title: Gas phase chemistry of Li+ with amides: the observation of LiOH loss in mass spectrometry.
abstract: Collision-induced dissociation (CID) of Li(+) adducts of three sets of compounds that contains an amide bond, including 2-(4, 6-dimethoxypyrimidin-2-ylsulfanyl)-N-phenylbenzamide, its derivatives and simpler structures was investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Observed fragment ions include those that reflect loss of LiOH. Other product ions result from the Smiles rearrangement and direct C-S bond cleavage. MS/MS of H/D exchange products demonstrated occurrence of a 1,3-H shift from the amide nitrogen atom to the phenyl ring of these compounds. The LiOH loss from Li(+) adducts of amides was further examined by CID of [M + Li](+) ions of N-phenylbenzamide and N-phenylcinnamide. Loss of LiOH was essentially the sole fragmentation reaction observed for the former. For the latter, both losses of LiOH and H(2)O were discovered. The presence of electron-donating substituents of the phenyl ring of these compounds was found to facilitate elimination of LiOH, while that loss was retarded by electron-withdrawing substituents. Proposed fragment ion structures were supported by elemental compositions deduced from ultrahigh resolution Fourier transform ion cyclotron resonance tandem mass spectrometry (FTICR-MS/MS) m/z value determinations. Density functional theory-based (DFT) calculations were performed to evaluate potential mechanisms for these reactions.
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou, 310027, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Guo
authors.forename: Yuping
authors.initials: Y
authors.lastname: Zhou
authors.forename: Pengyuan
authors.initials: P
authors.lastname: Liu
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Chai
authors.forename: Yuanjiang
authors.initials: Y
authors.lastname: Pan
mesh_terms: D001549:Benzamides / Q000737:chemistry*; D002414:Cations, Monovalent / Q000737:chemistry; D002934:Cinnamates / Q000737:chemistry; D041961:Deuterium Exchange Measurement; D005740:Gases / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D018020:Lithium Compounds / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*
chemical_list: D001549:Benzamides; D002414:Cations, Monovalent; D002934:Cinnamates; D005740:Gases; D007477:Ions; D018020:Lithium Compounds; C028467:lithium hydroxide