Structure, bonding and reactions within protonated acetone–methanol cluster ions

Structures and Dissociation Channels of Protonated Mixed Clusters around a Small Magic Number: Infrared Spectroscopy of ((CH3)3N)n–H+–H2O (n = 1–3)

“…This means that all the OH (and NH) groups are hydrogen-bonded at this size. This is clear evidence of the closed-shell isomers 3I and/or 3II , which has been suggested by the magic number behavior in mass spectrometry. − The coexistence of isomer 3III is clearly excluded. The broadened absorption centered at 2900 cm –1 appears in the observed spectra, and some relatively sharp features overlap with this broadened band.…”

“…For protonated (TMA) n −H + −NH 3 and (pyridine) n −H + −NH 3 , Wei et al have obtained a similar conclusion. 27 Very recently, Chiang et al have studied metastable and collision-induced dissociation channels of a similar system, (acetone) n −H + − CH 3 OH, and their results also support the scenario by Wei et al 28 Chiang et al have performed density functional theory (DFT) calculations, and they have shown that the loss of the central methanol moiety in the hydrogen-bond network is an energetically possible and favored process in the dissociation.…”

“…No time-dependent information is available in this study, and intermediate processes in the dissociation are unknown at present. The previous mass spectrometric studies have suggested a conversion from a closed-shell structure to a charge–dipole structure prior to the dissociation. , Chiang et al have calculated dissociation energies in a similar system, (acetone) 2 –H + –CH 3 OH, which also has a hydrogen-bonded closed-shell structure and the central methanol evaporates in the metastable decay, and they have shown that the fragmentation of the methanol is the energetically favored dissociation path . We also calculated the dissociation energies of (TMA) 2 –H + –H 2 O (isomer 2I and 2II ) and (TMA) 3 –H + –H 2 O (isomer 3I and 3II ) at the ωB97X-D/6-311+G(2d,p) and M06-2X/6-311+G(2d,p) levels.…”

“…23,27 Chiang et al have calculated dissociation energies in a similar system, (acetone) 2 −H + −CH 3 OH, which also has a hydrogen-bonded closed-shell structure and the central methanol evaporates in the metastable decay, and they have shown that the fragmentation of the methanol is the energetically favored dissociation path. 28 We also calculated the dissociation energies of (TMA) 2 −H + −H 2 O (isomer 2I and 2II) and (TMA) 3 −H + − H 2 O (isomer 3I and 3II) at the ωB97X-D/6-311+G(2d,p) and M06-2X/6-311+G(2d,p) levels. Both the DFT methods give quite similar trends and the results are summarized in Table 2.…”

Acetone Dimer Hydrogenation under Vacuum Ultraviolet: An Intracluster Trimolecular Dissociation Mechanism

“…Actually, jet-cooled clusters have been well recognized to be ideal systems for investigating the intermolecular proton transfer as the cluster structures, and rovibronic states are certain before and after the reactions without the interference of the solvent environment. − On the other hand, photoionization studies are often used to study thermodynamic and bonding information on hydrogen bonded clusters. − For example, under vacuum ultraviolet (VUV) radiation, photoionization and photoinduced dissociation of an ethanol dimer were studied, where carbonium ions were observed and followed a Wagner–Meerwein rearrangement after surmounting the barriers of intra- and intermolecular methyl migrations. Also, dimethyluracil was found to readily dissociate in VUV radiation and produce a protonated monomer, where the proton transfer occurred from the methyl groups instead of the aromatic C–H groups .…”