Electronic structure, molecular electrostatic potentials, vibrational spectra in substituted calix[n]arenes (n = 4, 5) from density functional theory

Electronic structure, molecular electrostatic potential, and vibrational frequencies of para-substituted calix[n]arene CX[n]-R (n = 4, 5; R = H, NH(2), t-Bu, CH(2)Cl, SO(3)H, NO(2)) and their thia analogs (S-CX[n]-R; with R = H and t-Bu) in which sulfur bridges two aromatic rings of CX[n] have been derived from the density functional theory. A rotation around CH(2) groups connecting the phenol rings engenders four, namely, cone, partial cone, 1,2-alternate, and 1,3-alternate CX[n]-R conformers. Of these, the cone conformer comprising of large number of O1-H1···O1' interactions turns out to be of lowest energy. Normal vibration analysis reveal the O1-H1 stretching frequency of unsubstituted CX[n] shifts to higher wavenumber (blue shift) on substitution of electron-withdrawing (NO(2) or SO(3)H) groups, while electron-donating substituents (NH(2), t-Bu) engender a shift of O1-H1 vibration in the opposite direction (red shift). The direction of frequency shifts have been analyzed using natural bond orbital analysis and molecular electrostatic potential (MESP) topography. Furthermore, calculated (1)H NMR chemical shift (δ(H)) in modified CX[n] hosts follow the order: H1 > H3/H5 > H7(a) > H7(b). The δ(H) values in CX[4] are in consonant with the observed (1)H NMR spectra.     

Ionic Interactions of Calcium Sulfate Dihydrate in Aqueous Sodium Chloride Solutions: Solubilities,Densities, Viscosities,Electrical Conductivities,and Surface Tensions at 35 <Superscript>∘</Superscript>C

The thermodynamic, volumetric, transport, and surface properties, solubilities, densities, viscosities, electrical conductivities, and surface tensions of calcium sulfate dihydrate in aqueous sodium chloride solutions have been measured at 35 C, with a view to determine the ionic interactions that occur in these solutions. The experimental density values have been used to calculate the mean apparent molar volumes of the ternary mixtures. Viscosity values have been analyzed using different empirical equations and the experimental values of the viscosity were combined with conductivity to yield the Walden product. Molar surface energies have been computed using experimental surface tension data. The experimental data have been fitted to polynomial equations by a least-squares analysis to obtain the coefficients and their standard errors. Results have been examined in the light of structure making or structure breaking effects of the various ions present in the solutions.     

Zirconyl Chloride Promoted Highly Efficient Domino Synthesis of New 1, 2, 3, 4-Tetrahydroquinoline Derivatives in Water

The tetrahydroquinoline moiety is present in various natural products, and many tetra- hydroquinoline derivatives exhibit a broad range of biological activities1. Therefore, it has attracted continuous interest to develop methods for the synthesis of tetr…     

Graph splicing systems

In this paper, extended graph splicing systems are defined. It is shown that when strings are represented as linear graphs, any recursively enumerable set can be generated by an extended graph splicing system. It is also shown that the computational completeness of extended graph splicing systems can be proved under some constraints too.     

Organotin derivatives of (arylazo)benzoic acids : I. Preparation,spectrophotometric titrations and IR spectra

Organotin derivatives of some (arylazo)benzoic acids have been prepared, and investigated by spectrophotometric titration and IR spectroscopy. The organotin (o-arylazo)benzoates are generally penta-coordinated, but those containing a hydroxyl group in the 2-position, e.g., triorganotin o-(2-hydroxy-5-methyl-benzeneazo)benzoate, are hexa-coordinated. The tetracarboxy derivatives contain two different types of tin—carboxylate bonds, as shown by two IR absorptions, at 1700 (ester-like) and 1620 cm^?1 (chelated).     

Nonreductive deiodination of ortho-iodo-hydroxylated arenes using tertiary amines

A convenient and nonreductive deiodination is reported for the ortho-iodo-hydroxylated arenes including derivatives of quinolinol, phenol, and naphthol. Tertiary amines pyridine, triethylamine, and N-methylmorpholine in the presence of water initiated deiodination of ortho-iodo-hydroxylated arenes without affecting para-iodine and other reduction-susceptible groups. This reported method also works efficiently for polyiodinated systems. Simplicity, short reaction times, and absence of reducing catalyst are features of this method.     

Experimental estimation of the interaction parameter eO for ZnN

The use of dislocation measurements in Zinc single crystals reveals the presence of a yield point or flow stress corresponding to a Stages I–II (elastic to elastic-plastic) transition. This is commonly attributed to the presence of interstitials such as N. The mathematical models of Seeger and Dorn and Rajnak are used to evaluate certain microstructural parameters. These correlate favourably with experimental values. The excess work done over that to overcome the Peierls and frictional forces is then calculated per pair of pinning interstitials and equated to the energy of formation of a molecule of Zn₃N₂ which is believed to form. The results show that this assumption does lead to the stochiometry Zn₃N₂, thus verifying mathematical parameters from different equations using work-energy concepts. Use of the mechanical equivalent J also seems to indicate a favourable correlation for the stochiometry of Zn₃N₂, and for e_O as calculated calorimetrically.