核心素养视角下人教版新旧教材中“硫及其化合物”的对比分析*

选取人教版新旧必修化学教材中的“硫及其化合物”单元作为研究对象,基于新课标中化学学科核心素养的培养视角,明确了新课标对“硫及其化合物”的素养定位后,对新旧教材中该单元的引言、正文、栏目和插图进行对比分析。对比分析结果显示,新教材“硫及其化合物”的内容侧重“证据推理与模型认知”素养的培养,其次是“宏观辨识与微观探析”“科学态度与社会责任”素养,而在素养水平上则侧重水平1和2维度的培养,符合新课标对该主题单元的学业要求和素养定位。     

Which Factors Determine the Reactivity and Regioselectivity of Free Radical Substitution and Addition Reactions?

The relative importance of bond strength, steric effects, and polarity in determining the rate and orientation of free radical subsitution and free radical addition reaction is considered. The factors which control substitution reaction (radical transfer reaction) are gathered together as five “rules”, and a similar five “rules” are proposed for addition rections. These “rules” are shown to be special cases of two “laws” which govern all free radical reactions.     

Molecular beam reaction of K atoms with sideways oriented CF3I

Reactive scattering is observed for K + CF₃I → KI+CF₃ where the CF₃I is oriented “sideways” with the I end pointing towards or away from the detector. Angular distributions are extremely broad and completely different from “heads” and “tails” orientations. Maximum signal corresponds to the “towards” orientation although reactivity of the two orientations is equivalent.     

Size‐ and Orientation‐Selective Encapsulation of C70 by Cycloparaphenylenes

The size‐ and orientation‐selective formation of the shortest‐possible C₇₀ peapod in solution and in the solid state by using the shortest structural unit of an “armchair” carbon nanotube (CNT), cycloparaphenylene (CPP), has been studied. [10]CPP and [11]CPP exothermically formed 1:1 complexes with C₇₀, thereby giving the resulting peapods. A van′t Hoff plot analysis revealed that the formation of these complexes in 1,2‐dichlorobenzene was mainly driven by entropy, whereas the theoretical calculations suggested that the formation of the complex in the gas phase was predominantly driven by enthalpy. C₇₀ was found to exist in two distinct orientations inside the CPP cavity, namely “lying” and “standing”, depending on the specific size of the CPP. The theoretical calculations and the X‐ray crystallographic analysis revealed that the interactions between [10]CPP and the short axis of C₇₀ in its lying orientation were isotropic and similar to those observed between [10]CPP and C₆₀. However, the interactions between [11]CPP and C₇₀ in its standing orientation were anisotropic, thereby involving the radial deformation of [11]CPP into an ellipsoidal shape. This “induced fit” maximized the van der Waals interactions with the long axis of C₇₀. Theoretical calculations revealed that the deformation occurred readily with low energy loss, thus suggesting that CPPs are highly radially elastic molecules. These results also indicate that the same type of radial deformation should occur in CNT peapods that encapsulate anisotropic fullerenes.     

Morphological mechanics of springy polymers

The mechanics of “springy” or “hard elastic” row-crystallized polymers were investigated. It was found that their unique tensile and physical properties could be explained by adhesive fracture mechanics and simple beam deflection. The deformed lamellae had an apparent negligible modulus of flexural rigidity. An adhesive failure model was designed which duplicated all the tensile characteristics of springy polymers, including constant lateral contraction, critical stress, peel stress, rehealing, energetic elasticity, and cyclic strain behavior. The ideal relative density change as a function of strain was found to be the same for all springy polymers. Dynamic infrared analysis showed that the molecular orientation decreased during the deformation of springy polypropylene films. The latter is due to the deflection of lamellae. Rehealing was accompanied by a time-dependent reversal of orientation. The enthalpic elasticity is derived from the strain energy of the lamellar network.     

