Prediction of excess molar volumes of binary mixtures of organic compounds from refractive indices

The excess molar volumes of 51 binary mixtures containing diverse groups of organic compounds: alcohols (methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, and heptan-1-ol), (cyclo-) alkanes (hexane, heptane, octane, nonane, decane, undecane, dodecane, and cyclohexane), esters (diethyl carbonate and ethyl chloroacetate), aromatics (o-xylene, m-xylene, p-xylene, and ethylbenzene), ketones (acetone), and ethers (anisole), were predicted from the refractive index data, using three types of equations coupled with several different mixing rules for refractive index calculations: the Lorentz-Lorenz, Dale-Gladstone, Eykman, Arago-Biot, Newton, and the Oster. These systems were chosen since they belong to different classes of organic species forming molecular interactions and intermolecular forces during mixing resulting in positive or negative, smaller or larger deviations from ideal behaviour. The obtained results were analysed in terms of the applied equation and mixing rule, the nature of compounds of the mixtures and the influence of alkyl chain length of the alkane or alcohol molecule. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Methyl 2‐benzamido‐4‐(3,4‐dimethoxyphenyl)‐5‐methylbenzoate and N‐{5‐benzoyl‐2‐[(Z)‐2‐methoxyethenyl]‐4‐methylphenyl}benzamide

Methyl 2‐benzamido‐4‐(3,4‐dimethoxyphenyl)‐5‐methylbenzoate, C₂₄H₂₃NO₅, (Ia), and N‐{5‐benzoyl‐2‐[(Z)‐2‐methoxyethenyl]‐4‐methylphenyl}benzamide, C₂₄H₂₁NO₃, (IIa), were formed via a Diels–Alder reaction of appropriately substituted 2H‐pyran‐2‐ones and methyl propiolate or (Z)‐1‐methoxybut‐1‐en‐3‐yne, respectively. Each of these cycloadditions might yield two different regioisomers, but just one was obtained in each case. In (Ia), an intramolecular N—H...O hydrogen bond closes a six‐membered ring. A chain is formed due to aromatic π–π interactions, and a three‐dimensional framework structure is formed by a combination of C—H...O and C—H...π(arene) hydrogen bonds. Compound (IIa) was formed not only regioselectively but also chemoselectively, with just the triple bond reacting and the double bond remaining unchanged. Compound (IIa) crystallizes as N—H...O hydrogen‐bonded dimers stabilized by aromatic π–π interactions. Dimers of (IIa) are connected into a chain by weak C—H...π(arene) interactions.     

Effect of reactive gas pressure on the plasma parameters during triode ion plating of Cr−C films

Mechanical properties and the average chemical composition of Cr?C hard coatings deposited by means of triode ion plating strongly depends on the partial pressure of the reactive gas (C₂H₂) during the deposition. The partial pressure of the acetylene has to be higher (\(p_{C_2 H_2 } = 1.5 \times 10^{ - 3} mbar\)) and much tighly controlled than the partial pressure of N₂ during the deposition of CrN. The shape of energy spectra measured by PPM 421 are similar in both cases, with the energy peak at about 50 eV. This energy corresponds to theU _pl and to the potential measured on the crucible. The intensity of ions originating from the C₂H₂ is much lower than the intensity of nitrogen ions. Only the¹²C⁺, CH _x ^Emphasis>+ group and C ₂ ⁺ ions were definitely detected.     

Optimization of Bioactive Phenolics Extraction and Cosmeceutical Activity of Eco-Friendly Polypropylene-Glycol–Lactic-Acid-Based Extracts of Olive Leaf

Olive leaf is a rich source of phenolic compounds with numerous activities related to skin health and appearance. In this study, a green extraction method was developed using eco-friendly solvents: polypropylene glycol (PPG), lactic acid (LA), and water. The optimal extraction conditions were established, including solvent, extraction time, technique (magnetic stirrer vs. ultrasound-assisted extraction), and herbal material/solvent ratio. The composition of the solvent mixture was optimized using a mixture design. The content of phenolic compounds, including oleuropein and verbascoside, was determined using high-performance liquid chromatography (HPLC) and spectrophotometric methods. Using different extraction conditions, three extracts were prepared and their phytochemical compositions and antioxidant and skin-related bioactivities were investigated. The extracts were excellent inhibitors of elastase, collagenase, tyrosinase, and lipoxygenase. The best activity was shown by the extract richest in phenolics and prepared using magnetic-stirrer-assisted extraction for 20 min, with 0.8 g of herbal material extracted in 10 mL of PPG/LA/water mixture (28.6/63.6/7.8, w/w/w), closely followed by the extract prepared using the same extraction conditions but with 0.42 g of herbal material. The investigated PPG/LA/water mixtures contributed to the overall enzyme-inhibitory activity of the extracts. The prepared extracts were appropriate for direct use in cosmetic products, thus saving the time and energy consumption necessary for the evaporation of conventional solvents.     

