CRYSTAL AND MOLECULAR STRUCTURES OF TWO ISOMERS OF DIETHYL 2, 3-DICYANO-2, 3-DIPHENYLSUCCINATE

Diethyl 2, 3-dicyano-2, 3-diphenylsuccinate was prepared through the oxidative coupling of ethyl α-cyanophenylacetate with Cu~(++)-TMEDA-O_2 system. The product gave, upon chromatography, two crystalline compounds 1 and 2. The single crystals of 1 and 2 were identified by X-ray crystallographic analysis to be meso-and racemie-diethyl 2,3-dicyano-2,3-diphenylsuccinate respectively. It is noteworthy that in the molecules of 1 and 2 there is a remarkable lengthening effect of the bond length for the central C—C bond, i. e. 1: 1.585; 2: 1.62. It is also observed that there is steric hindrance between the substituent groups attached to the two carbon atoms of the central C—C bond respectively. These data provide the structural basis for the facile dissociation into radicals and the action of polymerization initiator of the title compound. CNDO/2 calculation of charge density and Wiberg bond order for compound 1 yields the results, which are consistent with the crystallographic data.     

PHOTOREDUCTION OF ALKYL VIOLOGENS AND POLYVlOLOGENS IN 2-PROPANOL AQUEOUS SOLUTION

In order to study the effect ofalkyl chain length and the polymer effect on the photoreduction behavior of some viologens, a series of alkyl viologen, polyviologen and bisviologen compounds have been synthesized. In the presence of excess 2-propanol, the initial photoreduction of alkyl viologens and polyviologens follow the peudo--seeond--order reaction, the calculated rate constants are related to the alkyl chain length: In addition, the intramoleeular association of radical cations of polyviologens has been found even in dilute solution. However the extent of association is varied with the aikyl chain length. The observed polymer effect of polyviologens in the photoreduetion is significant which can be explained in terms of the nature of second order reaction.     

PURIFICATION OF CARBON MONOXIDE BY PRESSURE-SWING ADSORPTION

The effects of valence state of copper supported on charcoal on the CO adsorption perfor-mance and CO desorption kinetics were investigated by means of XPS and TG.The results indicate thatCO may be selectively adsorbed on the Cu(I)sites and the desorption is a second order reaction with anactivation energy of 24.27kJ/mol.Using a bench-seale PSA apparatus,CO can be purified fromCO-N_2 and CO-CO_2-N_2 gas mixtures separately with CO concentration increases from 31％,25％to98％,96％,net desorption of 26ml/g,22ml/g and recovery of about 95％.     

SYNTHESES AND STRUCTURAL STUDIES OF Mo-Fe-S-CLUSTER COMPOUNDS Ⅶ.SPECTROSCOPIC STUDY OF THE [MoFe_3S_4] CUBANE UNIT IN (Bt_4N)4(Mo_2Fe Sa(SR)_12] AND RELATED COMPOUNDS

<正> INTRODUCTION. In the study of nitrogenases, scientists have proposed many models for the active center of MoFe protein and for FeMoco. All of them contain a basic structural unit [FeS_2M] (M=Fe or Mo). We have reported some structural regularities in a series of linear Mo-Fe-S compounds. In order to investigate the electron distribution and the synergism of metal atoms within a Mo-Fe-S cluster with [MoFe_3S_4] cubane unit, we have synthe     

SYNTHESIS OF MESOGENIC POLYESTERS WITH 2-DICHLOROMETHYLHYDROQUINONE MOIETIES

A series of novel mesogenic polyesters with 2-dich1oromethylhydroquinone moieties weresynthesized by polycondensation of the novel diacyl chloride monomer 2-dichloromethyl-1, 4-bis (4'-chloroformylbenzoyl) oxybenzene-(I) with α,ω-polymethylenediols including ethyleneglycol, 1, 4-butanediol, 1, 6-hexanediol and 1, 10-decanediol. The diacyl chloride monomerwas synthesized by simultaneous transformations of both the carboxy and formaldehydegroups of 2-formyl-1, 4-bis (4'-carboxybenzoyl) oxybenzene into acyl chloride anddichloromethyl groups respectively. The syntheses of the monomer (I) and the polymers werereported.     

RESEARCH ON THE POLYCONDENSATION KINETICS OF ω-AMINO-ACIDS*

In our previous report, it was discovered that the polycondensation of 9-amino-nonanoic acid follows second order from the beginning up to the extent of reaction, p, around 99%, and after which the reaction changes rapidly to third order. In this paper, we wish to report that this change of the reaction order from second to third occurred also in the polycondensation of 6-aminocaproic acid and 11-amino-undecanoic acid. The transition region lay again at p around 99%. It may be concluded that this is a general rule in the polycondensation of the ω-amino-acids (monomers of the A—B type), and the controversial results that appeared in the literature may be cleared up by our experiments.     

