The electron affinities of the radicals formed by the loss of an aromatic hydrogen atom from Adenine, Guanine, Cytosine, Uracil, and Thymine

The major ion formed in Negative Ion Chemical Ionization Mass Spectrometry of Adenine, Guanine, Cytosine, Uracil and Thymine is the dehydrogenated anion, The CURES EC procedure for optimizing Austin Model-1 Multiconfigurational Configuration Interaction semi-empirical calculations is applied to the electron affinities of the corresponding dehydrogenated bases and N-H bond dissociation energies. These calculated values will be compared with Literature values of the gas phase acidities of the purines and pyrimidines. The N-H bond dissociation energies are about 3.95 eV for Guanine, Adenine, and Thymine and 4.08 eV for Cytosine and Uracil, The electron affinities of the radicals are A(MinH) = 3.50 eV, G(MinH) = 3.46 eV, C(MinH) = 3.38 eV, U(MinH) = 3.48 eV, T(MinH) = 3.46 eV. (C) 1998 Academic Press.