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O. P. Balaj, C. -K. Siu, Iulia Balteanu, B. S. Fox-Beyer, M. K. Beyer and V. E. Bondybey. Base-Catalized Hydrogen/Deuterium Exchange between Water and Acetonitrile in AnionicWater Clusters. J. Phys. Chem. A, 108, pp. 7506-7512, 2004.

Abstract: An H/D-exchange reaction involving the methyl group of acetonitrile is observed in the small anionic water cluster OH-(CD3CN)(H2O)2. In this cluster, a randomization of H and D atoms takes place, and in subsequent collisions with CD3CN, the potentially partially deuterated acetonitrile is replaced by the fully deuterated species. In sequential collisions, fully deuterated clusters OD-(CD3CN)(D2O)2 are obtained as final products. The H/D-exchange does not occur in OH-(CD3CN)(H2O)3 or larger clusters. Density functional calculations show that in these larger species, the OH- no longer directly attacks the methyl group, and the barriers for H/D-exchange become higher than those for ligand loss reaction channels. This is a very subtle influence of solvation on an H/D-exchange reaction in the gas phase, where a relatively acidic methyl group encounters a strongly basic reaction partner.

Keywords: hydrogen exchange, anionic water clusters, progresive deuteration

Posted by Balaj O. Petru


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