ON POLYMORPHISM OF Ca_2SiO_4·CaCl_2

<正> The structure of β-Ca3(SiO4)Cl2 is reported and the structural difference between α-and β-Ca3(SiO4)Cl2 and the mechanism of polymorphic transformation are discussed.     

Study on the reaction of triple helix poly(A:2I) with Cu~(2+)

The effect of Cu2+ on the triple-stranded helical structure of poly(A:2I) was studied by means of circular dichroism spectral method with the help of ultraviolet spectral and ethidium bromide fluorescence probe methods. It was found that Cu2+ destabilizes the structure of the triple helix poly(A:2I) and induces its structural transformations, meanwhile, the transformations can be partially reversed by a higher NaCl concentration. The structural transformations may be expressed by the following scheme: poly(A:2I) - poly(A:I) + poly(I)- poly(A) + 2poly(I)     

RING-OPENING POLYMERIZATION OF PROPYLENE SULFIDE CATALYZED BY BIMETALLIC OXO ALKOXIDE

It was shown that the polymerization rate of propylene sulfide is second order with respect tomonomer concentration and half order with respect to catalyst concentration. A mechanism ofbimolecular coordinated propagation of propylene sulfide and association of the catalyst in thepolymerization system were proposed. The activation energy of polymerization was measured as12.2±0. 5 kcal/mole. Chain transfer constants of monomer and solvent were calculated. Thechange of molecular weight and molecular weight distribution with conversion was followed by GPCwhich was improved by adding LiCl to eluant.     

THE FORMATION AND CRYSTAL STRUCTURE OF DIHYDRONITIDINE AND DISCUSSION OF ANTICANCER MECHANISM OF NITIDINE CATION

The paper reports the formation and crystal structure of dihydronitidine, expounds thereasons and conditions of easily formed oxynitidine, and discusses anticancer mechanism ofnitidine (cation). The crystallographic parameters of dihydronitidine are: space group P2_(1/n),a= 12.54(1), b = 9. 148(5), c = 14.748(8)A, β= 92. 12(6)°,Z =4. 4108 independent reflec-tions were collected within the range of 3°≤2θ≤54°, of which 2137 intensity data with I≥3σ(I) were used in the structural determination. The crystal structure has been refined byfull matrix least-square method to a final R of 0.050.     

STUDY ON THE ADSORPTION OF PHENOL BY CHITOSAN FROM AQUEOUS SOLUTION

The effects of pH, initial concentration and temperature on the adsorption of phenol by chitosan were investigated in this paper. The isothermal data was applied to Langmuir linear and the Freundlich linear isotherm equation, and the thermodynamic parameters （AH, AG, AS） were calculated according to the values of binding Langmuir constant, KL. Results indicated that the adsorption between chitosan and phenol was significantly physical in nature, the negative ΔH constant at lower temperature confirmed that more phenol was adsorbed by chitosan at lower temperature. The kinetics of the sorption process of phenol on chitosan was investigated using the pseudo-first order and pseudo-second order kinetics, and results showed that the second order equation model provided the best correlation with the experimental results.     

USING MEASURING METHOD TO FIND AREA OF ENCLOSED PLANE REGION AND VOLUME OF ENCLOSED SPACE REGION

Two simple methods to calculate the area and volume called improved square gridmethod and cube cutting method are proposed in this paper. For any plane curve orspace surface satisfying certain conditions, by our method, the error of measurement isof the second infinitive order of measuring unit (the side length of the square grid or theside length of the little cube) when the unit is small enough. And when some properties ofthe curve or the surface can be found or its varying bounds can be evaluated, it is pointedout, in order to make the error smaller than any given value, how small the length of themeasuring unit should be.     

A PRELIMINARY STUDY ON THE THEORY OF THE SECOND AND THIRD ORDER DERIVATIVE ADSORPTION CHRONOPOTENTIOMETRY FOR A REVERSIBLE REACTION

The equations of the second and third order derivative curves of timewith respect to potential for a reversible process in adsorption chronopotentiometryare derived and experimentally verified.     

