Effect of temperature and concentration on the structure of tert-butyl alcohol/water mixtures: near-infrared spectroscopic study

The effect of temperature and concentration on the structure of tert-butyl alcohol/water binary mixtures in the alcohol-rich region (X(H2O) < 0.3) has been studied by using Fourier transform near-infrared (FT-NIR) spectroscopy. The obtained results demonstrate that the addition of a small amount of water to tert-butyl alcohol (2-methyl-2-propanol, abbreviated as TBA) leads to minor changes in the structure of neat TBA and suggest that molecules of TBA in the mixture are in the same environment as those in pure TBA. The bands of water are red-shifted in the mixture relative to bulk water, implying that the molecules of water in TBA are involved in stronger hydrogen bonding. The present experimental data give no evidence for the existence of nonbonded water in the mixture. Even at a very low content of water, the main NIR bands of water (nu(2) + nu(3) and nu(1) + nu(3)) have two components showing markedly different behavior upon an increase in temperature. From the power spectra, it is seen that the extent of intensity changes due to the free OH groups of TBA is smaller in the mixture relative to pure TBA. All of these results support the model of chain-end bonding of water molecules to TBA associates. An increase in X(H2O) reduces the population of nonbonded OH groups of TBA, yet both processes do not appear at the same rate. The amount of bonded OH groups of water increases faster than that of the nonbonded ones. It seems that the water-water interaction becomes more important as X(H2O) increases. At high alcohol content, the position of the CH alkyl stretching bands is constant, evidencing a negligible role of the hydrophobic hydration in the mixture.     

Interactions of temperature-responsive anionic polyelectrolytes with a cationic surfactant

The interactions of temperature-responsive copolymers of sodium 2-acrylamido-2-methyl-1-propanesulfonate (AMPS) and N-isopropylacrylamide (NIPAM) with a cationic surfactant, dodecyltrimethylammonium chloride (DTAC), have been studied. The content of AMPS in the copolymers ranged from 1.1 to 9.6 mol%. The surface activity was higher for the polymers with lower AMPS content. It was found that DTAC undergoes association with the polymer chain, forming mixed polymer-surfactant micelles. The values of cac for the polymers were found in fluorescence studies using pyrene as the fluorescent probe. They were in the range 0.9-3.6x10(-3) M and were lower for polymers with higher AMPS content. An increase in DTAC concentration up to about its cmc results in a decrease of the LCST (lower critical solution temperature) of the copolymers, while further increase above the cmc results in an increase of the LCST. The minimum value of LCST in the presence of the surfactant is lower than the LCST of NIPAM homopolymer.     

Expansion of the aromatic part of Cinchona alkaloids. Annulation of quinolines with phenoxazine motifs

An oxidative cross-coupling strategy for quinoline ring annulation in Cinchona alkaloids has been developed. Key-reaction optimization by changing oxidants and adjusting the nucleophilicity of the 2-aminophenols led to cupreine and cupreidine expanded with the phenoxazinone unit in 56–75% yield. The stereochemical integrity of the obtained alkaloid structures was confirmed by combined experimental and computed CD and NMR data. The conformational study revealed a fast equilibrium of the three conformers, differing in the orientation of the pyrido[a-3,2]phenoxazine moiety.     

The synthesis of 1-biphenyl-4-alkyl-[1,2,3]-triazoles and their mesomorphic behaviour

A series of 1-biphenyl-4-alkyl-[1,2,3]-triazole-based liquid crystal compounds were synthesised via a fast and efficient microwave mediated ‘Click Reaction’ and their phase behaviour is presented. Most of the 1-(3-fluorobiphenyl)-4-alkyl-[1,2,3]-triazole compounds exhibited a smectic A phase with relatively low transition temperatures compared to previously examined aryl-triazole-based mesogens. Small angle X-ray scattering measurement indicated the existence of deep smectic phase for some cases. Structural variations gave rise to different phase behaviour in these triazole-based compounds.     

Improved Protocol for Mononitration of Phenols with Bismuth(III) and Iron(III) Nitrates

A simple and efficient multigram procedure was developed for the selective mononitration of various activated phenols. The reaction proceeded smoothly with 0.5 equivalents of Bi(NO₃)₃ · 5H₂O or Fe(NO₃)₃ · 9H₂O in acetone at ambient temperature or at reflux. The desired products were isolated in 62–93% total yield and essentially no overnitrated compounds were detected.     

Micro 2D-TLC of Selected Plant Extracts in Screening of Their Composition and Antioxidative Properties

Micro two-dimensional separations were performed on polar bonded stationary phases of the type cyanopropyl-silica using non-aqueous eluents (polar modifier dissolved in n-heptane) as the first direction eluents and aqueous eluents (organic modifier—MeOH dissolved in water) as the second direction eluents. The chromatographic process was performed in micro scale using 5 × 5 cm plates, small volumes of eluents and 10 μL of plant extracts to obtain satisfying separation. Plates developed in horizontal chambers were dried and observed in UV light (254 nm and 366 m) photographed by digital camera and derivatized by DPPH to detect antioxidants (free radical scavengers) or derivatized by Naturstoff reagent to detect phenolic compounds (characteristic luminescence of some phenolic compounds). The above experiments give the possibility to construct fingerprints for investigated Polygonum hydropiper, Betula verrucosa and Pulmonaria officinalis extracts. It can be used in quality control of the plant material and its antioxidative activity. Novelty of the paper is the micro-scale of the separation by two-dimensional thin layer chromatography mode. For the first time two-dimensional separation of plant extracts on 5 × 5 cm plates in two directions is performed.     

Secondary electron microscopy and transmission electron microscopy studies of carbon nanotubes in C-Ni films

Carbon nanotubes films have been studied with SEM and TEM. The studied films were obtained using a two step method: PVD process and CVD process. Strongly defected and curled carbon nanotubes containing Ni nanoparticles formed the film with thickness of about 300–400 nm. Observed carbon nanotubes were of lengths from 100 nm to 300 nm and did not stick to each other.