Effect of alkali metal cationization on the collision‐induced decomposition of alkyl per‐ O ‐acetyl‐2‐deoxy‐2‐halo‐α‐ O ‐mannopyranosides

The effect of alkali metal cationization on the collision‐induced decomposition of alkyl per‐ O ‐acetyl‐2‐deoxy‐2‐bromo‐and‐iodo‐α‐ O ‐mannopyranosides was studied. The bromo sugars gave fairly abundant MH + , whereas for the iodo sugars the MH + ions were insignificant. However, both the bromo and the iodo derivatives gave abundant M + alkali metal ion complexes. In contrast to the behaviour of the MH + ion, the [M + Li] + , [M + Na] + and [M + K] + ions of these compounds do not decompose by loss of the C(1) substituent. Elimination of AcOH is the preferred fragmentation pathway of [M + Cat] + . Elimination of HX occurs only after loss of AcOH and CH 2 CO from MH + , whereas [M + Cat] + directly loses HX. The elimination of HX is more pronounced from [M + Na] + and [M + K] + than from [M + Li] + . Loss of AcOLi is an additional fragmentation route observed in the case of the decomposition of [M + Li] + ion.