Proton-transfer reactions within ionized methanol clusters: Mass spectrometric and molecular orbital studies

✍ Scribed by Sun Young Lee; Dong Nam Shin; Soo Gyeong Cho; Kyung-Hoon Jung; Kwang Woo Jung

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 743 KB
• Volume: 30
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1190300706

✦ Synopsis

Abstract

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.