碱金属硫酸盐-SDS-PEG三维浓度变化对SDS的束缚胶束聚集数的影响

采用稳态荧光猝灭技术测定了三种碱金属(Li, Na或K)硫酸盐-SDS-PEG三元体系中SDS(十二烷基硫酸钠)的束缚胶束聚集数N_b, 考察了SDS浓度c、碱金属硫酸盐浓度c_e及PEG(聚乙二醇)浓度c_p变化时SDS的N_b的变化规律. 对SDS的N_b数据进行二次响应面分析, 得知SDS的N_b是c的线性增大函数、c_e的对数函数以及c_p的反比例函数, 据此对SDS的N_b实验值建立含二次交互作用项的函数表达式. 按上述表达式进行回归, 得到相应于Li₂SO₄, Na₂SO₄或K₂SO₄体系的系数a₀～a₈. 据此计算得到SDS的N_b预期值并与实验值进行比较, 其间的绝对误差在3以内, 相对误差在4%以内. 该结果为用SDS的N_b 预测表面活性剂-大分子软模板的尺寸和化学微环境、并用于调控所制备的金属纳米粒子的大小提供依据.     

Hochdruckuntersuchungen zur Löslichkeit von Stickstoff in Wolfram

The paper reports investigations about the solubility of nitrogen in tungsten at nitrogen pressures up to 30 MPa (300 bar). The solubility of nitrogen obeysSieverts' law in the whole pressure range and can be represented by the equation logC _N=1/2 logp _{N 2}+4.0–9520/T (C _N in wt·ppm.p _{N 2} in bar,T in K).

     

Stability Constants of Zinc and Cadmium Complexes of 2-Hydroxypropene-1,3-Diamine-N,N,N",N"-Tetraacetic Acid

Stability constants of complexes of 2-hydroxypropene-1,3-diamine-N,N,N",N"-tetraacetic acid with Zn²⁺ and Cd²⁺ ions have been determined by potentiometric titration in a KNO₃ supporting electrolyte at 298.15 K and ionic strengths of 0.1, 0.5, and 1.0. The results obtained were extrapolated to the zero ionic strength of the solution using a one-parameter equation.     

Kinetics and mechanism of the reaction between N-and N,N′-methyl ethylenediamines and palladium(II) chloro complexes in aqueous acid medium

The substitution of N-alkyl substituted ethylenediamines for chloride ions in the rapidly equilibrating system has been investigated in aqueous acid medium. The kinetic data can be accommodated by the general rate law where n = 0, 1, or 2 and m = 0, 1, or 2, depending on whether none, one, or two methyl groups are attached to the two nitrogen atoms of ethylenediamine. Reaction with the most heavily substituted ethylenediamine, namely, N₂N₂en discloses a change of the mentioned rate law to on going from a lower to a higher chloride ion concentration range. This change in the mathematical form of the rate law can be explained in terms of an ion-pair association of N₂N₂enH⁺ and free chloride ions.     

Reaction of O(1D) with N2O

O(¹D), produced from the photolysis of N₂O at 2139 Å, reacts with N₂O in accord with: We have used the method of chemical difference to obtain an accurate measure of k₂/k₃ = 0.59 ± 0.01. Furthermore, the quantum yield of production of O(³P), either on direct photolysis or on deactivation of O(¹D) by N₂O, is less than 0.02 and probably zero.     

Relation between total energy,electronic potential at the nucleus,and chemical potential of positive ions

Simple density functional theory gives the following relation between the energy E_{Z, N} of an ion of nuclear charge Z and N electrons, the potential V(0) created at the nucleus by the electronic cloud, and the chemical potential μ Using Hartree—Fock values for V(0) and μ, this equation has been tested in several isoelectronic series with 3 ≤ N ≤ 28. The importance of the term 3Nμ/7 increases as the degree of ionization increases.     

Relativistic theory of binding energies of heavy positive ions

The self-consistent relativistic Thomas–Fermi theory of heavy positive ions with N electrons and nuclear charge Ze is shown to lead to a chemical potential μ which has the scaling property with ? = α²Z², α being the fine structure constant. Combining this with the Layzer–Bahcall expansion for the total energy E(Z, N), namely, it is proved that the coefficients E_nm (N) at large N have the asymptotic behavior N^n–2m/3#1/3. The corresponding result for the scaling of the relativistic Thomas–Fermi energy is Scaling properties of the higher order terms in E_nm (N) and E(Z, N) are also proposed.     

