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671.
Synthesis of N‐Substituted(Thiazol‐2‐ylidene)pyrazol‐5‐amine Derivatives via Condensation of Pyrazolylthioureas with ω‐Bromoacetophenones
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Alaa A. Hassan Yusria R. Ibrahim Ashraf A. Aly Essmat M. El‐Sheref Alan B. Brown 《Journal of heterocyclic chemistry》2014,51(3):610-617
1‐Substituted 3‐[3‐methyl‐1H‐pyrazol‐5‐yl]thioureas react with ω‐bromoacetophenones forming N‐substituted(thiazol‐2‐ylidene)pyrazol‐5‐amine derivatives. Rational for these conversations are presented. 相似文献
672.
Evaluation of analytical performance and reliability of direct nanoLC‐nanoESI‐high resolution mass spectrometry for profiling the (xeno)metabolome
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Mass spectrometry (MS) profiling techniques are used for analysing metabolites and xenobiotics in biofluids; however, detection of low abundance compounds using conventional MS techniques is poor. To counter this, nanoflow ultra‐high‐pressure liquid chromatography‐nanoelectrospray ionization‐time‐of‐flight MS (nUHPLC‐nESI‐TOFMS), which has been used primarily for proteomics, offers an innovative prospect for profiling small molecules. Compared to conventional UHPLC‐ESI‐TOFMS, nUHPLC‐nESI‐TOFMS enhanced detection limits of a variety of (xeno)metabolites by between 2 and 2000‐fold. In addition, this study demonstrates for the first time excellent repeatability and reproducibility for analysis of urine and plasma samples using nUHPLC‐nESI‐TOFMS, supporting implementation of this platform as a novel approach for high‐throughput (xeno)metabolomics. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
673.
Abderrahmane Mezroua Kamel Khimeche Michel H. Lefebvre Mokhtar Benziane Djalal Trache 《Journal of Thermal Analysis and Calorimetry》2014,116(1):279-286
The influence of porous ammonium perchlorate (POAP) on the thermomechanical and combustion behavior of solid rocket propellants based on polyvinylchloride binder has been investigated. Differential scanning calorimetry, differential thermogravimetry, dynamic mechanical thermal analysis, and scanning electronic microscopy measurements were used for thermomechanical and thermal decomposition properties assessment. The results obtained indicate that lower glass transitions of the propellants and catalytic effect of combustion are obtained with POAP. 相似文献
674.
Dr. Abdessamad Benidar Dr. M. Merced Montero‐Campillo Dr. Al Mokhtar Lamsabhi Prof. Manuel Yáñez Dr. Michaelle Bouilloud Dr. Jean‐Claude Guillemin Prof. Otilia Mó 《Chemphyschem》2014,15(3):530-541
A series of six small alkylmercury hydrides of the general formula RHgH with R=methyl, ethyl, n‐propyl, isopropyl, n‐butyl, and 3‐butenyl were obtained by reduction in vacuo of the corresponding mercury halide with tributyltin hydride in the presence of a radical inhibitor. These very reactive compounds, which have to be removed from the reaction mixture as they are formed, were characterized by 1H NMR and 13C NMR spectroscopy. The IR spectra of n‐propyl‐, isopropyl‐, n‐butyl‐, and 3‐butenylmercury hydride were recorded for the first time. All compounds were then studied by density functional theory calculations on the basis of a recent theoretical assessment for alkylmercury compounds performed by our group. Comparison of the experimental and theoretical results allowed the assignment of the vibrational modes in an unambiguous way, in spite of the low intrinsic stability of some of the derivatives investigated. The experimental procedure implemented for registering the IR spectra of these unstable species in the gas phase allowed us to obtain reasonable estimates of their lifetimes. 相似文献
675.
Alaa A. Hassan Aboul‐Fetouh E. Mourad Ashraf H. Abou‐Zeid 《Journal of heterocyclic chemistry》2008,45(2):323-328
676.
Alaa Eldin M. Abdel-Hady 《Transition Metal Chemistry》2008,33(7):873-878
A kinetic study of the oxidation of [Co(H2L)(H2O)2]2+ (H2L = N,N-bis (salicylaldehyde-1,2-diaminoethane) Schiff base) by periodate in aqueous solution was performed over pH (2.3–3.4) range,
(0.1–0.5) mol dm−3 ionic strength and temperatures 20–35 °C for a range of periodate and complex concentrations. The reaction rate showed a
first-order dependence on both reactants and increased with pH over the range studied. The effects of Cu(II) and Fe(II) on
the reaction rate were investigated over the (1.0–9.0) × 10−5 mol dm−3 range. The reaction was inhibited as the concentration of Cu(II) increased, and it was independent on Fe(II) concentrations
over the ranges studied. An inner-sphere mechanism is proposed for the oxidation pathways of both the protonated and deprotonated
CoII complex species. 相似文献
677.
