The structures of 2, 5-pyrrolidinedione (succinimide), its 15N labelled derivative, and of their nitranions have been studied on the basis of both quantitative IR spectra and ab initio RHF and MP2 calculations. The theory describes well the strong frequency decrease (down to 138cm− 1) and the twofold increase in both the intensity and splitting of the carbonyl stretching bands, caused by the conversion of the succinimide molecule into the nitranion. ...
