排序方式: 共有61条查询结果,搜索用时 0 毫秒
21.
Diels-Alder addition of azomethines to isatoic anhydride in a solvent-free and eco-friendly condition is investigated using
a microwave oven. The product is exclusively 2,3-diaryl-2,3-dihydroquinazolin-4(1H)-ones 4a-d. HOMO-LUMO energy of the iminoketene and the dienophiles were calculated using semi-empirical AM1 calculations. 相似文献
22.
Sumalatha Eda Baby Jyothsna Kota Prathap Kumar Thella Satyavathi Bankupalli Suresh K. Bhargava Rajarathinam Parthasarathy 《Chemical Papers》2017,71(10):1939-1951
Regeneration of carboxylic acids from the loaded-organic phase is an essential step to complete the reactive extraction process. A study on the regeneration of levulinic acid from loaded-organic phase (methyl isobutyl ketone + tri-n-octylamine + acid) was carried out using various techniques including NaOH, temperature swing, diluent swing, and tri-methylamine methods. Equilibrium data obtained show that among all the methods, the recovery of acid is the highest for the tri-methylamine method when the molar ratio of tri-methylamine to levulinic acid concentrations is greater than 1. Kinetic studies performed for the tri-methylamine method showed that there are no changes in the specific rate of extraction with changes in stirrer speed rate and phase volume ratio (V aq/V org), and the overall order of reaction is 1.5. Based on the effects of stirrer speed and phase volume ratio on the specific rate of extraction, the reaction was concluded to occur in the fast regime. Also, about 80% of acid was recovered by the evaporation of tri-methylamine phase at 104–140 °C. A detailed economic evaluation for the recovery of levulinic acid using reactive extraction for a feed rate of 2 m3 h?1 shows that the payback period for recovering capital investment is 0.49 years. 相似文献
23.
A novel regioselective synthesis of a number of functionalized 3-spiropyrrolizidine and 3-spiropyrrolidine oxindoles from Baylis-Hillman adducts of isatin and heteroaldehydes via [3+2] cycloaddition of azomethine ylides in excellent yields has been reported. 相似文献
24.
Neelakandan PP Nandajan PC Subymol B Ramaiah D 《Organic & biomolecular chemistry》2011,9(4):1021-1029
We synthesized a few novel cyclophanes CP-1 to CP-4 containing anthracene units linked together through different bridging and spacer groups and have investigated their interactions with various nucleosides and nucleotides. Of these systems, CP-1 and CP-3 showed selectivity for 5'-GTP and 5'-ATP as compared to other nucleotides and nucleosides, whereas negligible selectivity was observed with CP-2 and CP-4. Interestingly, CP-1, CP-2 and CP-3 exhibited significant binding interactions with the fluorescent indicator, 8-hydroxy-1,3,6-pyrene trisulfonate (HPTS), resulting in the formation of non-fluorescent complexes. Titration of these complexes with nucleosides and nucleotides resulted in the displacement of HPTS, leading to the revival of its fluorescence intensity. It was observed that 5'-GTP induced the maximum displacement of HPTS from the complex [CP-1·HPTS] with an overall fluorescence enhancement of ca. 150-fold, while 5'-ATP induced ca. 45-fold. Although the displacement of HPTS from the complexes [CP-2·HPTS] and [CP-3·HPTS] was found to be similar to that of [CP-1·HPTS], these complexes showed lesser selectivity and sensitivity. In contrast, negligible displacement of HPTS was observed from the complex [CP-4·HPTS] under similar conditions. These results indicate that CP-1, having a well-defined cavity and good electron acceptor (viologen), is capable of forming selective and stable complexes. Though CP-2 and CP-3 retain the good electron acceptor (viologen), their reduced aromatic surface and larger cavity, respectively, resulted in lesser sensitivity. In contrast, CP-4 having a large cavity and a poor acceptor (1,2-bis(pyridin-4-yl)ethene) showed negligible selectivity, thereby indicating the importance of cavity size, bridging unit and aromatic surface on biomolecular recognition properties of cyclophanes. 相似文献
25.
