The catalyst H3+xPMo12−x+6Mox+5O40 supported on SiO2 was developed for peroxidation of 1,3‐ and 1,5‐diketones with hydrogen peroxide with the formation of bridged 1,2,4,5‐tetraoxanes and bridged ...1,2,4‐trioxolanes (ozonides) with high yield based on isolated products (up to 86 and 90 %, respectively) under heterogeneous conditions. Synthesis of peroxides under heterogeneous conditions is a rare process and represents a challenge for this field of chemistry, because peroxides tend to decompose on the surface of a catalyst . A new class of antifungal agents for crop protection, that is, cyclic peroxides: bridged 1,2,4,5‐tetraoxanes and bridged ozonides, was discovered. Some ozonides and tetraoxanes exhibit a very high antifungal activity and are superior to commercial fungicides, such as Triadimefon and Kresoxim‐methyl. It is important to note that none of the fungicides used in agricultural chemistry contains a peroxide fragment.
Being better: A heterogeneous catalyst was developed for the peroxidation of 1,3‐ and 1,5‐diketones with hydrogen peroxide with the formation of bridged 1,2,4,5‐tetraoxanes and bridged 1,2,4‐trioxolanes with yield up to 86 and 90 %, respectively. A new class of antifungal agents for crop protection, that is, cyclic peroxides, was discovered. Some ozonides and tetraoxanes exhibit a very high antifungal activity and are superior to commercial fungicides.
Stereoelectronic interactions control reactivity of peroxycarbenium cations, the key intermediates in (per)oxidation chemistry. Computational analysis suggests that alcohol involvement as a third ...component in the carbonyl/peroxide reactions remained invisible due to the absence of sufficiently deep kinetic traps needed to prevent the escape of mixed alcohol/peroxide products to the more stable bisperoxides. Synthesis of β‐alkoxy‐β‐peroxylactones, a new type of organic peroxides, was accomplished by interrupting a thermodynamically driven peroxidation cascade. The higher energy β‐alkoxy‐β‐peroxylactones do not transform into the more stable bisperoxides due to the stereoelectronically imposed instability of a cyclic peroxycarbenium intermediate as a consequence of amplified inverse alpha‐effect. The practical consequence of this fundamental finding is the first three‐component cyclization/condensation of β‐ketoesters, H2O2, and alcohols that provides β‐alkoxy‐β‐peroxylactones in 15–80 % yields.
The use of an amplified inverse alpha‐effect for interrupting a cascade peroxidation process in a three‐component synthesis of β‐alkoxy‐β‐peroxylactones from β‐ketoesters, hydrogen peroxide and alcohols was developed.
Lower extremity deformities of patients with arthrogryposis multiplex congenita present a wide spectrum of severity and deformity combinations. Treatment goals range from merely ensuring comfortable ...seating and shoe wear, to fully independent and active ambulation, but the overarching intention is to help realize the patient’s greatest potential for independence and function. Treatment of hip and knee contractures and dislocations has become more interventional, whereas treatment of foot deformities has paradoxically become much less surgical. This article synopsizes the treatment strategies presented in September 2014 in Saint Petersburg, Russia at the second international symposium on arthrogryposis.
•Adsorbed water on TiO2 surprisingly enhance CO photooxidation at moderate coverage.•Peroxide species like TiOOTi and TiOOH are assumed to be key intermediates.•The formation of stable C-containing ...species is controlled by water coverage.
Effect of water coverage on photocatalytic activities of CO oxidation was investigated on two TiO2 samples: Hombikat UV 100 and Degussa P25. Surprisingly, the initial rate for CO photocatalytic oxidation over both TiO2 samples shows the extreme dependence with maximum with the increase of water coverage from zero (for fully dehydrated TiO2 samples) to one monolayer. The maximum of CO photooxidation rate was at ∼0.5 monolayer of adsorbed water for both TiO2 samples, wherein the catalytic activity was higher for TiO2 Hombikat UV 100 than TiO2 Degussa P25. It was concluded that the role of water is more complex than just a competition for adsorption sites between H2O and CO, and with moderate H2O coverages the positive influence of adsorbed water on CO photooxidation rate occurs. Different mechanisms of CO photooxidation on a fully dehydroxylated and partially hydrated TiO2 with participation of different oxidizing species generated under UV-irradiation were suggested.
A catalyst for the synthesis of ozonides and tetraoxanes under heterogeneous conditions was developed. This work reports an unprecedented class of fungicides with significant potential for ...agricultural applications. More information can be found in the Full Paper by A. O. Terent'ev et al. on page 4734.
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The treatment of titanium dioxide with acidified NaF solution results in a more than twofold increase in photocatalytic efficiency in the complete oxidation of ethanol vapor. This ...treatment was accompanied by considerable changes in the surface structure of TiO2, which were detected by diffuse scattering IR spectroscopy.
Studies of ultrasonic dehydration efficiency Khmelev, Vladimir N.; Shalunov, Andrey V.; Barsukov, Roman V. ...
Journal of Zhejiang University. A. Science,
04/2011, Letnik:
12, Številka:
4
Journal Article
Recenzirano
The aim of this investigation was to define the effectiveness of non-contact drying using ultrasonic vibrations. Disk radiators were used for carrying out experiments, and a special drying chamber ...was designed to provide resonant amplification of ultrasonic vibrations （from 130 to 150 dB）. Drying of ginseng and other vegetables demonstrated that the application of ultrasonic vibrations reduced power inputs by 20% in comparison with convective drying. It also led to a decrease of 6% in final moisture content, if the duration of drying was constant. The level of intensification of ultrasonic drying was high （up to 50 g for 1 kg of drying material）, which helped to lower the temperature of the drying agent and improve the quality of the dried products.
The relevance of the research is caused by the need to study the resistance of metals and their coatings to cavitation erosion in conditions of abnormally high temperatures, pressures, as well as in ...chemically aggressive environments in the form of acids, alkalis or aggressive gases (such as ozone). The main aim of the research is to develop specialized equipment for monitoring and detecting modes and dependencies of cavitation destruction of various metals and their coatings at abnormally high temperatures and overpressure, as well as methodology for determining (controlling) the resistance of metals and their coatings in cavitation fields. Objects: testing cavitation erosion under abnormal conditions using specially designed ultrasonic equipment for this task. Method: experimental method for studying cavitation erosion under abnormal conditions. This method is the development of the existing one regulated by the ASTM G32-10 «Standard test method for cavitation erosion». Results. To create, research and apply special materials and coatings that can ensure long-term reliable equipment operation the authors have proposed and developed a new method for monitoring the erosion resistance of metals and protective coatings under cavitation exposure in abnormal operating conditions, in terms of pressure and temperature. This method expands the capabilities of the ASTM G32-10 «Standard test method for cavitation erosion». Practical implementation of tests of cavitation erosion of metals and protective coatings under abnormal conditions will ensure the creation and application of new materials for use in various branches of human activity and industry.
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