Sigma complexes in the pyrimidine series. 4. Investigation of the electronic absorption spectra of anionic sigma complexes of 5-nitropyrimidine

Abstract

The electronic absorption spectra of sigma complexes of the Meisenheimer type, viz., the anions of potassium salts of 4H-5-nitro-4-acetonylpyrimidines, were investigated. The 5-nitropyrimidine molecule and its sigma complex involving the 4 position were subjected to quantum-chemical calculation by the simple MO LCAO method. It is shown that it is expedient to use the Forster-Dewar-Knott rule for the study of the electronic spectra of the indicated sigma complexes.