High speed spinning of poly(ethylene terephthalate)—II: Orientation induced mechanism of cold crystallization in pre-orientated yarns

The kinetics of the “cold crystallization” of poly(ethylene terephthalate) (PET) pre-orientated yarns are investigated both in isothermal and in non-isothermal dynamic conditions. The amorphous-crystalline, solid-solid transformation is analyzed in terms of the Avrami equation and of Ozawa's theory. The nucleation and growth mechanism is a function of PET amorphous molecular orientation and changes from a three dimensional (n = 4) to a two dimensional and one dimensional disc-like or rod-like growth. The molecular orientation may be defined as the best “nucleating agent” for PET overall rate of crystallization in the low temperature region.     

Conformational preference of 2,5-disubstituted phosphacymantrenes evidenced by the data of quantum chemical calculations and topology analysis of electron density

Quantum chemical calculations and topological analysis of the electron density distribution r(r) were performed in the framework of the “Atoms in molecules” theory for a series of 22,5-substituted phosphacymantrene derivatives. The electronic structure of the cyclic π-ligand caused by the donor-acceptor properties of the substituents determines the preferential orientation of the Mn(CO)₃ fragment relative to the heterocycle. The change in the number of bond paths between the Mn atom and heterocycle affects “fine” changes in the character of the M-π-interaction, depending on the nature of the substituents and orientation of the carbonyl groups.     

Continuous-saturation study of spin-lattice relaxation on the “main” and “satellite” lines of an oriented free radical

Electron-spin relaxation is investigated, through line-shape and continuous-saturation measurements, in a γ-irradiated single crystal of glycolic acid at room temperature. For the only orientation which gives fair line resolution, the experimental data allow determination of the ratio of the effective spin-lattice relaxation times for the “main” and “satellite” lines. Comparison of this ratio with those to be expected from various possible mechanisms suggests that spin-lattice relaxation in this system originates mainly from random modulation, by molecular torsional oscillations, of the intramolecular dipolar hyperfine interaction responsible for the spectral pattern.     

Mixed monolayers of polyvinylpyridine and low-molecular-weight substances

Studies were carried out at the water/air interface on mixed monolayers of a macromolecular substance with ionizable polar groups and a “horizontal” interface orientation, poly-2-vinylpyridine, and three lowmolecular-weight substances with a “vertical” orientation, stearic acid, methyl stearate and stearylamine, at 15°, 25° and 35 °C. The surface areas, collapse pressures and compressibility coefficients as a function of mole ratios showed compatibility between the components for all three twocomponent systems. The values of the enthalpy and entropy contributions to the free surface energy of mixing were found to be positive for the poly-2-vinylpyridine/stearic acid system and negative for the other two systems.     

Influence of molecular weight and spinning conditions on the crystalline morphology of polypropylene fibres

In the spinning of polypropylene the “smectic” phase generally appears in the as spun fibres obtained from high fluidity polypropylene (for example M̄_w = 118000) at 200°C and more. The amount of the “smectic” form decreases as the draw down ratio increases. At 200°C and for a draw ratio of 40 the “smectic” form is about 70% of the crystalline phase. At 200°C and for a draw ratio of to 130 or higher, only the monoclinic form is observed. At 180°C, and whatever is the draw ratio, only the monoclinic form is observed. For high-molecular - weight polypropylene (for example M̄_w = 320000) the “smectic” form has never been observed whatever is the spinning temperature within the range 220–260°C. The fibres with high amount of smectic phase show low orientation factors, whereas the fibres having only monoclinic form show the highest orientation factors. These results, compared with elongational behaviour of the polypropylene, suggest that the smectic form appears in the fibres as the elongation rate on the spinning line is lower than the relaxation rate of polypropylene chains.     

