Chemical processes in small water clusters - Proton transfer and CO2 uptake
Einar Uggerud, professor at the Department of Chemistry, will present new experimental evidence on how CO2 dissolves in water.
Among hydrogen-bonded systems, water is unique and the basis for all known forms of life. Clusters of water molecules, (H2O)n, constitute particularly attractive small-scale models for bulk water, and by introducing ionic or neutral molecules into a cluster, it becomes possible to investigate solvation in water at a fundamental level. The interaction between a small number of water molecules and polar or charged particles is in this respect essential. In the lecture it will be demonstrated how careful studies of H/D exchange upon reactions with D2O provides direct insight into proton mobility and proton exchange as a function of cluster size, and it is possible to relate this to structure and acidity. Furthermore, we present new experimental and computational data on the uptake of CO2 in small water clusters containing hydroxide ion, and suggest a general mechanism, also applicable to bulk water and thereby to CO2 uptake in oceans. This mechanism avoids intermediate H2CO3 by combining the CO2 hydrolysis and the protolysis step in one. The general mechanistic picture is consistent with low enthalpy barriers and that the limiting factors are largerly of entropic nature.