Quenching of N2(A3Σu+) by O2, O,N, and H

Metastable N₂(A³Σ_u⁺), υ = 0, υ = 1, molecules are produced by a pulsed Tesla-type discharge of a dilute N₂/Ar gas mixture. Rate coefficients for quenching these metastable levels by O₂, O, N, and H were obtained by time-resolved emission measurements of the (0, 6) and (1, 5) Vegard–Kaplan bands. In units of cm³/mole · sec at 300°K and with an experimental uncertainty of ±20%, these rate coefficients for N₂(A³Σu⁺) are Within the limits of error these coefficients apply to quenching N₂(A³Σ_u⁺) υ′ = 1 as well.     

First‐Principles Prediction of Nucleophilicity Parameters for π Nucleophiles: Implications for Mechanistic Origin of Mayr’s Equation

Quantitative nucleophilicity scales are fundamental to organic chemistry and are usually constructed on the basis of Mayr’s equation [log k=s(N+E)] by using benzhydrylium ions as reference electrophiles. Here an ab initio protocol was developed for the first time to predict the nucleophilicity parameters N of various π nucleophiles in CH₂Cl₂ through transition‐state calculations. The optimized theoretical model (BH&HLYP/6‐311++G(3df,2p)//B3LYP/6‐311+G(d,p)/PCM/UAHF) could predict the N values of structurally unrelated π nucleophiles within a precision of ca. 1.14 units and therefore may find applications for the prediction of nucleophilicity of compounds that are not readily amenable to experimental characterization. The success in predicting N parameters from first principles also allowed us to analyze in depth the electrostatic, steric, and solvation energies involved in electrophile–nucleophile reactions. We found that solvation does not play an important role in the validity of Mayr’s equation. On the other hand, the correlations of the E, N, and log k values with the energies of the frontier molecular orbitals indicated that electrostatic/charge‐transfer interactions play vital roles in Mayr’s equation. Surprising correlations observed between the electrophile–nucleophile C? C distances in the transition state, the activation energy barriers, and the E and N parameters indicate the importance of steric interactions in Mayr’s equation. A method is then proposed to separate the attraction and repulsion energies in the nucleophile–electrophile interaction. It was found that the attraction energy correlated with N+E, whereas the repulsion energy correlated to the s parameter.     

Integral–geometrical consideration of density matrices

The ensemble N-representability problem for the k-th order reduced density matrix (k-RDM ) as well as the problem of reconstruction of the N-particle system density matrices (N-DM ) from a given k-RDM are studied. The spatial parts of the k-RDM expansion in terms of spin tensorial operators Θ are represented using particular values (at specially chosen ) of the Radon transform of the N-DM spatial parts (or their sums) ??_Nλ(x′ | x″) (here, is a d-plane in the n-space ?ⁿ of x = (x′, x″)), with n = 6N, d = 3 (N ? k), x′ ≡ (r′₁, ?, r′_N), x′ ≡ (r₁″, ?, r″_N ()). In this way, the problem is reduced to investigation of the properties of the functions . For a normalizable N – DM , it is proved that are bounded functions. The properties of implied by the N-DM permutational symmetry, Hermiticity, and positive definiteness are found. A formal procedure of reconstruction of all N-DM corresponding to a given k-RDM is proposed. © 1995 John Wiley & Sons, Inc.     

Pertraction of U(VI) through liquid membranes using monoamides as carrier ligands: experimental and theoretical studies

Pertraction of U(VI) from HNO₃ feed into water through flat-sheet supported liquid membrane containing a series of monoamides, viz. N,N-dihexylhexanamide (DHHA), N,N-dihexyloctanamide (DHOA) and N,N-dihexyldecanamide (DHDA), as the carrier ligands were studied. The results obtained with monoamides were compared with those obtained with TBP, a contemporary ligand to monoamides. The permeation of U(VI) was primarily governed by the distribution ratio of U(VI) by the ligands. A mathematical equation was derived by solving the mass balance equation on the feed side and the receiver side of the membrane which fitted well to a series of experimental results in the present work.

