Application of quasi-equilibrated thermodesorption of hexane and cyclohexane for characterization of porosity of zeolites and ordered mesoporous silicas

Quasi equilibrated temperature programmed desorption and adsorption (QE-TPDA) of hexane and cyclohexane was applied for characterization of zeolites 5A, ZSM-5, 13X, Y, NaMOR and ordered mesoporous silicas MCM-41, MCM-41/TMB, SBA-15 and HMS. Similar QE-TPDA profiles of hexane and cyclohexane with a single desorption maximum were observed for the wide pore zeolites. No adsorption of cyclohexane for zeolite 5A and a single desorption maximum for ZSM-5 were found, while two-step desorption profiles of hexane were observed for these zeolites. Similar values of the adsorption enthalpy and entropy of hexane and cyclohexane were obtained by fitting the Langmuir model functions for the zeolites X and Y. For NaMOR and ZSM-5 larger differences in these parameters were found. A single desorption peak found at low temperatures in the QE-TPDA profiles of hexane and cyclohexane for the studied silicas was attributed to the multilayered adsorption on their mesopore surface. The adsorption isobars calculated from the thermodesorption profiles were fitted with the BET function. This way values of the specific surface area and the adsorption heat were calculated. Additionally values of the initial heat of adsorption were found by fitting the Henry’s law to the high-temperature sections of the linearized isobars. The largest deviations from the BET and Henry functions and the largest values of the adsorption heats found for SBA-15 indicated the greatest heterogeneity of the adsorption sites on its surface.     

The charging of the carbon nanotube/oligothiophene interphase as studied by in situ electron spin resonance/UV-Vis-NIR spectroelectrochemistry

A detailed in situ Electron Spin Resonance (ESR)/UV-Vis-NIR spectroelectrochemical study of the oligothiophene/single walled carbon nanotube (SWCNT) interphase is presented to provide an insight into the interaction of nanotubes with oligothiophenes. Used as electrode materials these composites are followed in situ with respect to the paramagnetic and diamagnetic states formed upon electrochemical charging. The variation of the oligomer chain length and the type, position and number of substituents at the oligomer is used to understand the structural influence on the formation of the charged states in the material upon electrochemical reaction. For β,β'-dihexylsexithiophene (β,β'-DHST)-SWCNT the enlarged current in the composite and a decreased radical cation concentration can be explained by the formation of π-dimers. By interaction with SWCNTs the π-dimerization of oligothiophenes and the formation of multi π-stack structures occur. For α,ω-dicyano-β,β'-dibutylquaterthiophene (DCNDBQT)-SWCNT a new paramagnetic structure of the oligomer is formed as an intermediate which undergoes follow-up reactions. Using different substituted oligothiophenes their interaction with nanotubes can be understood with respect to the structure of the oligomer.     

Synthetic studies on the solanacol ABC ring system by cation-initiated cascade cyclization: implications for strigolactone biosynthesis

We report a new method for constructing the ABC ring system of strigolactones, in a single step from a simple linear precursor by acid-catalyzed double cyclization. The reaction proceeds with a high degree of stereochemical control, which can be qualitatively rationalized using DFT calculations. Our concise synthetic approach offers a new model for thinking about the (as yet) unknown chemistry that is employed in the biosynthetic pathways leading to this class of plant hormones.     

Quantification of omega-3 fatty acids in dietary supplements and cooking products available on the polish market by thin-layer chromatography—densitometry

JPC – Journal of Planar Chromatography – Modern TLC - The effect of omega-3 fatty acids in the human body is multidirectional. They are used in cancer and cardiovascular disease...     

Diastereoselective lower rim (1S)-camphorsulfonylation as the shortest way to the inherently chiral calix[4]arene

[structure: see text]. A diastereomeric mixture of chiral 25-(1S)-camphorsulfonyloxy-26-isopropoxycalix[4]arene 2a (de 15%) and 25-isopropoxy-26-((1S)-10-camphorsulfonyl)calix[4]arene 2b has been obtained by asymmetrical lower rim (1S)-camphorsulfonylation of the monoisopropoxycalix[4]arene. Pure diastereomer 2a has been obtained by simple crystallization, and its absolute configuration has been determinated by X-ray analysis. Enantiomerically pure inherently chiral 5,11-dibromo-26-isopropoxycalix[4]arene 4 has been synthesized by the upper rim dibromination of the diastereomer 2a followed by hydrolytical removal of the auxiliary camphorsulfonyl group.     

