| Abstract
| - The average solution aggregation state of the ester interchange catalyst 1, obtained by mixing 1equiv of NaOt-Bu and 3 equiv of NaOC6H4-4-t-Bu, was determined to be 4.0 by vapor pressureosmometry (VPO) in THF. Low-temperature 1H NMR spectra of 1 indicated that the THF solutioncontained a mixture of tetrameric clusters. On the basis of symmetry arguments and the sensitivityof the different species to the alkoxide/aryloxide ratio, the compounds were determined to be mixedclusters with 0:4, 1:3, 2:2, and 3:1 mixtures of the NaOt-Bu and NaOC6H4-4-t-Bu components. Ona per −Ot-Bu basis, each cluster has a similar absolute activity, though the aryloxide-rich catalystsare significantly longer-lived. Unlike 1, catalysts containing ortho-substituted aryloxides, 2, do notgive a strictly statistical distribution of clusters, and the activities of these catalysts depend onsteric and electronic factors, though the absolute rate differences are not large.
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