Nuclear magnetic resonance spectroscopy nitrogen-15—hydrogen coupling constants in oximes

Nitrogen-15—hydrogen coupling constants between ¹⁵N-labeled oximes and α-C-protons, ³J(¹⁵NH), of two series of E/Z ketoximes were studied in CCl₄, CDCl₃, CF₃COOH, and DMSO-d₆. ¹⁵N-substituted-methyl phenyl ketoximes constituted the first series and ¹⁵N-substituted-methyl 2-quinoxalinyl ketoximes the second series studied. Substituents in the first group were H, Me, t-Bu, NMe₂, OMe, Cl, Br and I; in the second they were H, NEt₂, and Cl. |³J(¹⁵NH)| values for the isomers wherein the aliphatic substituent was anti to the oximino hydroxy group were always larger then those for the syn related isomers, permitting assignment of oxime stereochemistry to even a lone oxime diastereomer. Additionally, geminal nitrogen-15—hydrogen coupling, ²J(¹⁵NH) effects were observed in some compounds.     

Thermodynamic Properties of Styrenetricarbonylchromium, α-Methylstyrenetricarbonylchromium,and p-Methylstyrenetricarbonylchromium in the Range 0-450 K

The thermodynamic properties of styrenetricarbonylchromium, -methylstyrenetricarbonylchromium, and p-methylstyrenetricarbonylchromium were studied with adiabatic vacuum and dynamic calorimeters. The heat capacity in the range 5-450 K (error about 0.3% in most cases) and the temperatures and enthalpies of the phase transitions were determined. The experimental data were used to calculate the thermodynamic functions C ⁰ _p(T), H ⁰(T) - H ⁰(0), S ⁰(T), and G ⁰(T) - H ⁰(0) for the range from 0 to 330-400 K, and also the isochoric heat capacity C _v and its lattice (_Cv,latt) and atomic (C _v,at) contributions for the range from 0 K to T ⁰ _m; the parameters = C ⁰ _p/C _v were evaluated. The thermodynamic properties were considered in relation to the composition and structure of the compounds.     

Viscoelasticity and birefringence of polyisoprene

The complex Young's modulus, E^*(ω), and the complex strain-optical coefficient, O^*(ω), which is the ratio of the birefringence to the strain, were measured for polyisoprene (PIP) over a frequency range of 1 ～ 130 Hz and a temperature range of 22 ～ ?100°C. The imaginary part of O^*, O″, was positive at low frequencies and negative at high frequencies. The real part, O′, was always positive and showed a maximum. The complicated behavior of O^* could be understood by the assumption that E^* = E_R^* + E_G^* and O^* = C_RE_R^* + C_GE_G^*, where E_R^* and E_G^* were complex quantities and C_R and C_G were constants. The C_R value, equal to the ordinary stress-optical coefficient measured in the rubbery plateau zone, was 2.0 × 10^?9 Pa^?1. The C_G value, defined as the ratio O″/E″ in the glassy zone, was ?1.1 × 10^?11 Pa^?1. The E_G^*, which was the major component of E^* in the glassy zone, showed almost the same frequency dependence as that of polystyrene and polycarbonate. The E_R^*, which was dominant in the rubbery zone, was described well by the bead-spring theory. The temperature dependence of the E_G^* was stronger than that of the E_R^*. This difference caused the breakdown of the thermorheological simplicity for E^* and O^* around the glass-to-rubber transition zone. © 1995 John Wiley & Sons, Inc.     

Nitrogen-15 coupling constants: Geminal coupling, 2J(15NH), in cis- and trans-aldonitrones and vicinal coupling, 3J(15NH), in cis-and trans-ketimines,oxaziridines and nitrones

