title: Structural elucidation of direct analysis in real time ionized nerve agent simulants with infrared multiple photon dissociation spectroscopy.
abstract: Infrared multiple photon dissociation (IRMPD) was used to generate vibrational spectra of ions produced with a direct analysis in real time (DART) ionization source coupled to a 4.7 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The location of protonation on the nerve agent simulants diisopropyl methylphosphonate (DIMP) and dimethyl methylphosphonate (DMMP) was studied while solutions of the compounds were introduced for extended periods of time with a syringe pump. Theoretical vibrational spectra were generated with density functional theory calculations. Visual comparison of experimental mid-IR IRMPD spectra and theoretical spectra could not establish definitively if a single structure or a mixture of conformations was present for the protonated parent of each compound. However, theoretical calculations, near-ir IRMPD spectra, and frequency-to-frequency and statistical comparisons indicated that the protonation site for both DIMP and DMMP was predominantly, if not exclusively, the phosphonyl oxygen instead of one of the oxygen atoms with only single bonds.
authors.affiliation: Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, USA.
authors.forename: Julia L
authors.initials: JL
authors.lastname: Rummel
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Steill
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: Cesar S
authors.initials: CS
authors.lastname: Contreras
authors.forename: Wright L
authors.initials: WL
authors.lastname: Pearson
authors.forename: Jan
authors.initials: J
authors.lastname: Szczepanski
authors.forename: David H
authors.initials: DH
authors.lastname: Powell
authors.forename: John R
authors.initials: JR
authors.lastname: Eyler
mesh_terms: D002619:Chemical Warfare Agents / Q000032:analysis*; D005583:Fourier Analysis; D013058:Mass Spectrometry / Q000379:methods; D009943:Organophosphorus Compounds / Q000032:analysis*; D017785:Photons; D011522:Protons; D013055:Spectrophotometry, Infrared / Q000379:methods*
chemical_list: D002619:Chemical Warfare Agents; D009943:Organophosphorus Compounds; D011522:Protons; C031116:dimethyl methylphosphonate; C023477:diisopropyl methylphosphonate