Enthalpic Interaction for α-Amino Acid with Alkali Metal Halides in Water

The studies of the enthalpic interaction parameters, hxy, hxyy and hxxy, of alkali metal halides with glycine, α-alanine and α-aminobutyric acid were published. Synthetic considering of the results of the studies, some interesting behaviors of the interaction between alkali metal halides and the α-amino acids have been found. The values of hxy will increase with the increase of the number of carbon atoms in alkyl side chain of amino acid molecules and decrease with the increase of the radius of the ions. The increasing of the salt‘s effect on the hydrophobic hydration structure as the radii of anion is more obvious than as that of cation. The value of hxxy will regularly decrease with the increase of the number of carbon atoms in the alkyl chain of amino acids and linear increase with the increase of the radius. But the relation of hxxyWith the radius of cations is not evident. The value of hxyywill increase with the increase of the radii of the ions. As the increase of the number of carbon atoms of amino acids, hxyy is decreas for the ions which have lager size and there is a maximum value at α-alanine for the ions which have small size. The behaviors of the interaction mentioned above were further discussed in view of electrostatic and structural interactions.     

Study on the Radius of an Electrical Spherical Micelle： Functional Theoretical Approach

For the purpose of eliminating restriction, the Poisson-Bokzmann (PB) equation, which represents the potential of the electrical double layer of spherical miceUes, can be solved analytically only under the lower potential condition, a kind of iterative method in functional analysis theory has been used. The radius of the spherical particle can be obtained from the diagram of the second iterative solution of the potential versus the distance from the center of the particle. The influences of the concentration of the ions, the charge number of ions, the aggregation number of the particle, the dielectric constant of solvent and the temperature of system on the radius also have been studied.     

INFLUENCE OF THERMAL AND NON—THERMAL EFFECTS OF ULTRASOUND ON ISOTHERMS OF PHENOL ON NKAⅡ RESIN

Adsorption equilibrium experiments of phenol on the NKA II resin are separately conducted in the presence and absence of ultrasound at ambient temperature.The isotherm of phenol on the polymer adsorbent in the presence of ultrasonic field is firstly reported.Results indicated that the isotherm of phenol determined in the presence of ultrasound is lower than that in the absence of ultrasound.In addition,experiments also show that the use of ultrasound to the adsorption system of the phenol aqueous solution and NKA Ⅱ resin could cause the rising of the temperature of the system in the order of 6^-C.The effect of ultrasound on the isotherm of the phenol on the NKA Ⅱ resin mostly ascribes to the thermal effect and the non-thermal effect of ultrasonic field.and the role of the later is greater than that of the former.     

POLARIZATION OF TIGHT JUNCTION DURING THE PROCESS OF ITS FORMATION

By the freeze-etching technique, electron microscopic observations of the formation of the tight junction of embryonic cells of Cynops orientalis were carried out. Three states were recorded: isolated fragments of junctional strands occurred at the lateral membrane, the isolated fragments connected to form a more or less continuous band and finally a typical bandlike structure was observed at the apical border of the cell. They represent the transitional stages of the polarization of the tight junction. The dependence of the polarization on the appearance of the segmentation cavity and the interrelationship between the polarization and the domains of the epithelial cells were discussed.     

EVOLUTION OF SHORELINES ALONG THE NORTH BANK OF HANGZHOU BAY DURING THE LATE STAGE OF THE HOLOCENE TRANSGRESSION

Based upon the analyses of the sedimentary characteristics, the parallelism of longitudinal streams of the netty drainage system in Shanghai coastal plain to the ancient shorelines, the hydrodynamics in the northern bank of the Hangzhou Bay and the distribution of sites of ancient cultural remains, this paper indicates that during the period of 7000—4000 a B. P., the south spit of the Changjiang River mouth developed southward, and only stretched to the nearshore area of Jinshanwei. The southern end of the spit was a compoundrecurved one. In addition, the evolution of the shoreline west of Jinshanwei during the same period is discussed.     