Nitrogen-15-hydrogen ²J(¹⁵NH), ¹⁵N, ¹³C ¹J(¹⁵N¹³C) and ¹³C, H ¹J(¹³CH) coupling constants have been measured and their signs determined for cis-and trans-[9-anthryl(¹³C)methylene](²H₃)methylamine (¹⁵N)-oxide. Values of ²J(¹⁵NH) were of similar magnitude (～2 Hz) but were of opposite sign. The results are compared and contrasted with those reported for related imino and quaternary imino systems. Vicinal ³J(¹⁵NH) coupling constants have been measured in cis- and trans-¹⁵N-[1-(α-naphthyl)ethylidene]benzylamine and ¹⁵N-[1-(p-nitrophenyl)ethylidene]-t-butylamine and were found to be larger when the imino methyl group was cis to the nitrogen lone pair. The corresponding cis and trans ketonitrones formed by photoisomerization of the derived oxaziridines had ³J(¹⁵NH) values of c. 3.3 Hz. A study of the signs and magnitudes of observed and calculated ¹⁵N,H coupling constants for all of the ¹⁵N labelled imines, oxaziridines, imine N-oxides (nitrones) and similar model systems which were synthesized is described.     

Thermodynamics of phenylated polyphenylene between 0 and 340 K

In an adiabatic vacuum calorimeter, the temperature dependence of the heat capacity C _p of phenylated polyphenylene and initial comonomer 1,4-bis(2,4,5-triphenylcyclopentadienone-3-yl)benzene was studied between 6 and 340 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield their energies of combustion DUcomb were measured. From the experimental data, the thermodynamic functions C _p ⁰ (T), H ⁰(T)-H ⁰(0), S ⁰(T)-S⁰(0), G ⁰(T)-H ⁰(0) were calculated from 0 to 340 K, and standard enthalpies of combustion ΔH _comb ⁰ and thermodynamic parameters of formation-enthalpies ΔH _f ⁰, entropies ΔH _f ⁰, Gibbs functions ΔG _f ⁰ - of the substances studied were estimated at T=298.15 K at standard pressure. The results were used to calculate the thermodynamic characteristics (ΔH _f ⁰ ,ΔS _f ⁰, ΔG _f ⁰) of phenylated polyphenylene synthesis in the range from 0 to 340 K. This revised version was published online in July 2006 with corrections to the Cover Date.     

Aquation of chloropentaamminecobalt(III) Perchlorate in chloride-ion containing water–nonaqueous solvent mixtures

The equilibrium quotients for the formation of Co(NH₃)₅Cl²⁺ from Co(NH₃)₅OH₂³⁺ and Cl^? were 3.74±0.25 M^?1 and 6.07±0.54 M^?1 at 45.0°C in 10:1 mole ratio water: dimethyl sulfoxide and in 25 w/w % aqueous ethanol, respectively, and those forthe formation of the ion pair Co(NH₃)₅OH₂³⁺ . Cl^? were 1.21±0.20 M^?1 and 1.58±0.17 M^?1, respectively, in the same solvents. The aquation and anation rateconstants were determined at 45.0°C for these two solvents over the range of chloride-ion concentrations 0.0 ≤ [Cl^?] ≤ 0.9 M. The aquation rate constant was essentially independent of chloride-ion concentration in each solvent over this range. The inverse of the pseudo-first-order anation rate constant was linearly dependent on the inverse of the chloride-ion concentration in each solvent. The least squares relationships between (1/k_an) and (1/[Cl^?]) gave intercepts and ratios of intercept to slope which were analyzed interms of I_d and D mechanisms. It was concluded that the data were not satisfied by a D mechanism, but that they were consistent with an I_d mechanism.     

2-甲基-2-丁醇的低温热容和热力学性质

本文用精密自动绝热量热仪测定了2-甲基-2-丁醇在80～305 K温区的热容,从热容曲线(Cp-T) 发现三个固－固相变和一个固－液相变, 其相变温度分别为T = 146.355, 149.929, 214.395, 262.706 K。从实验热容数据用最小二乘法得到以下四个温区的热容拟合方程。在80～140K温区, Cp,m = 39.208 + 8.0724X - 1.9583X2 + 10.06X3 + 1.799X4 - 7.2778X5 + 1.4919X6, 折合温度X = (T –110) / 30; 在 155 ～ 210 K温区, Cp,m = 70.701 + 10.631X + 12.767X2 + 0.3583X3 - 22.272X4 - 0.417X5 + 12.055X6, X = (T –182.5) /27.5; 在220 ～ 250 K温区, Cp,m = 99.176 + 7.7199X - 26.138X2 + 28.949X3 + 0.7599X4 - 25.823X5 + 21.131X6, X = (T – 235)/15; 在 270～305 K温区, Cp,m =121.73 + 16.53 X- 1.0732X2 - 34.937X3 - 19.865X4 + 24.324X5 + 18.544X6, X = (T –287.5)/17.5。从实验热容计算出相变焓分别为0.9392, 1.541, 0.6646, 2.239 kJ×mol-1; 相变熵分别为6.417, 10.28, 3.100, 8.527 J×K-1×mol-1。根据热力学函数关系式计算出80～305 K温区每隔5 K的热力学函数值 [HT –H298.15]和 [ST –S298.15]。     

