1. Hydrogen Bond Rearrangements and Interconversions of H<SUP>+</SUP>(CH<INF>3</INF>OH)<INF>4</INF>H<INF>2</INF>O Cluster Isomers
- Author
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Jiang, J. C., Chaudhuri, C., Lee, Y. T., and Chang, H.-C.
- Abstract
Rearrangement of hydrogen bonds in the protonated methanol−water cluster ion H+(CH
3 OH)4 H2 O is analyzed. The analysis, based on ab initio calculations performed at the B3LYP/aug-cc-pVTZ//6-31+G* and MP4/ 6-311+G*//B3LYP/6-31+G* levels of computation, provides information about potential minima, transition states, and pathways for the hydrogen bond rearrangement processes. Results of the analysis are compared systematically to the experimental measurements for H+(CH3 OH)4 H2 O, where two distinct charge-centered (H3 O+ and CH3 OH2 +) isomers have been identified in a supersonic expansion by fragment-dependent vibrational predissociation spectroscopy (Chaudhuri et al. J. Chem. Phys.2000 , 112, 7279). Revealed by the calculations, the lowest energy pathway for the transition from an open noncyclic hydronium-centered isomer [H3 O+(CH3 OH)4 ] to a linear methyloxoium-centered isomer [CH3 OH2 +(CH3 OH)3 H2 O] involves three stable intermediates and four transition states. The transition can go through either all four-membered ring isomers or a mixture of four-membered and five-membered ring intermediates. The latter is an energetically more favorable process because of less strain involved in the five-membered ring formation. A barrier height of <2.5 kcal/mol (after zero-point energy corrections) is predicted, suggesting that rapid interconversions among different isomers can occur at room temperature for this particular cluster cation.- Published
- 2002
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