Theoretical Study of the Mechanism of the Nitro-Nitrite Rearrangement and Its Role in Gas-Phase Monomolecular Decomposition of C-Nitro Compounds

Semiempirical, ab initio, and density functional theory calculations were used to study the primary act of gas-phase monomolecular decomposition of certain C-nitro compounds and their radical cations, associated with the nitro-nitrile rearrangement. It was shown that the reaction fails to occur with all neutral molecules of aliphatic nitro compounds (except for fluoronitromethane and fluoronitroethene) and has a much lower barrier with the corresponding radical cations. An important role of the nitro-nitrile rearrangement in gas-phase decomposition of aromatic nitro compounds was demonstrated.     

Influence of molecular structure on the C-N bond strength in the nitroalkane series: II. Nitroethane,fluoronitroethanes, chloronitroethanes,and fluorochloronitroethanes

The equilibrium geometric parameters, enthalpies of formation of molecular and radical species, and dissociation energies of the C-N bond at 0 and 298 K were determined by the B3LYP density functional method for nitroethane, fluoronitroethanes, chloronitroethanes, and mixed fluorochloronitroethanes. Trends in variation of the geometric and electronic parameters of the molecules, enthalpies of formation, and dissociation energies were discussed.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1835–1841.Original Russian Text Copyright © 2004 by Khrapkovskii, Chachkov, Shamov.For communication I, see [1].This revised version was published online in April 2005 with a corrected cover date.     

Empirical and ab initio computation of thermochemical parameters of amino acids: V. Non-canonical L-amino acids

Using a set of computational methods, we have evaluated the basic thermochemical characteristics of the ten non-canonical L-amino acids, other than α-acids.     

Mechanism of Hydrolysis of 1,1,1-Trisubstituted Hyposilatranes and Hypogermatranes

Russian Journal of Organic Chemistry - According to DFT calculations, hydrolysis of 1,1,1-trisubstituted hyposilatranes and hypogermatranes proceed in one stage and have lower activation energies...     

On template synthesis in the ternary system Ni(II)-thiosemicarbazide-diacetyl

A new complexation process in the ternary system Ni(II)-hydrazinomethanethioamide (thiosemicarbazide)-2,3-butanedione (diacetyl) has been studied. Complexation occurs in an aqueous ethanol solution and in nickel(II) hexacyanoferrate(II) gelatin-immobilized matrix systems. It has been shown that, under these conditions, the process involves the “self-assembly” (template synthesis) of Ni(II) macrotricyclic complexes with a new chelating ligand—4,5-dimethyl-1,8-dimercapto-2,3,6,7-tetraaza-1,3,5,7-octatet-raene-1,8-diamine with the (NSSN) coordination of donor atoms to the metal atom.     

Empirical and ab initio computation of the thermochemical parameters of amino acids: I. Monoamino carbonic acids and monoamino dicarbonic acids and their amides

Using different computation methods main thermochemical characteristics of ten standard L-α-amino acids of monoamino carbonic and monoamino dicarbonic series were obtained.     

Quantum-chemical calculation of molecular structures of (5656)macrotetracyclic 3d-metal complexes “self-assembled” in quaternary systems M(II) ion-ethanedithioamide-formaldehyde-ammonia by the density functional theory method

The geometric parameters of (5656)macrotetracyclic complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) with the NNNN-coordination of donor sites of the chelant formed by the template reactions in the M(II)-ethanedithioamide-formaldehyde-ammonia systems have been calculated by the OPBE/TZVP hybrid density functional theory (DFT) method with the use of the Gaussian09 program package. In all complexes, five-membered chelate rings (almost identical to each other in each complex) are nonplanar. For all M(II) ions under consideration, two additional six-membered nonplanar chelate rings formed as a result of template “cross-link” are turned at considerable angles with respect to the five-membered rings. The six-membered rings are located on different sides of the NNNN plane of the nitrogen donor atoms.     

Calculation of geometric parameters and energies of macrocyclic metal chelates in the ternary M(II) ion-thiocarbamoylmethanamide-formaldehyde systems

The thermodynamic and geometric parameters of isomeric macrotricyclic Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) complexes that can, in principle, be the products of the reaction of corresponding hexacyanoferrates(II) with thiocarbamoylmethanamide H₂N-C(=S)-C(=O)-NH₂ and formaldehyde in gelatin-immobilized matrix implants have been calculated by the hybrid B3LYP density functional theory method with the use of the 6–31G(d) basis set and the Gaussian 98 program package. For any of the M(II) ions under consideration, the most stable complexes have the MN₄ metal chelate cores. The bond lengths and bond angles in these complexes have been reported, and it has been stated that the five-membered chelate rings in the complexes are not strictly planar. The additional six-membered chelate ring resulting from template cross-linking is also nonplanar and, in some cases, is turned at a rather large angle to the five-membered rings.     

Mechanism of Hydrolysis of 2,2-Disubstituted Silocanes and Germocanes and 1-Substituted Silatranes and Germatranes

According to DFT quantum chemical calculations, hydrolysis of 2,2-disubstituted silocanes and germocanes is characterized by lower energies of activation and slightly lower positive Gibbs energies than the hydrolysis of the corresponding silatranes and germatranes. The annular configuration of the hydrolysis products is stabilized by the transannular interaction N→X (X = Si, Ge) and intramolecular hydrogen bonding.