A study of formation and fragmentation of ionic metal complexes of substituted benzoic and cinnamic acids with Al(III)-glycerol by fast atom bombardment mass spectrometry

Substituted benzoic and cinnamic acids were studied by FAB mass spectrometry using matrix-based Al(III) ions. Complex ions derived from these acids, such as (M + 117)(+) (117 = (Al + glycerol - 2H)(+)), (M + 159)(+) (159 = [2Al + 2glycerol - 5H - 74(epoxypropanol)](+)), and (M + 233)(+) (233 = (2Al + 2glycerol - 5H)(+)), when subjected to collisionally activated dissociation (CAD), gave an ion corresponding to (M - OH)(+). Formation of this ion was explained by the transfer of the carboxylic -OH group to the (Al + glycerol - 2H)(+), (2Al + 2glycerol - 5H - 74)(+), and (2Al + 2glycerol - 5H)(+) portion of the complexes. This transfer is more pronounced in the case of meta- and para-substituted acids. The CAD of the (M + 117)(+) ions yielded (M + Al(III))(+) ions resulting from the insertion of Al(III) into the carboxylic acid, which was followed by the elimination of CO to produce (M + Al(III) - CO)(+) ions. Interpretation of spectral data was clarified by study of the formation and fragmentation of ions produced from deuterated benzoic and cinnamic acids.