Syntheses of diaza-18-crown-6 ligands containing two units each of 4-hydroxyazobenzene,benzimidazole, uracil,anthraquinone, or ferrocene groups

Six new diaza-18-crown-6 ligands each containing two aromatic side arms with responsive functions were prepared. Diaza-18-crown-6 containing two 4-hydroxyazobenzene ( 3 ) or two 4 -hydroxy- 4′ -(dimethyl-amino)azobenzene ( 4 ) substituents were prepared via a one-pot Mannich reaction. Diaza-18-crown-6 containing two benzimidazole ( 5 ), two uracil ( 6 ) or two 9,10-anthraquinone ( 7 ) substituents were prepared by treating the diazacrown with the appropriate chloromethyl-containing compound. Reductive amination using sodium triacetoxyborohydride, diaza-18-crown-6 and ferrocenecarboxaldehyde was used to prepare bisferrocene-substituted diaza-18-crown-6 ( 8 ). Interactions of compounds 3 , 5 , and 6 with Na⁺, K⁺, Ba²⁺, Ag⁺, and Cu²⁺ were evaluated by a calorimetric titration technique at 25° in methanol. All three ligands form more stable complexes with Ag⁺ and Cu²⁺ ( 5 forms a precipitate with Ag⁺) than with Na⁺ and K⁺. Ligand 5 also forms a highly stable complex with Ba²⁺.     

Dehalogenation of polymers prepared by atom transfer radical polymerization

Polymers prepared by atom transfer radical polymerization (ATRP) have well‐defined end groups, predetermined by the initiator used. A typical initiator is an alkyl halide from which the halogen is transferred to one chain end. To remove the halogen end group, dehalogenation with trialkyltin hydride has been used. Procedures for the removal of the polymer halogen end groups are described, one of them being a one‐pot reaction where the dehalogenation of the polymer chain ends occurs immediately after polymerization.     

Branched polyether with multiple primary hydroxyl groups: polymerization of 3-ethyl-3-hydroxymethyloxetane

Cationic polymerization of 3-ethyl-3-hydroxymethyloxetane gives branched, soluble macromolecules with multiple glycolic end groups. There are approximately 3–4 “normal” units per one branched unit.     

Kinetics and Characterization of Degradation Products of Dihydralazine and Hydrochlorothiazide in Binary Mixture by HPLC-UV,LC-DAD and LC–MS Methods

Dihydralazine and hydrochlorothiazide were stored at high temperature and humidity, under UV/Vis light and different pH, as individual drugs and the mixture. Then, a sensitive and selective HPLC-UV method was developed for simultaneous determination of dihydralazine and hydrochlorothiazide in presence of their degradation products. Finally, the degradation products were characterized through LC-DAD and LC–MS methods. Dihydralazine was sensitive to high temperature and humidity, UV/Vis light and pH?≥?7. At the same time, it was resistant to acidic conditions. Hydrochlorothiazide was sensitive to high temperature and humidity, UV/Vis light and changes in pH. Its highest level of degradation was observed in 1 M HCl. Degradation of the drugs was higher when they were stressed in the mixture. In the case of dihydralazine, the percentage degradation was 5–15 times higher. What is more, dihydralazine became sensitive to acidic conditions. Hydrochlorothiazide was shown to be more sensitive to UV/Vis light and pH?>?4. Degradation of dihydralazine and hydrochlorothiazide followed first-order kinetics. The quickest degradation of dihydralazine was found to be in 1 M NaOH while of hydrochlorothiazide was in 1 M HCl (individual hydrochlorothiazide) or at pH 7–10 (hydrochlorothiazide in the mixture). A number of new degradation products were detected and some of them were identified by our LC-DAD and LC–MS methods. In the stressed individual samples, (phenylmethyl)hydrazine and 1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide were observed for the first time. Interactions between dihydralazine and hydrochlorothiazide in the mixture were confirmed by additional degradation products, e.g., 2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1,4-trioxide.     

Heteroatom‐Doped Carbon Dots (CDs) as a Class of Metal‐Free Photocatalysts for PET‐RAFT Polymerization under Visible Light and Sunlight

A key challenge of photoregulated living radical polymerization is developing efficient and robust photocatalysts. Now carbon dots (CDs) have been exploited for the first time as metal‐free photocatalysts for visible‐light‐regulated reversible addition–fragmentation chain‐transfer (RAFT) polymerization. Screening of diverse heteroatom‐doped CDs suggested that the P‐ and S‐doped CDs were effective photocatalysts for RAFT polymerization under mild visible light following a photoinduced electron transfer (PET) involved oxidative quenching mechanism. PET‐RAFT polymerization of various monomers with temporal control, narrow dispersity (?≈1.04), and chain‐end fidelity was achieved. Besides, it was demonstrated that the CD‐catalyzed PET‐RAFT polymerization was effectively performed under natural solar irradiation.     

