How does quenching a reaction work

The first mechanism is based upon an unsuccessful hydrogen atom transfer and may occur through two different direct and stepwise routes. The second mechanism is based on an unsuccessful charge transfer reaction that occurs exclusively in a direct fashion.

We show that the efficiency of the two quenching mechanisms is substantially due to the existence of two different types of conical intersections between the excited and ground state potential energy surfaces of the reacting bimolecular system. Sinicropi, W. Nau and M. Olivucci, Photochem. To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

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You do not have JavaScript enabled. Please enable JavaScript to access the full features of the site or access our non-JavaScript page. Monitoring a kinetic reaction is straight-forward, provided that the reaction does not proceed to a appreciable extent during the time it takes to make an individual measurement. As you might expect, this requirement places a serious limitation on a kinetic method of analysis.

One solution to this problem is to stop, or quench the reaction by adjusting experimental conditions. For example, many reactions show a strong pH dependency, and may be quenched by adding a strong acid or a strong base. The illustration below shows a typical example for the enzymatic analysis of p -nitrophenylphosphate using the enzyme wheat germ acid phosphatase to hydrolyze the analyte to p -nitrophenol.

The reaction has a maximum rate at a pH of 5. Increasing the pH by adding NaOH quenches the reaction and converts the colorless p -nitrophenol to the yellow-colored p -nitrophenolate, which absorbs at nm. See author's posts. Your email address will not be published.

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