HD exchange kinetics of alcohols and protonated peptides: Effects of structure and proton affinity

The kinetics of gas‐phase HD exchange reactions of a series of protonated amino acids and peptides with deuterium‐substituted alcohols (D2O, CH3OD, C2H5OD and 1‐C4H9OD) were studied in an external source Fourier transform mass spectrometer. The number of exchanges observed on the time‐scale of these experiments ranged from one to the total number of ‘labile’ substrate hydrogens, depending on the amino acid and the deuterating reagent. Exchange efficiencies, k/kADO, varied from