The chemical reaction of 4-bromobenzoylchloride and 2-aminothiazole in the presence of potassium thiocyanate yielded a white solid formulated as C 15 H 10 BrN 3 OS 2 , which consists of ...4-bromobenzamido and 2-benzothiazolyl moieties connected by a thiourea group. The 4-bromobenzamido and 2-benzothiazolyl moieties are in a trans conformtion (sometimes also called s -trans due to the single bond) with respect to the N—C bond. The dihedral angle between the mean planes of the 4-bromophenyl and the 2-benzothiazolyl units is 10.45 (11)°. The thiourea moiety, —C—NH—C(=S) —NH— fragment forms a dihedral angle of 8.64 (12)° with the 4-bromophenyl ring and is almost coplanar with the 2-benzothiazolyl moiety, with a dihedral angle of 1.94 (11)°. The molecular structure is stabilized by intramolecular N—H...O hydrogen bonds, resulting in the formation of an S (6) ring. In the crystal, pairs of adjacent molecules interact via intermolecular hydrogen bonds of type C—H...N, C—H...S and N—H...S, resulting in molecular layers parallel to the ac plane.
Display omitted
•Activated carbon prepared from a lignin/urea/K2CO3 mixture provides a high specific surface area and a large pore volume.•Part of the urea nitrogen present in the mixture is retained ...as heterocyclic nitrogen in the solid phase after activation/carbonization.•Pore development is thought to proceed through interactions between K-species and C–N forms.
The present work focuses on the role of nitrogen in the development of pores in activated carbon produced from lignin by K2CO3 activation, employing a fixed bed reactor under a high-purity He stream at temperatures of 500–900°C. The specific surface area and pore volume obtained by activation of lignin alone are 230m2/g and 0.13cm3/g at 800°C, and 540m2/g and 0.31cm3/g at 900°C, respectively. Activation of a mixture of lignin and urea provides a significant increase in the surface area and volume, respectively reaching 3300–3400m2/g and 2.0–2.3cm3/g after holding at 800–900°C for 1h. Heating a lignin/urea/K2CO3 mixture leads to a significant decrease in the yield of released N-containing gases compared to the results for urea alone and a lignin/urea mixture, and most of the nitrogen in the urea is retained in the solid phase. X-ray photoelectron spectroscopy and X-ray diffraction analyses clearly show that part of the remaining nitrogen is present in heterocyclic structures (for example, pyridinic and pyrrolic nitrogen), and the rest is contained as KOCN at ≤600°C and as KCN at ≥700°C, such that the latter two compounds can be almost completely removed by water washing. The fate of nitrogen during heating of lignin/urea/K2CO3 and role of nitrogen in pore development in activated carbon are discussed on the basis of the results mentioned above.
Monosubstituted ureas are important scaffolds in organic chemistry. They appear in various biologically active compounds and serve as versatile precursors in synthesis. Monosubstituted ureas were ...originally prepared using toxic and hazardous phosgene equivalents. Modern methods include transamidation of urea and nucleophilic addition to cyanate salts, both of which suffer from a narrow substrate scope due to the need for a strong acid and prolonged reaction times. We hereby report that ammonium chloride can promote the reaction between amines and potassium cyanate to generate monosubstituted ureas in water. This method proceeds rapidly under microwave irradiation and tolerates a broad range of functional groups. Unlike previous strategies, it is compatible with other nucleophiles, acid‐labile moieties, and most of the common protecting groups. The products precipitate out of solution, allowing facile isolation without column chromatography.
Ammonium chloride promotes the selective formation of monosubstituted ureas under microwave irradiation. Most nucleophiles, acid‐labile functionalities, and protecting groups are well tolerated in this reaction. By avoiding transition metals and mineral acids, this methodology offers a more sustainable alternative for the synthesis of monosubstituted ureas and their analogs.
The one‐step synthesis of 14Cpotassium cyanate from 14Curea is described with product characterization by gravimetric specific activity as well as a novel TLC system. The storage, stability, and ...repurification of 14Cpotassium cyanate are also discussed.
