Fourier transform ion cyclotron resonance study of ion‐molecule reactions of [M – OCH 3 ] + ions of methyl 2,3,4,6‐tetra‐ O ‐methyl‐d‐hexopyranosides with ammonia

Glycosidic oxocarbenium ions A 1 + were formed by isobutane chemical ionization from methyl 2,3,4,6‐tetra‐ O ‐methyl‐β‐ D ‐mannopyranoside, methyl 2,3,4,6‐tetra‐ 0 ‐methyl‐β‐ D ‐galactopyranoside and methyl 2,3,4,6‐tetra‐ O ‐methyl‐β‐ D ‐glucopyranoside (the ring ‐ O‐being converted into O ), and then‐ reaction with ammonia was studied by Fourier transform ion cyclotron resonance Spectrometry. Very slow formation (reaction efficiency 0.6‐1.4%) of the adduct ion [A 1 + NH 3 ] 4 was observed as the main process for carefully thermalized ions A 1 + . Interestingly, the efficiency of the adduct ion formation depends on the sterochemistry of ions A 1 + .