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1.
A new and easy protocol for the formation of substituted 4,5-dihydro-1,2,4-triazin-6(1H)-ones was developed on solid support. The heterocyclic compounds were formed by nucleophilic reaction of hydrazine on thioamide esters. As cyclization was concomitant with cleavage from the support, substituted 4,5-dihydrotriazinones were obtained in high purity. 相似文献
2.
Positive and negative chemical ionization (CI) mass spectrometry is studied for hydrofluorocarbons (HFCs), hydrofluorocarbon ethers (HFEs), and perfluoroalkenes (PFCs) using various kinds of reagent gas. While no quasi-molecular ion was observed under electron impact ionization for saturated MFCs, [M-F]+ is detected under CI conditions using methane as a reagent gas. Mechanisms for the generation of [M-F]+ are discussed. Furthermore, nitrogen monoxide can be used as a reagent gas to observe [M + NO]+ for many HFCs and HFEs. In negative mode chloroform is also available to generate [M + Cl]− for HFCs and HFEs containing -CHF- groups. 相似文献
3.
This study examines the reagent gas pressure and ion source temperature dependence for dimethyl ether chemical ionization (DME CI) mass spectra recorded with an external source ion trap mass spectrometer (ITMS). Information for better controls of the reagent gas pressure in order to obtain fair CI spectra is provided. The origin of M+? ions observed in DME CIMS is discussed in detail. Furthermore, the ion source temperature effect on the DME CI is also investigated. 相似文献
4.
As part of a programme to synthesize thione derivatives with pentacyclo[5.4.0.02,6.03,10.05,9]undecane moieties it was decided to sulfurize the monoacetal 6 of pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione 2. Unexpectedly the diol 9 was isolated as the product. 相似文献
5.
Summary A method for the determination of low relative molecular mass carboxylic acids (C1–C4) in water is reported. The acids are converted to p-bromophenacyl esters prior to a glass-capillary gas chromatographic separation. By utilizing electron-caputre detection the detectability is substantially improved compared to flame-ionization detection. A comparison of three different ways to treat the water samples and to produce the derivatives is made. It is shown that the , p-dibromoacetophenone reagent decomposes to a small extent which limits the utility of the reagent. Nevertheless a detection limit for formic acid of approximately 2.5 mgl–1 is obtained. The method is applied to the determination of formic and acetic acids in a paper kraft water sample. 相似文献
6.
Liangnian He Yanping Luo Kai Li Guangfu Yang Mingwu Ding Xiaopeng Liu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2675-2678
A convenient one-pot synthesis of fused phosphorus-heterocycles with biological activity via the cyclization reactions of Lawesson's reagent with bifunctional substrates is reported. 相似文献
7.
David M. Rackham 《光谱学快报》2013,46(8):517-520
Paper 16 in this series1, 2, 3 was concerned with the equilibrium binding constants (K) of the shift reagent Europium tris (2, 2, 6, 6-tetramethylheptane-3, 5-dionate), Eu(thd)3, with primary, secondary and tertiary amines. One nitrogen heterocycle, pyridine, and two of its derivatives (see Table) were included. In the present paper we describe the binding constants for a further 9 nitrogen containing heterocycles and relate these to basicity and steric effects. 相似文献
8.
Susana Meseguer-Lloret Carmen Molins-Legua Pilar Campins-Falco 《International journal of environmental analytical chemistry》2013,93(7):475-489
A selective and sensitive method based on the ammonium derivatisation with o -phthaldialdehyde (OPA) and N -acetyl-cysteine (NAC) has been developed for ammonium determination in real water samples. The proposed procedure has been compared with ammonium reference methods such as Nessler reagent method and ammonium selective electrode. All procedures have been chemometrically tested and compared in terms of the main analytical properties. These procedures have been used to determine ammonium in unknown water samples. The OPA-NAC reagent method does not present any systematic error (proportional or constant), while Nessler reagent presents both of them for some samples assayed. The ammonium selective electrode is free of corrigible systematic errors, however presents amine interference. The OPA-NAC ammonium method is able to achieve a detection limit (LOD) of 0.07 mg/L in the sample, with a linear dynamic range up to 1.4 mg/L of ammonium. 相似文献
9.
10.
This paper describes an acoustic method for inducing rotating vortex flows in microchannels. An ultrasonic crystal is used to create an acoustic standing wave field in the channel and thus induce a Rayleigh flow transverse to the laminar flow in the channel. Mixing in microchannels is strictly diffusion-limited because of the laminar flow, a transverse flow will greatly enhance mixing of the reactants. This is especially evident in chemical microsystems in which the chemical reaction is performed on a solid phase and only one reactant is actually diffusing. The method has been evaluated on two different systems, a mixing channel with two parallel flows and a porous silicon micro enzyme reactor for protein digestion. In both systems a significant increase of the mixing ratio is detected in a narrow band of frequency for the actuating ultrasound. 相似文献