Vibrational study of a benzyl carbanion: deprotonated 2,4-dinitrotoluene

The bare deprotonated 2,4-dinitrotoluene [DNT-H]− anion, formed by electrospray ionization and trapped in a Paul ion-trap, has been investigated by IR multiple photon dissociation (IRMPD) spectroscopy and quantum chemical calculations at the B3LYP/6-311++G** level. IRMPD spectra were recorded in the 950–1800 cm−1 fingerprint range and interpreted by comparison with the calculated IR absorption spectra for different low-lying isomers. The sampled [DNT-H]− species is found to involve deprotonation at the methyl group, yielding a benzyl carbanion 1, previously described as an amine complex in solution and here characterized by vibrational spectroscopy as an unperturbed gaseous species. Anion 1 is the most stable species among [DNT-H]− isomers. © 2012 American Institute of Physics.