Knowledge Bank

The fundamental vibrations for several molecules of the structural form shown below where $X=CH2$, NH, O, or S, and $Y=CH$, or N, are assigned based on IR and Raman vapor spectra recorded here. The proposed assignments have been aided by suing scale factors to adjust the respective AM1 force fields. A generally consistent set of scale factors to adjust the respective AM1 force fields. A generally consistent set of scale factors is being built up for the similar modes from this class of molecules. The predictive value of the scaled AM1 force field for this class is now quite good.[FIGURE]