Analytical Chemistry and Spectroscopy
Wiley InterScience Backfile Collection 1832-2000
The mass spectrometric fragmentation behaviour of four monosubstituted pyridazines (phenyl-3- and phenyl-4-pyridazinylmethanol, phenyl-3-pyridazinyl and phenyl-4-pyridazinyl ketone) was investigated. Fragmentation pathways were established by combined interpretation of the data obtained from high resolution measurements and from low-energy collision-activated dissociation mass spectra of the molecular ions as well as of several important fragment ions. A clear differentiation between these 3- and 4-substituted 1,2-diazines is possible for both sets of pyridazines. Only the spectra of the 3-isomers exhibit an abundant [M—H]+ peak, which indicates a cyclization of these ions involving one ring nitrogen atom. Another difference between the two isomeric phenylpyridazinylmethanols is the loss of OH from the molecular ion, as detected for the C-3 substituted compound only. For the phenylpyridazinyl ketones, the loss of CO from the molecular ion, which is only observed with the 3-isomer, permits an unequivocal differentiation.
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