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51.
Rawashdeh-Omary MA Rashdan MD Dharanipathi S Elbjeirami O Ramesh P Dias HV 《Chemical communications (Cambridge, England)》2011,47(4):1160-1162
{[3,5-(CF(3))(2)Pz]Ag}(3) (1) films exhibit selective/reversible sensing of small-organic-molecule (SAM) vapors, which readily switch-on bright-green (benzene or toluene) or bright-blue (mesitylene) luminescence that switches-off upon vapor removal. Vapors of electron-deficient SAMs or non-aromatic solvents did not attain luminescence switching and were not adsorbed. 相似文献
52.
Synthesis of some novel pyrazolo[1,5-a]pyrimidine derivatives and their application as disperse dyes
Al-Etaibi AM Al-Awadi NA El-Apasery MA Ibrahim MR 《Molecules (Basel, Switzerland)》2011,16(6):5182-5193
A series of novel monoazo-disperse dyes containing pyrazolo[1,5-a]pyrimidine structures were synthesized starting with the coupling reaction between ethyl cyanoacetate and 4-hydroxybenzenediazonium chloride, followed by treatment of the resulting hydrazone product with hydrazine hydrate. The pyrazolohydrazone 6 is then treated with either 2,4-pentandione and enaminonitrile or aryl-substituted enaminoketones to give the target pyrazolo[1,5-a]pyrimidine dyes 7 and 15a-d. Structural assignments to the dyes were made using NMR spectroscopic methods. A new high temperature method, using microwave heating, was employed to apply these dyes to polyester fibers. Most of the dyed fabrics tested displayed moderate light fastness and excellent washing fastness properties. 相似文献
53.
The Feynman path integral Monte Carlo approach has been coupled to the gauge including atomic orbital formalism in order to analyse the absolute magnetic shieldings of the benzene nuclei under the conditions of thermal equilibrium. The Hamiltonian employed in the derivation of ensemble averaged NMR quantities is of the Hartree-Fock type. The basis set used is of 6–31G quality. The spatial delocalization of the atoms leads to a deshielding of both types of benzene nuclei relative to the shieldings experienced at the minimum of the potential energy surface. This deshielding has to be traced back to bond length elongations in thermal equilibrium. The influence of the nuclear fluctuations on the NMR parameters of benzene is quantum driven up to temperatures of 400 K; classical fluctuations are of minor importance in this low-temperature window. 相似文献
54.
Binary mixtures formed from components of the five homologous series of the 4-(4-substituted phenylazo)phenyl-4-alkoxybenzoates Ia-e were prepared and their mesophase behaviour characterized. Transition temperatures of the mixtures prepared were measured by differential scanning calorimetry and identified by polarizing optical microscopy. Each binary combination was made from components bearing a terminal alkoxy group with the same number of carbon atoms (kept constant at n = 6, 8, 10, 12, 14 or 16), while the other substituent (X) was different—CH3O, CH3, Cl, NO2, or CN. Phase diagrams were constructed for the various systems in order to investigate the effect of the terminal substituent X, as well as of the alkoxy chain length, on the phase behaviour of mixed systems. 相似文献
55.
Nouria A. Al-Awadi Bobby J. George Hicham H. Dib Maher R. Ibrahim Yehia A. Ibrahim Osman M.E. El-Dusouqui 《Tetrahedron》2005,61(34):8257-8263
Gas-phase pyrolysis (static and FVP) of 1-aroylbenzotriazoles gave the corresponding substituted benzoxazole, benzimidazole, benzamide, N-phenylbenzamide, phenanthridin-6(5H)-one derivatives and 1-cyanocyclopentadiene. The present kinetic and mechanistic findings also provide further evidence of the involvement of biradical or carbene reactive intermediates in the reaction pathway of gas-phase pyrolysis of benzotriazoles. 相似文献
56.
57.
The rates of thermal decomposition of 1-methacryloyl-3-phenylthiourea (1a), 1-methacryloyl-3-(4-nitrophenyl)thiourea (1b), 1-methacryloyl-3-(4-chloro phenyl)thiourea (1c), 1-methacryloyl-3-(4-methylphenyl)thiourea (1d), 1-methacryloyl-3-(4-methoxyphenyl)thiourea (1e), poly-1-methacryloyl-3-phenylthiourea (2) and 1-acryloyl-3-phenylthiourea (3) have been measured between 390 and 465 K. The reactions were homogeneous and unimolecular with log A = 11.48, 11.48, 11.81, 11.43, 11.11, 11.21 and 11.87s−1 and Ea = 119.7, 111.93, 120.07, 121.94, 120.84, 124.64 and 122.68 kJ mol−1, respectively. Product analysis was used to outline feasible pathways for the elimination reaction of the compounds under study. 相似文献
58.
59.
A. Maher 《Journal of sound and vibration》1980,70(2):213-220
A simple approximation, with allowance for rigid body motion, is presented for the lowest non-zero frequency of a discrete system. The procedure is an extension and modification of that previously used to obtain a bound formula [1]. Illustrative examples and comparisons with known results are presented. 相似文献
60.
The occurrence, distribution and speciation of selenium in Australian marine biota is discussed. Biochemical pathways for the accumulation of selenium by marine organisms are also postulated. Comparison of the levels of selenium in macroalgae, fish, crustaceans and molluscs indicates that preferential accumulation of selenium by particular taxa does not occur. Phaeophyta have significantly lower selenium concentrations than Rhodophyta and Chlorophyta. Fish have lower selenium contents in muscle tissues than molluscs and crustaceans. Marine animals with different dietary intake (planktonic vs herbivorous vs carnivorous) are not observed to have significantly different levels of selenium (P>0.05). Selenium in all the organisms studied was predominantly associated with free amino-acids or protein residues and was not present as characterizable inorganic selenium species (SeO32?, SeO42?). These results indicate that selenium is probably only incorporated into biota for specific biochemical purposes with any exces selenium being excreted or eliminated. 相似文献