A simple and rapid protocol for the synthesis of phenacyl derivatives using macroporous polymer-supported reagents

This article describes the use of Amberlite IRA-910 with different counter ions as excellent polymer-supported reagents in nucleophilic substitution reactions. The versatility of this protocol allowed the synthesis of a diversified library of phenacyl derivatives with high yields. The polymeric reagents can be reloaded several times with no loss of their efficiency.     

Plasmon photoelectric effect from alkali halides

The existence of the plasmon photoelectric effect was postulated elsewhere by one of the authors. In the plasmon photoelectric effect, incident photons excite plasmons in the solid; the decay of plasmons excites electrons. The emergence of these electrons from the solid is responsible for a group of photoelectrons of definite energy. The existence of the plasmon photoelectric effect is confirmed by comparison of spectral photoelectric yield data with electron energy loss spectra in 16 alkali halides. The presence of the plasmon photoelectric effect explains additional peaks observed with some alkali halides in the energy spectra of photoelectrons. These peaks were not understood previously.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 7–16, October, 1974.     

A facile and one pot synthesis of 1,4-disubstituted-1H-1,2,3-triazoles from terminal alkynes and phenacyl azides prepared from styrenes by CAN oxidant and sodium azide

A facile and green synthesis of 1,4-disubstituted-1H-1,2,3-triazoles is reported. The reaction of α-azido ketones and terminal alkynes in the presence of [CuSO₄ (H₂O)₅/sodium ascorbate] in a mixture of H₂O/polyethylene glycol 400 as solvent afforded the corresponding 1,4-disubstituted triazoles at ambient temperature with short reaction times and at high yields. The corresponding α-azido ketones were directly prepared in situ from various substituted styrenes using the oxidant cerium ammonium nitrate and sodium azide in oxygen-saturated methanol.     

Combustion synthesis of nano-sized tungsten carbide powder and effects of sodium halides

The synthesis of nano-size tungsten carbide powder has been investigated with a WO₃ + Mg + C + carbonate system using alkali halides. The effects of different types of alkali halides on combustion temperature and tungsten carbide formation were discussed. Sodium fluoride had a notable effect on the particle size of the product and the degree of transformation from the initial mixture. A small amount of ammonium carbonate activated the carburization of tungsten carbide by the gas phase carbon transportation. X-ray diffraction data and particle analysis showed that the final product synthesized from a WO₃–Mg–C–(NH₄)₂CO₃–NaF system contains pure-phase tungsten carbide with a particle size of 50–100 nm.     

Light scattering from hydrogen and deuterium halides

Light scattering measurements along the coexistence line show that reorientation in liquid HCl, DCl, and HBr is strongly hindered at low temperature and collision limited on approaching the critical point. Discrepancies with NMR data are observed.     

Sol-gel synthesis of rare-earth-doped lanthanum halides for highly efficient 1.3-microm optical amplification

Praseodymium- and dysprosium-doped lanthanum halide powders have been synthesized by a sol-gel-reactive-atmosphere approach. Emission at 1.3mum from a sol-gel-derived material was observed for the first time to our knowledge. Measured lifetimes corresponded to radiative quantum efficiencies of approximately 8% for Pr(3+):LaF(3), 72% for Pr(3+):LaCl(3), and 78% for Dy(3+):LaCl(3) . The spectroscopic properties of these hosts are shown to be comparable with those of melt-grown single-crystal analogs, verifying the ability of inexpensive and low-temperature solution-based methodologies to produce low-phonon-energy materials.     

简易Mie散射数值计算方法的研究

在回顾光散射理论发展史的基础上,分析了常规Mie散射计算实现过程中的问题,并论述一种改进的简易Mie散射数值计算方法。参照科学记数法定义了一种“EDecimal”类型的数据结构及其基本数学运算和三角函数运算。采用动态链表技术实现了高效的C++ Mie散射计算程序。该程序不仅可以用来处理极端条件下的Mie散射计算,而且显著降低了算法的时间复杂度,提高了执行效率。与相同精度要求下采用Wiscombe编写的MIEV0程序的计算结果进行了比较,并指出此程序精确可靠。     

Graded-index mid-infrared planar optical waveguides made from silver halides

Since the index of refraction of AgCl(x)Br(1-x) (x<1) is higher than that of AgCl, by diffusing Br(-) ions into AgCl it was possible to control the index and thus obtain planar waveguides made from silver chlorobromide (AgClBr) on a AgCl substrate. Silver halides are transparent in the mid IR, and it was therefore possible to characterize the waveguides by transmission of 10.6-mum CO(2)-laser radiation through them. In a typical case, the thickness was optically measured and was found to be 65mum , and the propagation loss was 16 dB/cm. The output-beam profile distribution was determined experimentally and found to be well correlated with a numerical analysis simulation based on a ray-tracing model of the eikonal equation. Planar waveguides that are transparent in the mid IR will likely be useful in numerous applications.     

Neutral beam sputtering of positive ion clusters from alkali halides

Neutral argon atom beams of 15 keV energy have been used to sputter alkali halides and the ejected positive ions have been analysed in energy, mass and angular distribution.

The use of a neutral beam, rather than an ion beam, minimizes surface charge and the deflection of ejected ions by electrostatic interaction with a charged incident beam.

A cluster component of the form K₂Cl⁺, K₃Cl⁺ ₂ and higher members of the series is found for all alkali halides studied.     

