Abstract:

The preparation of chiral binaphthol is a common experiment in colleges and universities, and the determination of enantiomeric purity is an important part of the experiment. The Bull-James Assembly between binaphthol and a mixture of 2-formylphenylboronic acid and (S)-(-)-1-phenylethylamine as chiral reagent was observed. Based on this, an experiment was designed to determine the enantiomer purity of binaphthol via ¹H NMR. The results show that the enantiomer purity of (±)-BINOL can be accurately calculated from the NMR signals of the enantiomer mixture generated by the reaction. There is a good linear relationship (R²=0.9999) between the (R)-BINOL ratio calculated from the selected proton signal and the given ee value. This method can quickly complete the measurement of a large number of student samples, and produce a small amount of waste liquid. Students can have a further understanding of NMR technology through this experiment.

Key words: Nuclear magnetic resonance (NMR), Binaphthol (BINOL), Enantiomeric purity, Enantiomeric excess