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61.
Supported nano‐amorphous alloy NiB/MCM‐41 catalysts were prepared by chemical reductive deposition. The as‐prepared catalysts were characterized by XRD, SEM, TEM, EDAX, ICP, and N2 adsorption‐desorption. The amorphous alloy structure of NiB active sites, mesoporous structure of catalysts, and higher BET area have been proved by the experiments. The catalysts have given excellent catalytic activity and selectivity in the production of 3‐(N‐benzyl)‐amino‐4‐methoxy‐ acetanilide from 3‐amino‐4‐methoxy‐acetanilide and benzaldehyde. 相似文献
62.
Alexej Bubnov Miroslav Kašpar Vladimíra Novotná Věra Hamplová Milada Glogarová Nadia Kapernaum 《Liquid crystals》2013,40(11):1329-1337
A new series of materials with a chiral fragment derived from lactic acid and a methoxy group as lateral substituent in different positions of the molecular core was synthesised and investigated. Derivatives with ester or ether linkages of the non‐chiral chain were also studied. Depending on the molecular structure, cholesteric, twist grain boundary smectic A (TGBA*), chiral smectic A (SmA*) or chiral smectic C (SmC*) phases were detected. In derivatives with the ester linkage and a methoxy group at the nearest and the next nearest phenyl ring to the non‐chiral chain these phases completely disappear. On the other hand, a methoxy group on the phenyl ring close to the chiral chain provides a compound with low layer shrinkage at the SmA*–SmC* phase transition (“de Vries” behaviour). The temperature dependence of the spontaneous polarisation, the tilt angle, the layer spacing as well as the complex permittivity were studied and the results discussed in terms of molecular structure. 相似文献
63.
Moon Suk Kim Kwang Su Seo Gilson Khang Sun Hang Cho Hai Bang Lee 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5784-5793
Diblock copolymers consisting of methoxy poly(ethylene glycol) (MPEG) and poly(?‐caprolactone) (PCL), poly(δ‐valerolactone) (PVL), poly(L ‐lactic acid) (PLLA), or poly(lactic‐co‐glycolic acid) (PLGA) as biodegradable polyesters were prepared to examine the phase transition of diblock copolymer solutions. MPEG–PCL and MPEG–PVL diblock copolymers and MPEG–PLLA and MPEG–PLGA diblock copolymers were synthesized by the ring‐opening polymerization of ?‐caprolactone or δ‐valerolactone in the presence of HCl · Et2O as a monomer activator at room temperature and by the ring‐opening polymerization of L ‐lactide or a mixture of L ‐lactide and glycolide in the presence of stannous octoate at 130 °C, respectively. The synthesized diblock copolymers were characterized with 1H NMR, IR, and gel permeation chromatography. The phase transitions for diblock copolymer aqueous solutions of various concentrations were explored according to the temperature variation. The diblock copolymer solutions exhibited the phase transition from gel to sol with increasing temperature. As the polyester block length of the diblock copolymers increased, the gel‐to‐sol transition moved to a lower concentration region. The gel‐to‐sol transition showed a dependence on the length of the polyester block segment. According to X‐ray diffraction and differential scanning calorimetry thermal studies, the gel‐to‐sol transition of the diblock copolymer solutions depended on their degrees of crystallinity because water could easily diffuse into amorphous polymers in comparison with polymers with a crystalline structure. The crystallinity markedly depended on both the distinct character and composition of the block segment. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5784–5793, 2004 相似文献
64.
Supramolecular hydrogen bonded liquid crystals are formed by methoxy hydroquinone (MHQ) and alkyloxy benzoic acids are isolated and characterised. MHQ formed double hydrogen bonds with p-n-alkyloxy benzoic acids. Fourier Transform–Infrared studies confirm the hydrogen bond formation in the complex. Polarising Optical Microscopic (POM) studies revealed the textural information, while the transition and enthalpy values are experimentally deduced from Differential Scanning Calorimetry (DSC) studies. Phase diagram has been constructed from the POM and DSC data, respectively. Experimental data of optical tilt angle in Smectic C phase have been fitted to a power law and it has been observed that the temperature variation of the tilt angle follows Mean Field theory prediction. Present homologous are compared with hydroquinone alkyloxy benzoic acids complexes and the influence of methyl group on the occurrence of phases and its transition temperatures are discussed. 相似文献
65.