     

A Nucleophilicity Scale for the Reactivity of Diazaphospholenium Hydrides: Structural Insights and Synthetic Applications

Nucleophilicity parameters (N, s_N) of a group of representative diazaphospholenium hydrides were derived by kinetic investigations of their hydride transfer to a series of reference electrophiles with known electrophilicity (E) values, using the Mayr equation log k₂=s_N(N+E). The N scale covers over ten N units, ranging from the most reactive hydride donor (N=25.5) to the least of the scale (N=13.5). This discloses the highest N value ever quantified in terms of Mayr's nucleophilicity scales reported for neutral transition‐metal‐free hydride donors and implies an exceptional reactivity of this reagent. Even the least reactive hydride donor of this series is still a better hydride donor than those of many other nucleophiles such as the C?H, B?H, Si?H and transition‐metal M?H hydride donors. Structure–reactivity analysis reveals that the outstanding hydricity of 2‐H‐1,3,2‐diazaphospholene benefits from the unsaturated skeleton.     

Pyrolysis of 2-phenylethylamines heats of formation of aminomethyl radicals R2NCH2 · (R = H,CH3)

A kinetic study of the very low-pressure pyrolysis of ethylbenzene (I), 2-phenylethylamine (II), and N,N-dimethyl 2-phenylethylamine (III) above 900 K yields the heats of formation of aminomethyl (A) and N,N-dimethylaminomethyl (B) radicals: ΔH_{?, 300 K}(A) = 30.3 and ΔH_{?, 300 K}(B) = 27.5 kcal/mol. The difference of stabilization energies E_s, (relative to methyl radicals): Δ = E_s(B) ? E_s(A) = (2 ± 1) kcal/mol, conforms to similar effects in methyl substituted alkyl and amino free radicals.     

Vibration–vibration energy exchange between 15N14NO and CO

The temperature dependence of the vibration–vibration energy transfer between the v₃ mode of ¹⁵N¹⁴NO and the first vibrational level of CO was determined over a range of 680 to 1300°K using a shock tube. Several mixtures of ¹⁵N¹⁴NO? CO were tested, diluted in 95% Ar. The resulting exothermic transfer probabilities for the reaction, are compared to previous work on N₂O—CO. The results for ¹⁵N¹⁴NO? CO exhibit a more pronounced direct temperature dependence than for N₂O—CO even though the process has a closer resonance (ΔE = 59 cm^?1 for ¹⁵N¹⁴NO? CO and ΔE = 81 cm^?1 for N₂O? CO).     

Kinetic evidence for the occurrence of kinetically detectable intermediates in the cleavage of N‐ethoxycarbonylphthalimide under N‐methylhydroxylamine buffers

The kinetics of the aqueous cleavage of N‐ethoxycarbonylphthalimide (NCPH) in CH₃NHOH buffers of different pH reveals that the cleavage follows the general irreversible consecutive reaction path NCPH ENMBC A B , where ENMBC, A , and B represent ethyl N‐[o‐(N‐methyl‐N‐hydroxycarbamoyl)benzoyl]carbamate, N‐hydroxyl group cyclized product of ENMBC, and o ‐(N‐methyl‐N‐hydroxycarbamoyl)benzoic acid, respectively. The rate constant k_{1 obs} at a constant pH, obeys the relationship k_{1 obs} = k_w + k_n^app [Am]_T + k_b[Am]_T², where [Am]_T is the total concentration of CH₃NHOH buffer and k_w is first‐order rate constant for pH‐independent hydrolysis of NCPH. Buffer‐dependent rate constant k_b shows the presence of both general base and general acid catalysis. Both the rate constants k_{2 obs} and k_{3 obs} are independent of [Am]_T (within the [Am]_T range of present study) at a constant pH and increase linearly with the increase in a_OH with definite intercepts. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 95–103, 2002     

Nucleophilicities and carbon basicities of pyridines

Rate and equilibrium constants for the reactions of pyridines with donor‐substituted benzhydrylium ions have been determined spectrophotometrically. The correlation equation log k(20 °C)=s(N+E), in which s and N are nucleophile‐specific parameters and E is an electrophile‐specific parameter, has been used to determine the nucleophilicity parameters of various pyridines in CH₂Cl₂ and aqueous solution and to compare them with N of other nucleophiles. It is found that the nucleophilic organocatalyst 4‐(dimethylamino)pyridine (DMAP) and tertiary phosphanes have comparable nucleophilicities and carbon basicities despite widely differing Brønsted basicities. For that reason, these reactivity parameters are suggested as guidelines for the development of novel organocatalysts. The Marcus equation is employed for the determination of the intrinsic barriers of these reactions.     

