Stereochemical applications of mass spectrometry. II—Chemical ionization mass spectra of isomeric dicarboxylic acids and derivatives

摘要: The H2 and CH4, chemical ionization mass spectra of the cis dicarboxylic acids, maleic citraconic acid, show much more extensive loss H2O from [MH]+ than trans isomers, fumaric acid mesaconic acid. Similarly, esters a facile ROH (R=alkyl or phenyl) do Similar differences are observed in isomeric phthalic isophthalic acids derivatives, where ortho isomers fragmentation meta isomers. for is attributed to elimination involving interaction between two carboxylate functions forming stable cyclic anhydride structure fragment ion. By contrast metu requires symmetry-forbidden [1,3]-H migration carboxyl protonated species cannot lead structure. cyclohexane-1,2-dicarboxylic essentially identical [IMH]+ Experiments using deuterium labelling group interactions both maleanilic phthalanilic related anhydrides imides also reported, as electron impact diphenyl maleate, fumarate, phthalate,