Premium
The analysis of pH‐dependent protonated conformers of 1‐hydroxyethylidene‐1,1‐diphosphonic acid by means of FT‐Raman spectroscopy, multivariate curve resolution and DFT modelling
Author(s) -
Barnard Werner,
Paul Sylvia O.,
van Rooyen Petrus H.,
Cukrowski Ignacy
Publication year - 2009
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2343
Subject(s) - protonation , raman spectroscopy , chemistry , conformational isomerism , spectroscopy , analytical chemistry (journal) , resolution (logic) , nuclear magnetic resonance spectroscopy , molecule , stereochemistry , ion , organic chemistry , physics , quantum mechanics , optics , artificial intelligence , computer science
1‐Hydroxyethylidene‐1,1‐diphosphonic acid (HEDP) solutions in the pH range 0.98–13.00 were analysed using FT‐Raman spectroscopy and 31 P and 23 Na NMR spectroscopy. Vibrational bands for different protonated species were observed in the Raman spectra, whereas only a single NMR signal that shifted with pH was observed for all samples over the entire pH range. No significant shift in the 23 Na NMR signal was observed, confirming that formation of Na + (aq) complexes did not take place; hence, no interference with the different protonated forms of HEDP occurred. Vibrational bands were assigned using density functional theory(DFT)‐calculated spectra of the most likely conformers in solution. Multivariate curve resolution was performed on the Raman spectra in the region containing the PO stretching vibrations to determine the number of protonated species formed over the entire pH range. Chemometric analysis compares very favourably with the experimental species distribution diagram which was generated using the reported log K H values. Copyright © 2009 John Wiley & Sons, Ltd.