Abstract
Lanthanide shift reagent, Eu(DPM)3, has been used for the analysis of the isomeric mixtures (1, 3-, 1, 2- and 2, 3-butanediol) by taking advantage of the dif ferences in the chemical shift gradients of the methyl protons with proton NMR at 60 MHz.
The chemical shift gradients of the methyl protons for 1, 3-, 1, 2-, and meso-form and dl-form of 2, 3- butanediol were 6.40, 5.63, 12.6 and 10.9, respectively.
The resonances for the methyl protons were in the envelope centered 1.2 ppm in the spectrum for a CDCl3 solution of the isomeric mixture. However, by addition of 0.84 mole of Eu(DPM)3 per mole of butanediol isomeric mixture, the methyl protons for each of the components gave a resolved resonance in order of 1, 2-, 1, 3-, and dl-form and meso-form of 2, 3-butanediol from high field as predicted by the chemical shift gradients. By using the calibration curves, it was possible to determine the proportion of isomers by the peak areas of methyl protons with errors of about 2%.
