Chemical Research in Chinese Universities

Studies on the Reactivities of Undecatungstogallates K_n[GaW₁₁O₃₉M(H₂O)]· xH₂O(M=Mn, Co, Ni, Cu, Cr, Fe or Zn)

LIU Jing-fu, ZHAN Xiao-peng, WANG Fu-quan, LI Guo-ping, YANG Qi-hua, WANG Jing-ping

1995, 11(1): 1-8.

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ndecatungstogallates K_n[GaW₁₁O₃₉M(H₂O)]· xH₂O (M=Mn, Co, Ni, Cu,Cr, Fe or Zn) were prepared and their redox properties in solution were investigat-ed using polarographic and cyclic voltammographic methods.Experimental resultsindicated that the heteropolyanions underwent two-step, two-electron tungsten re-duction processes, and each reduction process was accompanied by protonation.The complexes of Cu and Mn exhibit voltammetric redox features corresponding toreduction of Cu^Ⅱ to Cu^Ⅰ and oxidation of Mn^Ⅱ to Mn^Ⅲ and Mn^Ⅳ.The title het-eropolyanions show catalysis effect on olefin epoxidation by iodosylbenzene or hy-drogen peroxide.

An Oscillation Condition for an Electrode-separatedPiezoelectric Sensor in Non-electrolyte Liquid

SHEN Da-zhong, HUANG Ming-shan, LIN Song, NIE Li-hua, YAO Shou-zhuo

1995, 11(1): 9-15.

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An oscillation condition was proposed and experimentally verified for an elec-troderaeparated piezoelectric sensor (ESPS) in non-electrolyte liquid, it was ex-pressed as C_s≥2R_qωC_o²/[Y+(1+Y²)^1/2-2RqωC_o, where C_s is the solution capaci-tance, R_q, C_o and ω are the motional resistance, static capacitance and resonant an-gle frequency of the crystal, respectively.And Y＝tgθ, where θ is the phase shift inthe oscillator.The relationships between the minimum cell constant needed for ES-PS to oscillate and each of the following parameters, permittivity, density and vis-cosity of the liquid as well as the oscillator phase shift were discussed.The″ cease-to-oscillate″ frequency of ESPS was measured.The oscillation ability of ESPSin-creases with increasing permittivity or decreasing density and viscosity of the liq-uid.An oscillator with a larger Yvalue is helpful to drive ESPS.

Fluorescence Enhancement of Samarium-Thenoyl-trifluoroacetone-CetyltrimethylammoniumBromide-Triton X-100 by Scandium

ZHU Gui-yun, LIU Ping, SI Zhi-kun, HU Jing-tian

1995, 11(1): 16-21.

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A fluorescence enhancement phenomenon shown by adding scandium ion to thesamarium-thenoyltrifluoroacetone (TTA)-cetyltrimethylammonium bromide(CTMAB)-Triton X-100(TX-100) system was observed and the effect of the condi-tions on the system was studied in detail.The excitation and emission wavelengthswere 370 nm, 565 nm, 603 nm and 645 nm, respectively.The optimum conditionsforming Sm-Sc-TTA-CTMAB-TX-100 system were that the concentration of Sc³⁺was equal to 5.0× 10^-5 mol/L, pH was 7.7.Under these conditions, the fluores-cence intensity can be increased about 10 times higher than that of the system con-taining no Sc³⁺, and it was a linear function of the concentration of samariumn therange of 1.0 × 10^-9-4.0 × 10^-7 mol/L.The detection limit was 6.0 ×10^-10 mol/L.This system was used for the spectrofluorimetric determination of samarium withsatisfactory results.The nature of enhanced fluorescence was explained using in-tramolecular and intermolecular energy transfer theory.

Direct Electron-transfer Reaction of Cytochrome Cat a Bare Spectrographic Graphite Electrode

YU Ai-min, CHEN Hong-yuan, HAN Ji-lin

1995, 11(1): 22-27.

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The electrochemistry of cytochrome Cwas investigated at a spectrographicgraphite electrode.In phosphate buffer solution (pH= 7.0), cytochrome Cshowedstable and quasi-reversible response.The formal potential E^o' was 0.015 V (at 25℃, vs.SCE) and the heterogeneous electron transfer rate constant k_s obtainedvaried form 1.10×10^-3 cm · s^-1 to 1.80k×10^-3 cm · s^-1.The thermodynamic pa-rameters of the electron transfer reaction of cvtochrome Cwas also estimated.Fur-thermore, the effect of the various electrode surface states on the electrochemistryof cytochrome Cwas discussed.

Two Novel Cell Division Type PGRs

LI Zheng-ming, QIAO Li-xin, ZHAO Zhong-ren, LIU Tian-lin

1995, 11(1): 28-31.

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Twenty-eight new N-2-thiazolyl and thiazolinyl-N'-substituted phenylureaswere synthesized by the reaction of the heterocycles and substituted phenyl iso-cyanates.Their cytokinin activity was examined by cucumber cotyledon expansionbioassay.N-thiazolyl and N-thiazolinyl-N'-(m-chlorophenyl )-ureas showed a goodPGRactivity in comparison to Kinetin.The structure/activity relationship was dis-cussed.

