140890-91-1Relevant academic research and scientific papers
Kinetics and Mechanism of the Addition of Triphenylphosphoniocyclopentadienide to Tetrahalo-p-benzoquinones. Part 2. Reaction with Bromanil and Iodanil
Valero, Rosa,Pla, Francisco Perez,Palou, Juan,Hall, C. Dennis,Speers, Peter
, p. 425 - 434 (2007/10/02)
The reaction of tetrahalo-p-benzoquinones with triphenylphosphoniocyclopentadienide yields 6-(triphenylphosphino-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.
THE KINETICS AND MECHANISM OF THE REACTION OF ONIUM CYCLOPENTADIENYLIDES WITH TETRAHALO-p-BENZOQUINONES
Hall, C. Dennis,Speers, Peter,Valero, Rosa,Pla, Francesco Perez,Denney, Donald B.
, p. 249 - 254 (2007/10/02)
The reaction of triphenylphosphonium cyclopentadienylide (1) with halogen-substituted p-benzoquinones (4) is shown to give a new class of dipolar (zwitterionic) dyes (5) containing phosphorus.The general structure of these molecules has been investigated by a combination of mass spectrometry and multinuclear (1H, 13C and 31P) nmr using the specialist techniques of DEPT spectroscopy, homonuclear (COSY) and heteronuclear 2-D nmr.In addition, stopped-flow (uv/visible) techniques have been used to study the kinetics of the reactions and hence demonstrate that the rate-limiting step is nucleophilic addition of the ylid nucleophile to the quinone, followed by a rapid loss of halide ion.This mechanism follows the classical pattern associated with nucleophilic aromatic substitution in activated aryl halides. - Key words: dipolar dyes containing phosphorus.
