LINEAR ENTHALPY RELATIONSHIPS BETWEEN HEATS OF FORMATION OF COMPLEX COMPOUNDS AND HEATS OF PRO TONATION OF LIGANDS——COPPER(Ⅱ)-N-(PARA-SUBSTITUTED PHENYL) GLYCINES

The heats of protonation of N-(para-substituted phenyl) glycines (R—C_6H_4—NHCH_2COOH, R=CH_3O, CH_3, H, C1) and the heats of formation of these amino acids with copper(Ⅱ) have been determined calorimetrically at 25℃ in 30% (v/v) ethanol in the presence of 0.1M sodium perchlorate. The data obtained conform nicely to the equation △H_(ML)-Q-β△H_(HL) where △H_(ML) denotes the heats of formation of complex compounds, △H_(HL) denotes the heats of protonation of the ligands, and Q and β are constants.     

Studies of Thermodynamic Properties and Relative Stability of Polybrominated Xanthones by Density Functional Theory

The thermodynamic properties of xanthone(XTH) and 135 polybrominated xanthones(PBXTHs) in the standard state have been calculated at the B3LYP/6-31G* level using Gaussian 03 program.The isodesmic reactions were designed to calculate the standard enthalpy of formation(△fHθ) and standard free energy of formation(△fGθ) of PBXTH congeners.The relations of these thermodynamic parameters with the number and position of Br atom substitution(NPBS) were discussed,and it was found that there exist high correlation between thermodynamic parameters(entropy(Sθ),△fHθ and △fGθ) and NPBS.According to the relative magnitude of their △fGθ,the relative stability order of PBXTH congeners was theoretically proposed.The relative rate constants of formation reactions of PBXTH congeners were calculated,Moreover,the values of molar heat capacity at constant pressure(Cp,m) from 200 to 1000 K for PBXTH congeners were also calculated,and the temperature dependence relation of them was obtained,suggesting very good relationships between Cp,m and temperature(T,T-1 and T-2) for almost all PBXTH congeners.     

全氟和多氟有机化合物的化学特性——全氟正丙基与全氟异丙基自由基之形成难易度的动力学研究

本文报道全氟异丙基自由基[5(i)]与全氟正丙基自由基[5(n)]的相对形成速度。在50—80℃之间测定了R_FOF(CF_3)[R_F=i-C_3F_7,3(i);R_F=n-C_3F_7,3(n)]自由基β-断裂与攫卤反应的相对比速k_r(i),k_r(n),从而求得了5(i)与5(n)的相对形成速度的比值(k_β(i):k_β(n)]。它们在50℃时为540—680,在80℃时为400—590,此值远远大于碳氢系列自由基的相应比值。最后又计算了3(i)与3(n)的各β-断裂反应活化参数与攫卤反应活化参数差之差,△G~≠(i-n),△H~≠(i-n),△S~≠(i-n)。这些数据表明5(i)形成速度之所以远远大于5(n),熵和焓均起作用,前者可能更为重要。看来,上述熵的差别反映了3(i)的CF_3侧基使分子中若干旋转自由度受到了限制。     

AROMATIC AND HETEROCYCLIC DINITRILES AND THEIR POLYMERS ⅩⅢ. POLYMERIZATION KINETICS OF BENZONITRILE AND THE STRUCTURE OF PRODUCTS

The polymerization kinetics of benzonitrile were studied, and the formation rate constants of s-triazine structure and linear polymer were determined. The influence of polymerization temperature and the amount of zinc chloride as catalyst on the ratio of linear to cyclic structure were also investigated, and the obtained results were discussed.     

ESR STUDIES OF SPIN-TRAPPED RADICALS IN GAMMA-IRRADIATED POLYCRYSTALLINE PYRIMIDINE NUCLEOSIDES——CYTIDINE, DEOXYCYTIDINE, URIDINE AND DEOXYURIDINE

Room-temperature free radicals produced in four gamma-irradiated polycrystalline pyrimidine nucleosides (cytidine, deoxycytidine, uridine and deoxyuridine) were studied by an improved spin trapping and ESR methods with NtB (nitroso-t-butane) serving as the spin trap. The presence of three types of radicals was ascertained in all samples, i.e. —C(5)H—C(6) H_2—and —C(5)H_2—C(6)H— base radicals, and —C(5')H_2— ribose radical evolving from HOC(5')H—C(4')H<. In addition, radicals in which the unpaired electron was located on ribose C(1') and C(4') sites were tentatively distinguished. Stress was laid on the discussion of the mechanism of formation of ribose radicals.     

