Regioselectivity in the 1,3-dipolar cycloaddition of nitrile oxides to N-(3,5-dichlorophenyl)itaconimide

Summary The regioselectivity of the nitrile oxide cycloaddition with 3,3-methylene-1-(3,5-dichlorophenyl)-2,5-pyrrolidindione (1) is discussed. Arylnitrile oxides add regioselectively to the carboncarbon double bond of1, giving exclusively spiro-isoxazolines3a–k, whereas acetonitrile oxide gives both adducts3l and4l. AM1 calculations of the reactants and cycloadducts were performed, the regiochemistry of the cycloaddition seems to be controlled by steric effects. Reduction of3a with NaBH₄ in the presence of magnesium perchlorate at –20 °C was regio-and stereoselective to yield the hydroxylactams9a and10a, whereas hydroxymethylisoxazoline14a was obtained in the absence of Mg(ClO₄)₂.Part XXX in the series 1,3-Dipolar Cycloaddition on Heterocycles. Part XXIX [27]     

Thermal properties of lithium hydrogenhexavanadate

The thermal properties of LiHV₆O₁₆·(5.5H₂O were studied in air atmosphere by DTA, DTG and TG in the temperature interval 20–800°. The studied compound is thermally unstable. In the course of the third step of mass loss, it decomposed with the formation of new phases. On further heating, reaction between these phases took place. A mixture of V₂O₅ and LiV₃O₈ was obtained as final product.

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Zusammenfassung Die thermischen Eigenschaften von LiHV₆O₁₆·5.5H₂O wurden in Luftatmosphäre im Temperaturintervall von 20 bis 800 °C durch DTA, DTG und TG untersucht. Die untersuchte Verbindung ist thermisch instabil. Im Verlaufe der dritten Stufe des Gewichtsverlustes zersetzt sich die Verbindung unter Bildung neuer Phasen, die bei weiterem Erhitzen miteinander reagieren. Als Endprodukt wurde ein Gemisch von V₂O₅ und LiV₃O₈ erhalten.

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, 20–800° LiHV₆O₁₆· 5,5H₂O. . , . V₂O₅ LiV₃O₈.

     

Analogue Realizations of Fractional-Order Controllers

An approach to the design of analogue circuits, implementingfractional-order controllers, is presented. The suggestedapproach is based on the use of continued fraction expansions;in the case of negative coefficients in a continued fractionexpansion, the use of negative impedance converters is proposed.Several possible methods for obtaining suitable rational appromixationsand continued fraction expansions are discussed. An exampleof realization of a fractional-order I controlleris presented and illustrated by obtained measurements.The suggested approach can be used for the control of veryfast processes, where the use of digital controllers isdifficult or impossible.     

Determination of heavy metals in welder's working environment using nuclear analytical methods

Technological process of welding is significant source of pollution of working environment with heavy metals. Evaluation of chemical quality of working environment was made by means of radionuclide X-ray fluorescent analysis and activation analysis with fast neutrons. Welding aerosols were sampled by filtration method on Synpor 4 membrane ultra-filters. For selected types of welding filter metals, determination of heavy metals in aerosols was performed.