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Six isomeric C20 alkylthiophenes were synthesized in order to prove the occurrence of such compounds in various deep sea sediments. As expected from the analogy with the corresponding saturated hydrocarbons, 2- and 3-heptadecylthiophene have considerably longer relative retention times than the isomeric isoprenoid compounds, i.e. 2- and 3-(4,8,12-trimethyltridecyl)thiophene and 3- and 4-methyl-2-(3,7,11-trimethyldodecyl)thiophene. Covats retention indices for all compounds were determined by isothermal analysis at 190°C on two different silicone-coated capillary columns. The mass spectra of the monoalkylated thiophenes show a base peak at m/z 98 corresponding to a Mcafferty rearrangement product in the case of the 3-substituted isomers, whereas a simple benzylic cleavage dominates in the mass spectra of 2-alkylthiophenes. 4-Methyl-2-(3,7,11-trimethylodecy)thiophene is an exception from this simple rule because also shows the McLafferty rearrangement as dominant fragmentation. Two of the isoprenoid thiophenes are prominent compounds in various deep sea sediments. 相似文献
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A multidimensional GC-system containing two capillary columns of different polarities, operated within a double oven instrument, was used for the optimized separation of complex isomeric mixtures of various types of chlorinated aromatic compounds such as PCB, PCDD, or PCDF. Electron capture was applied parallel to flame ionization detection to obtain sensitive signals of the PCB or PCDD and the n-alkane standards required for identification by Kovats indices, respectively. Electron capture detection within a valvelessly operated MDGC system forced changes in the usual instrumental set-up, the live-switching coupling piece being located within the second oven of the double oven instrument. This oven is operated isothermally to ensure optimal and interference-free detection, for stable flow conditions within the coupling piece and for the determination of the isothermal retention indices (Kovats), which are much more suitable for identification by retention than the so-called “linear” indices. 相似文献
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在分子拓扑理论的基础上,提出一种新的拓扑指数——连接性指数~mG,其中。计算了12个系列94种分子的~0G、~1G值,发现~0G或~1G与这些化合物的Kovts指数具有很好的相关性。该模式计算方法简单,使用方便,预测结果理想。 相似文献
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J. Bermejo M. D. Guillen 《International journal of environmental analytical chemistry》2013,93(1-2):77-86
Abstract Biparameter equations, in which one parameter is the boiling point of the solutes and the other is any of their physicochemical properties able to account for dispersive solute-stationary phase interactions, are obtained by regression analysis. These equations permit the calculation of Kovats retention index (IR ) for aliphatic and aromatic hydrocarbons in complex mixtures with standard deviations close to experimental error. The linear change of regression coefficients with the work temperature allow us to obtain equations suitable for calculating IR at any temperature on a given stationary phase. Furthermore, accurate values for the magnitudes included in the equations can be obtained starting from IR values. When alkylbenzenes are separated on polar phases, such as Carbowax 20M, it is necessary to add a new parameter accounting for inductive interactions. Once again, regression coefficients, except that of the boiling point which remains constant, change linearly with the polarity of the phase (Tarjan's scale) enabling the obtaining of an equation for calculating IR on any stationary phase at a given work temperature, although constant deviations between calculated and experimental IR , on polymeric stationary phases, are found. 相似文献
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引种欧洲香型玫瑰精油化学成分研究 总被引:4,自引:0,他引:4
用毛细管气相色谱/质谱联用技术和气相色谱Kovats指数双重定性方法,从保加利亚,法国,土耳其和摩洛哥四国引种的欧洲香型玫瑰的精油中分别鉴定出94个化合物,其主要赋香成分与原生产国家的十分接近。这一研究结果为首次报道并在中国扩大种欧洲香型玫瑰提供了科学依据。 相似文献
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Vapor pressures and the molar enthalpies of vaporization of the linear aliphatic alkanediamines H2N–(CH2)n–NH2 with n = (3 to 12) have been determined using the transpiration method. A linear correlation of enthalpies of vaporization (at T = 298.15 K) of the alkanediamines with the number n and with the Kovat’s indices has been found, proving the internal consistency of the measured data. 相似文献