Predicted vibrational frequencies and assignment of the spectra of uracil and its n,n-dideutero derivative by quantum chemical methods

A recent theoretical study on the vibrational spectrum and force field of maleimide (ref.1) lead to scale factors transferable to molecules of similar structure (ref.2). The theoretical vibrational spectrum of uracil (refs.2–3) calculated from scaled CNDO/2 force constants using the scale factors of ref.1 agrees better with the experimental results (ref.4) than former calculations by $\text{ab initio}$ STO-3G (ref.5) or MINDO/3 (ref.6) methods. The scaled CNDO/2 force field of uracil has also been used to predict the normal frequencies of a set of its deuterated derivatives.