MICROENVIRONMENTAL EFFECTS OF THE HELICAL CONFORMATIONS OF AMYLOSE AND ITS DERIVATIVES——CATALYTIC EFFECTS OF SODIUM CARBOXYMETHYLAMYLOSE ON THE HYDROLYSIS OF VARIOUS ESTERS OF N-ALKYL-3-HYDROXYPYRIDINIUM IODIDE

Hydrolysis of various carboxylic esters of N-alkyl-3-hydroxypyridinium iodide(2—5) has been studied, both in the absence and in the presence of sodium carboxymethylamylose(NaCMA 1). In the absence of Na-CMA, the hydrolysis of all four substrates follows 2nd-order kinetics when HPO_4~- and CH_3CO_2~- ions are used as the attacking nucleophites. In the presence of 1, however, the course of the reaction depends on the structure of the substrates. For 2 and 3, the observed rate constants k_(obs) are independent of the eoncentration of 1 added, but for those with long hydrocarbon chains, i. e. 4 and 5, the hydrolysis follows MichaelisMenten kinetics. All other experimental results also indicate the formation of supramolecular(incluston) complexes between the Na-CMA host molecules in helical conformations and theesters 4 and 5. In comparison with the bimolecular processes in the bulk phase, the catalytic efficiencies(k_c/K_d) of these supramolecular systems are 3.7×10~4 and 1.7×10~4 times that of the aceta     

Thermodynamics of Stability Constant of Binary Complex of Nicotinamide with Mn^＋＋

The stability constants of the binary complexes of Mn^2 with nicotinamide (NA) were determined from potentiometric pH titrations data at 15.0,25.0 and 35.0℃ and I = 0.1,0.2,0.4 molL^-1 (NaClO4). The formation of binary 1:1 , 1:2 NA-Mn complexes at three different temperatures and the influence of three different ionic strength on their stability were reported. The thermodynamic parameters (△f^0,△Sf^0,△Hf^0) for the complex formation reaction were estimated from stability constant at different temperatures.     

THE CATALYTIC EFFECTS OF OXYGEN AND AMINES IN THE REDOX-INITIATED DIMERIZATION OF N-VINYLCARBAZOLE*

The redox reaction between N-vinylcarbazole (NVC) and various oxidants including Ce(Ⅳ), Fe(Ⅲ)and benzoylperoxide in methanol proceeds via the initial formation of the NVC N-cation radical which in turn leads to the formation of the NVC cyclic dimer, trans-1,2-dicarbazylcyclobutane. Molecular oxygen and a few arylamines are able to accelerate the rate of the formation and increase the yield of the dimer. The mechanism of this process and the functions of oxygen and arylamines are presented as follows: The participation of molecular oxygen is to facilitate the dissociation of the resulting reduced metal ion and the NVC N-cation radical ion pair or charge transfer complex, thereby releasing the free NVC N-cation radical and increase the rate of the formation and yield of the dimer. The arylamine in this reaction between NVC and oxidants can be viewed as electron transfer agent between NVC and the oxidant. Because the amines are present in small amount relative to the oxidants and can be regenerated in pr     

A COMPARISON OF THE DETERMINATION OF STABILITY CONSTANTS OF COMPLEXES OF Cd(Ⅱ)WITH AMINO ACIDS AND SIMPLE PEPTIDES USING MICRO—pH—METRIC TITRATIONS AND CYCLIC VOLTAMMETRY

This paper reports the determination of stability constants for complexes of Cd(Ⅱ)with Gly,Ala,Val,Asp,Gly—Asp,Asp Gly,Gly—Gly and Gly—Gly—Gly using both micro—pH—metric titra-tions and the application of convolution—deconvolution cyclic voltammetry at 25℃ and I=0.10 mol·dm~(-3)(KNO_3).Stability constants were calculated from pH—metric data using the SUPERQUAD com-puter program and cyclic voltammograms were collected,stored and manipulated using the EG and GCONDECON 300 software.A considerably larger ligand:metal ratio(e,g.50:1)was possible usingvoltammetry.Evaluation of results from the two techniques suggests that stability constants for thespecies[CdL_2]and[CdL_3]are reliable when calculated fromvoltammetry while those for[CdL]are morereliable when determined by pH-metric titration.     