INTERANNUAL VARIATION OF EARTH ROTATION,El Nio EVENTS AND ATMOSPHERIC ANGULAR MOMENTUM

In this paper the multi-stage digit filter is used to analyse the data of Earth rotation represented by the length of day, ΔLOD. The results show that the interannual variations of Earth rotation, which are in the time scale of several years but not quasi-periodic terms, exist in the long periodic fluctuations. They induce the relative variation in the length of day of 0.3×10~(-8).Comparing the series of length of day with the data of temperature departure of the sea surface in the equatorial area of the eastern Pacific, we found that the deceleration and acceleration of the interannual rate of Earth rotation are consistent with the warming up and down of sea temperature in the equatorial area very well. This means that every El Nio event always occurs after the turning of acceleration of the interannual rate of Earth rotation to deceleration.According to the strong interannual variation in the length of day and strong warming of the sea surface temperature in the equatorial area between 1982 and 1983     

COMPARATIVE RESEARCH ON ENVIRONMENTAL EVOLUTION BETWEEN THE RECION OF ANTARCTIC GREAT WALL STATION AND CHINA

Through comparative analysis between the environmental changes in the region of KingGeorge Island in Antarctic and the characteristics of environmental evolution in the differentregions of China, the paper reveals the important similarity of the environmental evolutionbetween the two regions. The fine correspondence relations between the environmentalchanges of King George Island region in Antarctic, the glacial activities on the mountainousterrain in the western part of China, and the oscillation of the northern boundary of sub-tropical zone in the eastern part of China pointed out in this study serve as evidence to sup-port the interaction between the Northern and Southern Hemispheres. The uniformity of theclimatic changes of the King George Island region in Antarctic with the changes of sea levelof China and the world also supports the similarity of the trend of global changes in tem-perature since the Holocene. One must pay attention to the macroscopic and integrated studyof the whole earth in order     

Bonded excimer in stacked adenines:Semiclassical simulations

The nonradiative decay of a π-stacked pair of adenine molecules,one of which was excited by an ultrafast laser pulse,is studied by semiclassical dynamics simulations.This simulation investigation is focused on the effect of the formation of bonded excimer in stacked adenines on the mechanism of ultrafast decay.The simulation finds that the formation of the bonded excimer significantly lowers the energy gap between the LUMO and HOMO and consequently facilitates the deactivation of the electronically excited molecule.On the other hand,the formation of the chemical bond between two stacked adenines restricts the deformation vibration of the pyrimidine of the excited molecule due to the steric effect.This slows down the formation of the coupling between the HOMO and LUMO energy levels and therefore delays the deactivation process of the excited adenine molecule to the electronic ground state.     

RELATIONSHIP BETWEEN Φ(z/l,X) RULE OF CHEMICAL PROCESSES IN SEAWATER AND HSAB PRINCIPLE——PRINCIPLE OF LEAST Σ AND CHEMICAL MODEL OF SEAWATER

This article reports on the application of the (z/l, X) rule of chemical processes in seawater to the study of the Principle of Hard and Soft Acids and Bases (HSAB). One result is the establishment of new scales of the hardness-softness of acids and bases which are more complete than those in the literature.Based on the principle of HSAB as well as abundant experimental data, we developed a new general principle of marine chemistry viz. the principle of least . Application of the principle of least has produced good results in the study of chemical model of the major constituents of seawater, the chemical speciation of trace elements, inorganic ion exchange reactions, the Irving-Williams aeries of transition elements, etc. Our investigations indicate that chemical models of the major constituents of seawater should take into consideration the formation of chloride ion pairs.     

DFT study of the IR and Raman spectra of a fluorescent dendron built from cyclotriphosphazene core

Combined experimental and theoretical studies on molecular structure of the zero generation dendron, built from the hexafunctional cyclotriphosphazene core, with five OC₆H₄(CH₂)₂NHSO₂C₁₀H₆N(CH₃)₂ terminal groups and one oxybenzaldehyde group G₀ are reported. The Fourier transform Raman and IR spectra of G₀ have been recorded. Conformations of low energy isomers of G₀ have been studied at quantum-chemical level. The optimized geometry has been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. The theoretical geometrical parameters, harmonic vibrational frequencies, IR intensities and Raman scattering activities are predicted in a good agreement with the experimental data. It was found that dendron molecule G₀ has a concave lens structure with planar OC₆H₄CHO fragments and slightly non-planar cyclotriphosphazene core. Relying on DFT calculations the bands of the core and terminal groups were assigned. The frequencies of ν(NH) bands in the IR spectrum reveal the presence of the H-bonds in the dendron.     

