Solid state a.c. conductivity and FT-IR spectral analyses for the conflicting effects of proton mobility and association in some azophenol derivatives of cyclic phosphazene

Variable strength H-bonding affects the mobility and so electric conduction of protons differently. Also, variable extent mesomerism modifies electric conduction with varying dielectric features. Both these molecular modifiers are properly cited using azophenol derivatives as model compounds for discussion of their consequences in the varying features of electric conduction. The electric permittivity shows low-frequency dispersion characteristic of ionic conduction over mobile charge carries; the mobility shifts at a critical temperature T _c, being structure dependent. The frequency-dependent Z′′-Z′ layout changes with temperature from linear at low temperatures to semicircular above T _c within a frame of temperature-sensitive dipole-ionic mediated conduction. The a.c. conductivity, σ_ac, increases with frequency and temperature and becomes frequency insensitive, like d.c. conductivity, σ_dc, above the T _c because of the escalating contribution from the d.c. conduction. The mesomeric structure seems to prompt a dipole-based electric conduction of high relaxation energy over the strongly associated phenolic protons that may be thermally activated above the T _c into a much lower relaxation energy protonic conduction of up to two orders higher conductivity. The protonic conduction emerges at a T _c that falls with a drop in the relaxation energy following a similar order of increasing proton mobility and mesomerism in the azophenol derivatives: azocatechol>azoquinol>azoresorcinol. On the molecular level, variable temperature infrared spectroscopy reveals higher proton mobility and mesomerism for the azocatechol derivative that demonstrates its higher protonic conductivity at lower T _c and relaxation energy, compared to the azoquinol and azoresorcinol derivatives. This is well verified in the light of conflicting intramolecular H-bonding that assists the proton mobility in azocatechol whereas it associates the protons in azoresorcinol more than in azoquinol. Electronic Publication     

Microwave-assisted extraction of zearalenone from wheat and corn

A microwave-assisted extraction (MAE) method has been developed for determination of zearalenone in wheat and corn by LC-MS with an atmospheric pressure chemical ionization interface (APCI). Matrix effects were minimized by use of matrix-matched standard curves for quantification of the analyte. The limit of quantification (LOQ) of the method was 30 ng g(-1) in wheat and 20 ng g(-1) in corn. The rapid LC-MS method enabled analysis of the extracts without clean-up, thereby reducing analyte losses, the time required for the analytical procedure, and costs. A factorial design approach was used to examine the effect on extraction efficiency of the main extraction conditions - time, temperature, and solvent. On the basis of results from statistical assessment extraction was performed with 1:1 (v/v) methanol-acetonitrile at 80 degrees C for 5 min. When these extraction conditions were applied to a wheat sample from a recently conducted international proficiency test, 92% (103 ng g(-1)) of the assigned zearalenone concentration (112 ng g(-1)) in the test material was obtained. This result was within the uncertainty (u) range of the assigned value of the test material (u=+/-15.8 ng g(-1), alpha=0.05) thereby demonstrating the accuracy of the method was sufficient. The precision of the whole method was also confirmed to be adequate, because the observed relative standard deviation (RSD) of 12% (n=10) also fulfils the quality criteria recommended by European guidelines for in-house method validation.     

Mathematical studies of Kekulé structures

The perfect matching vector and forcing and the Kekulé-vector of cata-benzenoids are defined. Two theorems are given which set the sufficient and necessary conditions for HKZ-vector (Harary et al. J Math Chem 6:295, 1991) and Kekulé-vector in cata-benzenoids. Additional two theorems are obtained which give sharp bounds for the modules of HKZ- and Kekulé vectors. Dedicated to Professor Tadeusz Marek Krygowski on the happy occasion of his 70th birthday.     

Chemische Vitamin D<Subscript>3</Subscript>-Bestimmung in Lebertran

The different aspects of Vitamin D₃ determination and the data reported in the literature are discussed. The spectrophotometric determination of Vitamin D₃ in cod-liver oil is carried out after the alkaline saponification, extraction of unsaponified parts, precipitation of accompanying sterols and the column- and thin-layer chromatographic purification and separation of vitamin D₃ on 40 cm plates from other vitamins. The dyestuff α-naphtholbenzein is suited well as standard substance for the better location and identification of vitamin D₃ zone on the thin-layer plate. The results obtained from the chemical method were checked through the simultaneous biological determination.     

