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Determination of rate constants by ESI-MS: extension of the delayed reactant labeling method

Autoři: Váňa Jiří | Petrović Vladimir | Terencio Thibault | Roithová Jana

Rok: 2017

Druh publikace: ostatní - přednáška nebo poster

Strana od-do: nestránkováno

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Jazyk	Název	Abstrakt	Klíčová slova
eng	Determination of rate constants by ESI-MS: extension of the delayed reactant labeling method	In recent years we have focused our attention on development of a new method for determination of rate constants of reactions proceeding in solution by means of ESI-MS.1,2 The Delayed reactant labeling approach is based on mixing of isotopically labeled and unlabeled reactants in different reaction times. The mutual evolution of equivalent, labeled and unlabeled signals in the ESI-MS spectrum reflects the kinetics of the relevant species in solution. We present here an extension of this methodology with employing differently substituted reactants instead of isotopically labeled ones. We have investigated a palladium catalyzed reaction and followed formation of palladium containing complexes. Hence, introduction of substituents with different masses helped to overcome a problem of a signal overlap caused by the rich isotopic pattern of palladium. The different substitution of reactants causes a different ESI response of analogous complexes (i.e. the same concentrations of the given complexes in solution does not automatically lead to the same signals in the ESI-MS spectrum). This problem is accounted for in the method and can be separated out in the extraction of the rate constants. We demonstrate this approach on palladium catalyzed C–H activation reaction of substituted acetanilides. The Hammett analysis of the rate constants obtained by our method for a series of meta and para substituted acetanilides provides the ρ value of -1.4, which is in agreement with values reported for similar C–H activations. Comparison of the results with those obtained from UV-Vis measurements and theoretical calculations shows a nice agreement and were further used for deeper analysis of reaction mechanism.	ESI-MS, rate constant, palladium catalyzed reaction

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