Kinetic studies of the reaction of phenacyl bromide derivatives with sulfur nucleophiles

The reaction of the substituted phenacyl bromides 1a–e and 2a–e with thioglycolic acid 3 and thiophenol 6 in methanol underwent nucleophilic substitution S_N2 mechanism to give the corresponding 2‐sulfanylacetic acid derivatives 4a–e, 5a–e and benzenethiol derivatives 9a–e, 10a–e. The reactants and products were identified by mass spectra, infrared and nuclear magnetic resonance. We measured the kinetics of these reactions conductometrically in methanol at a range of temperatures. The rates of the reactions were found to fit the Hammett equation and correlated with σ‐Hammett values. The ρ values for thioglycolic acid were 1.22–1.21 in the case of 4‐substituted phenacyl bromide 1a–e, while in the case of the nitro derivatives 2a–e they were 0.39–0.35. The ρ values for thiophenol were 0.97–0.83 in the case of 4‐substituted phenacyl bromide 1a–e, while in the case of the nitro derivatives 2a–e they were 0.79–0.74. The Brønsted‐type plot was linear with a α = ?0.41 ± 0.03. The kinetic data and structure‐reactivity relationships indicate that the reaction of 1a–e and 2a–e with thiol nucleophiles proceeds by a concerted mechanism. The plot of log k₄₅ versus log k₃₀, the plot log(k_x,3‐NO2/k_H) versus log(k_x/k_H), and the Brønsted‐type correlation indicate that the reactions of the thiol nucleophiles with the substituted phenacyl bromides 1a–e and 2a–e are attributed to the electronic nature of the substituents. Copyright © 2011 John Wiley & Sons, Ltd.     

Studies on the opto-electronic properties of alkali halides from optical electronegativities

A simple method of evaluating refractive indices from Duffy's optical electronegativity values is proposed. In the proposed empirical relations the optical electronegativity for the anion as well as the cation are taken into consideration in order to obtain refractive indices in alkali halides. The refractive indices so obtained are used in the evaluation of electronic polarizabilities in these compounds and the results are found to be in good agreement with the standard values.     

Surface energy for brittle fracture of alkali halides from lattice dynamics

A lattice dynamics approach to the surface energy γ for brittle fracture of several ionic crystals is presented, based on recent work on surface dynamics and a reformulation of a model previously worked out for metals. The model requires the knowledge of the crystal structure, the eigenfrequencies and eigenvectors of the normal modes of vibration, as well as an analytical definition of the critical interplanar displacement appropriate to the cleavage mode. Some temperature dependent values of γ are also computed for the (100) and (110) planes. Qualitatively the results indicate the correct cleavage systems for all cases and quantitively are reasonably consistent with the available experimental values.     

Photoelectron spectra of halides

High resolution photoelectron spectra, obtained with He I (584 Å) resonance radiation, are reported for ClF, ClF₃, BrF₃ and BrF (partial spectrum). In some cases Ne I (736–744 Å) radiation has also been used. Spinorbit and vibrational fine structure is resolved for the ground ²II states of ClF⁺ and BrF⁺; values obtained for ClF⁺ and ζ = 630 cm^-1, v′ = 870 cm^-1, and for BrF⁺ ζ = 2600 cm^-1, v′ = 750 cm^-1. From the vibrational envelope of the X ²∏ states, a bond length change of δr _e (-)0·10 Å for ClF⁺ and BrF⁺ is estimated. Ab initio SCF-MO calculations for ClF and ClF₃ are used to aid in the interpretation of the spectra via Koopmans' theorem. A considerable amount of charge delocalization in the trifluorides is inferred from the photoelectron spectra, and this is borne out by the calculations.     

Photoluminescence of mercurous halides

Mercurous halides show strong orange luminescence at 77°K when excited at energies above the fundamental absorption edge. At room temperature this luminescence is strong only in the chloride and bromide. Spectral features, including band maxima and half widths of both excitation and emission spectra are also temperature dependent. At 77°K a strong green luminescence was observed from the Hg₂Cl₂. Both Hg₂F₂ and Hg₂I₂ exhibited weak green emission, while no luminescence was observed from Hg₂Br₂ in this spectral region. The common orange luminescence is tentatively attributed to structural defects unique to mercurous salts, while the green emission is ascribed to an unspecified impurity center.     

Radiolysis of alkali halides

This paper reviews the extensive work pertaining to the creation of colour centres in alkali halides. After a brief historical survey the various mechanisms put forth to account for defect creation are examined in turn and the experimental evidence which supports or belies each of these is presented. After demonstrating from published experimental work that the defects created are of the Frenkel rather than the Schottky type and after consideration of the early stage, extrinsic coloration process, the Valey mechanism and its variants are discussed. Next, the direct displacement model proposed by Balarin is considered and, finally, the recent excitonic mechanism proposed by Pooley and Hersh is examined in detail. The conclusion reached is that, although the excitonic mechanism appears to be much the more preferable model yet proposed, a number of points need careful consideration and experimental study before it can be accepted as having general validity.     

Conformational analysis of allyl halides from the calculation of indirect spin-spin coupling

A theoretical study on the conformation of allyl halides from the calculation of nuclear spin-spin coupling constants by adopting the finite perturbation theory (FPT), is carried out in terms of the self-consistent, semi-empirical INDO (intermediate neglect of differential overlap) approximation of molecular orbital theory. Results of the calculations performed using ‘s’ and ‘p’ valence orbitals alone (‘sp’ basis) at INDO level approximation seem to replicate the experimental trend quite satisfactorily. Despite the overall agreement of the theoretical values with the experimental ones, the uncertainties in the INDO parametrization scheme lead to overestimation of certain coupling constants. The calculations also show that the orientation of the coupled protons with respect to the substituent halogen atom is an important factor to be considered.