Electron impact mass spectrometric studies of 2-methyl, 2-phenyl, 2-(1-piperidyl), 2-(2/3/4-pyridyl), piperidino and pyrido[4,3-D]-pyrimidin-4-ones

Pentti Oksman, Kalevi Pihlaja, F. Fülöp, Imre Huber, G. Bernáth, Mati Karelson, Antti Perkson

Research output: Contribution to journalArticle

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Abstract

The title compounds were investigated to characterize their structure and fragmentation mechanisms by EI electron impact mass spectrometry (EI-MS) and collisionally activated decomposition. The results obtained on magnetic sector instruments show that the compounds fragment similarly whether the substituent at C-2 is phenyl or 3/4-pyridyl. If, however, it is methyl, 2-pyridyl or I-piperidyl, the balance of fragmentations is different. All the studied compounds are stable and give an intense molecular ion peak. A great difference exists between the fragmentation patterns of the piperidino compounds and those of the more aromatized pyrido compounds. The loss of hydrogen aromatizes the piperidino derivatives to some extent, especially the 2-(2-pyridyl)-substituted compounds, forcing them towards a more planar structure. In 2-(2-pyridyl) derivatives an intramolecular hydrogen bond between the 3N-H and the 2-pyridyl nitrogen atoms strengthens the effect. Deuterated analogs were used to clarify hydrogen rearrangements and to confirm ion structures. Semiempirical AM1 calculations were carried out on 70 tautomeric model structures. The results are not in contrast to the MS results and they support, e.g., the proposed intramolecular hydrogen bonding between the 3N-H and the 2-(2-pyridyl) nitrogen.

Original languageEnglish
Pages (from-to)1845-1858
Number of pages14
JournalRapid Communications in Mass Spectrometry
Volume12
Issue number23
DOIs
Publication statusPublished - 1998

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Hydrogen
Hydrogen bonds
Nitrogen
Ions
Derivatives
Electrons
Model structures
Mass spectrometry
Decomposition
Atoms

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy

Cite this

Electron impact mass spectrometric studies of 2-methyl, 2-phenyl, 2-(1-piperidyl), 2-(2/3/4-pyridyl), piperidino and pyrido[4,3-D]-pyrimidin-4-ones. / Oksman, Pentti; Pihlaja, Kalevi; Fülöp, F.; Huber, Imre; Bernáth, G.; Karelson, Mati; Perkson, Antti.

In: Rapid Communications in Mass Spectrometry, Vol. 12, No. 23, 1998, p. 1845-1858.

Research output: Contribution to journalArticle

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T1 - Electron impact mass spectrometric studies of 2-methyl, 2-phenyl, 2-(1-piperidyl), 2-(2/3/4-pyridyl), piperidino and pyrido[4,3-D]-pyrimidin-4-ones

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AU - Pihlaja, Kalevi

AU - Fülöp, F.

AU - Huber, Imre

AU - Bernáth, G.

AU - Karelson, Mati

AU - Perkson, Antti

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N2 - The title compounds were investigated to characterize their structure and fragmentation mechanisms by EI electron impact mass spectrometry (EI-MS) and collisionally activated decomposition. The results obtained on magnetic sector instruments show that the compounds fragment similarly whether the substituent at C-2 is phenyl or 3/4-pyridyl. If, however, it is methyl, 2-pyridyl or I-piperidyl, the balance of fragmentations is different. All the studied compounds are stable and give an intense molecular ion peak. A great difference exists between the fragmentation patterns of the piperidino compounds and those of the more aromatized pyrido compounds. The loss of hydrogen aromatizes the piperidino derivatives to some extent, especially the 2-(2-pyridyl)-substituted compounds, forcing them towards a more planar structure. In 2-(2-pyridyl) derivatives an intramolecular hydrogen bond between the 3N-H and the 2-pyridyl nitrogen atoms strengthens the effect. Deuterated analogs were used to clarify hydrogen rearrangements and to confirm ion structures. Semiempirical AM1 calculations were carried out on 70 tautomeric model structures. The results are not in contrast to the MS results and they support, e.g., the proposed intramolecular hydrogen bonding between the 3N-H and the 2-(2-pyridyl) nitrogen.

AB - The title compounds were investigated to characterize their structure and fragmentation mechanisms by EI electron impact mass spectrometry (EI-MS) and collisionally activated decomposition. The results obtained on magnetic sector instruments show that the compounds fragment similarly whether the substituent at C-2 is phenyl or 3/4-pyridyl. If, however, it is methyl, 2-pyridyl or I-piperidyl, the balance of fragmentations is different. All the studied compounds are stable and give an intense molecular ion peak. A great difference exists between the fragmentation patterns of the piperidino compounds and those of the more aromatized pyrido compounds. The loss of hydrogen aromatizes the piperidino derivatives to some extent, especially the 2-(2-pyridyl)-substituted compounds, forcing them towards a more planar structure. In 2-(2-pyridyl) derivatives an intramolecular hydrogen bond between the 3N-H and the 2-pyridyl nitrogen atoms strengthens the effect. Deuterated analogs were used to clarify hydrogen rearrangements and to confirm ion structures. Semiempirical AM1 calculations were carried out on 70 tautomeric model structures. The results are not in contrast to the MS results and they support, e.g., the proposed intramolecular hydrogen bonding between the 3N-H and the 2-(2-pyridyl) nitrogen.

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