An efficient one-pot synthesis of quinazoline-2,4(1H,3H)-diones was developed. First, the reactions of anthranilic acid derivatives with potassium cyanate afforded the corresponding urea derivatives. ...Then, cyclization of the urea derivatives with NaOH afforded the monosodium salts of benzoylene urea. Finally, HCl treatment afforded the desired products in near-quantitative yields. This is an eco-efficient method because all the reactions were carried out in water, and the desired products were obtained simply by filtration. The aqueous filtrate was the only waste generated from the reaction. We scaled up the reaction to 1 kg starting material, thus establishing an alternative approach for the green synthesis of quinazoline-2,4(1H,3H)-diones in the chemical and pharmaceutical industries.
A fast and efficient method is described for the one-pot synthesis of 2,4(1H,3H)-quinazolinediones by cyclization reaction of anthranilic acid derivatives with potassium cyanate and acetic acid in ...PEG. Good to high yields of the products obtain in short reaction times with simple work-up.
This study involved a comparison of the antimicrobial efficacy of several beef hide decontamination interventions to identify those that more effectively reduced levels of Escherichia coli O157:H7 ...and Salmonella. Whole beef hides were inoculated with E. coli O157:H7 and Salmonella and decontaminated with sprays of solutions of acetic acid (AA; 10%, 55°C), lactic acid (LA; 10%, 55°C), sodium hydroxide (SH; 3%, 23°C), sodium metasilicate (SM; 4%, 23°C), or sodium hydroxide (1.5%), followed by high-pressure washing with chlorinated (0.02%) water (SHC; both applied at 23°C) or water (W; 23°C) or by deluging with solutions of potassium cyanate (PC; 2.4%, 30°C) or sodium sulfide (SS; 6.2%, 30°C). All spraying treatments (AA, LA, SH, SM, and SHC) resulted in removal of visual organic material, whereas the dehairing treatments (PC and SS) successfully removed hair along with visual organic material. The PC, SS, and SHC treatments resulted in the greatest reductions of E. coli O157:H7 (P < 0.05), by 5.1, 4.8, and 5.0 log CFU/cm2, respectively. The SS and SHC treatments decreased Salmonella by 4.2 and 4.4 log CFU/cm2, respectively, compared with the water treatment, which reduced levels by 1.7 log CFU/cm2 (P< 0.05). The SH, AA, and LA treatments also lowered both E. coli O157:H7 and Salmonella by at least 2.0 log CFU/cm2. The treatments that were effective in this study deserve further consideration for commercial implementation as hide decontamination interventions.
Cu/Zn superoxide dismutase (SOD) mutations are involved in about 20% of all cases of familial amyotrophic lateral sclerosis (FALS). Recently, it has been proposed that aberrant copper activity may be ...occurring within SOD at an alternative binding, and cysteine 111 has been identified as a potential copper ligand. Using a commercial source of human SOD isolated from erythrocytes, an anomalous absorbance at 325 nm was identified. This unusual property, which does not compromise SOD activity, had previously been shown to be consistent with a sulfhydryl modification at a cysteine residue. Here, we utilized limited trypsin proteolysis and mass spectrometry to show that the modification has a mass of 32 daltons and is located at cysteine 111. The reaction of SOD with sodium sulfide, which can react with cysteine to form a persulfide group, and with potassium cyanide, which can selectively remove persulfide bonds, confirmed the addition of a persulfide group at cysteine 111. Gel electrophoresis and glutaraldehyde cross‐linking revealed that this modification makes the acid‐induced denaturation of SOD fully irreversible. Furthermore, the modified protein exhibits a slower acid‐induced unfolding, and is more resistant to oxidation‐induced aggregation caused by copper and hydrogen peroxide. Thus, these results suggest that cysteine 111 can have a biochemical and biophysical impact on SOD, and suggest that it can interact with copper, potentially mediating the copper‐induced oxidative damage of SOD. It will be of interest to study the role of cysteine 111 in the oxidative damage and aggregation of toxic SOD mutants.
A rapid and efficient method for the synthesis of N-carbamoyl-L-amino acids is reported. The procedure, involving the reaction between urea and α-amino acids sodium salts, was performed under ...microwave conditions using an unmodified domestic microwave oven. A careful study of the operative conditions indicated proline (1d) as the less reactive substrate and phenylglycine (1e) as the more reactive one among all the α-amino acids tested. Substitution of urea with potassium cyanate produced a low conversion into the corresponding N-carbamoyl derivative, and a possible explanation of this result is reported.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
PDF
