Kinetics and mechanism of the addition of triphenylphosphoniocyclopentadienide to tetrahalo-p-benzoquinones. Part 2. Reaction with bromanil and iodanil

Autor:	Rosa Valero, C. Dennis Hall, Francisco Pérez Pla, Juan Palou, Peter Speers
Rok vydání:	1992
Předmět:	chemistry.chemical_classification Addition reaction Chemistry Stereochemistry Kinetics General Medicine Medicinal chemistry Quinone Hydrogen halide chemistry.chemical_compound Reaction rate constant Betaine Ylide E1cB-elimination reaction
Zdroj:	J. Chem. Soc., Perkin Trans. 2. :425-433
ISSN:	1364-5471 0300-9580
DOI:	10.1039/p29920000425
Popis:	The reaction of tetrahalo-p-benzoquinones with triphenylphosphoniocyclopentadienide yields 6-(triphenylphosphonio-3′-cyclopentadienyl)-2,3,5-trihalocyclohexa-2,5-diene-1,4-dione (4a–d), a new class of zwitterionic dyes containing phosphorus. The rate-limiting step has been found to be the addition of the ylide to the quinone through a highly polar betaine intermediate. The elimination of hydrogen halide from the betaine, is of the E2 or E1cB type for the bromanil system and of the E1 type for iodanil. SCF–AM1 calculations suggest that the E1cB path is energetically favoured relative to the E1 elimination path.
Databáze:	OpenAIRE
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