Synthesis of Some 1,3-Thiazole, 1,3,4-Thiadiazole, Pyrazolo[5,1-c]-1,2,4-triazine, and 1,2,4-Triazolo[5,1-c]-1,2,4-triazine Derivatives Based on the Thiazolo[3,2-a]benzimidazole Moiety

3-(3-Methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile was synthesized by refluxing ethyl 3-methylthiazolo[3,2-a]benzimidazole-2-carboxylate, acetonitrile, and sodium hydride. Treatment of 3-(3-methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile with phenyl isothiocyanate, in the presence of KOH, furnished the corresponding potassium salt which was converted into thioacetanilide derivative upon neutralization. The thioacetanilide derivative reacts with α-chloroacetylacetone and ethyl α-chloroacetoacetate to give the 1,3-thiazole derivatives, while the reaction of the'thioacetanilide derivative with hydrazonyl chlorides gave 1,3,4-thiadiazole derivatives. On the other hand, 3-(3-methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile reacted with the diazonium salt of both 3-phenyl-5-amino-(1H)-pyrazole and 5-amino-l,2,4-(1H)-triazole to afford the corresponding hydrazones. The latter hydrazones underwent an intramolecular cyclization upon boiling in pyridine to give pyrazolo[5,1-c]-1,2,4-triazine and 1,2,4-triazolo[5,1-c]-1,2,4-triazine derivatives. Moreover, the behavior of thiazolo[3,2-a]benzimidazol-3(2H)-one towards phenyl isothiocyanate followed by the reaction with α-chloroketones or hydrazonyl chlorides was investigated. Some of the latter compounds exhibited moderate effects against some bacterial and fungal species.     

Effect of gamma-irradiation on surface and catalytic properties of CuO−ZnO/Al2O3 system

A copper, zinc and aluminium mixed oxides sample having the nominal composition 0.25 CuO/0.03 ZnO/Al₂O₃ was prepared by impregnating Al(OH)₃ with copper and zinc nitrate solutions, drying at 100 °C then heating in air at 600 °C. The obtained solid was exposed to different doses of -rays (20–160 Mrad). The surface characteristics namelyS _BETV_P andr of different treated adsorbents were determined from N₂ adsorption isothems measured at –196 °C. The catalytic activity of various irradiated solids was determined by following up the kinetics of CO-oxidation by O₂ at 150–200 °C. The results showed that the doses up to 80 Mrad resulted in no significant change in theS _BET but increased slightly theV _P (20%) of the treated adsorbents. The irradiation at 160 Mrad caused an increase of 20% in theS _BET of the irradiated solid sample. The catalytic activity increased progressively by increasing the dose, a dose of 160 Mrad brought about an increase of 140% in the catalyst's activity. The apparent activation energy of the catalytic reaction decreased monotonically by increasing the absorbed dose of -rays which was attributed to a parallel induced decrease in the value of pre-exponential term of the Arrhenius equation. The observed increase in the catalytic activity due to -irradiation has been interpreted as a result of increasing the concentration of catalytically-active sites contributing in chemisorption and catalysis of CO-oxidation via a possible fragmentation of CuO crystallites.     

Synthesis of 4′-Carboxy-benzo-30-crown-10 and a Thermodynamic Study of Its Complexes with Thallium and Alkali Cations in Acetonitrile Solution

A synthetic procedure has been developed for the preparation of 4-carboxy-benzo-30-crown-10. The formation of Na+, K+, Rb+, Cs+ and Tl+ complexes with the large crown ether was investigated conductometrically in acetonitrile solution at various temperatures. The formation constants of the resulting 1:1 complexes were determined from the molar conductance-mole ratio data. It was found that the stability of the complexes vary in the order Tl+ > K+ > Rb+ > Cs+ > Na+. The data obtained in this study support the existence of a wrap around structure for the above complexes in solution. The enthalpy and entropy of complexation reactions were determined from the temperature dependence of the formation constants. In all cases, the complexes were enthalpy stabilized but entropy destabilized. The resulting TS° vs. H°plot showed a fairly good linear correlation, indicating the existence of an entropy-enthalpy compensation in the large crown complexation reactions.     

Green oxidations. The use of potassium permanganate supported on manganese dioxide

Permanganate supported on active manganese dioxide can be used effectively for the oxidation of organic compounds under heterogeneous or solvent-free conditions. The residue that remains after extraction of the organic products, manganese dioxide, can be recycled, making the process infinitely sustainable, in theory. The use of this approach for the oxidation of arenes, alcohols and sulfides is described.     

