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The gas-phase enthalpies of formation of 1,1- and 1,2-dinitroethane and corresponding radical products were calculated using G3B3, CBS-QB3 composite methods and DFT B3LYP level of theory with various basis sets. The enthalpies of the C–N, C–C bonds dissociation and activation enthalpies for HONO elimination were also calculated and compared with available experimental data. It was found that G3B3 calculations do provide a reasonable way to tackle the problem of the decomposition channels of 1,1- and 1,2-dinitroethane. Four main mechanisms for gas-phase decomposition of 1,1- and 1,2-dinitroethane were studied using G3B3 model chemistry. HONO elimination seems to be the most favorable mechanism for the decomposition of 1,2-dinitroethane. However, the difference in energies of the HONO elimination and C–N homolytic bond cleavage in 1,1-dinitroethane does not allow to favor any of these channels, especially at the working temperature. Gauche conformation of 1,2-dinitroethane is calculated to be the lowest-ene...

Hydrogenation reaction of ethene on free Ir4 cluster was theoretically investigated using DFT B3LYP level of theory with LanL2Dz basis set. It was found that hydrogen molecule adsorption proceeded without an apparent transition state structure and the adsorption energy was predicted to be −93.7 kJ/mol. Two possible channel of hydrogenation reaction were investigated. Distortion of cluster frame and high values of activation energies make these channels unfavorable. It was shown that inclusion of magnesium oxide (MgO) support model in our calculations account for a considerable variation of geometric parameters of Ir4 cluster. The bonding of a single carbon ligand to the supported tetrahedral Ir4 cluster at the on-top site was also modeled to probe changes in geometric parameters in comparison with unsupported cluster. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011