Conformational and vibrational study of di-n-butyl and di-sec-butylphosphonates by MM/QM method

A conformational search by MM/QM method was undertaken for the di‐n‐butyl and di‐sec‐butylphosphonates. The normal mode frequencies and the corresponding vibrational assignments were examined by three theoretical methodologies: AM1, HF/6‐31G*, and B3LYP/6‐31G*. These results were compared with those obtained from the experimental spectra. It was possible to arrive at an accurate spectral assignment, including the region between 1200 and 850 cm−1, which is the most difficult region for spectral assignment. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006