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United States Department of Agriculture

Agricultural Research Service

Title: Role of Inductive Effect in Solvent-Cation Binding Observed in Electrosprayionization Mass Spectrometry

Authors
item Striegel, Andre
item Piotrowiak, Piotr - UNIV OF NEW ORLEANS, LA
item Cole, Richard - UNIV OF NEW ORLEANS, LA

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 7, 1997
Publication Date: N/A

Technical Abstract: Electrospray ionization (ESI) mass spectrometry has been used in conjunction with computer modeling to investigate binding tendencies of alkali metal cations to low molecular weight solvents. Intensities of peaks corresponding to solvated alkali cations were found to decrease with increasing ionic radii of the cations (Li > Na > K aproximately equal to Cs) in either dimethyl acetamide or dimethyl formamide. When LiCl was added to an equimolar mixture of dimethyl formamide (DMF), dimethyl acetamide (DMAc), and dimethyl propionamide (DMP), gas-phase solvated lithium cations appeared in the ESI mass spectrum. The abundances of solvent adducts of Li**+ in the ESI mass spectrum decreased in the order DMP > DMAc much greater than DMF. This ranking correlates with the relative strength of the inductive effect exhibited by the alkyl group adjacent to the carbonyl function on each solvent. Electron donation thus appears to play a large role in the stabilization of the lithium cation attached to the carbonyl oxygen. This proposition is supported by computer modeling studies of electrostatic potentials. Relative intensities of [Solvent + Li]**+ peaks in equimolar mixtures of alcohols indicate preferential solvation of Li**+ in the order propanol > ethanol > methanol. These experiments suggest a prominent role of the inductive effect in determining relative intensities of solvated cation peaks in the ESI mass spectrum for a series of homologous solvents.

Last Modified: 12/18/2014
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