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101.
A simple and quick ultra performance liquid chromatography method (UPLC) has been developed for determination of methyl paraben (MP) and its major metabolites p‐hydroxybenzoic acid (pHBA) and phenol (Phe), following its biotransformations in Eisenia foetida. After different exposure time to paper contact test, the presence of methyl paraben and his biotransformation products in adult earthworms was monitored. Determination of its metabolites was achieved with a BEH (bridged ethane‐silicon hybrid) C18 column (2.1×50 mm i.d., 1.7 µm particle size), using methanol/water/phosphoric acid as mobile phase, under a gradient elution program, and a PDA (photo‐diode array) detection (quantification with MaxPlot in the range 210–400 nm). The absorption of MP did not exceed 30% and in the first 4–6 h after exposure only minute amounts of pHBA and Phe were detected in the worm homogenates. After 48 h of exposures, almost 70% of absorbed MP was already metabolized to Phe and around 20% could be found as pHBA. 相似文献
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The ketonization of vinyl alcohol in aqueous solution has been studied by means of ab initio calculations, using the STO -3G basis set. The intervention of a chain of two water molecules reduces dramatically the potential barrier. This result agrees with experimental facts. 相似文献
107.
Andreas Winter Christian Friebe Manuela Chiper Martin D. Hager Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2009,47(16):4083-4098
A series of main‐chain metallopolymers ( P1–P10 ) was prepared by the self‐assembly of rigid‐linear π‐conjugated bis(terpyridine) monomers ( 1–10 ) with ZnII ions and was fully characterized. The polymerization was additionally confirmed by UV/vis titration experiments. A strong increase in viscosities (around 1.6 times) relative to those of the monomer solutions was found. The thermal stability of P1–P10 compared with that of 1–10 was enhanced as a result of the metallopolymerization. The electro‐optical properties of the materials were investigated in detail. Tuning of the electrochemical and photophysical properties was enabled; thus, bright purple to green photoluminescent (PL) emission (PL quantum yields of 0.12–0.81) for P1–P10 was observed in solution with the emission color strongly depending on the nature of the π‐conjugated bis(terpyridine) system. Thin homogeneous films of P6 were prepared by solution processing, that is, spin‐coating and inkjet‐printing, and exhibited intense yellow PL emission in the solid state. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4083–4098, 2009 相似文献
108.
Manuela Martín‐Zarco Santiago Toribio Joaquín C. García‐Martínez Julián Rodríguez‐López 《Journal of polymer science. Part A, Polymer chemistry》2009,47(23):6409-6419
A series of polyamido amine (PAMAM) dendrimers (Generations 2, 3, 4, and 6) fully functionalized at their periphery with first‐ and second‐generation poly (phenylenevinylene) (PPV) dendrons have been efficiently prepared. MALDI‐TOF mass spectrometry proved to be particularly useful for the characterization of the new hybrid dendrimers as well as for the estimation of the average number of PPV dendrons attached to the surface. The optical absorption and emission properties of these systems were studied. The materials display extremely high molar extinction coefficients and emit blue light with only slightly lower fluorescence quantum yields than the corresponding free dendrons. Self‐quenching interactions between PPV units were not observed in THF. However, the luminescence properties underwent a dramatic change when toluene was used as the solvent. The lower polarity of toluene caused shrinkage of the PAMAM structure and brought the PPV chromophores closer together, leading to self‐quenching interactions and excimer formation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6409–6419, 2009 相似文献
109.
An eco-friendly tandem tosylation/Ferrier N-glycosylation of amines catalyzed by Er(OTf)3 in 2-MeTHF
Monica Nardi Natividad Herrera Cano Antonio De Nino Maria Luisa Di Gioia Loredana Maiuolo Manuela Oliverio Ana Santiago Diletta Sorrentino Antonio Procopio 《Tetrahedron letters》2017,58(18):1721-1726
Er(OTf)3 in 2-MeTHF provides a new and eco-friendly process for Ferrier glycosylation of sulfonamides and amino acids with various N-nucleophiles.The stereoselective synthesis of 2,3-unsaturated-N-pseudoglycals was carried out with 3,4,6-tri-O-acetyl-d-glucal and different nucleophiles affording good results in a short time. 相似文献
110.
Solvent effect on the tautomers' stabilities of protonated N,N‐dimethylnitrosamine: The role of hydrogen bonds network 下载免费PDF全文
Railton B. de Andrade Elizete Ventura Silmar A. do Monte 《International journal of quantum chemistry》2017,117(4)
DFT calculations have been applied in order to study the free energies of the structures corresponding to the three different protonation sites of N,N‐dimethylnitrosamine (DMNA). The solvent effect has been taken into account through the study of clusters consisting of protonated DMNA and up to four explicit water molecules, either in the absence or in the presence of a continuum (CPCM) solvation model. Addition of water molecules has been done by a careful screening procedure through which all important hydrogen bonds are likely to be considered. Protonation of DMNA makes all their lone pairs no longer available for hydrogen bond formation with water molecules, such that hydrogen bonds have been observed, for almost all structures, only between water molecules and between one water molecule and the protonated DMNA, in this latter case intermediated by the proton. The stabilities of the solvated structures are governed not only by the number of hydrogen bonds but also by the positions of the water molecules involved in these bonds, as well as by which of them donate or accept H atoms. Our results indicate that oxygen protonation is the most favorable one, regardless of the presence of water molecules. In vacuum protonation at the N‐amino ( 2a ) is approximately as favorable as protonation at the N nitroso ( 2c ). However, in water the former protonation is by far the less favorable one. Our best estimates for the ΔG values in bulk solvent are: ΔG( 2a ) ≈ 17.9, ΔG( 1c ) ≈ 4.3, and ΔG( 2c ) ≈ 4.9 kcal/mol. 相似文献