Kuwait's total diet study: dietary intake of organochlorine, carbamate, benzimidazole and phenylurea pesticide residues

The State of Kuwait in cooperation with the U.S. Food and Drug Administration (FDA) conducted a Total Diet Study (TDS) to estimate intakes of pesticide residues by the population. The levels of organochlorine (OC) pesticides, carbamates, benzimidazoles, and phenylureas in the TDS core list are reported here. The TDS core list was established through a national food consumption survey. All food items (140 for the Kuwaiti adult) were prepared as eaten and analyzed for the pesticides mentioned above. The FDA's multiresidue methods in Volume I of the Pesticide Analytical Manual were used in gas, liquid, and gel permeation chromatographic analyses. Only vegetable and fruit samples contained pesticide residues (mg/kg), including the carbamates 1-naphthol (1.4) and 3H-carbofuran (0.94) in carrots; the OC pesticide vinclozolin (0.47), 3H-carbofuran (0.66), and fenuron (0.6) in kiwi fruit; the OC pesticide procymidone (0.32) and carbendazim (0.5) in grapes; 3H-carbofuran (5.0) in apricots; the OC pesticides captan (0.013) and thiabendazole (0.63) in pears; captan (0.035) in plums; and carbendazim (0.4) in mandarin oranges. The levels of 3H-carbofuran found in both apricots and kiwi fruit exceeded the maximum residue limits (MRLs) of the Food and Agriculture Organization/World Health Organization (FAO/WHO) of the United Nations. The daily intakes of pesticides by the different population groups are discussed in light of the FAO/WHO acceptable daily intakes.     

Mass spectral studies on steroidal compounds—V: Rings B and A seco 5-keto compounds in the cholestane series

The mass spectra of several structurally related ring B seco 5-keto compounds (I to VII) have been examined. The mass spectra of I, II, III and IV are conspicuous by an intense peak at m/e112(C₇H₁₂O) and those of V (highest mass peak at [M ? CH₃COOH]), VI and VII by a prominent peak at m/e 100 (C₇H₁₀O), which apparently results from McLafferty rearrangement involving 5-keto function and an appropriate γ-hydrogen at C-8 and C-11. This rearrangement, leading to the aforementioned ions, is of diagnostic value in the characterisation of such compounds. The mass spectrum of VIII exhibits a prominent ion peak at m/e 332 (C₂₃H₄₀O) resulting from McLafferty rearrangement involving the 5-keto function and C2? H. This offers an excellent means of differentiating between the isomeric acids (III and VIII). The fragmentation pathways suggested are supported by accurate mass measurement of the salient fragment ions and in some cases by appropriate metastable peaks.     

Determination of crossed-second-order field shift in8 F and6 F terms of 4f 6(7 F)6s configuration of sm+

We report here the experimental evaluation of crossed-second-order (CSO) effects in the field shift of⁸ F and⁶ F terms of 4f ⁶(⁷ F)6s configuration of singly ionised samarium. Our experimental value of CSO field shift difference between⁸ F and⁶ F terms for¹⁴⁸Sm and¹⁵⁴Sm is ?11.8(3.2) mK, which is in good agreement with the theoretical value of ?13.8 mK evaluated using known parameters.     

Synthesis and spectroscopic studies of complexes containing the Schiff base 1-acetylferrocene(thio)semicarbazone

Summary [RuCl₂(CO)₂] _n reacts with the Schiff base 1-acetylferrocenethiosemicarbazone, [Fe(-Cp)(-C₅H₄MeC=NN-HCSNH₂)] to give [Fe(-Cp)(-C₅H₄MeC=NN-HCSNH₂)RuCl₂(CO)₂] and with 1-acetylferrocenesemicarbazone [Fe(-Cp)(-C₅H₄MeC=NN-HCSNH₂)] to give [Fe(-Cp)(-C₅H₄MeC=NN-HCSNH₂)RuCl₂-(CO) ₂]. Spectroscopic data indicate that the Schiff bases act as bidentate ligands and coordinate to ruthenium via the hydrazinic N and either the S or O atoms, respectively, giving stable heterobimetallic complexes, which have been characterized by i.r. and ¹H-n.m.r. spectroscopies, and elemental analyses.Part of this work was presented at the First International Conference in Chemistry and its applications in Doha, Qatar, 1993.     

Cellulose nanocrystals from bleached rice straw pulp: acidic deep eutectic solvent versus sulphuric acid hydrolyses

The present work aims to investigate the feasibility of oxalic acid-choline chloride deep eutectic solvent (OA-ChCl DES), which serves as a promising green solvent that utilized in the acidic deep eutectic solvent (DES) hydrolysis. Oxalic acid-choline chloride DES cellulose nanocrystal (OA-ChCl DES CNC) was isolated from the bleached DES treated pulp (BP) through the acidic DES hydrolysis using 1:1 molar ratio of OA-ChCl DES. The functional groups, crystallinity index, morphological structure, particle size, zeta potential, thermal stability and surface chemistry of the OA-ChCl DES CNC were compared with the sulphuric acid cellulose nanocrystal (SA-CNC) that prepared via sulphuric acid hydrolysis. The findings revealed the presence of negatively charged carboxyl groups on OA-ChCl DES CNC surface after the acidic DES hydrolysis. The physicochemical analyses verified that the OA-ChCl DES CNC was in nano-sized range with polydispersity index (PdI) of 0.56, indicating slightly monodispersed nanoparticles. A stable OA-ChCl DES CNC colloidal suspension with zeta potential value of ?52.1?±?5.2 mV was obtained. The OA-ChCl DES CNC outweighed the SA-CNC in term of thermal stability (288 °C) despite having a slightly lower crystallinity index (76.7%). In fact, the OA-ChCl DES CNC with a yield of 55.1% was achieved through the acidic DES hydrolysis, suggesting that the OA-ChCl DES was capable of promoting efficient cleavage of strong hydrogen bonds in BP.

Graphic abstract