对氨基苯甲酸热力学性质的量热和热分析研究

在80～400 K温区,用高精度全自动绝热量热仪测定了对氨基苯甲酸摩尔热容,得到摩尔热容随温度的变化的关系式为：     

Substituent Conformational effects in vicinal 13C?13C spin–spin coupling constants

A series of 7-¹³C-labeled o-substituted toluene derivatives and carboxyl-¹³C-isocrotonic and crotonic acid were synthesized and studied by ¹³C NMR spectroscopy to obtain ¹³C? ¹³C spin-spin coupling constants involving the labeled carbon. The cis ³J(CC) values were different from those in previous studies in that these J(CC) values were relatively small and the usual dependence of ³J(CC) on the s-character of the terminal carbon was reversed. Further, a strong dependence of ³J(CC) on the conformational orientation of a terminal carbonyl group was shown to exist. Through-space interactions of the two coupling carbons were shown to contribute to these ‘anomalous’ results, and thus it was shown the cis carbon-carbon couplings may not be directly related to geometrically equivalent proton-proton couplings, as are other carbon-carbon couplings.     

Isotope Shifts of Nitrogen around 800 nm

The Doppler-limited absorption spectra of ¹⁴N and ¹⁵N atoms were measured around 800 nm using concentration modulation spectroscopy to study their isotope shifts. The nitrogen atoms were generated by discharging molecular nitrogen buffered with helium in a homemade discharge tube. The isotope shifts of four multiplets (3s⁴P_J→3p⁴D_J^o, 3s⁴P_J→3p⁴P_J^o, 3s²D_J→5s²P_J^o, and 3p²P_J^o→5s²D_J^o) were measured and their J-dependent specific mass shifts were observed and discussed.     

Thermodynamic Properties of Tetraphenyltetrahydroxycyclotetrasiloxane,Octaphenyltetrahydroxytricyclooctasiloxane, Octaphenylpentacyclosilsesquioxane,and Polyphenylsilsesquioxane in the Range 0-300 K

The temperature dependences of the heat capacities of crystalline tetraphenyltetrahydroxycyclotetrasiloxane, octaphenyltetrahydroxytricyclooctasiloxane, and octaphenylpentacyclosilsesquioxane and of glassy polyphenylsilsesquioxane were measured in the range 6-300 K with an adiabatic vacuum calorimeter, with an accuracy of 0.3%. From these data, the thermodynamic functions C ⁰ _p (T), H ⁰(T) - H ⁰(0), S ⁰(T) - S ⁰(0), and G ⁰(T) - H ⁰(0) of these substances were calculated for the range 0-300 K. The standard entropies of their formation from elements at 298.15 K, _f S ⁰, and the entropies of mutual transformations of these substances in the range 0-298.15 K were calculated.     

Metabolic turnover rates of carbon and nitrogen stable isotopes in captive juvenile snakes

