Generation and characterization of ionic and neutral methylene isothiocyanate by a combined tandem mass spectrometry and computational study

Abstract

AbstractThe heterocumulene, methyleneisothiocyanate ion, CH2NCS+ (1a+), is generated by the dissociative electron ionization of 2‐mercaptoimidazole. This conclusion follows from tandem mass spectrometry experiments and theoretical calculations at the B3LYP/6‐311G** and G2/G2(MP2) levels. The calculations predict that 1a+ is separated by high energy barriers from its isomers CHNCHS (1b+), CHNCSH (1d+), CNCHSH (1e+) and CHNHCS (1f+). The low energy metastable ions 1a+ dissociate by loss of HCN via the pathway 1a+ → 1b+ → HCS+ + HCN. Neutralization‐reionization experiments confirm the theoretical prediction that the hitherto unknown heterocumulene CH2NCS. is a stable species in the rarefied gas phase. Copyright © 2004 John Wiley & Sons, Ltd.