Insertion kinetics measurements spectroscopy

The chaimel-flow electrode has often been employed for analytical or detection purposes as it can easily be inserted in a flow cell, but it has also found use in the investigation of the kinetics of complex electrode reactions. In addition, chaimel-flow cells are immediately compatible with spectroelectrochemical methods, such as UV/VIS and ESR spectroscopy, pennitting detection of intennediates and products of electrolytic reactions. UV-VIS and infrared measurements have, for example, been made possible by constructing the cell from optically transparent materials. 

The insertion of O2 into the Pd- H bond of 1 was readily monitored by H and P H NMR spectroscopy, and the reaction was found to proceed with a second-order rate law, first order in [1] and first order in [O2]. No experimental evidence for a radical process was found the rates were reproducible and no effects of light or radical inhibitors on the reaction were observed. A kinetic isotope effect (KIE) of kjj/kp = 5.8(5), measured using the analogous palladium deuteride complex, (tBupcp)pdD, implicated the breaking of the Pd-H bond in the rate-determining step of the reaction. 

To illustrate the advantages and possible pitfalls of in-line measurements by IR spectroscopy with a light-fiber-coupled ATR probe, a recently investigated polyurethane solution polymerization will be discussed shortly. The principle experimental setup is outlined in Figure 45, which also shows the ATR diamond probe head as enlarged insert. In this reaction vessel, the polymerization of 4,4 -diphenylmethane diisocyanate (MDl) and 1,4-butanediol (1,4-BDO) in a 50/50% (v/v) chloroform/diglyme solution was monitored at temperatures between 40 and 70 °C. The background of the variable-temperature measurements was the determination of the reaction kinetics and the calculation... 

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