Determination of Kinetic Parameters by the Frequency Dependence of the NMR Coalescence Temperature.
ILLINOIS UNIV URBANA DEPT OF CHEMISTRY
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A method is described in which one determines the rate parameters for chemical exchange between two equally populated uncoupled sites by measuring the dependence upon NMR resonance frequency of the temperature at which the corresponding two high-resolution lines coalesce. The method is relatively simple and, when applicable, gives good accuracy with modest effort. It was tested by observing the coalescence of the methyl group resonances due to internal rotation in neat dimethyl-formamide, -acetamide and -propionamide, at 60,100 and 220 MHz. The results include an entropy of activation for the three compounds, and an enthalpy.
- Physical Chemistry