Benzoylation of 2(3H)-benzothiazolones in the Presence of 8 Equivalents of Zinc Chloride in N,N-dimethylformamide

The use of the mixture of aluminum chloride-N,N-dimethylformamide 1,2 (AlCl 3 -DMF, 11:1) reagent in the Friedl-Crafts C acylation reaction of 2(3H)-benzothiazolones was previously reported. 3 These acylations reactions were found to proceed with high regioselectivity. The precise position of acylation was uniquivocally assigned by x-ray single-crystal defraction in the case of 6-benzoyl-2(3H)-benzothiazolone. 4 The assignment of the position of acylation was extended to other compounds by the use of high-field 1 H-NMR . 3     

Chemical composition and antioxidant activities of essential oils and methanol extracts of three wild Lavandula L. species

A comparative study of essential oil composition, polyphenol content and antioxidant activities of Lavandula coronopifolia, Lavandula multifida and Lavandula stoechas subsp. stoechas were reported. Qualitative and quantitative variations in the composition of oils according to species were shown. Lavandula coronopifolia's oil was characterised by high proportions of trans-β-ocimene (26.9%), carvacrol (18.5%), β-bisabolene (13.1%) and myrcene (7.5%). The main components of L. multifida oil are carvacrol (65.1%) and β-bisabolene (24.7%). Lavandula stoechas oil is rich in fenchone (34.3%) and comphor (27.4%). The total phenolic and flavonoid contents also significantly varied among species. Lavandula coronopifolia exhibits the highest phenolic and flavonoid contents (31.3?mg GAE?g(-1) and 16.3?mg RE?g(-1), respectively), followed by L. multifida (30.8?mg GAE?g(-1) and 12.3?mg RE?g(-1)). Methanolic extracts and essential oils displayed significant antioxidant activities. The level of antioxidant capacity varied according to extracts and species.     

Metal complexes as color indicators for the determination of acid-base properties of solid catalysts

The Lewis acid-basicity of a solid catalyst was determinated by using solution of Cu(tmen) (acac) (NO₃) and Fe(phen)₂ (CN)₂ as Lewis acid-base indicators.     

Characterization and modelling of guillotine constraints

This paper focuses on guillotine cuts which often arise in real-life cutting stock problems. In order to construct a solution verifying guillotine constraints, the first step is to know how to determine whether a given cutting pattern is a guillotine pattern. For this purpose, we first characterize guillotine patterns by proving a necessary and sufficient condition. Then, we propose a polynomial algorithm to check this condition. Based on this mathematical characterization of guillotine patterns, we then show that guillotine constraints can be formulated into linear inequalities. The performance of the algorithm to check guillotine cutting patterns is evaluated by means of computational results.     

Electrochemical urea biosensor based on Proteus mirabilis urease immobilized over polyaniline PANi-Glassy carbon electrode

In this study, a novel, sensitive electrochemical enzyme-based biosensor for urea detection was presented. This biosensor combines a three-electrode system consisting of a classic Glassy Carbon Electrode (GCE) as the working electrode, a platinum counter electrode, and Ag/AgCl as the reference electrode. To construct this urea platform, a GCE was modified with a polyaniline (PANi) film. Then, bacterial urease from Proteus mirabilis was immobilized on the modified GCE (P_m-Urease-PANi-GCE). For the characterization of surface modification, Cyclic Voltammetry (CV) and Scanning Electron Microscope (SEM) were applied, while the Square Wave Voltammetry (SWV) technique was performed for urea detection. The main analytical characteristics of the P_m-Urease-PANi-GCE biosensor showed a good linear range from 0.1 to 10 mM of urea, a limit of detection (LOD) of 0.1 mM, a Michaelis-Menten K_m of 0.23 mM, and a sensitivity value 46 μA/mM/cm². This biosensor allows the detection of urea in solutions, and it could be improved for further medical, environmental, or engineering applications.     

Potassium Fluoride on Alumina: One-Pot Synthesis of Allyl Dithioesters by Tandem Condensation- Alkylation-Sigmatropic Rearrangement

Methylene ketones adsorbed on KF-alumina at room temperature react quickly with carbon disulfide and two equivalents of allyl chloride. The products undergo sigmatropic rearrangement, to give the corresponding allyl ketodithioesters.     

Hydrophobic functionalization of cotton-based textile fabrics through a non-fluorinated sol–gel route

The hydrophobic functionalization of cotton-based fabrics has been achieved through a non-fluorinated sol–gel route. This functionalization is based on the dilution of a hexadecyl-modified (C16) alkoxide within a sol–gel derived crystalline suspension (CS) of titanium oxide in liquid solution. This latter suspension exhibits excellent stability, which allows the preparation of mixed C16-TiO₂ sols using a same CS over a long period of time. Mixed sols can then be impregnated on various kinds of substrates, including textile fabrics. Fourier transform infrared spectroscopy, as well as optical, atomic force, and scanning electron microscopy, have been used to study chemical and morphological features arising from such sols. Wettability measurement are then presented and discussed in relation to chemical and morphological features. It is shown that this sol–gel route flexibly yields a marked hydrophobic behavior on cotton-based textile fabrics.     

Tranchage et prolongement des courants positifs fermés

Sans résumé Re?u le 11 octobre 1995 / Version revisée re?ue le 20 fevrier 1996