NMR of dissolved water in ultrathin and thick membranes of cellulose acetate

Wide-line proton magnetic resonance spectra of thick (100 μ) and ultrathin (0.25 μ) membranes of cellulose acetate have been obtained in the “bone-dry” state and in the wet state up to 2.5% water by weight. The NMR spectra were recorded with the membrane face aligned parallel and perpendicular to the magnetic field direction. The first derivative spectra of wet thick membrane (above 0.4% water) show a sharp center peak and at least one broad outer peak, both in the parallel and perpendicular orientations. The spectra of wet ultrathin membrane, on the other hand, show a pseudodoublet in the perpendicular orientation and a broad singlet in the parallel orientation. The differences in the spectra of the thick and ultrathin membranes are discussed in terms of “free” and restricted water believed to arise from the differences in the structure of thick and ultrathin membranes.     

Morphology and Orientation of PP-Structural Foam Moldings

Abstract

An experimental study was conducted to investigate the interaction between the macrostructure and morphology of PP-structural foam moldings made by gas-counter pressure process by egression of foamed melt from the core of the molding. The structural foam moldings, center-gated cylindrical plate “disc” (diameter 1800 mm. high 11 mm) were produced on an in-line injection molding machine KuASY 800/250, varying the shot weight and melt temperature. The polymer used was isotactic polypropylene “Buplen” 7523 with 1 wt% chemical blowing agent (azodicarbonamide) added. The morphology, orientation, and processes of non isothermal phase transition have been studied using polarized optical microscopy, SALS, DSC and birefringence. Samples were cut from the discs at different distances from the gate. The presence of a two-layered structure was observed in the solid skin: an outer smectic layer and an inner particular crystalline layer. The thickness of the smectic layer and size of spherulites from skin to the foamed core were determined. The orientation in radical and tangential direction of the flow and perpendicular to the disc surface were studied in mold filling and egression stage. The fixed orientation in final moldings is a complex picture of bubble growth, bubble orientation and shear flow. It was found that the radical orientation decreases with the distance from the gate. Maximum orientation is located in the solid skin, and minimum in the foamed core, and was shown by means of a birefringence profile.     

EPR spin flip transitions in some metal dithiolenes

Small line widths (ΔB_pp ≅ 0.25–0.40 mT) in the EPR spectra of ⁶³Cu²⁺ in the matrices of some transition metal dithiolenes permit the observation of not-so-easily realizable proton spin flip transitions even at room temperature and at low microwave power. These transitions, studied in four different lattices as a function of crystal orientation, microwave power and temperature, have been found to be from the protons of the counter ions and a few ångströms away from the unpaired electron-containing metal centre. It has been possible to identify the protons and estimate their distances from the metal centre by two different methods. A temperature-dependent evaluation of the distance parameters as well as the observation of the “double” and “triple” flips are reported. The differential saturation of the “main” and “satellite” (due to spin flip) lines studied by the CW saturation method has provided information on the mechanism of spin relaxation in these systems.     

Anisotropic Conductivity at the Single‐Molecule Scale

In most junctions built by wiring a single molecule between two electrodes, the electrons flow along only one axis: between the two anchoring groups. However, molecules can be anisotropic, and an orientation‐dependent conductance is expected. Here, we fabricated single‐molecule junctions by using the electrode potential to control the molecular orientation and access individual elements of the conductivity tensor. We measured the conductance in two directions, along the molecular plane as the benzene ring bridges two electrodes using anchoring groups (upright) and orthogonal to the molecular plane with the molecule lying flat on the substrate (planar). The perpendicular (planar) conductance is about 400 times higher than that along the molecular plane (upright). This offers a new method for designing a reversible room‐temperature single‐molecule electromechanical switch that controllably employs the electrode potential to orient the molecule in the junction in either “ON” or “OFF” conductance states.     

