Is it possible to use the 31 P chemical shifts of phosphines to measure hydrogen bond acidities ( HBA )? A comparative study with the use of the 15 N 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, H 2 O, and CH 3 OH 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 31 P chemical shifts Me 3 PO. This method is more reliable than the use of the 15 N NMR chemical shifts of Me 3 N. This work shows that the 31 P NMR chemical shifts of Me 3 P cannot be used. The raison of the difference between Me 3 P on one hand and Me 3 PO and Me 3 N on the other will be discussed.