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Proton‐transfer reactions within ionized methanol clusters: Mass spectrometric and molecular orbital studies
Author(s) -
Lee Sun Young,
Shin Dong Nam,
Cho Soo Gyeong,
Jung KyungHoon,
Jung Kwang Woo
Publication year - 1995
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1190300706
Subject(s) - chemistry , ion , methanol , protonation , mass spectrometry , proton affinity , dimer , electron ionization , molecular orbital , ionization , proton , molecule , ab initio , electron transfer , electron affinity (data page) , analytical chemistry (journal) , organic chemistry , physics , chromatography , quantum mechanics
Proton‐transfer reactions that proceed within methanol cluster ions were studied using an electron impact time‐of‐flight mass spectrometer. When CH 3 OH seeded in helium is expanded and ionized by electron impact, the protonated species, (CH 3 OH) n H + , are the predominant cluster ions in the low‐mass region. In CH 3 OD clusters, both (CH 3 OD) n H + and (CH 3 OD) n D + ions are observed. The ion abundance ratios, (CH 3 OD) n H + /(CH 3 OD) n D + , show a tendency to decrease as the methanol concentration increases, which is apparently related to the cluster structure and reaction energetics. The results suggest that the effective formation of (CH 3 OD) n H + ions at low concentration of CH 3 OD in the expansion is the result of the relatively facile rotation of methanol molecules within the smaller clusters that tend to form at low CH 3 OD concentration. Ab initio molecular orbital calculations were carried out to investigate the rearrangement and dissociative pathways of ionized methanol dimer. Ion‐neutral complexes, [CH 3 OH 2 + …O(H)CH 2 ] and [CH 3 OH 2 + …OCH 3 ], are found to play an important role in the low‐energy pathways for production of CH 3 OH 2 + + CH 2 OH (and OCH 3 ) from ionized methanol dimer.