Isomerization of Glycoluril Dimer and Trimer Related to Cucurbituril Formation
| Autoři | |
|---|---|
| Rok publikování | 2013 |
| Druh | Konferenční abstrakty |
| Fakulta / Pracoviště MU | |
| Citace | |
| Popis | Dimerization of paraformaldehyde and glycoluril in acidic aqueous solution yields an S-shaped dimer as solely kinetic product. In an intermolecular process it transforms to the thermodynamically more stable C-shaped dimer. Same results were observed for trimer. Rate constants for reaction from S- to C-shaped dimer is about one order of magnitude faster than the backward reaction. They accelerate with increasing temperature.Gibbs free energy of isomerization increases with increasing temperature.Activation energy for conversion of C- to S-isomer is 1.5-times higher.Isomerization to C-shaped dimer is enthalpically favoured but entropically disfavoured. During CB-synthesis first two glycoluril units condensate to S-shaped dimer which then converts to the C-shaped. Oligomerization takes place from both isomers at the same time. |
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