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1.
The conformational equilibria of a homogeneous series of cis and trans 2-alkoxy-4-phenyl-2,3-dihydropyran[2,3-c] pyrazoles have been investigated by a graphical method, and the preferences are rationalized in terms of steric interactions between the 4 and 5-substituents and of the anomeric effect.The anomeric interaction depends upon the nature of the alkoxy group and the conformational free-energy differences correlate with the steric parameters Es. 相似文献
2.
The reaction of 2-phenyl- and 1-methyl-2-phenylindole with nitrogen dioxide or with nitrous acid (NaNO2-CH3COOH) in benzene leads mainly to the formation of the isonitroso and 3-nitroso indole derivatives, respectively. When reacted with nitrous acid, 1-methyl-2-phenylindole gives also the corresponding azo-bis-indole in good yields. The reaction of indole with nitrogen dioxide leads to 2-(indol-3-yl)-3H-indol-3-one as the main product together with small amounts of 2-(indol-3-yl)-3H-indol-3-oxime; whereas the major product obtained when the same indole is reacted with nitrous acid is represented by 2-(indol-3-yl)-3H-indol-3-oxime. The reaction of 3-alkyl substituted indoles with nitrogen dioxide is rather complex and results in the formation of different nitro indoles, whereas nitrosation is observed when nitrous acid is used. Crystal structures of 2-(indol-3-yl)-3H-indol-3-one and of 4-nitro-N-acetyltryptamine have been determined by X-ray analysis. 相似文献
3.
CM Silva MF Duarte ML Mira MH Florêncio K Versluis AJ Heck 《Rapid communications in mass spectrometry : RCM》1999,13(12):1098-1103
Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
4.
Catarina IV Ramos Flávio Figueira Marcelo D Polêto Francisco ML Amado Hugo Verli João PC Tomé M Graça PMS Neves 《Journal of mass spectrometry : JMS》2016,51(5):342-349
Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
5.
Michele Astolfi Giorgio Rispoli Gabriele Anania Elena Artioli Veronica Nevoso Giulia Zonta Cesare Malag 《Molecules (Basel, Switzerland)》2021,26(2)
User-friendly, low-cost equipment for preventive screening of severe or deadly pathologies are one of the most sought devices by the National Health Services, as they allow early disease detection and treatment, often avoiding its degeneration. In recent years more and more research groups are developing devices aimed at these goals employing gas sensors. Here, nanostructured chemoresistive metal oxide (MOX) sensors were employed in a patented prototype aimed to detect volatile organic compounds (VOCs), exhaled by blood samples collected from patients affected by colorectal cancer and from healthy subjects as a control. Four sensors, carefully selected after many years of laboratory tests on biological samples (cultured cells, human stools, human biopsies, etc.), were based here on various percentages of tin, tungsten, titanium, niobium, tantalum and vanadium oxides. Sensor voltage responses were statistically analyzed also with the receiver operating characteristic (ROC) curves, that allowed the identification of the cut-off discriminating between healthy and tumor affected subjects for each sensor, leading to an estimate of sensitivity and specificity parameters. ROC analysis demonstrated that sensors employing tin and titanium oxides decorated with gold nanoparticles gave sensitivities up to 80% yet with a specificity of 70%. 相似文献
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7.
It is here described the comparison of extraction efficiency of some solutions (acetate buffer, deionized water, diluted HNO3 and EDTA) frequently adopted in literature for evaluating the elemental solubility in airborne particulate matter. This comparison was performed considering the distribution of As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, S, Si, Sb, Sn, Sr, Ti, V, Zn between the extractable and mineralized residual fractions on the NIST 1648 certified material, PM10 real samples and size-segregated samples, collected by a 13-stage impactor.The extracting solutions were evaluated by comparing extractive efficiencies and robustness towards some factors, such as acidity and concentration of complexing species, that have great environmental variability and that could be able to modify the extractive efficiency.Furthermore, extraction methods application to size-segregated samples allowed estimating the selectivity of extracting solutions towards dimensionally characterized emission sources, as dusts originated from abrasion and road dust re-suspension.On the basis of the obtained results, it was possible to define the main advantages and disadvantages resulting from the use of different extracting solutions, necessary to make possible the comparison of environmental studies carried out in different extractive conditions and to start up a proper study for harmonizing extracting procedures. 相似文献
8.
Silvia Canepari Elisabetta Marconi Maria Luisa Astolfi Cinzia Perrino 《Analytical and bioanalytical chemistry》2010,397(6):2533-2542
A quick and reliable analytical method for the separation and quantification of extractable Sb(III) and Sb(V) in atmospheric
particulate matter (PM) by ion chromatography(IC)-inductively coupled plasma-mass spectrometry (ICP-MS) has been optimized,
validated on pairs of real, equivalent PM10 samples and applied to a field monitoring campaign in a urban site. Both Sb(III) and Sb(V) forms were detected in real samples
with Sb(III)/Sb(V) ratios up to 1.5. These two Sb species accounts only for a portion, of variable magnitude, of the total
extractable Sb (10–70%); anyway, no other soluble Sb species were detected in the samples. The analysis of size-segregated
samples collected by a 13-stage impactor showed that the recovery of [Sb(III) + Sb(V)] versus total extractable Sb is almost
quantitative in the coarse fraction while it is below than 10% in the fine fraction. In the extracted solution from particles
below 1 μm we could highlight the presence of Sb-containing suspended solid nano-particles, which probably constitute the
missing fraction. The contribution of nano-particles can be estimated as the difference between ICP-MS and IC-ICP-MS data,
as small size solid bodies are able to pass through the nebulizer and reach the plasma torch, while they are retained by the
chromatographic column. The aggregation state of these nano-particles seems to be easily altered when they are suspended in
a water solution; a similar behavior could be hypothesized when in contact with biological fluids. It has been confirmed that
brake pad abrasion is the prevalent source of Sb(III) in PM and that Sb(V) may be formed by oxidation during the braking processes.
Differing from other environmental matrices, there is no evidence of any spontaneous oxidative conversion within the two species. 相似文献
9.
Angelo Alberti Paola Astolfi Mylne Campredon Lucedio Greci Maurizio Guerra Dante Macciantelli Elena Plescia 《Magnetic resonance in chemistry : MRC》2010,48(1):25-37
The reactions of six differently substituted photochromic spiro[indoline‐naphtopyrans] with ·NO or ·NO2 under normal daylight conditions have been investigated by means of EPR spectroscopy along with those of three structurally related spiro[indoline‐benzopyrans]. The spectra due to cyclic oxynitroxides originating from double trapping of biradicals by ·NO were observed with the three latter derivatives, this finding being in agreement with previous results. Similar signals were also observed with the six former compounds, but in this case they were responsible for just a minor component of the spectra, the main spectral signals being due to hitherto unreported paramagnetic species that on the basis of their spectral parameters are identified as iminoxy radicals. DFT calculations at the B3LYP/6‐31G* level carried out on a variety of radicals support this assignment. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
Paola Astolfi Patricia Carloni Riccardo Castagna Lucedio Greci Pierluigi Stipa Corrado Rizzoli 《Journal of heterocyclic chemistry》2004,41(6):971-974
1‐Nitroso‐2‐naphthol and 2‐nitroso‐1‐naphthol, both in the isonitroso form, react with benzyl bromides in THF and in the presence of triethylamine affording, in low yields, the corresponding O‐benzyl oximes and 2‐aryl naphthoxazoles in a 1:1 ratio, approximately. The structures of O‐benzyl oximes and naphthoxazoles isolated have been determined by X‐ray analysis. 相似文献