Nonisothermal Kinetics of Sub‐Solidus Phase Transitions in C10Zn,C16Zn and Their Binary System

Nonisothermal kinetics of the solid‐solid phase transition in (n‐C₁₀H₂₁NH₃)₂ZnCl₄(C₁₀Zn), (n‐C₁₆H₃₃NH₃)₂ZnCl₄(C₁₆Zn) and their binary system were determined by Kissinger and Ozawa methods from DSC measurements. The activation energy E_a of the binary system shows a waving dependence on W_C10Zn%, which is caused by not only an intermediate (C₁₀H₂₁NH₃)(n‐C₁₆H₃₃NH₃)ZnCl₄ but also three solid solution ranges (α, β, γ) in the phase diagram of C₁₀Zn‐C₁₆Zn. The variations of the layer d‐spacing are also convenient for the above result.     

长链烷基季铵盐插层氧化石墨的结构变化

基于改进的Hummers法制备氧化石墨(GO),并以长链烷基季铵盐(C_nTAB)对其进行插层处理;通过改变C_nTAB的链长、浓度,得到系列C_nTAB/GO插层复合物。采用XRD和元素分析对产物的最大底面间距及C_nTAB插入量进行表征。结果表明,随着C_nTAB链长的增长、C_nTAB浓度的增大,C_nTAB/GO插层复合物的最大底面间距逐渐增大。C_nTAB通过离子键作用和疏水键作用插入到GO层间,在GO片层上的吸附规律符合修正型(Modified)Langmuir模型,即C_nTAB以单分子层吸附在GO片层上。根据C_nTAB/GO插层复合物最大底面间距及C_nTAB插入量的变化规律分析,得出C_nTAB在GO层间的排布模式有单层平躺模式、类双层平躺模式、单层倾斜模式和单层直立模式。     

The formation of intercalation compounds of MoS2 with cations of alkali metals and alkylammonium from monolayer dispersion of molybdenum disulfide

Ion-exchange interaction of the monolayer aqueous dispersion obtained by hydration of crystalline LiMoS₂ with Li, Na, K salts and alkyiammoniiim halides is studied. Intercalation compounds of MoS₂ with hydrated inorganic cations as well as hitherto unattainable intercalation compounds of MoS₂ with alkylammonium cations are shown to be formed under these conditions. The composition and structure of these compounds are investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 672–674, April, 1993.     

The structure of bis(trimethylammonium) undecachlorotriantimonate(III) [(CH3)3NH]2Sb3Cl11 containing a novel antimony(III) anion

The structure of [(CH₃)₃NH]₂Sb₃Cl₁₁ (space group P2₁/n; a = 10.374(2), b = 23.723(5), c = 11.884(2) Å, = 113.46(3)°; V = 2682.9(9) ų) consists of a structurally novel [Sb₃Cl^2– ₁₁] anion and two crystallographically nonequivalent trimethylammonium cations. The anion is composed of three deformed octahedra in the asymmetric part of the unit cell. The octahedra are connected with each other by edges and corners forming a characteristic polyanionic layer. Trimethylammonium cations, one ordered and one disordered, are connected to the inorganic sublattice by N—H···Cl hydrogen bonds.     

Effects of liquid chromatography mobile phase buffer contents on the ionization and fragmentation of analytes in liquid chromatographic/ionspray tandem mass spectrometric determination

The effects of liquid chromatography mobile phase buffer contents on the ionization and fragmentation of drug molecules in liquid chromatographic/ionspray tandem mass spectrometric (LC/MS/MS) determination were evaluated for simvastatin (SV) and its hydroxy acid (SVA). The objective was to improve further the sensitivity for SV by overcoming the unfavorable condition caused by the formation of multiple major adduct ions and multiple major fragment ions when using ammonium as LC mobile phase buffer. Mobile phases (70:30 acetonitrile-buffer, 2 mM, pH 4.5) with buffers made from ammonium, hydrazine or alkyl (methyl, ethyl, dimethyl or trimethyl)-substituted ammonium acetate were evaluated. Q1 scan and product ion scan spectra were obtained for SV in each of the mobile phases under optimized conditions. The results showed that, with the alkylammonium buffers, the alkylammonium-adducted SV was observed as the only major molecular ion, while the formation of other adduct ions ([M + H](+), [M + Na](+) and [M + K](+)) was successfully suppressed. On the other hand, product ion spectra with a single major fragment ion were not observed for any of the alkylammonium-adducted SVs. The affinity of the alkylammoniums to SV and the basicity of the alkylamines are believed to be factors influencing the formation and abundance of molecular and fragment ions, respectively. Methylammonium acetate provided the most favorable condition among all the buffers evaluated and improved the sensitivity several-fold for SV in LC/MS/MS quantitation compared with that obtained using ammonium acetate buffer. Better precision for SV in both Q1 and SRM scans was observed when using methylammonium buffer compared with those using ammonium buffer. The mobile phase buffer contents did not seem to affect the ionization, fragmentation and chromatography of SVA. The results of this evaluation can be applied to similar situations with other organic molecules in ionspray LC/MS/MS determination.     

