J. Phys. Org. Chem. 30, e3690 (2017)

DOI: 10.1002/poc.3690

Is it possible to use the 31P chemical shifts of phosphines to measure hydrogen bond acidities (HBA)? A comparative study with the use of the 15N chemical shifts of amines for measuring HBA

The geometries, energies, and nuclear magnetic resonance (NMR) chemical shifts of 3 bases (trimethylphosphine, trimethylamine, and trimethylphosphine oxide), their 3 protonated cations, and 15 hydrogen-bonded complexes (corresponding to the HF, HNC, HCN, HCCH, H2O, and CH3OH Brønsted acids) have been calculated at the B3LYP/6-311++G(d,p) level. The determination of hydrogen bond acidities by NMR is classically performed using the 31P chemical shifts Me3PO. This method is more reliable than the use of the 15N NMR chemical shifts of Me3N. This work shows that the 31P NMR chemical shifts of Me3P cannot be used. The raison of the difference between Me3P on one hand and Me3PO and Me3N on the other will be discussed.