Joly N Jarmoumi C Massoui M Essassi el M Martin P Banoub JH 《Rapid communications in mass spectrometry : RCM》2008,22(6):819-833
Electrospray ionization tandem mass spectrometry (ESI-MS/MS) using a hybrid QqToF-MS/MS instrument has aided the structural characterization and differentiation of a novel series of medicinal synthetic 1-N-glycoside-quinoxalinone derivatives. These derivatives 7 and 8 are formed by an amino bond between the cyclic N-1 of the quinoxaline moiety and the C-6 position of a fully protected methyl or allyl alpha-D-mannofuranoside 3 and 4, and subsequent deprotection of the mannopyranoside moiety. In general the novel synthetic quinoxaline derivatives afforded the protonated molecules in ESI. The breakdown routes of the protonated molecules were rationalized by conducting low-energy CID-MS/MS analyses. In addition, re-confirmation of the various established fragmentation routes was achieved by conducting a series of ESI-CID-QqTof-MS/MS product ion scans on various selected precursor ions, which were initiated by CID in the atmospheric pressure/vacuum interface using a higher declustering potential. ESI-QqToF-MS/MS analysis has proven to be a specific and very sensitive method for the structural identification in the gas phase of these novel glycoquinoxalinamine derivatives. 相似文献
678.
This study describes the preparation of mucoadhesive chitosan nanoparticles containing metronidazole (MZ) intended for colon‐specific delivery. The chitosan nanoparticles were prepared by the ionic gelation method and their in vitro properties were studied. The release profiles of MZ from the nanoparticles were determined by UV–Vis absorption measurement at λmax 278 nm. Scanning electron microscopy was used for morphology observation. The nanoparticles exhibited mucoadhesive properties, which diminished with increasing drug content. The nanoparticles with a particle size range between 200 and 300 nm exhibited excellent mucoadhesive properties. The results show that the formulated nanoparticles have succeeded in controlling the release of MZ over a 12‐hr period. In conclusion, the release of MZ was found to be dependent upon the composition of the nanoparticles, the ratio of the components and possible particle size, as well as bioadhesive ability. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
679.
Multivariate spectrophotometric calibration and liquid chromatographic (LC) methods were applied to the determination of 2 multicomponent mixtures containing diprophylline, guaiphenesin, methylparaben, and propylparaben (Mixture 1), or clobutinol, orciprenaline, saccharin sodium, and sodium benzoate (Mixture 2). For the multivariate spectrophotometric calibration methods, principal component regression (PCR) and partial least-squares regression (PLS-1), a calibration set of the mixtures consisting of the components of each mixture was prepared in 0.1 M HCl. Analytical figures of merit such as sensitivity, selectivity, limit of quantitation, and limit of detection were determined for both PLS-1 and PCR. The LC separation was achieved on a reversed-phase C18 analytical column by using isocratic elution with 20 mM potassium dihydrogen phosphate, pH 3.3-acetonitrile (55 + 45, v/v) as the mobile phase and UV detection at 260 and 220 nm for Mixture 1 and Mixture 2, respectively. The proposed methods were validated and successfully applied to the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing the 2 multicomponent combinations. 相似文献
680.
Lamsabhi AM Mó O Yáñez M Salpin JY Haldys V Tortajada J Guillemin JC 《The journal of physical chemistry. A》2008,112(42):10509-10515
The reaction of aminoacrylonitrile, a species of astrochemical interest, with Ni(+)((2)D(5/2)) was investigated by means of mass spectrometry techniques and density functional theory calculations. The dominant fragmentations in the MIKE spectrum correspond to the loss of [C2,N,H3], HCN, and NH3, the loss of H2 being very minor. The structure and bonding of the different aminoacrylonitrile-Ni(+) complexes were investigated at the B3LYP/6-311G(d,p) level of theory. The same approach was employed in our survey of the corresponding potential energy surface. This survey indicates that the [C2,N,H3] neutral product can be formed either as ketenimine (CH2CNH) or acetonitrile. The formation of the latter is significantly more exothermic but involves slightly higher activation barriers; so very likely, both isomers are produced along the reaction process. The lost of HNC is not competitive with the loss of HCN, because when the former is formed the products lie higher in energy and the corresponding mechanisms involve energy barriers above the entrance channel. The loss of NH3 is associated with the formation of a complex between cyanoacetylene, HCCCN, which is very abundant in the interstellar media, and Ni(+). 相似文献