Metabolic turnover rates (m) of δ¹⁵N and δ¹³C were assessed in different tissues of newly hatched captive‐raised corn snakes (Elaphe guttata guttata) fed maintenance diets consisting of earthworms (Eisenia foetida) that varied substantially in δ¹⁵N (by 644‰) and δ¹³C (by 5.0‰). Three treatments were used during this 144 day experiment that consisted of the same diet throughout (control), shifting from a depleted to an enriched stable isotope signature diet (uptake), and shifting from an enriched to depleted stable isotope signature diet (elimination). Values of δ¹³C in the liver, blood, and muscle of the control snakes reached equilibrium with and were, respectively, 1.73, 2.25 and 2.29 greater than in their diet, this increase is called an isotopic discrimination factor (Δδ¹³C = δ¹³C_snake ? δ¹³C_food). Values of δ¹⁵N in snake tissues did not achieve equilibrium with the diets in any of the exposures and thus Δ¹⁵N could not be estimated. Values of metabolic turnover rates (m) for δ¹³C and δ¹⁵N were greater in liver than in muscle and blood, which were similar, and relative results remained the same if the fraction of ¹⁵N and ¹³C were modeled. Although caution is warranted because equilibrium values of stable isotopes in the snakes were not achieved, values of m were greater for δ¹³C than δ¹⁵N, resulting in shorter times to dietary equilibrium for δ¹³C upon a diet shift, and for both stable isotopes in all tissues, greater during an elimination than in an uptake shift in diet stable isotope signature. Multiple explanations for the observed differences between uptake and elimination shifts raise new questions about the relationship between animal and diet stable isotope concentrations. Based on this study, interpretation of feeding ecology using stable isotopes is highly dependent on the kind of stable isotope, tissue, direction of diet switch (uptake versus elimination), and the growth rate of the animal. Copyright © 2009 John Wiley & Sons, Ltd.     

LiYF4晶体中Ho3+离子真空紫外吸收光谱的理论解析

运用配位场理论方法获得了Ho3+离子低自旋4f95d组态的谱项和J-光谱多重态,根据电偶极跃迁选律合理地解析了LiYF4晶体中Ho3+离子在真空紫外区(120～160 nm)的吸收光谱,4个主要的吸收峰分别被归属为从基态(5I8)到Ho3+离子的低自旋4f95d组态的自旋允许跃迁。     

Studies on the structure-activity relationship of delta-sleep inducing peptide

DSIP and its fourteen analogs as well as three short peptides were synthesized by solid phase method. The design of the analogs was based on the consideration of the introduction of D-amino acid into the molecules to inhibit the enzymatic hydrolysis and the introduction of amino acids with a hydrophobic side chain. The modification was placed on the position of 1, 3, 4, 5, 8 and 9, e.g. D- Trp¹, Tyr¹, Tyr¹ Phe⁵, D-Trp¹ Phe⁸, Trp^3,4, D-Trp^1,3,4 Phe⁸, D-Trp3^,4 Phe⁸ D-Glu⁹, D-pF-Phe^3,4 Phe⁸ D-Glu⁹, Phe⁵, Glu⁵ Asp⁹, Tyr⁶ Asp⁹, Asp⁹ and Ala⁷-DSIP as well as Trp-Ala-Gly-Gly-Asp, Trp-Ala-Gly-Gly-Glu and Trp-Gly-Glu. DSIP and Phe⁵-DSIP were also prepared by pentafluorophenyl ester method. The purity of the synthetic peptides was checked by amino acid analysis, elemental analysis, thin layer chromatography and paper electrophoresis. The biological assay showed that the analogs of D-Trp¹, Tyr¹, Tyr¹ Phe⁵ and Ala⁷-DSIP as well as three short peptides were inactive whereas Phe⁵-DSIP showed similar activity as that of synthetic DSIP.     

Thermodynamics of C70 fullerence in the 0–390 K temperature range

The temperature dependence of heat capacity of C₇₀ fullerene was studied by calorimetry in the range between 6 and 390 K. Phase transitions were established and their thermodynamic characteristics were determined. From the experimental data obtained, the thermodynamic functionsH ^o (T)-H ^o(0),S ^o(T),G ^o(T)-H ^o(0) for temperatures between 0 and 390 K were calculated. The results were used to calculate the standard values of Δ_f S ^o, Δ_f G ^o, and logK _f ^o for the formation of C₇₀ from graphite. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 647–650, April, 1998.     

Substituent effects on one-bond 15N?13C couplings in N,N-dimethylanilines and nitrobenzenes. Effect of steric inhibition of conjugation

The ¹J(¹⁵N¹³C) values for a series of ring-substituted N,N-dimethylaniline-¹⁵N derivatives and a series of nitrobenzene-¹⁵N derivatives were measured from the ¹³C spectra. In the nitrobenzenes, small changes in ¹J(¹⁵N¹³C) are attributed to the inductive effect of the substituents, since steric inhibition of conjugation has little effect on the magnitude of the coupling. In contrast, steric inhibition of nitrogen lone-pair delocalization in N,N-dimethylaniline derivatives markedly reduces the value of ¹J(¹⁵N¹³C). Theoretical calculations of ¹J(¹⁵N¹³C) values for the two series of compounds were made using standard INDO parameters and a ‘sum-over-states’ perturbation approach. Fair agreement between the calculated and experimental values is found.     