Interactions of oxidative radicals with N-phosphoryl dipeptide derivatives

The interactions of oxidative radicals (Br2 , HO etc.) with N-phosphoryl dipeptide derivatives (NDM-TrpOMe and NDT-MetOMe) have been investigated by using pulse radiolysis at different pH values. Ithas been found that Br2 and HO radicals oxidize the Met-site and Trp-site in the dipeptide derivatives via formation of the three-electron-bonded intermediate and indolyl radical simultaneously. Then the intramolecular electron transfer along the peptide backbone occurs. The rate constants of electron transfer, k, have been determined and the reaction mechanism has been deduced.     

THE INHERENT LIMIT TO C_2 YIELDIN OXIDATIVE COUPLING OF METHANE

The hetero-homogeneous processes, especially, the oxidations ofmethane, ethane and ethylene in gas-phase and in the presence of catalystswere studied. The main factors in oxidative coupling of methane were classi-fied into two types according to their effects on the reactions. The inherent lim-it of the C_2 yield was discussed from the reaction condition point of view. Aview toward the inherent limit, i. e., a way to avoid the inherent limit by oper-ating at high selectivity, high C_2 concentration, efficient product separation andmethane circulating operation, was proposed. The methods to enhance theC_2 selectivity and the C_2 concentration in the exit gas, and the method for effi-cient product separation were investigated. In the simulation experiment a prod-uct gas with C_2 concentration of 90 (v/v)％, and C_2 selectivity of 85％ (basedon carbon number), was produced under the reaction conditions of 10(at)％~La_2O_3/SrO catalyst, T=800℃, τ=0.012g·s·cm~(-3), P_(CH_4)/Po_2=9, Po_2=10kPa and atmospheric pressure.     

ORIGIN OF MONOAMINERGIC INNERVATION OF THE NUCLEUS RAPHE MAGNUS——A COMBINED MONOAMINE HISTOCHEMISTRY AND FLUORESCENT RETROGRADE TRACING STUDY IN THE RAT

By the use of the fluorescent retrograde tracer, Fast Blue (FB), in combination with monoamine fluorescence histochemistry, the origin of monoaminergic input to the region of the nucleus raphe magnus (NRM) was investigated in the rat. After mieroinjection of FB into the NRM, a great number of FB-laboled NA-containing cells were found in the region of the nucleus reticularis lateralis (corresponding to A1 NA areas), the reticular formation just dorsolateral to the nucleus olivaris inferior (corresponding to the A3 NA area), the ventral part of the locus coeruleus (A6 NA area), and the lateral parts of the nucleus raphe dorsalis (B7 area). In the other NA cell groups of the brain stem, FB-labeled cells could not be observed. Serotoninergic input originating from nucleus raphe obscurus (B2), nucleus raphe pallidus (B1) and nucleus raphe pontis (BS-B6) to the NRM was also observed. A large number of cells containing serotonin (5-HT) in the B2 and B6 areas were labeled by FB, while only a few FB-labeled 5-HT     

THE EFFECTS OF SOLVENTS ON THE INTRAMOLECULAR PROCESSES ——NMR STUDY

The influences of methanol-d_4(MeOD), dimethylsulfoxide-d_6 (Me_2SO(D)) and dioxane(C_4H_8O_2) solvents on the intramolecular processes are studied by NMR. It has been shown that the addition of these solvents in CdEGTA complex aqueous solution can increase the rate constant (k) of the nitrogen inversion and decrease the activation energy of this process. The linear relations between In(k) and the reciprocal of the solvent dielectric constants (1/ε) are obtained for all the three solvents.     

Photosensitized oxidation of tryptophan and tyrosine by aromatic ketones: A laser flash photolysis study

Photochemical processes of benzophenone (BP) and xanthone (XT) with tryptophan (TrpH) and tyrosine (TyrOH) were studied using the laser flash photolysis technique.It has been observed that the triplet state of BP and XT reacted with TrpH and TyrOH by hydrogen transfer with the formation of BP and XT ketyl radicals and oxidized radicals of TrpY and TyrOY.The related rate constants of these reactions were determined in this paper.The free energy changes (G) of these reactions suggested that the proposed hydrogen transfer mechanism was thermodynamically feasible.These results provide theoretical foundation for further studying structural effects on the photochemical behaviors of proteins with triplet state BP and XT.     