One-pot synthesis of some 2H-Pyran-2-one derivatives

A one-pot synthesis of various 2H-pyran-2-one derivatives 5–19 starting from methyl ketones 1 , N,N-dimethylformamide dimethyl acetal and N-acylglycines 3 in acetic anhydride is described.     

Synthesis of 1-aryl-1-phenylpropenes using an alkylation-rearrangement-methylation-isomerization one-pot reaction sequence

(Z/E)-1-(2-Methoxyaryl)-1-phenylpropenes have been prepared in good yields by heating a mixture of a phenolic substrate, cinnamyl chloride, tetramethylammonium chloride and K₂CO3 in polyethyleneglycol at 180°C. The one-pot synthesis proceeds through four discrete reaction steps: alkylation of the phenol with cinnamyl chloride, Claisen rearrangement, O-methylation and double-bond migration. The configuration of one crystalline product was determined using a single-crystal X-ray diffraction analysis. The thermodynamic and structural features of the products were evaluated using computational chemistry techniques.      

Synthesis of some N-substituted isonicotinamides

A one-pot transformation of some cyclic 1,3-dicarbonyls 1 with N-(isonicotinoyl)glycine 2 and one-carbon synthons in acetic anhydride to the corresponding N-substituted isonicotinamides (pyridine-4-carbox-amides) 7-9 containing a fused pyran-2-one ring is described. Compound 8 was further converted with some nitrogen-containing nucleophiles either to the corresponding quinoline- 2,5 -diones 10-11 or 5-hydra-zonobenzopyran-2-ones 14-15. Under more severe conditions the compound 8 gave with hydrazine 5-hydrazonoquinoline derivative 12 or even 13 . Hydrazoic acid transformed compound 8 to the pyrano-[3,2-c]azepine system 16 . Diazotization of 1-amino derivative 10 gave deaminated product 11.     

Application of energy dispersive X‐ray fluorescence spectrometry for the characterization of plastic materials in synthetic polymer conservation work

Plastic artifacts archived in museums deteriorate with time and require proper care by conservators to prevent their degradation and to maintain the objects in good condition. Degradation processes depend on the type of plastic and conditions of storage. Knowledge of the chemical composition of plastic artifacts is thus very important and facilitates conservation work. The capabilities of energy dispersive X‐ray fluorescence spectrometry with monochromatic excitation were investigated for possible characterization of the plastic materials used in artifacts from museum collections. For this purpose, a simple and suitable nondestructive analytical protocol was developed on the basis of the intensity of the coherent and the incoherent scattered excitation radiation from artifacts, compared with scattering from typical plastic materials such as polyethylene, polyvinyl chloride, and polypropylene. Fifteen plastic artifacts, such as souvenirs, household wares, and toys, were characterized in this way according to their chemical composition. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and characterization of new triazenide salts

Stable triethylammonium triazenide salts were obtained on treatment of the appropriate triazenes with triethylamine. Those salts are described and fully characterized for the first time and are used for the preparation of alkoxycarbonylvinyltriethylammonium triazenides, which are prone to transesterification.     

The influence of hard-baking temperature applied for SU8 sensor layer on the sensitivity of capacitive chemical sensor

SU8, the near-UV photosensitive epoxy-based polymer was used as a sensor layer in the capacitive chemical sensor, ready for integration with a generic double-metal CMOS technology. It was observed that the response of the sensor slowly increases with the temperature applied in hard-baking process as long as it remains below 300°C. At this temperature the response of the sensor abruptly increases and becomes almost threefold. It was shown that fully crosslinked structure of the sensor layer becomes opened and disordered when the sensor is hard-baked at temperatures between 300°C and 320°C, that is, still well below the degradation temperature of the polymer. These changes in chemical structure were analyzed by Fourier-transform infrared spectroscopy. The temperature-dependent changes of the sensor layer structure enable one to prepare a combination of capacitive chemical sensors with good discrimination between some volatile organic compounds.