Application of NMR spectroscopy of chiral association complexes 11—Rotation about the C(sp2)—C(aryl) Bond in 2,6-Difluorobenzamides Studied by 19F NMR

The energy barrier to rotation about the C(sp²) C(aryl) single bond in non-planar N,N-dimethyl-, N,N-tetramethylene-, N,N-diisopropyl-2,6-difluorobenzamides and in N,N-dimethyl-2-chloro-6-fluorobenzamide was investigated by ¹⁹F{¹H} NMR in the presence of an optically active shift reagent. The free energy of activation was calculated from the coalescence temperature of the fluorine signals; the calculation was accomplished using the simple, approximative equation and, also, by the graphical procedure including the (eigen) line width, i.e. without the broadening caused by two-site exchange. A distinct effect of the size of the N-substituents on the ΔG_c‡values was observed, in accordance with expectation.     

Gas-phase ozonolysis of cis- and trans-dichloroethylene

Dichloroethylene (DCE), either cis or trans, was reacted with O₃ at 23°C in both N₂ and O₂ buffered mixtures. Both reactant consumption and product formation were monitored by infrared spectroscopy and, in some cases, O₃ consumption was monitored by ultraviolet absorption. For thoroughly dried mixtures, the initial products were only HCClO and O₂, but geometrical isomerization also occurred. The stoichiometry of the overall reaction always was The HCClO was unstable and disappeared slowly in a first-order reaction which was, at least in part, heterogeneous. The products were CO and HCl so that the stoichiometric reaction was The rate law was complex. The rate was always faster in N₂ than in O₂. In the N₂ buffered reaction, inhibition occurred as the reaction progressed and O₂ was produced. From the reactant and product decay curves, the following rate behavior was established: where high and low concentrations are relative terms for the initial pressure ranges covered ([DCE]₀ = 0.21?78.4 torr, [O₃]₀ = 0.30?6.76 torr). The rate coefficients k₂, k₃, and k₄ were larger for the trans-DCE than the cis-DCE, and for each isomer they were larger in N₂ than in O₂ buffered reactions. The ozonolysis can be explained in terms of the mechanism where R₂ is DCE, RO is HCClO, and RO₂ is HCClO₂. Rate ceofficients are computed. The isomerization is first order in [O₃] and approximately first order in [DCE] for the limited kinetic data we were able to obtain. The isomerization does not appear to be explained by the reverse reactions of reactions (6), (7), and (9). Presumably isomerization occurs through some other route.     

Synthese von Cadmiumnitrid Cd3N2 durch thermischen Abbau von Cadmiumazid Cd(N3)2 und Kristallstrukturbestimmung aus Röntgen‐Pulverbeugungsdaten

Synthesis of Cadmium Nitride Cd₃N₂ by Thermolysis of Cadmium Azide Cd(N₃)₂ and Crystal Structure Determination from X‐ray Powder Diffraction Data Cadmium nitride Cd₃N₂ was obtained by thermolysis of cadmium azide Cd(N₃)₂ at 2·10^?6 mbar and 210 °C. It was obtained as a black, crystalline powder which becomes brown in air due to formation of cadmium amide Cd(NH₂)₂. The crystal structure of Cd₃N₂ was determined from X‐ray powder diffraction data and refined by the Rietveld method ( , a = 10.829(9) Å, V = 1270(3) ų, Z = 16, R(F²) = 0.1196). Cd₃N₂ crystallizes in the anti‐bixbyite structure type and is isotypic to Ca₃N₂.     

Mechanisms of Molecular Mobility of Oxygen and Nitrogen in Carbon Molecular Sieves

Molecular mobility of oxygen, O₂, and nitrogen, N₂, in Carbon Molecular Sieves, CMS, was investigated using the Frequency Response, FR, technique to identify mass-transfer mechanisms and related kinetic time constants. The FR data showed that O₂ mobility in four types of CMS was dominantly controlled by surmounting surface-barrier resistances, whereas the mobility of both O₂ and N₂ in pellets of a fifth CMS type obeyed the Fickian diffusion model. Temperature and pressure dependences of surface-barrier penetration time constants were obtained for O₂ and N₂ in several of those CMS materials. The kinetic time constants of surface-barrier penetration were related to Langmuir-type rate constants, which indicates that kinetic behavior of O₂ therein could also be interpreted in terms of a Langmuir-kinetics equation.