Structure and Reactivity of Mixed Alkali Metal Alkoxide/Aryloxide Catalysts

Autor:	Rebecca M. Kissling, Michel R. Gagné
Rok vydání:	2001
Předmět:	Steric effects chemistry.chemical_compound chemistry Vapor pressure osmometry Organic Chemistry Inorganic chemistry Alkoxide Cluster (physics) Proton NMR Physical chemistry Reactivity (chemistry) Alkali metal Catalysis
Zdroj:	The Journal of Organic Chemistry. 66:9005-9010
ISSN:	1520-6904 0022-3263
DOI:	10.1021/jo016105h
Popis:	The average solution aggregation state of the ester interchange catalyst 1, obtained by mixing 1 equiv of NaOt-Bu and 3 equiv of NaOC(6)H(4)-4-t-Bu, was determined to be 4.0 by vapor pressure osmometry (VPO) in THF. Low-temperature (1)H NMR spectra of 1 indicated that the THF solution contained a mixture of tetrameric clusters. On the basis of symmetry arguments and the sensitivity of the different species to the alkoxide/aryloxide ratio, the compounds were determined to be mixed clusters with 0:4, 1:3, 2:2, and 3:1 mixtures of the NaOt-Bu and NaOC(6)H(4)-4-t-Bu components. On a per -Ot-Bu basis, each cluster has a similar absolute activity, though the aryloxide-rich catalysts are significantly longer-lived. Unlike 1, catalysts containing ortho-substituted aryloxides, 2, do not give a strictly statistical distribution of clusters, and the activities of these catalysts depend on steric and electronic factors, though the absolute rate differences are not large.
Databáze:	OpenAIRE
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