Search results for "Derivative"
showing 10 items of 1074 documents
Derivative Fourier transform infrared spectrometric determination of ethanol in alcoholic beverages
1994
Abstract A derivative Fourier transform infrared (FT-TR) spectrometric procedure was developed for the direct determination of ethanol in alcoholic beverages, from beers to spirit samples. The method is based on first-order derivative FT-IR measurements between the peak at 1052 cm −1 and the valley at 1040 cm −1 , which are present in aqueous solutions and alcoholic beverages, by using a micro flow transmittance cell with ZnSe windows and a spacer of 0.029 mm. The method involves the accumulation of ten scans and provides accurate results in the determination of ethanol in alcoholic beverages without requiring any previous chemical treatment of the sample or a previous separation or extract…
Determination of sertraline in rat plasma by HPLC and fluorescence detection and its application toin vivopharmacokinetic studies
2012
A simple, rapid, and sensitive HPLC method based on 9H-fluoren-9-ylmethyl chloroformate derivatization for the quantification of sertraline in rat plasma has been developed, requiring a plasma sample of only 0.1 mL, which was deproteinized and derivatized for 5 min in two single steps. The obtained derivative was stable at room temperature and was determined by HPLC using a fluorescence detector. The analytical column was a C(18) column and the mobile phase was acetonitrile and water (80:20, v/v). Calibration curves were linear in the range of 10-500 ng/mL. The limit of detection was approximately 3 ng/mL, and the lower limit of quantification was established at 10 ng/mL. The bias of the me…
Analytic first and second derivatives for the CCSDT-n (n = 1–3) models: a first step towards the efficient calculation of CCSDT properties
2000
Analytic first and second derivatives of the energy are implemented for closed-shell systems described by the CCSDT-n (n=1, 1b, 2 and 3) and CC3 electron correlation models. A detailed discussion of the computational requirements of these calculations is given, along with diagrammatic formulas for all relevant quantities. The method is applied to calculate the nuclear magnetic shielding of H2O, CO and N2O and the structure and properties of propadienylidene.
Diastereoselective Synthesis of Dialkylated Bis(phosphino)ferrocenes: Their Use in Promoting Silver-Mediated Nucleophilic Fluorination of Chloroquino…
2017
International audience; The diastereoselective synthesis of dialkylated ferrocenyl bis(phosphane)s bearing aryl, alkyl, and hetero- or polycyclic substituents on the phosphino groups is reported, together with their characterization in the solid state by X-ray structure analysis and in solution by multinuclear NMR spectroscopy. Introduction of various alkyl groups on the ferrocene backbone, namely, tert-butyl, isopropyl, and trimethylsilyl, has a significant influence on the stereoselectivity of the ensuing lithiation/phosphination reactions. Only the introduction of the tert-butyl groups ensures both a high yield and perfect diastereoselectivity, which leads to the exclusive formation of t…
The pyrrole moiety as a template for COX-1/COX-2 inhibitors
2000
Aroyl- and thiophene-substituted pyrrole derivatives have been synthesized as a new class of COX-1/COX-2 inhibitors. The inhibition of COX-1 was evaluated in a biological system using bovine PMNLs as the enzyme source, whereas LPS-stimulated human monocytes served as the enzyme source for inducible COX-2. The determination of the concentration of arachidonic acid metabolites was performed by HPLC for COX-1 and RIA for COX-2. Variation of the substitution pattern led to a series of active compounds which showed inhibition for COX-1 and COX-2. Structural requirements for the development of COX-1/COX-2 inhibitors are discussed.
Hydroxypropylmethylcellulose films for the ophthalmic delivery of diclofenac sodium
2012
Abstract Objectives The aim of this study was to prepare diclofenac/hydroxypropylmethylcellulose (HPMC) and diclofenac-loaded nanoparticles/HPMC films as potential systems for ocular delivery. Methods Two different concentration of the polymer were used: 1.5 and 2.0% w/v. Chitosan–hyaluronic acid nanoparticles were prepared by the ionotropic gelation technique. Nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, drug encapsulation efficiency and rheological studies. In-vitro drug studies and corneal penetration release studies were carried out. Drug release mechanism was finally evaluated by fitting the Ritger and Peppas equation to data. In addit…
Mechanistic details of the domino reaction of nitronaphthalenes with the electron-rich dienes. A DFT study
2008
Abstract The reaction of 1-nitronaphthalene ( 1 ) with the Danishefsky diene ( 2 ) to give the dihydrophenanthrene derivative 11 has been theoretically studied using DFT methods. This reaction is a domino process that is initialized by a polar Diels–Alder reaction between 1 and 2 to give the formally [2 + 4] cycloadduct 3 . The subsequent concerted elimination of nitrous acid ( 4 ) from 3 yields 11 . Analysis of the global reactivity indices as well as the thermodynamic data for this domino process indicate that while the large electrophilic character of 1 together with the large nucleophilic character of 2 are responsible for the participation of these reagents in a polar Diels–Alder react…
Mechanical and thermal behaviour of networks with “flexible” and “rigid” chains
1996
“Rigid-rod” telechelics were synthesized via repetitive Diels-Alder reaction of biscyclohexadienes and bis(1,2,4-triazoline-3,5-diones). The bistriazolinediones were used in slight excess. The rigidity of the building blocks and the molecular weight were varied. Various amounts of these reactive telechelics are used to crosslink cis-1,4-polybutadiene. The mechanical and the thermal properties of these two-component networks were investigated by stress-strain, differential scanning calorimetry and dynamic-mechanical measurements. The occurrence of microphase separation between the “rigid” and the “flexible” components is discussed to explain the properties of these materials.
Structural investigation of four-centre photopolymerisation of bis-phthalamic bis-chalcone derivative in the crystalline state
1997
By combining the results obtained from an electron diffraction tilting series with solid state NMR and powder X-ray diffraction, it was possible to determine the unit cell parameters and space group of BPABC crystals grown from DMAA solution both before and after irradiation. Subsequently semi-empirical quantum mechanical and packing energy calculations led to a model structure which agreed well with all the electron diffraction data and thus provided insight into the cross-linking mechanism. © 1997 John Wiley & Sons Ltd.
Structural characterization of carane derivative stereoisomers - Potent local anesthetics
2002
The paper reports on structural investigation and phase analysis of a newly synthesized potent local anesthetic with chiral molecular structure. Absolute structure and absolute configuration on four chiral centres was determined using microcrystalline single-crystal difracti on with anomalous scattering of X-ray radiation azimuthal scan technique. Phase analysis for new compound (K P23SS) and its epimer (K P23 RS) was carried out using classical and synchrotron radiation powder difraction. Enantiopurity of the bulk material was verifed for both isomers by comparison of experimental and simulated high- resolution powder difraction diagrams. The presence of two new polymorphic phases of K P23…