A density functional elongation method for the theoretical synthesis of aperiodic polymers

The elongation method, a theoretical tool to synthesize the electronic states of polymers, is applied within the framework of the density functional approach and using a linear combination of Gaussian-type orbitals. In this treatment, the wave function of a cluster is localized and the interaction with an attacking monomer is self-consistently calculated according to the Kohn–Sham equation. The reliability and the applicability of our treatment are examined by the application to a random hydrogen molecule cluster, comparing the results with those obtained by the usual diagonalization method for the whole system. The results show that this treatment efficiently provides the electronic states of the end part of aperiodic polymers. © 1994 John Wiley & Sons, Inc.     

Determination of dissociation constants of sparingly soluble phenothiazine derivatives by second-derivative spectrophotometry

The dissociation constants (pK_a) for sparingly soluble phenothiazines (promazine, chlorpromazine, trifluoropromazine) in water were measured by second-derivative spectrophotometry. The intense background signals in the absorption spectra due to the turbidity caused by the precipitation of insoluble free base of the phenothiazine derivatives were eliminated in the second-derivative spectra, and the solubilities of the phenothiazine derivatives could be easily determined from the peak-to-trough lengths (D values) of the second-derivative signals. The pK_a values were calculated from the pH dependence of the D values. The pK_a values obtained agreed well with reported values and the standard deviations for 6–10 determinations were ? 0.02. The solubilities of the free bases of the phenothiazines were also determined.     

An energy-decomposition technique for the analysis of band structure and its application to polyphosphazene and its halogenated derivatives

An energy-decomposition technique is presented for the analysis of band structures of polymers and is applied to the π orbitals of polyphosphazene and its halogenated derivatives. In this treatment the orbital energy is decomposed into the contributions from individual atoms and bonds in the structure. Thereby, the shape of the energy band is elucidated as a function of atomic orbital interactions as well as structures of polymers. The trends of the k dependences for the individual contributions thus analyzed are consistent with those to be expected from the characters of the crystal orbitais. This method seems to be suitable for determining the effects of various substituents on the shape of the energy bands of polymers.     

Synthesis of (perfluoroalkyl)aryliodonium sulfonates [1]

(Perfluoroalkyl)aryliodonium halides [2] and -tetra- fluoroborates [3] were previously synthesized. We now wish to report the synthesis of several kinds of (perfluoroalkyl)aryliodonium sulfonates which are important as electrophilic perfluoroalkylating agents [4].     

Identification of the matrix shift: a fingerprint for neutral neon complex?

Ar-NiCO and Ne-NiCO have been predicted as novel neutral noble gas charge-transfer complexes, with binding energies of 7.70 and 2.16 kcal/mol, respectively, by the highly correlated coupled-cluster singles and doubles including a perturbational estimate of triple excitations calculations. The calculated shifts in the Ni-C-O bending frequency are 48 and 36 cm(-1) for Ar-NiCO and Ne-NiCO, while the corresponding experimental matrix shifts are 46 and 36 cm(-1), respectively. The anharmonicity effects for these frequencies are verified to be very small. The interaction between a noble gas atom and NiCO is discussed through natural population analyses and the electron density difference map. We further examined the noble gas matrix effects on the geometrical structure and vibrational frequencies of NiCO by performing density functional theory calculations for the Ng31-NiCO (Ng = Ar, Ne, He) system. The present results will inspire the further experimental investigation on the complexes of noble gas and transition metal compounds generated in the matrix isolation experiments.     

Ab initio MO study on [3 + 2] annulation using beta-phenylthio-acryloylsilanes with alkyl methyl ketone enolates and its through-space/bond interaction analysis

Ab initio through-space/bond interaction analysis was applied to [3 + 2] annulation based on Brook rearrangement using beta-phenylthio-acryloylsilanes with alkyl methyl ketone enolates. An uncertain reaction mechanism, wherein a bulky cyclopentenol with large substituents on the same side of the five-membered ring was obtained as a major product, can be explained by the low activation energy of its reaction pathway. Intramolecular orbital interactions related to the carbanion generated by Brook rearrangement preferentially provide the stabilization of the reaction pathway to the bulky cyclopentenol (major product) compared with that provided to the non-bulky cyclopentenol (minor product). In addition, ab initio molecular orbital calculations suggest the existence of an E/Z conformational inversion after Brook rearrangement. This result accurately explains the loss of the E/Z stereochemical integrity in the starting materials of the experiment.     

Investigation of methyl tert-butyl ether levels in river-, ground-, and sewage-waters analyzed using a purge-and-trap interfaced to a gas chromatograph-mass spectrometer

River water collected from 27 sites in 21 rivers, groundwater from 66 sites in 34 cities, and 2 sewage plants in the Niigata Prefecture, Japan (total 301 samples) were analyzed for methyl tert-butyl ether (MTBE) using an improved purge-and-trap-GC-MS method. The amount of MTBE found in water samples from the 27 river sites ranged from 0.003 to 5.3 microg l(-1). MTBE was found in all 27 sites during winter but it was found at only 9 sites and 14 sites, respectively, during the summer. MTBE was found most frequently (in 21 sites) at levels ranging from 0.003 to 0.009 microg l(-1) during February. The highest levels of MTBE were always found in the samples collected from the same site. The amount of MTBE found in sewage water samples ranged from <0.003 to 0.025 microgl(-1). No significant differences were observed between the amounts of MTBE recovered from inflow and outflow waters. Relatively high levels (0.02-0.034 microg l(-1) ) of MTBE were found in January at two sites, which were located on the upper course of the Shinano River. MTBE levels ranged from 0.004 to 0.035 microgl(-l) and from 0.005 to 0.041 microgl(-1) at the mouths of the Shinano River and Agano River, respectively. The levels of MTBE in groundwater collected from 66 sites in 34 cities in Niigata Prefecture ranged from <0.003 to 5.9 microg l(-1).     

Nontotally symmetric trifurcation of an SN2 reaction pathway

A new type of reaction pathway which involves a nontotally symmetric trifurcation was found and investigated for a typical S_N2‐type reaction, NC^‐ + CH₃X → NC? CH₃ + X^‐ (X = F, Cl). A nontotally symmetric valley‐ridge inflection (VRI) point was located along the C_3v reaction path. For X = F, the minimum energy path (MEP) starting from the transition state (TS) leads to a second‐order saddle point with C_3v symmetry, which connects three product minima of C_s symmetry. For X = Cl, four product minima have been observed, of which three belong to C_s symmetry and one to C_3v symmetry. The branching path from the VRI point to the lower symmetry minima was determined by a linear interpolation technique. The branching mechanism is discussed based on the reaction path curvature and net atomic charges, and the possibility of a nonotally symmetric n‐furcation is discussed. © 2015 Wiley Periodicals, Inc.     

Unmixedness of some weighted oriented graphs

Journal of Algebraic Combinatorics - Let $$D=(G,\mathcal {O},w)$$ be a weighted oriented graph whose edge ideal is I(D). In this paper, we characterize the unmixed property of I(D) for each one of...