Normal coordinate analyses of three isomeric acetylpyridines and acetophenone

Normal coordinate analyses for 2-, 3- and 4-acetylpyridine and acetophenone were carried out employing a systematic procedure based on a modified vale nce force held that is comparable to those used previously for different ar omatic molecules, The general valence force fields (GVFF) were determined u sing a set of 41 parameters (25 planar and 16 non-planar) for the above com pounds to compare the observed wavenumbers with the calculated values satis factorily with an average error of 7.0 cm(-1) (0.82%) for in-plane and 9.2 cm(-1) (1.60%) for out-of-plane modes. On the basis of the calculated poten tial energy distribution, certain revisions of the previous assignments wer e made. The decomposition of the normal mode wavenumbers into those related to different internal coordinates is discussed. Copyright (C) 2000 John Wi ley & Sons, Ltd.