Theoretical study on the size consistency of the second and third order energies of the multireference perturbation theory

The size consistency of the second and third order energies of the multireference perturbation theory(Chen F, Davidson E, Iwata S. Int J Quant Chem, 2002, 86: 256) is investigated theoretically with a su-per-molecular model composed of N-hydrogen molecules separated by a large distance. It is found that the two perturbation series corresponding to two Hamiltonian partitions are not size consistent at the second and third order. However, two size consistent forms are suggested for two Hamiltonian parti-tions at the second order, if some approximations to the denominators of the original second order energies are assumed.     

THE CHARACTERISTICS AND MOTION MODEL OF INSULIN MONOMER

The extensive conformational comparisons among the determined structures of the differeat species and crystal forms of insulin and the varied insulin derivatives were performed by using the least-squares superimposition technique and the graphics technique. The results of the investigation showed that the structure of molecule I in 2Zn insulin was closer to that of the natural monomer; the conformational difference between two molecules of a dimer came out during dimerization and it was further improved and stabilized during the hexamerization and packing of hexamers in crystal; through the hinge peptides, such as A10, B4, B8, B24, B20 and B23, there was a flexible relative motion among the structural segments in the insulin molecule, and the residues at the B-chain C-terminal might have a shift of more than 10; the mobility for each residue side-chain was very different due to the different surroundings.     

CRYSTAL STRUCTURE OF Pt（dppe）（SPh）2

<正> Anaerobic reaction of Pt (dppe)Cl2 (dppe = Ph2PCH2CH2PPh2) with NaSPh and elemental selenium affords complex Pt(dppe)(SPh)2,which crystallizes in the monoclinic system space group C2/c with a=14. 392(7) ,b=16. 380(7) ,c=14. 266(5) A ,β=86. 44(4)°,V=3342(5) A3,Z = 4,Dc=1. 613g/cm3,and μ(MoKa) = 44. 813 cm-1. The final structural refinement converged with unweighted and weighted R factors of 0. 041 and 0. 057 for 2206 observed reflections (I>3σ(I)). X-ray analysis shows that the Pt atom in Pt(dppe)(SPh)2 is at the center of the approximately planar tetragon of two P atoms and two S atoms.     

STUDIES ON THE CRYSTAL STRUCTURE OF Al-(L-TRYPTOPHAN) INSULIN AT 2.1RESOLUTION

In order to study the biological effect of alterations to the N-terminus of the insulin A-chain, we have determined the crystal structure of Al-(L-Trp) insulin and discovered that it belongs to the trigohal system with space group R3. The parameters oof the unit cell are a=b=80.3A, c=37.5A. The model was adjusted and refined by using a stereochemically-restrained least squares program, assisted by manual revision of the model based on the difference Fourier map, to a final R-factor of 0.195. The main and side chains of both Al-(L-Trp) residues in the asymmetric unit are well ordered. It was found that the Al-Trp residue of molecule I occupied two distinct positions. We have proposed from the results of the three-dimensional structure that the 4-zinc insulin hexameric form is a stored state of insulin molecules in a conformation of low activity. The structural details of the insulin molecule and its structure and function relationship have also been discussed.     

STUDY ON THE POLING PROPERTIES OF NONLINEAR OPTICAL ACTIVE DERIVATIVE OF POLY (p-HYDROXYSTYRENE):(PS)O-DCV

In this paper, the poling properties of (PS)O-DCV, a derivative of poly (p-hydroxystyrene ), was reported. The investigations showed that the thermochromism correction, which was neglected in the literatures, should be considered in the measurements of order parameter of poled films with electrochromism technique Here, another linear optical method, IR and polarized IR spectra for characterizing of poled films was suggested first time. The bulk second nonlinear optical coefficient d_(33) of poled films could be estimated by measured order parameter semi-qualitatively.     

EPR SPECTRA OF THE HIGH Tc SUPERCONDUCTOR YBa_2Cu_3O_7

<正> INTRODUCTION. The research on a series of high T_c Y-Ba-Cu-O superconductors since its dxscovery has been found interesting. Preparations and structural studies concerning this field, as well as some spectroscopic work on the study of the superconductive mechanism have been reported. In this communication, we report the EPR studies of the superconductor YBa_2Cu_3O_7 both at room temperature and at liquid N_2 temperature.     

A NORMAL COORDINATE ANALYSIS OF THE DIANION [fe_2S_2Cl_4]~2-

<正> Introduction. On the basis of the "Fragment Proposition" for the nitrogen fixing active center of the nitrogenase by Prof. Lu Jiaxi in 1981, a series of "fragment" compounds has been synthesized and characterized by sereral structural analysis methods. As a part of these works, a result of normal coordinates analysis on the [Fe_2S_2Cl_4]~(2-) dianion is reported in this paper.