Comprehensive ESI-MS and MS/MS analysis of aromatic hydrazones derived from nicotinic acid hydrazide

• Comprehensive ESI-MS and MSn analysis of aroylhydrazones are given.
• Structural isomers were distinguished by MS/MS.
• Homolytic cleavage and formation of radical cation were observed.
• Fragmentation patterns of protonated and sodiated species are presented.

Aroylhydrazones 1–13 derived from nicotinic acid hydrazide and differently substituted benzaldehyde or ketone (2-hydroxyacetophenone and 2-hydroxybenzophenone) were analysed by ESI-MS both in positive and negative ion mode. The influence of the solvent (acetonitrile, methanol, addition of formic acid, ammonium or sodium acetate) on signal intensities was investigated. A comprehensive study of fragmentation pathways of hydrazones using triple quadrupole and ion trap instruments is presented. Structural isomers of aroylhydrazones were distinguished by tandem mass spectrometry. Compounds 3 and 4 (derived from 3- and 4-hydroxy salicylaldehyde) as well as 8 and 9 (derived from 3- and 5-chloro salicylaldehyde) were distinguished by MS/MS as a result of “ortho effect”. The MS/MS spectra and fragmentation pathways of compounds 6 and 7 (derived from 3- and 4-methoxy salicylaldehyde, respectively) differ due to enolimino–ketoamino tautomeric interconversion of 6. Homolytic cleavage and formation of radical cation were observed for compound 11, bearing nitro group in meta position with respect to CN double bond. The fragmentation patterns of sodium adduct ions [M + Na]+ of the hydrazones were also investigated as the presence of an alkali metal influences the product-ion spectra.

Figure optionsDownload high-quality image (99 K)Download as PowerPoint slide