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] ‐• , C 7 H 6 O 9 N 6 ). 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. C 8 H 8 O 9 N 5 ), 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. 18 O‐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 SN 2 ‐type reaction, consequently evolving toward an ion‐dipole complex. The latter finally dissociates into deprotonated picric acid. Copyright © 2013 John Wiley & Sons, Ltd.