Synthesis and Use of 6-, 7-and 8-Membered P-Heterocycles

The synthesis of new families of P-heterocycles by reductive modifications, ring enlargement and Diels-Alder cycloaddition is described.     

Kinetics of nitric oxide oxidation

Nitrogen oxides are nowadays a subject of global concern. Several types of nitrogen oxides exist in the environment: N₂O, NO, NO₂, N₂O₃, N₂O₄, N₂O₅. The abbreviation NO _x usually relates to nitric oxide NO, nitrogen dioxide NO₂, and nitrous oxide N₂O. The first two are harmful pollutants for both environment and human health, whereas the third is one of the greenhouse gases. Implementation of stringent NO _x emission regulations requires the development of new NO _x removal technologies from exhaust gases. One of many proposals for NO _x emission reduction is the application of an oxidizing agent which would transform NO _x to higher nitrogen oxides with higher solubility in water. The main objective of the paper was to present the rate constant of nitric oxide oxidation, determined in our studies.     

Organoboron water,part I: Synthesis and multinuclear magnetic resonance studies on the structure of tetramethyldialuminoxane

The structure of tetramethyldialuminoxane was studied. The low‐temperature ¹H and ¹³C NMR spectra suggest that the methyl groups bridge the aluminum atoms in the dialuminoxane trimer. A new method of synthesis of methylaluminoxanes and tetramethyldialuminoxanes in the reaction of tetraethyldiboroxane (organoboron water) with trimethylaluminum (1:1 and 1:2 respectively) was applied to synthesize the investigated system. Copyright © 2004 John Wiley & Sons, Ltd.     

[(8a,9,9a‐η)‐9‐(η5‐Cyclopentadienyl)‐9‐nickelafluorenyl](η5‐pentamethylcyclopentadienyl)nickel(II)

The title compound, [Ni₂(C₅H₅)(C₁₀H₁₅)(C₁₂H₈)] or [Ni(C₁₀H₁₅){Ni(C₅H₅)(C₁₂H₈)}], is a rare example (and the first obtained from nickelafluorenyllithium) of an analogue of nickelocene in which the central Ni atom is coordinated to one pentamethylcyclopentadienyl ring and one nickelafluorenyl ring. Both rings lie almost parallel to one another: the dihedral angle between the planes which include these rings is 4.4 (1)°. Slip parameter analysis indicates that the bonding mode of the central Ni atom to the nickelacyclic ring is between η³ and η⁵. Two‐dimensional layers of molecules are formed by C—H...π interactions.     

Milk Proteins—Their Biological Activities and Use in Cosmetics and Dermatology

Milk and colostrum have high biological potential, and due to their natural origin and non-toxicity, they have many uses in cosmetics and dermatology. Research is ongoing on their potential application in other fields of medicine, but there are still few results; most of the published ones are included in this review. These natural products are especially rich in proteins, such as casein, β-lactoglobulin, α-lactalbumin, lactoferrin, immunoglobulins, lactoperoxidase, lysozyme, and growth factors, and possess various antibacterial, antifungal, antiviral, anticancer, antioxidant, immunomodulatory properties, etc. This review describes the physico-chemical properties of milk and colostrum proteins and the natural functions they perform in the body and compares their composition between animal species (cows, goats, and sheep). The milk- and colostrum-based products can be used in dietary supplementation and for performing immunomodulatory functions; they can enhance the effects of certain drugs and can have a lethal effect on pathogenic microorganisms. Milk products are widely used in the treatment of dermatological diseases for promoting the healing of chronic wounds, hastening tissue regeneration, and the treatment of acne vulgaris or plaque psoriasis. They are also increasingly regarded as active ingredients that can improve the condition of the skin by reducing the number of acne lesions and blackheads, regulating sebum secretion, ameliorating inflammatory changes as well as bestowing a range of moisturizing, protective, toning, smoothing, anti-irritation, whitening, soothing, and antiaging effects.