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. Keywords: substituted benzoic and trans-cinnamic acids, Al(III)-glycerol, FAB mass spectrometry, ionic metal complexes, collisionally induced dissociation, Al(III) insertion, carbonyl cations.