Copper-catalyzed NH/SH functionalization: A strategy for the synthesis of benzothiadiazine derivatives

A copper-mediated NS bond-forming reaction via NH/SH activation is described. This reaction occurs under mild conditions with high efficiency, step economy, and tolerates a wide variety of functional groups, providing an efficient means of accessing biologically important 1,2,4-benzothiadiazin-3(4H)-ones.     

Mechanism of rhodium(III)-catalyzed formal C(sp3)H activation/spiroannulation of α-arylidene pyrazolones with alkynes: A computational study

DFT calculations were performed to investigate the rhodium-catalyzed formal C(sp³)-H activation/ spiroannulation of α-arylidene pyrazolones with alkynes. The calculations indicate that the spiroannulation through the proposed C-C reductive elimination is kinetically unfeasible. Instead, the C-C coupling from the eight-membered rhodacycle was proposed to account for the experimental results     

A theoretical study on the alkene insertion step in Rh-Yanphos catalyzed hydroformylation

This paper studied the mechanism of the alkene insertion elementary step in the asymmetric hydroformylation （AHF） catalyzed by RhH（CO）2[（R,S）-Yanphos] using four alkene substrates （CH2=CH- Ph, CH2=CH-Ph-（p）-Me, CH2=CH-C（==O）OCH3 and CH2=CH-OC（=O）-Ph, abbreviated as A1-A4）. Interestingly, the equatorial vertical coordination mode （A mode） with respect to the Rh center was found for AI and A2 but not for A3 and A4, although the equatorial in-plane coordination mode （E mode） was found for A1 -A4. The relative energy of the E mode of the -q2-intermediates is lower than that of the A mode. In the alkene insertion step, Path 1 is more favorable than Path 2 for this system. As for AI and A2, there could be a transformation between 2eq and 2ax.     

Theoretical calculations of the substituent effect on molecular properties of the RCN⋯HF hydrogen-bonded complexes with R = NH2, CH3O,CH3, OH,SH, H,Cl, F,CF3, CN and NO2

DFT calculations with B3LYP and PBE1PBE functionals and 6–311++G(d,p) basis set have been performed in order to obtain molecular geometries, binding energies and vibrational properties of the RCN?HF H-bonded complexes with R = NH₂, CH₃O, CH₃, OH, SH, H, Cl, F, CF₃, CN and NO₂. As expected, it has been verified as a red-shift of the HF stretching frequency (ν_HF), in conformity with the elongation of the bond after complexation. On the other hand, the CN stretching frequency (ν_CN) is blue-shifted and corresponds to a shortening of the bond. The binding energies (ΔE_c), including BSSE and ZPVE corrections, show a linear correlation with several structural, electronic and vibrational properties. In particular, an important linear dependence between the binding energy and the calculated dipole moment of the free RCN molecule (μ_RCN) has been found. This result suggests that μ_RCN can be a useful quantity in order to predict the ability of this fragment to form a hydrogen-bond. The IR intensities of stretching and bending modes of complexed HF acid fragment are adequately interpreted through the atomic polar tensor of the hydrogen atom in HF using the modified CCFO model for infrared intensities. The new vibrational modes arising from complexation show several interesting features.     

Rh（Ⅱ） carbene S-H insertion into H2S via the stepwise mechanism

The mechanism of Rh(Ⅱ)carbene S-H insertion into H_2S in gas phase has been studied by B3LYP functional.Calculation results showed that the Rh(Ⅱ)carbene S-H insertion into H_2S took only stepwise channels and no concerted channels had been located, which was different from the Rh(Ⅱ)carbene C-H and O-H insertions.     

Exploring the activities of vanadium,niobium, and tantalum PNP pincer complexes in the hydrogenation of phenyl-substituted CN,CN, CC,CC, and CO functional groups

The structures and stability of the designed PNP pincer amido M(NO)₂(PNP) and amino ^HM(NO)₂(PN^HP) complexes [M = V, Nb, and Ta, PNP = N(CH₂CH₂P(isopropyl)₂)₂, PN^HP = HN(CH₂CH₂P(isopropyl)₂)₂] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H₂ environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal–ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-CN, Ph-CHNH, Ph-CHNH-Ph, Ph-CHNCH₂Ph, Ph-CCH, Ph-CHCH₂, Ph-CHO, and Ph-COCH₃, the reaction prefers either a two-step or one-step mechanism for the hydridic MH and protonic NH transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges.     

