Unexpected [M]+ radical ions deriving from the cleavage of CH bond in diarylmethylamines detected by electrospray mass spectrometry

• Two diarylmethylamines were analyzed using ESI-QTOF.
• Anomalous [M]+ ions were detected.
• The radical ions may be formed by losing an electron from CH bond.
• Solvent is not involved in the formation of [M]+

Two diarylmethylamines were analyzed using electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF). Anomalous [M]+ ions were detected. Interestingly, although 4-phenoxyphenol derivatives may produce radical ions by oxidation, the radical ions in diarylmethylamines detection may be formed by losing an electron from CH bond. It was found that both the electron-donating effect of 4-methoxyaniline group and conjugation effect of the two aryl groups play an important role in stabilizing the tertiary carbon radical. Tandem mass spectra further supported the proposed structure of [M] +. In addition, solvent is not involved in the formation of [M] +.

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