A Study on Organized Assemblies in the Aqueous Systems of Alkylammonium Chlorides

Various types of organized assemblies, including micelle, planar multi-bilayer, bent multi-bilayer, fingerprint-like multi-bilayer, and multilamellar vesicles, were found in the aqueous system prepared by only one simple surfactant—alkylammonium chloride with a hydrocarbon chain length of 10 or 12. Electron microscopic images of the assemblies are provided. The properties of the system were characterized by DSC, fluorescence, and absorption probing techniques. It was found that the structure and shape of molecular assemblies in this system can be adjusted by very simple physico-chemical measures, such as pH adjustment and alcohol or salt addition. The mechanisms of formation and transformation of various molecular assemblies were discussed based on the mixing effect of the cationic amphiphile and the nonionic amphiphile which is only a hydrolysis product of the former.     

Factors influencing enantiomeric recognition of primary alkylammonium salts by pyridino-18-crown-6 type ligands

Equilibrium constant (K), enthalpy change (H), and entropy change (S) values were determined for the interactions of a series of chiral pyridino-18-crown-6 type ligands with enantiomers of several primary alkylammonium salts in various solvents. Good enantiomeric recognition in terms of logK was observed in many systems with logK values greater than 0.4. The extent of enantiomeric recognition and the stabilities of the chiral crown ether-ammonium salt complexes were found to depend on the rigidity of the macrocyclic frame of the ligand, the type and arrangement of the donor atoms on the ligand, the bulkiness of the substituents on the ligand's chiral centers, the location of the chiral centers on the ligand, and the solvent. The effects of these factors on the extent of enantiomeric recognition and on the stabilities of the complexes were examined for the systems studied.     

Interactions in Aqueous Mixtures of Alkylammonium Chlorides and Sodium Cholate

The interactions of alkylammonium chlorides (the number of carbon atom per chain was either 12, 14, or 16) with sodium cholate have been investigated by a combination of techniques including light and electron microscopy, surface tension, conductivity, light scattering, and microelectrophoretic measurements. The phase behavior has strongly depended on the molar ratio and actual concentration of oppositely charged surfactants. The change in the composition of the aggregates leads to a shape transformation from globular to elongated micelles to open and/or closed bilayers (vesicles) and precipitation. The length of micelles has been found to decrease dramatically with the concentration shift to the micellar regions of either surfactant. Upon a moderate excess of one surfactant, the mean hydrodynamic diameter of aggregates increases and wormlike micelles and/or open and closed bilayers are formed. Microscopic observations of alkylammonium cholates (novel catanionic surfactants precipitated in and/or close to equimolar region) have shown the presence of a variety of morphologies including twisted ribbons, tubules and bundles of tubules.     

Adsorption of 1-butanol from water on modified silicate surfaces

The structure and the sorption properties of partially hydrophobized silicates (dodecylammonium and dodecyldiammonium vermiculites) have been investigated in aqueous solutions of 1-butanol. The alcohol is preferentially adsorbed on the surface. The interlayer composition is calculated from adsorption and x-ray diffraction data. In air-dried state the organic cations lie flat on the interlamellar surface. In aqueous butanol solutions, the basal spacing of dodecylammonium vermiculite gradually increases with the extent of butanol adsorption because the chains increasingly point away from the surface. The basal spacing of dodecyldiammonium vermiculite is virtually independent on the interlayer composition because the expansion of the interlayer space is sterically restricted and a relatively rigid structure is formed. The enthalpy of the displacement of water by 1-butanol has been determined by flow sorption microcalorimetry. The displacement process is endothermic.     

层状钙钛矿化合物 (n-CnH2n+1NH3)2ZnCl4非等温固-固相变动力学的确定

确定了具有层状钙钛矿结构,脂肪链C原子数从12到18四氯合锌酸二烷基铵(C_nH_2n+1NH₃)₂ZnCl₄系列化合物的非等温固-固相变动力学。采用Kissinger和Ozawa两种动力学模型,对不同温度下测定的每个样品DSC热分析曲线进行数据处理,计算固-固相变过程的活化能E_a。实验结果表明,随着C原子数的增加,脂肪链的有序度和刚度降低,导致固-固相变活化能E_a随C原子数的增大而降低。两种模型方法的计算活化能E_a的结果相一致。并且各个化合物的固-固相变反应级数不随升温速率和烷基链长变化而变化,总保持为1。