High quality zinc-blende CdSe quantum dots (QDs) have been synthesized through a novel two-pot solvothermal route employing non toxic and low cost materials without the use of inert atmosphere. The temperature is varied by maintaining the precursor amount a constant in all experiments. The X-ray powder diffraction (XRD) and high resolution transmission electron microscope (HRTEM) measurements indicate the occurrence of zinc-blende CdSe quantum dots (QDs) with the size ranging from 3.5 to 7 nm. The absorption spectra of the CdSe nanoparticles exhibit a blue shift, as an indication of the quantum confinement effect. The photoluminescence (PL) spectra of the CdSe nanoparticles confirm that the particles are monodisperse, size-tunable and possess enhanced luminescent property. 相似文献
26.
A.?R.?Baby Suganthi Amish?G.?Joshi P.?SagayarajEmail author 《Journal of nanoparticle research》2012,14(2):691
CdSe/CdS core/shell nanocrystals have been synthesized through a low cost and simple two-phase thermal route. The optical
spectroscopy and structural characterization evidenced the core/shell structure of the CdSe/CdS nanoparticles. The X-ray diffraction
patterns of CdSe and CdSe/CdS nanoparticles exhibited peak positions corresponding to those of their bulk cubic crystal structures.
The X-ray photoelectron spectroscopy data confirmed the elemental composition of the CdSe/CdS nanoparticles. The absorption
spectra of core/shell nanoparticles showed red shift with respect to the core CdSe nanoparticles. The photoluminescence study
indicates that the intensity of the emission maximum is considerably increased in the core/shell structure as compared with
the parent material, and the capping of CdS nanoparticles with CdSe material exhibit a near band-edge emission, indicating
a successful passivation by removing surface defects. The high-resolution transmission microscope images of the bare and core/shell
nanoparticles ascertained the monodispersed and well-defined spherical particles. The average particle sizes for CdSe and
CdSe/CdS nanoparticles are 2.5 and 5 nm, respectively, thus confirming, the larger diameter of CdSe/CdS core/shell nanostructure
than the core CdSe nanoparticles. 相似文献
27.
Mariana Mandelli de Almeida Nádia Araci Bou-Chacra Cibele Rosana Ribeiro de Castro Lima Jivaldo do Rosário Matos Elder Moscardini Filho Lucildes Pita Mercuri André Rolim Baby Telma Mary Kaneko Maria Valéria Robles Velasco 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2401-2406
The ursolic acid (UA) increases the skin’s barrier function and acts in epidermal differentiation of keratinocytes in the epidermis, promoting cell renewal. Besides the mentioned properties UA also has antioxidant, antimicrobial, and anti-irritant functions to cosmetic formulations. Thus, it is necessary formulation studies to insure the development of quality cosmetic products containing this active, increasing its antioxidant potential within nanoparticles. This study aims to characterize and evaluate the thermal behavior of UA in free and nanostructured forms, and both incorporated into a cosmetic base formulation, using thermogravimetry and differential scanning calorimetry. Through the study were observed that free UA, in the embedded nanoparticles and in base formulation exhibited different behavior in similar thermal profile and relative to the presence of UA. The UA remained stable to a temperature of 250 °C and the technique has been shown to be effective for characterizing UA, evaluate water content, and stability of the formulation base. 相似文献
28.
P. Dennis Christy N. Melikechi N. S. Nirmala Jothi A. R. Baby Suganthi P. Sagayaraj 《Journal of nanoparticle research》2010,12(8):2875-2882
The synthesis of TiO2 nanorods with anatase structure has been achieved from the necking of truncated nanoparticles by oriented attachment using titanium ethylenediaminetetraacetic acid (EDTA) chelated complex as a molecular precursor. The preparation was carried out under mild conditions using a simple solvothermal process. The influence of EDTA over the growth of nanocrystallites and the various other factors which contribute to the development of 1D TiO2 nanostructure are investigated. At a relatively lower temperature, titania nanopowders are obtained, and the anatase phase crystallization is verified by wide angle X-ray diffraction. The evolution of rod-shaped TiO2 with tapered edges has been confirmed by transmission electron micrographs. The well aligned lattice fringes of TiO2 nanorod towards [001] direction is investigated by HRTEM. The SEM images show the surface configuration of overall aggregates of titania crystallites consisted of primary particles which are densely packed in an orderly texture. The moderate shift in the absorption band towards higher energy region of the absorption spectrum confirms the weak carrier confinement effect in the sample. 相似文献
29.
30.
A facile, high yield stereoselective synthesis of functionalized diastereomeric 3-spirocyclopropane-2-indolones (10-17a,b) from the isomerised bromo derivatives of Baylis-Hillman adducts of isatin(2-9a,b) by reductive cyclization with sodium borohydride is reported. 相似文献