Die Umlagerung substituierter Aminoacrylderivate. Präparative anwendungsbreite

The addition of carboxylic acids to dimethylamino-propinal ( 1a ) and 4-dimethyl-amino-but-3-in-2-on ( 1b ) gives, after rearrangement of the very instable primary adducts ( 2 ), Z-3-acetoxy-N,N-dimethylacrylamides and -crotonamides 3 to 8 in excellent yields and in a stereospecific manner. Similarly, the adducts of HCl and HBr to the alkynes 1a and 1b may be rearranged at low temperature by traces of acid to cis/trans equilibria of 3-halo-acrylamides and -crotonamides 9 and 10 . - On the other hand, treatment of 3-alkoxy-3-dimethylaminoacrolein with traces of acid yields alkylesters of E-3-dimethylaminoacrylic acid ( 12 , X = OR). - The preparative aspects of the rearrangement are discussed, and a brief outline of the spectroscopic properties of the compounds 3 to 8 is given.     

Inclusion-dependent mechanism of modification of cyclodextrins with heterocycles

Mono(6-deoxy-dimethylpyridinium)-β-cyclodextrins have been synthesized in reaction of mono (p-toluenesulfonyl) derivative of β cyclodextrin with the appropriate lutidine under microwave irradiation and conventional conditions. The results indicate that the mechanism consists of inclusion complex formation.     

Analysis of urban dust (PM<Subscript>2</Subscript>/PM<Subscript>10-2</Subscript>) in Daejeon city by instrumental neutron activation analysis

Summary As part of an air pollution monitoring study, airborne particulate matter (PM₂/PM_10-2) samples were collected from 2000 to 2003 at two sampling sites in an urban region, Daejeon, the middle of Korea. Mass concentrations of both fine and coarse fractions and that of the black carbon in the fine particles were measured using the Gent stacked filter unit sampler and the smoke stain reflectometer, respectively. In the collected samples the concentrations of 24 elements were analyzed using instrumental neutron activation analysis. Monitored data were investigated for their temporal trends under different environmental conditions and their seasonal correlation patterns. Crustal enrichment factors were also estimated to establish the contribution between anthropogenic and crustal origin. Patterns for airborne particle matter (APM) and elemental concentrations, seasonal variation of some marker elements were investigated. The results can be applied for the investigation of further air pollution sources and for the evaluation of air quality.     

CdSe and CdSe/CdS nanorod solids

We demonstrate the self-organization of CdSe nanorods into nematic, smectic, and crystalline solids. Layered colloidal crystals of CdSe nanorods grow by slow destabilization of a nanocrystal solution upon allowing the diffusion of a nonsolvent into the colloidal solution of nanocrystals. The colloidal crystals of nanorods show characteristic birefringence, which we assign to specific spherulite-like texture of each nanorod assembly. To demonstrate the general character of nanorod self-assembly technique, CdSe/CdS heterostructure nanorods were organized into highly luminescent superlattices.     

Some Comments on the Matter Wave-light Wave Hypothesis

From the de Broglie matter wave hypothesis and Planck’s energy quantization law, and assuming conservation of energy in the absorption of a photon and its consequent conversion to kinetic energy of motion by a material particle initially at rest, one can deduce a simple mathematical relationship between the wavelength λ (or frequency ν), of the photon absorbed by the particle at rest, and the resulting de Broglie matter wave length, λ_D, of the particle with kinetic energy of motion of mv²/2. The relationship so deduced, λ_D∝√λ, suggests that visible wavelengths of light, from about 4000 ?, in the violet, to beyond about 7000 ?, in the red, on absorption by an electron at rest, lead to material electron wavelengths, λ_D, of the order of the size of the electron transfer proteins seen in the photosynthetic reaction centers of photosynthesizing organisms, at about a size of 50–100 ?. In addition to understanding the mechanism of photosynthesis as a material wave mediated phenomenon, further areas of importance of the relations pointed out in this paper are in the design of experiments to gain a deeper understanding of the basic tenets of wave mechanics, and in the use of tunable lasers to probe various properties of material waves, and to precisely control their properties for applications including lithography.     

Synthesis and polymerizability of 7,8-dicyano-7,8-diphenylquinodimethane

7,8-Dicyano-7,8-diphenylquinodimethane (DCDPQ) was prepared by oxidation of the dianion of α,α′-dicyano-α,α′-diphenylxylene. ¹H-NMR of a solution of the purified compound showed that the cis and trans isomers were present in a 1:1 ratio. Following further spectroscopic and electronic characterization the polymerizability of the title compound was investigated. DCDPQ did not homopolymerize at 65°C in the presence of AIBN. DCDPQ copolymerized with p-methoxystyrene and p-aminostyrene in the presence of AIBN at 65°C. Characterization of the latter two copolymers indicated that they were nearly alternating. The copolymerization between DCDPQ and p-aminostyrene proceeded in the absence of AIBN.