Can the ebselen derivatives catalyze the isomerization of peroxynitrite to nitrate?

The reaction of ebselen and its derivatives (1-7) with peroxynitrite anion (ONOO(-); PN) has been studied in gas phase and in aqueous, dichloromethane, benzene, and cyclohexane solutions using B3LYP/6-311+G(d,p)//B3LYP/6-311G(d,p) and PCM-B3LYP/6-311+G(d,p)//B3LYP/6-311G(d,p) approaches, respectively. It was shown that the reaction of 2 (R=H) with PN proceeds via 2 + PN --> 2-PN --> 2-TS1 (O-O activation) --> 2-O(NO(2)(-)()) --> 2-SeO + NO(2)(-) pathway with a rate-determining barrier of 25.3 (14.8) kcal/mol at the NO(2)(-) dissociation step (numbers presented without parentheses are enthalpies, and those in parentheses are Gibbs free energies). The NO(3)(-) formation process, starting from the complex 2-O(NO(2)(-)()), requires by (7.9) kcal/mol more energy than the NO(2)(-) dissociation process and is unlikely to compete with the latter. Thus, in the gas phase, the peroxynitrite --> nitrate isomerization catalyzed by complex 2 is unlikely to occur. It is shown that the NO(3)(-) formation process is slightly more favorably than the NO(2)(-) dissociation process for complex 4, with a strongest electron-withdrawing ligand R=CF(3). Therefore, complex 4 (as well as complex 6 with R=OH) is predicted to be a good catalyst for peroxynitrite <--> nitrite isomerization in the gas phase. Solvent effects (a) change the rate-determining step of the reaction 2 + PN from NO(2)(-) dissociation in the gas phase to O-O activation, which occurs with barriers of (13.9), (8.4), (8.4), and (8.2) kcal/mol in water, dichloromethane, benzene, and cyclohexane, respectively, and (b) significantly reduce the NO(2)(-) dissociation energy, while only slightly destabilizing the NO(3)(-) formation barrier, and make the peroxynitrite <--> nitrate isomerization process practically impossible, even for complex 4.     

Theoretical study of structure and stability of h+x (h2)n clusters

The ion clusters H⁺X· (H₂)_n (X = N₂, CO, O₂ and H₂ andn = 0, 1, 2) are investigated by means of SCF and CI computations in a double-zeta plus polarization gaussian basis It is found that hydrogen molecules attack the proton of H⁺X perpendicularly. The calculated stabilization energies are in agreement with experimental values of δH⁰.     

Plasma polymers containing sulfonate groups

Modification of plasma-polymers prepared from phenylsilane with sulfur trioxide was investigated by FT/IR spectroscopy and ESCA. The sulfonation of phenyl groups in the plasma-polymers occurred rapidly within 1 min when exposed to SO₃ gas. The S/C and O/C atomic ratios determined by ESCA for the modified polymers were 0.13₈ and 0.41₈, respectively. The sulfonation made the plasma-polymers electrically conductive. The conductivity was sensitive to moist atmosphere. The logarithm of the impedance at 120 Hz decreased linearly with increasing the relative humidity. The plasma-films containing sulfonate groups may be a new material for moisture sensor devices.     

Synthesis of vinylsilanes by palladium-catalyzed reaction of trimethylsilylallyl acetates with nucleophiles

Treatment of 1-trimethylsilylallyl and 3-trimethylsilylallyl acetates with nucleophiles (active methylene compounds and enamines) in the presence of a catalytic amount of Pd(PPh₃)₄ affords vinylsilane derivatives selectively.     

Novel Zn/ZnI2-promoted cross-coupling of acrylic acid esters with arylaldehydes to alpha-aroyladipic acid esters

Cross-coupling of alkyl acrylates and arylaldehydes was achieved by treatment with metallic zinc and zinc(II) iodide in DMF, giving dialkyl alpha-aroyladipates in moderate yields.     

Chirality-organized ferrocene receptor bearing podand dipeptide chains (-L-Ala-L-Pro-NHPyMe) for the selective recognition of dicarboxylic acids

[structure: see text] The ferrocene receptor bearing the podand dipeptide chains (-l-Ala-l-Pro-NHPyMe) was found to provide a chirality-organized binding site through two intramolecular interchain hydrogen bonds between CO (Ala) and NH (another Ala) of each podand dipeptide chain. The size-selective and chiral recognition of dicarboxylic acids was achieved by multipoint hydrogen bonds of the binding site.