Monte Carlo methods for polymer chains in two - dimensional geometries (polymers at surfaces and interfaces)

Coarse-grained models of polymers at interfaces can be defined such that their treatment by Monte Carlo simulation is most convenient and efficient for the problem at hand. This simulation strategy is briefly illustrated with three examples: (1) The orientational ordering of rigid rod-like polymers grafted to a surface, where “table methods” can be used, applying a fine discretization of the angles describing rod orientation. (2) Surface enrichment of one species in a polymer blend is treated by a semi-grand-canonical technique. (3) The number of configurations and structure of a star polymer attached with its center to a wall is studied by a “growth technique” generalizing simple sampling methods.     

Trajectory calculation results on the orientation of a diatomic molecule in collision with an atom

Orientational effects in collisions between a diatomic molecule and a noble gas atom are studied by classical trajectory calculations. A preferable ”perpendicular orientation“ of the molecule is found at the moment of closest approach of the atom. This orientational effect is more pronounced in collisions with heavy atoms.     

Cysteine adsorption on the Au(111) surface and the electron transfer in configuration of a scanning tunneling microscope: A quantum-chemical approach

Adsorption of two forms, molecule and radical, of amino acid L-cysteine (Cys) on the Au₁₂ cluster that simulates the (111) face of single-crystal gold is studied in the framework of the density functional theory. Effects of solvation of adsorbed Cys particles and lateral interaction in a monolayer are analyzed. The simulation predicts a commensurate adsorption energetics of the molecule and radical, with a difference between the “on-top,” “hollow,” and “bridge” positions. An analysis of lateral electrostatic interactions points to the stability of a cluster comprising six Cys particles, which conforms to the size of a fragment observed experimentally. Adsorption calculations are used to build three-dimensional isosurfaces (STM images), where the tungsten needle of the scanning tunneling microscope is simulated by a tungsten atom or by small clusters. The calculated images are sensitive to both the Cys shape and the orientation of adsorbed Cys particles. Calculation results are compared with fresh in situ submolecular-resolution STM data. Simulated images (with commensurate contributions made by sulfur atom and amino group) built for Cys radical adsorbed in the “on-top” position give best conformance to experiment.     

Nondiagonal second order intermolecular forces for interactions involving molecules

Very often only “diagonal” second order energies, varying as an even power of R^?1, occur in the multipole expansion of the interaction energy. However for many molecular interactions important “nondiagonal” second order energies, varying as an odd or even power of R^?1 can arise. This point is emphasized by a general discussion and by a detailed specific example, the interaction of an ionized dipolar molecule with a nondegenerate atom. Also some useful theorems, on the orientation average of various types of second order energies, are derived.     

Mechanisms of fracture in an oriented polystyrene

Fracture surfaces of an oriented polystyrene (by stretching 150% at 280°F) show many of the same features observed in the fracture of ordinary polystyrene: craze formation followed by quasi-viscous separation of the craze layer or by quasi-brittle fracture along the craze boundary. In cleavage fracture along the direction of orientation, advance fractures are initiated in flat areas covered, if at all, by an extremely thin layer of craze: the initiation of the “crazeles” fractures appears to arise from the orientation of the molecules rather than the presence of impurity particles.     

Evaluation of the orientation coefficient for the c axis in poly(ethylene terephthalate) fibers

The literature methods for the determination of the mean of the crystallite orientation distribution for the c axis, that is of the orientation coefficient f_c, for poly(ethylene terephthalate) (PET), based on the azimuthal scan of the (1 05) reflection, are reviewed. These methods appear unsuitable for samples presenting the “tilted orientation”; that is, the molecular chain axis inclined by some degrees with respect to the fiber axis, as frequently occurs for PET fibers. A new method for the determination of f_c for PET, also based on the azimuthal scan of the (1 05) reflection (which can be applied also to samples with “tilted orientation”), is proposed. This method implies as a first step the determination of the tilt angle, for which the complete fiber pattern is required. A possible simplifying assumption, which allows use of the sole azimuthal (1 05) profile and makes the method also applicable to poorly oriented samples (for which the determination of the tilt angle is not easy), is also discussed. © 1995 John Wiley & Sons, Inc.