AbstractThe structures of adduct ions formed between the nucleophiles HO−and CH3O−and various carbonyl compounds, such as aldehydes, esters and amides, have been probed in the gas phase by studying their proton affinity, collision‐induced dissociation pathways and chemical reactivity, using Fourier‐Transform Ion‐Cyclotron‐Resonance (FT‐ICR) Mass Spectrometry.Most of the generated adduct ions are shown to have stable, often proton‐bound, loosely associated structures as well as stable, covalently bound, tetrahe