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Updated: Jul 19, 2026

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
Effect of methylation on the pyrimidine-pyrimidine stacking interaction studied by (1)H NMR chemical shift
1Central Research Laboratory, University Medical School, Szigeti út 12, H-7624 Pécs Hungary.
Abstract:
Mutually induced proton chemical shift changes were measured for the mixed solutions of pyrimidine and its methylated forms in deuterium oxide at 35 degrees C. The chemical shift vs. concentration profiles were analyzed using a three-state decomposition model based on competitive self- and hetero-association dimer equilibria. The equilibrium constants show an increasing association tendency within the series pyrimidine-5-methyl-pyrimidine (0.23 +/- 0.02 M(-1)) < pyrimidine-4,6-dimethyl-pyrimidine (0.32 +/- 0.04 M(-1)) < 5-methyl-pyrimidine-4,6-dimethyl-pyrimidine (0.51 +/- 0.04 M(-1)). The upfield dimer shifts suggest an offset stacked geometry for the structure of associations between the parent molecule of the pyrimidine nucleobases and its methylated derivatives in aqueous solution.
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