Synthesis and Structure of R- ( + )-CamphorDerived N-Propionyl Sultam

HUANG Jin-xia, PAN Yi-Jun, XU Zhang-huang, CHEN Liao-rong, LUO Bao-sheng

1995, 11(1): 32-38.

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A potential chiral auxilliary, (+)-camphor derived N-propionyl sultam, wassynthesized from (+ )-camphor-10-sulphonyl chloride in four steps with enan-tiomerical purity.The molecular and crystal structures of the title compound weredetermined by single crystal diffraction analysis.The crystal belongts to monoclin-ic, space group P2₁ with cell dimentions a= 1.0502(4), b= 0.7252(1 ), c= 0.9363(2) nm, β= 108.3(5), V = 0.677 nm³, F(000) = 292 and Z= 2.The structuralcharacteristics with respect to the potential utility for the stereoselective alkylationat a-carbon of the N-propionyl group are discussed and explained based on ¹H-, ¹³C-NMR.MS and X-ray analysis.

Alkylation of Benzene with Propene over Hβ Zeolite──The Effect of Reaction Conditionson the Distribution of Products

MA Jun, SHEN Jian-ping, SUN Tie, JIANG Da-zhen

1995, 11(1): 39-44.

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The effects of reaction temperature, flow rate of carrier gas, space velocity andbenzene to propene ratio on the alkylation of benzene with propene over Hβ zeolitewere investigated.At lower flow rate of carrier gas and space velocity, higher ben-zene to propene ratio the formation of cumene is favoured due to the difference be-tween rates of reactions of the alkylation of benzene (or cumene) with propene andthe alkyltranslation of diisopropylbenzene with benzene.The propylbenzene is pro-duced directly by the alkylation of benzene with propene.

Studies on Solid State Reactions of Coordination Compounds (LXXI)──Solid State Reactions of o-Aminobenzoic Acid withCopper (Ⅱ) Acetate and Formate at Room Temperature

ZHENG Li-min, LIN Jian-jun, FU Yan, XIN Xin-quan

1995, 11(1): 45-49.

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Solid state reactions of o-aminobenzoic acid (HOAB) with Cu (OAc)₂·H₂O,Cu(HCOO)₂·4H₂O, anhydrous Cu(OAc)₂ and Cu (HCOO)₂ at room or close toroom temperature have been investigated.The product Cu(OAB)₂ with a high yieldwas synthesized very conveniently compared witb the solution phase method.Thekinetic behavior was studied by means of the isothermal electrical conductivity mea-surement.The reactivity was found to decrease in the order : Cu(OAc)₂· H₂O>Cu(OAc)₂>Cu(HCOO)₂·4H₂O>Cu(HCOO)₂, which was attributable to the crystalstructures of the copper salts.

EHMO Studies of Chemisorbed Dioxygen Specieson Na₂O and K₂O and of Their Interactionwith CH₄ and CH₃-Radical

SU Qiao-Juan, ZHANG Hong-bin, ZHOU Tai-jin, LIU Yu-da, LIN Guo-dong, TSAI Khi-rui

1995, 11(1): 50-57.

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With an improved EHMOmethod, three modes (flat-lying, vertical, and in-clined insertion) for adsorption and activation of dioxygen on (100), (110) and(111) surfaces of Na₂Oand of K,Ohave been exaniinecl, and the interaction ofthese dioxygen adspecies with CH₄ and with CH₃·(radical) from gas pliase liasbeen investigated.The results indicate that both oxides tend to forni less cliargedadspecies of dioxygen, with the flat-lying adsorption on (110) surface most favor-able energetically.All these cliemisorbed dioxygen species are capable of interactingeffectively with CH₄ and Abstract ing one hydrogen atom from the CH₄ molecule andtheir tendencies to reassociate with CH₃ ·, which would easily lead to deep oxida-tion of the fragments of hydrocarbons, are enhanced with inereasing negativecliarges on them.In comparison with Na₂O, K₂Ohas a little stronger tendency tostabilize less charged dioxygen adspecies; this has a close relation with the knownexperimental fact that K⁺ showed better promoting effect than Na⁺ in improving C₂-selectivity in methane oxidative coupling (MOC ).

Time-Resolved Photoluminescence Spectra of Porous Si

FEI Hao-sheng, HAN Li, CHE Yan-long, NIE Rui-juan, LI Tie-jin

1995, 11(1): 58-63.

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The photoluminescence spectra of porous Si have been studied.Its timere-solved luminescence spectra show a red shift of luminescencc peak with increasingdelay time after exciting and a nonexponential decay.Several spectral bands withdifferent Gaussian center appear by means of the decomposition of a spetrum.Theresuits of our experiments show quantum confined characters in porous Si, and wespeculate that the short wavelength band at 465 nm is the direct band froni P₁₅ to P₂₅.

Synthesis and ¹⁸³W NMR Characterizationof β-[(CeO )₃ (SiW₉O₃₄)₂]^14- Heteropolyanion

MENG Lu, LIU Jing-fu

1995, 11(1): 64-66.

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A Novel Method of the Preparation ofChemically Modified Electrodes

LI Gen-xi, LIAO Xiang-min, FANG Hui-qun, CHEN Hong-yuan

1995, 11(1): 67-70.

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