (N‐methyl‐N,2,4,6‐tetranitroaniline; Mw = 287 u) was studied using electrospray ionization in negative mode. The main species detected in the spectrum corresponds to the ion observed at m/z 318 (previously assumed to be the odd‐electron ion [tetryl + HNO]^‐?, C₇H₆O₉N₆). In this study, we show using D‐labeling combined with high‐resolution mass spectrometry that this species corresponds to an even‐electron anion (i.e. C₈H₈O₉N₅), resulting from the formation of a Meisenheimer complex between tetryl and the methanol used as the solvent. Fragmentation of this complex under CID conditions revealed an unexpected fragment: the formation of a 2,4,6‐trinitrophenoxide anion at m/z 228. ¹⁸O‐labeling combined with quantum chemical calculations helped us better understand the reaction pathways and mechanisms involved in the formation of this product ion. This occurs via a transition state leading to a SN₂‐type reaction, consequently evolving toward an ion‐dipole complex. The latter finally dissociates into deprotonated picric acid. Copyright © 2013 John Wiley & Sons, Ltd.     

Colorimetric Sensing of Nitroaromatic Energetic Materials Using Surfactant-Stabilized and Dithiocarbamate-Functionalized Gold Nanoparticles

Abstract

There is an increasing need for sensitive/selective determination of explosive traces in soil and post-blast debris for environmental and criminal investigations. A colorimetric sensor was developed to detect and quantify trinitrotoluene (TNT) and tetryl by the use of surfactant-stabilized and dithiocarbamate-functionalized gold nanoparticles (AuNPs). The sensor was manufactured by modifying the nanoparticles with the cationic surfactant cetyl trimethyl ammonium bromide and incorporating diethyldithiocarbamate (DDTC) in the AuNPs synthesis. DDTC firmly bound to AuNPs may show charge-transfer interactions with the —NO₂ groups of the analytes, and a color change proportional to analyte concentration accompanied the agglomeration of nanoparticles, at which the absorbances were recorded at 534?nm and 458?nm for TNT and tetryl, respectively. Although the limit of detection was 8?mgL^?1 (3.52?×?10^?5?molL^?1) for TNT and 0.8?mgL^?1 (2.78?×?10^?6?molL^?1) for tetryl, providing moderate sensitivity, the cost was greatly reduced compared to those of other thiol-functionalized AuNPs sensors. Possible interferences of other energetic substances in synthetic mixtures, of camouflage materials used in passenger belongings (e.g., detergent, sugar, caffeine, and paracetamol) and common soil ions were also examined. The method was statistically validated against a reference gas chromatography/mass spectrometry method. This sensor may pave the way for the manufacture of novel low-cost nitroaromatic explosive sensors made of DDTC-based pesticides.