Base-initiated Reformatsky condensations in the gas phase

Abstract

The ester enolate anion CH₂C(OEt)O^– reacts with acetaldehyde and with acetone in the gas phase to produce ‘stable’ adducts that are amenable to study by collisional activation and tandem mass spectrometry (MS/MS). The activated adducts and deprotonated β-hydroxy ethyl ester reference ions both decompose by elimination of H₂O, Et˙, H₂O followed by EtOH, and by a retro reaction to reform CH₂C(OEt)O^–. The losses of H₂O, Et˙, and EtOH are assigned to be characteristic of a species of tetrahedral geometry. These losses are, however, attenuated for the ion–molecule adducts because, in addition to existing as tetrahedral complexes, they are also formed as ion–dipole and proton-bound species.