Formation of [M + 15](+)  ions from aromatic aldehydes by use of methanol: in-source aldolization reaction in electrospray ionization mass spectrometry.
Unexpected [M + 15](+) ions were formed during the analysis of aromatic aldehydes by use of methanol in positive-ion electrospray ionization mass spectrometry. Aromatic aldehydes with electron-withdrawing groups or electron-donating groups were all tested to make sure the universality. All the aromatic aldehydes studied with methanol as the solvent could generate [M + 15](+) ion, and for most of them, the [M + 15](+) ion was more intense than the [M + H](+) ion. Deuterium-labeling experiment, high-performance liquid chromatography-MS experiment, collision-induced dissociation experiment, and theoretical calculations were performed to identify the formation of [M + 15](+) ion. The proposed reaction mechanism is a gas-phase aldol reaction between protonated aromatic aldehydes and methanol occurring in electrospray source. Understanding and using this unique gas-phase ion/molecule reaction can indeed offer a novel and fast approach for the direct identification of aromatic aldehydes.
Department of Chemistry, Zhejiang University, Hangzhou, 310027, China.
Lin
L
Wang
Yunfeng
Y
Chai
Peijun
P
Tu
Cuirong
C
Sun
Yuanjiang
Y
Pan
D000447:Aldehydes / Q000737:chemistry*; D001547:Benzaldehydes / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D007477:Ions / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D000447:Aldehydes; D001547:Benzaldehydes; D007477:Ions; C032175:benzaldehyde; D000432:Methanol