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11.
Boris Shivachev Rosica Petrova Petja Marinova Neyko Stoyanov Anife Ahmedova Mariana Mitewa 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(4):o211-o215
The crystal structures of four cycloalkanespiro‐4′‐imidazolidine‐2′,5′‐dithiones, namely cyclopentanespiro‐4′‐imidazolidine‐2′,5′‐dithione {systematic name: 1,3‐diazaspiro[4.4]nonane‐2,4‐dithione}, C7H10N2S2, cyclohexanespiro‐4′‐imidazolidine‐2′,5′‐dithione {systematic name: 1,3‐diazaspiro[4.5]decane‐2,4‐dithione}, C8H12N2S2, cycloheptanespiro‐4′‐imidazolidine‐2′,5′‐dithione {systematic name: 1,3‐diazaspiro[4.6]undecane‐2,4‐dithione}, C9H14N2S2, and cyclooctanespiro‐4′‐imidazolidine‐2′,5′‐dithione {systematic name: 1,3‐diazaspiro[4.7]dodecane‐2,4‐dithione}, C10H16N2S2, have been determined. The three‐dimensional packing in all of the structures is based on closely similar chains, in which hydantoin moieties are linked through N—H⋯S hydrogen bonding. The size of the cycloalkane moiety influences the degree of its deformation. In the cyclooctane compound, the cyclooctane ring assumes both boat–chair and boat–boat conformations. 相似文献
12.
13.
Eva Martínez-Ahumada Mariana L. Díaz-Ramírez Miriam de J. Velsquez-Hernndez Vojtech Jancik Ilich A. Ibarra 《Chemical science》2021,12(20):6772
MOFs are promising candidates for the capture of toxic gases since their adsorption properties can be tuned as a function of the topology and chemical composition of the pores. Although the main drawback of MOFs is their vulnerability to these highly corrosive gases which can compromise their chemical stability, remarkable examples have demonstrated high chemical stability to SO2, H2S, NH3 and NOx. Understanding the role of different chemical functionalities, within the pores of MOFs, is the key for accomplishing superior captures of these toxic gases. Thus, the interactions of such functional groups (coordinatively unsaturated metal sites, μ-OH groups, defective sites and halogen groups) with these toxic molecules, not only determines the capture properties of MOFs, but also can provide a guideline for the desigh of new multi-functionalised MOF materials. Thus, this perspective aims to provide valuable information on the significant progress on this environmental-remediation field, which could inspire more investigators to provide more and novel research on such challenging task.MOFs are promising candidates for the capture of toxic gases such as SO2, H2S, NH3 and NOx. Understanding the role of different chemical functionalities, within the pores of MOFs, is the key for accomplishing superior captures of these toxic gases. 相似文献
14.
Juan Bisceglia María B. García Rosana Massa María L. Magri Mariana Zani Gabriel O. Gutkind Liliana R. Orelli 《Journal of heterocyclic chemistry》2004,41(1):85-90
A method is described for the synthesis of bis(3‐aryl‐1‐hexahydropyrimidinyl)methanes 1, by condensation of N‐aryl‐1,3‐propanediarnines 2 with formaldehyde. The reaction mechanism involves N‐arylhexahydropyrimidines 3 as intermediates. Such compounds can also be prepared efficiently by a methylene exchange reaction between bis‐hexahydropyrimidines 1 and the corresponding diamines 2. The antimicrobial activity of compounds 1 was evaluated by the disk diffusion method and some of them showed moderate to good growth inhibition activity. 相似文献
15.
Liquid chromatographic determination of sotalol in plasma and urine employing solid-phase extraction and fluorescence detection 总被引:1,自引:0,他引:1
A liquid chromatographic method using a solid-phase extraction procedure for the quantification of sotalol in plasma and urine is described. Sotalol is eluted from an extraction column with ethyl acetate-acetonitrile (1:2) and, after separation by reversed-phase high-performance liquid chromatography on a mu Bondapak C18 column, is quantified by fluorescence detection at excitation and emission wavelengths of 240 and 310 nm, respectively. The method has been demonstrated to be linear over the concentration ranges 10-6000 ng/ml in plasma and 0.5-100 micrograms/ml in urine. Mean inter-assay accuracy of the method for plasma ranged from 93 to 100% and for urine from 102 to 114%; precision ranged from 0.5 to 1.6% for plasma over a concentration range of 200-4000 ng/ml and for urine from 0.7 to 2.0% at concentrations of 2-50 micrograms/ml. Mass spectrometry confirmed the presence of sotalol in isolated chromatographic fractions of plasma and urine extracts from subjects given sotalol orally. 相似文献
16.
Different physical chemical methods were used to study the thermochemical processes in a system involving a natural phosphate and complex acid salts of ammonium sulphate. The products of decomposition of the double ammonium salt and the products of their interactions with the phosphate were identified. The formation of ammonium and calcium polyphosphates and the disproportionation of P3O 10 5? and P2O 7 4? to PO 4 3? and PO 3 ? were found to depend on the circumstances of the thermal interactions. 相似文献
17.
Stereoselective synthesis of cruciferous indole phytoalexin (R)-(+)-1-methoxyspirobrassinin and its unnatural (S)-(−)-enantiomer was achieved by spirocyclization of 1-methoxybrassinin in the presence of (+)- and (−)-menthol and subsequent oxidation of the obtained menthyl ethers. Methanolysis of menthyl ethers in the presence of TFA afforded (2R,3R)-(−)-1-methoxyspirobrassinol methyl ether as well its unnatural (2S,3S)-, (2R,3S)-, and (2S,3R)-isomers. 相似文献
18.
Antonio Selva Pietro Traldi Luigi F. Zerilli Gian Gualberto Gallo 《Journal of mass spectrometry : JMS》1976,11(2):217-218
The retro 1,3-dipolar cycloaddition induced by electron impact on 3,5-diphenyl-1,2,4-oxadiazole is interpreted as a two-step process on the basis of the energetics and kinetics of the fragments [C7H5NO]+., [C6H5CN]+. and [C6H5CO]+. 相似文献
19.
Mariana Ramos-Estrada Gustavo A. Iglesias-Silva Kenneth R. Hall F. Kohler 《Fluid Phase Equilibria》2006,240(2):179-185
We use the Clausius–Clapeyron equation to calculate third virial coefficients at low reduced temperatures. This procedure gives an alternative to predict third virial coefficients in a region where the third virial coefficient is difficult to measure. We compare the results of this method with published third virial coefficient data. Calculated third virial coefficients have average percentage deviations within 5% of the experimental values at reduced temperatures between 0.8 and 1.0. 相似文献
20.
The 1H NMR spectra of rifamycin S in different solvents and at different temperatures strongly suggest the existence of a dominant conformer. The nine dihedral angles of the ansa chain from C-28 to C-19, considered conformationally flexible, were obtained from the vicinal interproton coupling constants by the Karplus equation and the proper alternative for each of them compares well with the corresponding values given by X-ray analysis in solid state.All the possible conformations derivable from the intrinsic alternatives of the NMR method were calculated for the ansa chain between C-28 and C-19 and, by applying geometrical considerations, such as closure of the polygonal path of the ansa and the steric incompatibility between the various atoms of the ansa and of the chromophore, only two of them appeared real. Thus, NMR spectroscopy can be used for studying the conformation of the ansa chain of rifamycins in solution. 相似文献