Thermochemistry of Aqueous Solutions of Alkylated Nucleic Acid Bases. X. Enthalpies of Hydration of Cytosine and some Methylated, Hydroxy and Methoxy Derivatives of Cytosine

Enthalpies of solution in water, vapor pressures, and enthalpies of sublimation were determined for cytosine and a number of crystalline derivatives of cytosine: 1-methylcytosine, 1-methyl-N ⁴-hydroxycytosine, 1,5-methyl-N ⁴-methoxycytosine, 1,N ⁴,N ⁴-trimethylcytosine, 1,5,N ⁴-trimethylcytosine, 1,5-dimethyl-N ⁴-methoxycytosine, and l,N ⁴-dimethyl-5-ethylcytosine. Enthalpies of hydration were calculated. The latter were analyzed on the basis of the group additivity method. The relation between enthalpy of hydration and polarity of compounds is discussed.     

Study of Activation and Inhibition of Certain Metal Ions to Amylase Catalyzed Reaction by Microcalorimetry

IntroductionMostcomplicatedreactionshappenedinlivingcrea tures ,amongthemenzymecatalyzedreactionisanimpor tantclass .Itissignificantinboththeoryandpracticetoinvestigateenzymecatalyzedreaction .Therearemanyex perimentalmethodssuchasspectrophotometry ,titrimetry ,isotopemethod ,microcalorimetryandsoon ,inwhichmi crocalorimetryisanewoneduetoitshighsensitivityandaccuracy .Wecanstudythewholeprocessoftheheatef fectusingamicrocalorimeter .Sincetheabsorptionorpro ductionofheatisanintrinsicpropertyofe…     

Measurement of dispersion numbers for 36 and 100% tri-isoamyl phosphate solvents equilibrated with aqueous nitric acid solutions

The cross sections for the ¹¹⁸Sn (n, α)¹¹⁵Cd, ¹²⁰Sn (n, α)^117gCd and ¹²⁰Sn (n, α)^117mCd reactions have been measured in the neutron energy range of 13.5–14.6 MeV using the activation technique and a coaxial HPGe γ-ray detector. The fast neutrons were produced by the T (d, n) ⁴He reaction. The neutron energies in the measurements were determined by cross section ratios for ⁹³Nb(n,2n)^92mNb and ⁹⁰Zr(n, 2n)^89m+gZr reactions. The results of present work were discussed and compared with theoretical calculation data, measurement results found in the literature and with the comprehensive evaluation data in ENDF/B-VII.0, CENDL-3.1, JENDL-4.0 libraries.     

Production possibility of <Superscript>61</Superscript>Cu using proton induced nuclear reactions on zinc for PET studies

Summary Excitation functions were measured by stacked-foil technique for the ^natZn(p,x)⁶¹Cu, ⁶⁶Zn(p,x)⁶¹Cu, ⁶⁸Zn(p,x)⁶¹Cu and ^natZn(p,x)⁶⁰Cu nuclear processes up to 100 MeV. The experimental cross sections were compared with published data. On the base of these excitation functions, the cross sections of ⁶⁴Zn(p,x)⁶¹Cu process were also deduced. Integral thick target yields were calculated for the ⁶⁴Zn(p,x)⁶¹Cu and ^nat,64Zn(p,x)⁶⁰Cu processes and irradiation parameters were elaborated for the ⁶¹Cu production via the ⁶⁴Zn+p reactions for low and middle energy accelerators. According to our calculations the yield of ⁶¹Cu amounts to 1.02 ^. 10¹¹ Bq ^. A^{-1 .} s^-1 (9.9 mCi ^.µ A^{-1 .} h^-1) from 19®10 MeV while it reaches 3.91 ^. 10¹¹ Bq ^. A^{-1 .} s^-1 (38 mCi ^{. µ} A^{-1 .} h^-1) in the energy range of 67®60 MeV.