STUDIES ON THE ESR CHARACTERISTICS OF FOUR PIPERIDINE NITROXYL RADICALS——CHARACTERISTICS IN THE SOLID STATE,CONCENTRATION EFFECTS AND SOLVENT EFFECTS IN SOLUTIONS

The ESR characteristics are studied for four piperidine nitroxyl radicals in the solidstate and in solutions. They all exhibited singlet ESR spectra in the solid state, but tripletspectra in solutions at a concentration lower than 1×10~(-2)M. The effects of the free radi-eal coneentration and the polarity trod the viscosity of solvents were observed and comparedon five ESR spectral parameters. Linear correlations could be found between the hyperfinesplitting constant A_N and the solvent polarity parameter, namely, Kosower Z value, Ex-perimental data showed also linear relations of the rotational correlation time τ of free rad-icals with the solvent viscosity, η. We have further found that the relative height of thehigh-field peak varied inversely with η. These ESR characteristics of nitroxyl radicals arediscussed.     

PHENOMENON OF LEFT-RIGHT SHIFTS OF S-SHAPED CURVE——THE EFFECT OF ORGANIC MATTER ON THE CURVES OF ION EXCHANGE pH RANGE

This paper deals with the effect of amino acid and humic acid on the ion exchange ratio (%)-pHS-shaped curves of the interactions between Cu, Pb, Zn, Cd and clays. The main results are: (i) Withthe increase of concentration of organic matters, S-shaped curve moves first to the left and then to theright, and △pH-(sh(L)) has a linear relationship with log (OB)_m. (ii) With the extent of a certain amountof organic matter, the sequence of △pH-(sh(L)) of heavy metals is Cu Pb Zn Cd, △pH-(sh(L)) has a linearrelationship with IogK_(OA). (iii) With the existence of different amino acids, the relationship between△pH-(sh(L)) of S-shaped curves of interaction between Cu and illite and IogK_(OA) for Cu and various aminoacids are linear. (iv) Quantitative explanations regarding the experimental phenomenon mentioned abovecan be written as the following equation: pH_((CIER))=-1/m{log[(α_1K_(OA)α_2(OB_m))/K_(RB_m)]?2}.(v) Discussion of the phenomenon of left-right shifts of S-shaped curve in terms of reaction mec     

Comparative Study on Thermodynamic Properties and Stabilities of Polychloro-phenazines and Polychlorinated Dibenzo-p-dioxin

The thermodynamic properties and molecular volumes （Vm） of 76 polychlorophenazines （PCPZs） have been calculated at the B3LYP/6-31G^＊ level by using density functional theory. The isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fG^θ） of PCPZ congeners. According to the relative magnitude of their △fG^θ, the order of relative stability of PCPZ congeners was theoretically proposed. Comparing the results with those of polychlorinated dibenzo-p-dioxin （PCDD） isomers, it was found that S^θ, △fH^θ, △fG^θ, Vm and the order of relative stability of PCPZ congeners were quite similar to those of PCDDs.     

STUDIES ON THE KINETICS OF PHOTOPOLYMERIZATION OF ACRYLONITRILE INITIATED BY ANILINE

The dependence of the rate of polymerization on the aniline concentration in the photopolymerization of acrylonitrile initiated by aniline was studied.The rate of polymerization of acrylonitrile increased with increasing of the aniline concentration and showed a maximum at first, then showed another increase after a minimum.This phenomenon was explained with the extinction coefficient of aniline at 313 nm,334 nm and 365 nm wavelengths.Similar results were obtained for the aniline derivatives.Therefore, the initiator exponents in the photopolymerization varies with the different concentrations of initiator and the square-root dependence can be obtained only at certain low concentrations, i.e. with low absorbance.     

A NEW CONVENIENT METHOD FOR THE SYNTHESIS OF PERFLUOROALKYL 2H-PYRROLE

The reaction between 2,5-Dimethylpyrrole (1) and R_FI (2)(R_F: a, Cl(CF_2)_4; b, Cl(CF_2)_6; c, Cl(CF_2)_8; d, n-C_6F_(13); e, n-C_8F_(17)) in the presence of Na_2S_2O_4-NaHCO_3 in acetonitrile resulted in the formation of 2-perfluoroalkyl-2,5-dimethyl-2H-pyrrole (3) as a major product in good yield.     

A Thermochemical Study on Complex Nickel（Ⅲ）L—α—Histidine

The formation enthalpy ofcomplex nickel(Ⅱ）-histidine(His)in water was determined by means of microcalorimetry in the temperature range of 298.15-323.15K.The standard enthalpy of the formation of Ni(His)2^2 (aq) was calculated.On the basis of the experimental and the calculated results,three thermodynamic parameters(the activation enthaly,the activation entropy and the activation free energy),the rate constants,three kinetic parameters(the apparent activation energy,the pre-exponential constant and the reaction order)of the formation reaction of the title complex were obtained.