Chemical state detection of dibutyl phosphate using 31P NMR chemical shift change

TLDR: In this article, chemical shift changes of 31P NMR were investigated for dibutyl phosphate (DBP) in several polar solvents and compared with tributyl phosphate.

Abstract: Chemical shift changes of 31P NMR were investigated for dibutyl phosphate (DBP) in several polar solvents and compared with tributyl phosphate (TBP). The chemical shift differences between DBP and TBP in the same solvents were found to reflect only the intermolecular interaction on P—OH in DBP, a moiety that is not present in TBP. Acid dissociation constants, Ka, in several polar solvents were determined using such chemical shift differences of DBP. The Ka determined in pure water is in good agreement with the literature value. The intermolecular interaction between alkaline ions and DBP was also investigated using a similar method. No interactions with Na+ ion and K+ ion were detected from chemical shift change. However, ion association between the tetramethylammonium ion and the DBP− ion was detected and the complex formation constant was determined as Kc = 0.49 ± 0.02 M−1. Key words: Fourier transform nuclear magnetic resonance spectrometry, dibutyl phosphate, chemical shift, acid dissociation, intermo...