No abstract

No abstract

The portions of the N,H, singlet potential energy surface corresponding to triaziridines (l), azimines (2) and triazenes (3) have been calculated by ah initio SCF using 3-21G, 6-31G, and 6-31G** basis sets. Minima and transition states were located by force gradient geometry optimization. The most important computation results are: 1) Triaziridines (1): The configuration at the 3 N-atoms is pyramidal. There are 2 stereoisomers, l a and lb. The c,t-isomer l a has less energy than the c,c-isomer lb. The 2 stereoisomerizations by N-inversion have rather high activation energies. The N,N bonds in 1 are longer and weaker (STO-3G estimation) than in hydrazine. The Nhomocycle 1 exhibits less ring strain than the C-homocycle cyclopropane or threemembered heterocycles. 2) Azimine (2): All 6 atoms are in the same plane. There are 3 stereoisomers, 2a, 2b, and 2c. The order of ground state"energies is ' ) Part 11, see [I]. ' )

The molecular structures and relative stabilities of nitric acid and its protonated species have been determined by SCF calculations. Protonation takes place preferentially at the hydroxylic oxygen atom, giving a complex of N O , ' and H,O. The dissociation energy [22 kcal mol-' (92 kJ mol-l) at 6-31 G"//44-31 G level] confirms that the production of NO,' could constitute the rate-determining step in aromatic nitration reactions.

By using a combination of mass spectrometric methodologies and density functional theory calculations [DFT/B3LYP/6-311 ϩϩ G(d, p)], it is proposed that the decarboxylation of metastable methyl benzoate molecular ions occurs via distonic and ion-neutral complex (INC) intermediates. The same INC involving a complex between the benzyl radical and protonated carbon dioxide is also generated upon decarboxylation of metastable phenylacetic acid molecular ions. Internal proton transfer within the INC produces in fine a mixture of toluene and isotoluene radical cations. (J Am Soc Mass Spectrom 2006, 17, 807-814)