N. Nizomov A. U. Kholov A. A. Ishchenko V. V. Ishchenko V. P. Khilya 《Journal of Applied Spectroscopy》2007,74(5):626-634
We have studied the characteristic features of the spectral fluorescence properties of natural compounds (umbelliferone and
herniarin) in aprotic and proton-donor solvents of different polarities. Based on quantum chemical analysis by the AM1 semiempirical
method of the changes in the electronic charge and bond orders in the ground state and the first excited state, we have interpreted
the anomalously high Stokes shifts and mirror symmetry of the absorption and fluorescence bands of these compounds in aprotic
solvents. We have established that the fluorescence spectra of umbelliferone in water, ethanol, alkaline and acidic solutions
differ considerably from the analogous spectra of herniarin. This is connected with detachment and transfer of a proton in
the neutral form of umbelliferone upon photoexcitation, with possible formation (depending on the pH of the medium) of an
anion, cation, or tautomer. Good agreement was achieved between the calculated and experimental values of the maxima for the
electronic bands of these forms.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 569–576, September–October, 2007. 相似文献
66.
Rhushirajeshwari M. Chalke 《高分子科学杂志,A辑:纯化学与应用化学》2017,54(9):556-564
Alkoxy substituted spirobifluorene derivatives namely 2,2′,7,7′-tetrabromo-3,6-bis(methoxy)-9,9′spirobifluorene (MSBF), 2,2′,7,7′-tetrabromo-3,6-bis(ethoxy)-9,9′spirobifluorene (ESBF), 2,2′,7,7′-tetrabromo-3,6-bis(butoxy)-9,9′spirobifluorene (BSBF), 2,2′,7,7′-tetrabromo-3,3′,6,6′-tetra(methoxy)-9,9′-spiro-9-silabifluorene (MSSiBF) and their key intermediates have been synthesised successfully. All compounds have been fully characterised by 1H and 13C NMR, FTIR, UV-visible spectroscopy, MS spectrometry. TGA analysis revealed good thermal stability. The systematic investigation on the solubility, thermostability and photophysical property of synthesized compound showed that alkoxy substituted spirobifluorene were unique in rigidity and have wide range of applications in molecular electronics and can be used as building units for optoelectronics material. 相似文献
67.
Kumar Biradha Hilary Jenkins M. Brad Peori Keith Vaughan Michael J. Zaworotko 《Journal of chemical crystallography》1999,29(9):1037-1041
The crystal and molecular structure of 1,3-di-2-[(4-methoxyphenyl)-1-diazenyl]imidazolidine (1) has been determined by single crystal X-ray diffraction analysis. This novel bis-triazene assumes a close-to planar structure with the aryltriazene moieties aligned in diametrically opposed directions, unlike many other previously reported bis-triazenes, which assume a folded structure. The structure of 1 is compared with the closely related, non-cyclic bis-triazene analogue (2), and also compared with the structure of the simple mono-triazene (3). Crystal data: 1 C17H20N6O2, monoclinic, space group C2/c, a = 34.948(3), b = 5.925(5), c = 8.1225(6) Å, = 100.8420(10)°, and V = 1652.0(2) Å3, for Z = 4. 相似文献
68.
69.
The kinetics of oxidation of 1‐methoxy‐2‐propanol and 1‐ethoxy‐2‐propanol by ditelluratocuprate(III) (DTC) in alkaline liquids has been studied spectrophotometrically in the temperature range of 293.2–313.2 K. The reaction rate showed first order dependence in DTC and fractional order with respect to 1‐methoxy‐2‐propanol or 1‐ethoxy‐2‐propanol. It was found that the pseudo‐first order rate constant kobs increased with an increase in concentration of OH? and a decrease in concentration of TeO42?. There is a negative salt effect. A plausible mechanism involving a pre‐equilibrium of a adduct formation between the complex and 1‐methoxy‐2‐propanol or 1‐ethoxy‐2‐propanol was proposed. The rate equations derived from mechanism can explain all experimental observations. The activation parameters along with the rate constants of the rate‐determining step were calculated. 相似文献
70.
Two new 5‐methoxyfuran‐3(2H)‐one derivatives, huaspenone A ( 1 ) and B ( 2 ), together with four known ones, i.e., aspertetronin A ( 3 ), aspertetronin B ( 4 ), gregatin E ( 5 ), and penicilliol A ( 6 ), were isolated from the cultures of an endophytic fungus Aspergillus sp. XW‐12, derived from the stems of Huperzia serrata. The structures of the new isolates were established by detailed interpretation of the 1D‐ and 2D‐NMR and HR‐ESI‐MS data. 相似文献