Spectrochemical Properties of Noncubical Transition Metal Complexes in Solution. XII. Angular Overlap Studies of Salicylideneethylenediamine Cu(II) Complex in Various Solvents

As a part of our general interest in the UV-Vis spectroscopy of multidentate mixed-donor ligands, the (salicylideneethylenediamine)Cu(II) complex has been prepared and characterized by elemental analyses, solubility in common solvents, molar conductivities, and ultraviolet (UV), and visible (Vis) spectroscopy. The combined results of spectrophotometric measurements and EPR spectra, as well as known the X-ray structure for solids, were used to determine the structure of the investigated complex in solutions. The spectra of [Cu(salen)] (H₂salen = salicylideneethylenediamine), were measured in various solvents at room temperature, resolved by Gaussian analysis, and angular overlap model (AOM) treated in C _2v symmetry. Because of overparametrization problems, the bis(salicylaldehyde)Cu(II) complex has been characterized and AOM treated. The results of this have been used for AOM studies of [Cu(salen)]. The effect of the solvents upon the - and -bonding ligand abilities is discussed.     

Thermogravimetry as a tool for measuring of fracturing fluid absorption in shales

A series of flame-retardant ethylene–vinyl acetate (EVA) composites with different contents of aluminum phosphate (AHP) and Trimer were prepared. The synergistic flame-retardant effects of the Trimer with AHP in EVA/AHP blends were studied by limiting oxygen index (LOI) tests, UL-94 tests, cone calorimeter tests, thermogravimetric analysis, and scanning electron microscopy (SEM). The LOI and UL-94 results showed that the system containing AHP and Trimer was very effective in improving the flame retardancy of EVA. When the mass ratio of AHP and Trimer was 3:1, the highest flame retardancy could be obtained, and when the flame-retardant loading was 30 wt%, the EVA/AHP/Trimer (7.5%) sample could achieve the V-0 rating in UL-94 tests, at the same time, its LOI value was 24.4%. The TG and DTG results showed that the addition of flame retardants catalyzes EVA decomposition in the first stage and generates a more stable char residue in the second stage. Consequently, an efficient reduction in the flammability parameters, such as heat release rate, total heat release, smoke production rate, and total smoke production could be observed. In addition, it was observed from the SEM observations of the morphological features that the AHP and Trimer combination, at the optimum proportion, could promote the formation of compact charred layers and prevent their cracking, which effectively protected the underlying materials from burning.     

The application of ultrafiltration for treatment of ships generated oily wastewater

The wastewaters collected from ships were preliminary separated in harbour installation into an oil fraction (slop oil) and the aqueous phase. The oil phase was then separated from slop oil, and the resulting water phase was subjected to the treatment in a coagulation/flotation process. The effluent (oil content 7–13 ppm) from these processes was further purified in biological wastewater treatment plant. A composition of bilge water is variable what affects the efficiency of coagulation/flotation process and the effluents may contain a significant amount of oil residues. The purification of effluents from coagulation/flotation process was performed in this work with ultrafiltration (UF), using FP100 membranes. The turbidity of obtained UF permeate was varied in the range of 0.08–0.26 NTU and the oil content was at a level of 0.9–1.1 ppm. Such purified water can be utilized for rinsing the oil–water separation devices located in the wastewater treatment plant, instead of tap water used so far. The obtained UF retentate contained 30 ppm of oil can be recycled to the coagulation/flotation process. Fouling of UF membranes was observed during the separation process, however, the FP100 membranes were effective cleaned with alkaline cleaning agents P3 Ultrasil 11.     

Multi-centred hydrogen bonds between water and perchlorate anion

Results of classical molecular dynamics simulations are presented for the re-orientational dynamics of water hydrogen bonded to perchlorate anion. Different mechanisms of bond formation are presented. Due to its regular tetrahedron geometry the perchlorate anion can make classical as well as bifurcated and trifurcated hydrogen bonds. The angular variation of water in the first solvation shell of perchlorate suggests the transitional character of multi-centred hydrogen bonds. As a result water molecules can slide around the anion.     

Ortho effect in the mass spectrometric behaviour of N(pyrimidin-4-yl)aminobenzoic acids and their methyl esters

Ortho-. meta- and para-isomers of N-(pyrimidin-4-yl)aminobenzoic acid and their methyl esters were investigated by electron impact mass Spectrometry. Their fragmentation was found to be strongly dependent on the position of the substituent in the aminobenzoic moiety. Two different kinds of ortho effect were studied and confirmed with the aid of deuterium-labelled derivatives.