title: Competitive proton and hydride transfer reactions via ion-neutral complexes: fragmentation of deprotonated benzyl N-phenylcarbamates in mass spectrometry.
abstract: The gas-phase chemistry of deprotonated benzyl N-phenylcarbamates was investigated by electrospray ionization tandem mass spectrometry. Characteristic losses of a substituted phenylcarbinol and a benzaldehyde from the precursor ion were proposed to be derived from an ion-neutral complex (INC)-mediated competitive proton and hydride transfer reactions. The intermediacy of the INC consisting of a substituted benzyloxy anion and a phenyl isocyanate was supported by both ortho-site-blocking experiments and density functional theory calculations. Within the INC, the benzyloxy anion played the role of either a proton abstractor or a hydride donor toward its neutral counterpart. Relative abundances of the product ions were influenced by the nature of the substituents. Electron-withdrawing groups at the N-phenyl ring favored the hydrogen transfer process (including proton and hydride transfer), whereas electron-donating groups favored direct decomposition to generate the benzyloxy anion (or substituted benzyloxy anion). By contrast, electron-withdrawing and electron-donating substitutions at the O-benzyl ring exhibited opposite effects.
authors: Department of Chemistry, Zhejiang University, Hangzhou, 310027, Zhejiang, China.
authors: Liqing
authors: L
authors: Yao
authors: Yunfeng
authors: Y
authors: Chai
authors: Cuirong
authors: C
authors: Sun
authors: Yuanjiang
authors: Y
authors: Pan
mesh_terms: D013058:Mass Spectrometry / Q000379:methods*; D008958:Models, Molecular; D048448:Phenylcarbamates / Q000737:chemistry*; D011522:Protons
chemical_list: D048448:Phenylcarbamates; D011522:Protons
keywords: benzyl N-phenylcarbamates; hydride transfer; ion-neutral complex; mass spectrometry; proton transfer