Results 1 - 10 of 11615
Results 1 - 10 of 11615. Search took: 0.031 seconds
|Sort by: date | relevance|
[en] An efficient method for the preparation of 8-benzylidene-4-phenyl-3,4,5,6,7,8-hexahydro-1H-quinazolin-2-ones/thiones from the reaction of aromatic aldehydes with cyclohexanone and urea or thiourea in the presence of Tetrabutylammonium hexatungstate, [TBA]2[W6O19], as an efficient, inexpensive catalyst under thermal and solvent-free conditions has been developed. Good yields, short reaction times, straightforward workup, reusability of the catalyst, and green conditions are the most obvious advantages of this procedure
[en] Muonium atoms add to the O atom of the carbonyl group of acetone to give the muonated free radical (CH3)C-O-Mu when the reaction takes place in water or hydrocarbons, but not when the acetone is localized in micelles. Micelles have no effect on the formation of muonated cyclohexadienyl radicals when muonium reacts with benzene under similar conditions. The addition reaction with acetone appears to have been subsumed by a faster alternative reaction in the micellar environment. Evidence is presented for this interpretation rather than for an inhibition of the radical or for a shift in the muon level-crossing resonance spectrum with hydrogen (muonium) bonding, though major shifts are seen for the spectrum of this radical in pure solvents of widely different dielectric constant. It is suggested that muonium's 'abstraction' reaction takes over in micelles because significant micelle-induced enhancement effects were previously observed in that type of reaction. The data are consistent with a rate constant for the abstraction reaction of muonium with acetone in micelles of >6 x 108 M-1 s-1. (author). 17 refs., 2 tabs., 4 figs
[en] Variable frequency ODMR experiments on a photoexcited triplet state molecule oriented in a single crystal host have been used to show that an anticrossing extists in the energy level diagram of the guest electron spins plus host nuclear spins at cross relaxation fields. As a consequence, the rate of energy transfer between guest and host is governed by nuclear spin-spin rather than the much slower spin-lattice relaxation. This has been confirmed by a direct measurement of the cross relaxation time (110 μs) is perdeuterobenzophenone in 4,4'-dibromodiphenylether, using microwave pulse techniques. (orig.)
[en] Full text:The nature, power of electron acceptor centers of new, V-P-O and V-P-O (Co) and V-P-O (Mo) catalysts with acetone adsorption have been studied. The existence of the different centers on the surface has been determined
[en] In recent years, among the problems of anthropogenic pollution of nature, the problem of exposure to organic substances of different classes has attracted great attention. Therefore, it is important to study the laws of the photochemical formation of oxygen-containing organic molecules, taking into account the anomalous phenomena occurring in the atmosphere. During the photooxidation of methane in the atmosphere, the most common hydrocarbon formaldehyde is formed. The average life span of formaldehyde in the atmosphere is approximately three hours. A study was made of the kinetic laws of formation of oxygen-containing (formaldehyde, formic acid and acetone) hydrocarbons during the photochemical conversion of air-methane mixtures.
[en] WO3-NiO core-shell nanorods were synthesized by thermal evaporation of a mixture of WO3 and graphite powders and immersion of the synthesized WO3 nanorods in an 20 mM of nickel(II) acetate tetrahydrate (Ni(OCOCH3)2·4H2O) solution followed by UV irradiation and annealing. Subsequently, multi-networked nanorod sensors were fabricated by connecting these nanostructures with electrodes. The sensing properties of pristine WO3 nanorod and WO3-NiO core-shell nanorod sensors toward acetone were examined. Subsequently, multi-networked nanorod sensors were fabricated by connecting these nanostructures with electrodes. The WO3-NiO core-shell nanorod sensor exhibited a stronger response to acetone gas and shorter response/recovery times than the pristine WO3 nanorod sensor. The pristine WO3 nanorods showed responses of approximately 1.36 to 200 ppm of CH3COCH3 at 300 ◦C. On the other hand, the WO3-NiO core-shell nanorods showed responses of 4.4 to the same concentration of CH3COCH3 at the same temperature. The coreshell nanorods exhibited response and recovery times of 51 s and 59 s, respectively for 200 ppm of CH3COCH3. On the other hand, the pristine WO3 nanorods exhibited response and recovery times of 51 s and 59 s, respectively, for the same concentration of CH3COCH3. NiO coating enhanced the selectivity of the WO3 nanorods for acetone as well as the sensitivity of the WO3 nanorods. The underlying mechanism of the enhanced response of the WO3-NiO core-shell nanorod sensor is also discussed in detail.
[en] The Raman line shape of the symmetric C = O stretching band at 1710 cm-1 has been measured in liquid acetone as a function of pressure from 1 bar to 4 kbar over the temperature range from -25 to 50 0C. The experimental data obtained show several unusual features. First, there is a frequency difference < deltaν> of about 7 cm-1 between the polarized and depolarized components. Sceond, the isotropic linewidth GAMMA/sub iso/ decreases with increasing density, in contrast to the opposite trend usually found in other liquids. Third, the second moment M2(V) of the isotropic band appears to decrease with increasing density. The consideration of the experimental linewidth and frequency data leads to a conclusion that intermolecular dipole--dipole coupling between polar acetone molecules are responsible for the observed unusual behavior of < deltaν>, GAMMA/sub iso/, and M2