Acylation of aromatic substrates with ketenes. II. Hammett–Brown studies on substituted aromatic compounds
Autor: | K. R. Fountain, Greg Gerhardt, Paul John, Pamela Heinze, Dave Maddox |
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Rok vydání: | 1980 |
Předmět: | |
Zdroj: | Canadian Journal of Chemistry. 58:1939-1946 |
ISSN: | 1480-3291 0008-4042 |
Popis: | Competition reactions using dimethylketene (DMK) – aluminum chloride complexes on a variety of substituted benzene derivatives gave partial rate factors. The logs of these Pfx values when plotted versus σ+ values gave two line segments of ρ = −6.59 for less active substrates, and ρ = −0.92 for more active substrates. Similar results were found for diphenylketene (ρ = −9.47 and −1.07).These results were rationalized by analogy to vinyl cation alkylations. A pair of π complexes (outer then inner) occur between initial approach of the reagent and final, product-determining π-complex formation. In one of these complexes the C=C bond of the ketene complex may be able to back-bond in a manner similar to that found in inorganic complexes of CO and metals. |
Databáze: | OpenAIRE |
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