Infrared Spectral Assignment of Pyrimidine and Pyrazine in the CH Stretching Region by an Effective Spectroscopic Hamiltonian

Mid-Infrared spectra of pyrimidine (PM) and pyrazine (PZ) were recorded in the gas phase using a multi-pass long path gas cell. The IR band structure of these compounds above and below 3000 cm⁻¹ is very broad and contains many humps and shoulders. These humps and shoulders are due to various higher quantum excitation of low-frequency vibrational modes, which participate in Fermi resonance with the nearby CH stretch fundamentals and appears in this region. We constructed an Effective Spectroscopic Hamiltonian (ESH) in a mixed local mode (LM) normal mode (NM) basis to assign the various overtone and combination bands in the CH stretching region of these compounds. The CH stretching vibrations of both PZ and PM were treated as symmetrized anharmonic Morse oscillators in local coordinates and the in-plane deformations down to 1000 cm⁻¹ were treated as normal coordinates. The ESHs were diagonalized and the resulting eigenvalues were subsequently fitted in a given parameter space with the experimentally observed bands. The eigenvalues of the converged Hamiltonian are the anharmonic frequencies and the transition intensities were obtained by summing the squared eigenvector components. The overtone and combination transitions near 3000 cm⁻¹ of both PM and PZ were identified and assigned from the eigenvector coefficients of the ESH matrix. The wavefunctions of a pure CH stretch, overtone of the HCC in-plane bend and due to Type 1 Fermi coupling (resonance between a fundamental with an overtones of a low frequency mode, in this case resonance between the CH strech and the overtone of HCC in-plane bending modes) has been demonstrated pictorially.     

CuLn complexes with a single μ-oximato bridge

Two original dinuclear (LnYb, 3 and LnEr, 4) and one trinuclear Cu^IILn^IIICu^II (LnGd, 5) complexes derived from a polydentate non symmetrical Schiff base ligand H₂L have been prepared. The ligand possesses two functions (phenol and oxime) able to coordinate the Ln ions, but structural studies (X-ray diffraction and powder X-ray diffraction) show that the Cu^II and Ln^III ions are only bridged by the oximato (NO) pair. The missing phenoxo bridge is replaced by a surprising pseudo-bridge involving one oxygen atom of the nitrato anion linked to the Cu and Ln ions according to a η²: η¹: μ mode. Although this latter contact has no role from the magnetic point of view, it introduces a large deformation of the unique bridging network. The CuYb complex 3 and the trinuclear CuGdCu complex 5 present antiferromagnetic interactions, with a J_CuGd interaction equal to ?1.25 cm^?1 in 5. The genuine single bridge can be considered as responsible for the antiferromagnetic character of the interaction.     

Nitrogen- and oxygen-bridged bidentate phosphaalkene ligands

An overview is given on synthesis and structures of new bidentate phosphaalkene ligands [(RMe₂Si)₂CP]₂E (E = O, NR, N^?) and (RMe₂Si)₂CPN(R′)PR′′₂. Exceptional properties of these ligands, extending beyond predictable properties of phosphaalkenes are: (i) the NSi bond cleavage of [(iPrMe₂Si)₂CP]₂NSiMe₃ with Au^I and Rh^I chloro complexes under mild conditions leading to binuclear complexes of the 6π-delocalised imidobisphosphaalkene anion [(iPrMe₂Si)₂CP]₂N^?, and (ii) the chlorotropic formation of molecular 1:2 Pd^II and Pt^II metallochloroylid complexes with novel ylid-type ligands [(RMe₂Si)₂CP(Cl)N(R)PR₂]^?, and the transformation of a P-platina-P-chloroylid complex into a C-platina phosphaalkene by intramolecular chlorosilane elimination. Properties of the heavier congeners [(RMe₂Si)₂CP]₂E (E = S, Se, Te, PR, P^?, As^?) and (RMe₂Si)₂CPEPR′′₂ (E = S, Se, Te) are also described.