N-Bromosuccinimide (NBS) catalyses the ring opening of various epoxides with different thiols in CH3CN at room temperature under mild reaction conditions. The corresponding β-hydroxysulphides are obtained in short reaction times and in good to high yields with nearly complete regioselectivity. The catalyst was compared with previously reported catalysts and only one that we have found [B(C6F5)3] gave the same regioselectivity, but the reaction time was much longer (4 h versus 5 min) and the yield was considerably lower. Zn(ClO4)2·6H2O gave slightly lower selectivity but higher yields. The reaction time was about 12 times longer.
A new diterpenoid, (13S)-9α,13α-epoxylabda-6β(19),15(14)diol dilactone (1), was isolated from Leonotis leonurus and the structure determined via NMR analysis. The compound causes significant changes in blood pressure of anaesthetized normotensive rats and exhibits a negative chronotropic effect.
Nitration of 4-hydroxybenzaldehyde afforded 2,6-dinitro-4-hydroxybenzaldehyde 2, which in the presence of thionyl chloride is converted to 4-chloro-2,6-dinitrobenzaldehyde 3. This compound is very reactive towards nucleophiles, and reacts easily with methoxyamine, affording the intermediate 4-aminomethoxy-2,6-dinitrobenzaldehyde 4. Reaction of 4 with N-t-butylhydroxylamine led to a new spin trap of the nitrone type, namely 4-aminomethoxy-3,5-dinitrophenyl-1-t-butylnitrone 6. The spin-trapping capabilities of the new compound have been tested in a classical system, in which short-lived radicals were generated by irradiation. The new compound 6 contains an acidic proton with a pKa value of 7.8, and removal of this by a base induces a colour change, from yellow to green-blue. In a similar way, a new stable nitronyl-nitroxide radical 8 has been obtained from the intermediate 4.
The dissolution of Icel-Aydincik dolomite in aqueous hydrochloric acid solution was investigated with respect to the effects of acid / dolomite mole ratio, solid / liquid ratio, particle size, stirring speed, time and temperature. It was observed that solubility of the dolomite ore increased with increasing acid / dolomite mole ratio, stirring speed, period of time, temperature, and with decreasing solid / liquid ratio and particle size. A kinetic model was applied to describe the dissolution and to analyse the kinetic data. By analysis of the experimental data, it was determined that the leaching process was controlled by the chemical surface reaction. The apparent activation energy of the leaching process was found to be 31.98 kJ mol-1.
Degradation studies of β-cyclodextrin polymers cross-linked with toluene-2,4-diisocyanate (TDI) and hexamethylene diisocyanate (HMDI) were carried out by exposing the polymers to different soil types for up to 120 days. The aim of the study was to determine the fate of these novel polymers in the environment. The polymers were either digested with sulphuric acid prior to performing a soil burial test or buried undigested. Results from the study indicate that the β-CD / TDI polymers with aromatic links underwent a greater mass loss during soil burial when first digested in sulphuric acid (ca. 50 % maximum mass loss). The β-CD / HMDI polymers, on the other hand, underwent the same mass loss for both the digested and undigested polymers (ca. 30 % maximum mass loss). Although the Fourier transform infrared (FTIR) spectroscopy data suggested no changes in the overall polymer structures, the scanning electron microscopy (SEM) micrographs revealed changes in the surface morphology of the polymers. Moreover, results of thermogravimetric analysis (TGA) point to polymer degradation under all conditions tested.
2-Alkylsubstituted benzimidazoles (3a-h) were prepared from the acid-catalyzed reaction of 4-methyl-1,2-phenylenediamine with corresponding carboxylic acids. Addition of these benzimidazoles to N-chloromethylbenzotriazole in the presence of sodium amide under reflux conditions gave the novel benzimidazole-substituted benzotriazoles (5a-f). IR and 1HNMR spectroscopy and elemental analysis were used for the identification of these compounds.
The three title reductant systems have significant advantages in generating aldehydes fromnitriles. These include : the utilization of convenient hydrogen sources, namely, sodium hypophosphite monohydrate and formic acid, respectively, and of the relatively inexpensive Raney nickel and Raney (Ni/Al) alloy; the convenience of conducting the reaction(s) in aqueous media at ambient temperatures and pressures, and avoiding the use of trapping agents (except when transforming glycosyl nitriles (vide infra)) and of hydrogen cylinders. Numerous examples of the utilization of the title systems are presented (mostly from the more recent literature) that demonstrate the utility of the respective methods in transforming a solo cyano group, or when accompanied by other chemosensitive functions in a structure, to the corresponding aldehyde. Such substrates include benzonitriles, glycosyl nitriles, O-, N- and S-containing heterocyclic nitriles, aliphatic-aromatic situations, and more complex fused heterocyclic and carbocyclic scaffolds. The review reports modifications of the title methods and several notable steric effects.
LiNi0.5Mn1.5O4 compounds were prepared through a solid-state reaction using various Ni precursors. The effect of the precursors on the electrochemical performance of LiNi0.5Mn1.5O4 was investigated. LiNi0.5Mn1.5O4 made from Ni(NO3)26H2O shows the best charge-discharge performance. The reversible capacity of LiNi0.5Mn1.5O4 is about 145 mA h g-1 and remained at 143 mA h g-1 after 10 cycles at 3.0 to 5.0 V. The XRD results showed that the precursors and dispersion method had significant effects on their structures. Pure spinel phase can be obtained with a high energy ball-milling method and Ni(NO3)26H2O as precursor. A trace amount of the NiO phase was detected in LiNi0.5Mn1.5O4 with the manual grinding method when Ni(CH3COO)26H2O, NiO and Ni2O3 were used as precursors.