Electron ionization mass spectra and tautomerism of 2-phenacylpyridines

European Journal of Mass Spectrometry
Olli MartiskainenKalevi Pihlaja

Abstract

The electron ionization mass spectra of 2-phenacylpyridine (ketimine form) and its 13 derivatives substituted in the benzene ring (1an: a R = H, b 3-Me, c 4-Me, d 4-NH(2), e 3-F, f 4-F, g 4-OMe, h 4-Cl,i 4-N(CH(3))(2),j 4-NO(2), k 4-CF(3), l 4-N(CH(2))(4), m 4- Br, n 3-Br) were recorded at 70 eV to determine the fragmentation routes and to screen the presence of their enolimine tautomers, (Z-)-2-(2-hydroxy-2-phenylvinyl)pyridines in the gas phase. The total ion currents (TIC) of the ions [MH](+), [MHCO](+), 2-PyCH(2)O(+), and RC(6)H(4)CO(+) (= ArCO(+) ) showed a fair or good correlation with the Hammett s constants (R = 0.859, 0.876, 0.912, and 0.926, respectively). The relative abundances (RA) of both the [MCO](+.) and the [MHCO](+) ion increased with the decreasing electron donating ability of the substituents and also correlated relatively well with the Hammett constants (R = 0.834 and 0.907, respectively). These observations, in comparison to the NMR results, show that the relative contribution of the ketimine tautomer also increases in the gas phase with the increasing electron donating ability of the phenyl substituent, i.e. the TIC of the ArCO(+) ion decreases whereas that of [MH](+) ion increases.

References

Dec 10, 1999·Journal of Mass Spectrometry : JMS·V KovacikK Pihlaja
Dec 13, 2002·Rapid Communications in Mass Spectrometry : RCM·Kalevi PihlajaHenryk Janota
Nov 11, 2003·Rapid Communications in Mass Spectrometry : RCM·Kalevi PihlajaAlexander Perjéssy

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Citations

Nov 6, 2007·Rapid Communications in Mass Spectrometry : RCM·Olli MartiskainenKalevi Pihlaja
Mar 4, 2009·Rapid Communications in Mass Spectrometry : RCM·Olli MartiskainenKalevi Pihlaja
Nov 15, 2006·Journal of Mass Spectrometry : JMS

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