An innovative approach is presented to interpret the refractive index of binary liquid mixtures. The concept of refractive index “before mixing” is introduced and shown to be given by the volume‐fraction mixing rule of the pure‐component refractive indices (Arago–Biot formula). The refractive index of thermodynamically ideal liquid mixtures is demonstrated to be given by the volume‐fraction mixing rule of the pure‐component squared refractive indices (Newton formula). This theoretical formulation entails a positive change of refractive index upon ideal mixing, which is interpreted in terms of dissimilar London dispersion forces centred in the dissimilar molecules making up the mixture. For real liquid mixtures, the refractive index of mixing and the excess refractive index are introduced in a thermodynamic manner. Examples of mixtures are cited for which excess refractive indices and excess molar volumes show all of the four possible sign combinations, a fact that jeopardises the finding of a general equation linking these two excess properties. Refractive indices of 69 mixtures of water with the amphiphile (R,S)‐1‐propoxypropan‐2‐ol are reported at five temperatures in the range 283–303 K. The ideal and real refractive properties of this binary system are discussed. Pear‐shaped plots of excess refractive indices against excess molar volumes show that extreme positive values of excess refractive index occur at a substantially lower mole fraction of the amphiphile than extreme negative values of excess molar volume. Analysis of these plots provides insights into the mixing schemes that occur in different composition segments. A nearly linear variation is found when Balankina’s ratios between excess and ideal values of refractive indices are plotted against ratios between excess and ideal values of molar volumes. It is concluded that, when coupled with volumetric properties, the new thermodynamic functions defined for the analysis of refractive indices of liquid mixtures give important complementary information on the mixing process over the whole composition range. 相似文献
Summary It is known that the response of the FID is proportional to the number of carbon atoms in hydrocarbon molecules. If there
is a heteroatom in the molecule, the response of the FID decreases. It is possible to calculate the sensitivity to any organic
molecule if the signal-decreasing effect of a heteroatom or functional group is known. The sensitivity of a detector to an
organic molecule containing heteroatoms is referenced to normal hydrocarbons by means of the effective carbon-atom number
(ECN). Several authors have dealt with the determination ofECN values of different molecules and the effective carbon-atom number increment (ECNinc) values for different functional groups and heteroatoms. In our previous work [1]ECNinc values of several components were studied for homologous series. In this study we have investigated the effects of molecule
structure upon ECN values by comparing theECNinc of functional groups which are attached to molecules of different structure. 相似文献
Densities, speeds of sound and the refractive indices of binary systems containing alkanes (hexane, heptane, octane and nonane) with aromatic compounds (benzene, toluene and ethylbenzene) at T = 283.15 and 298.15 K under atmospheric pressure were determined over the whole composition range. From the experimental results, the derived and excess properties (excess molar volumes, isentropic compressibility, excess molar isentropic compressibility and refractive index deviations) at T = 283.15 and 298.15 K were calculated and satisfactorily fitted to the Redlich–Kister equation. 相似文献
A novel column characterization test mixture is developed for use in comprehensive two-dimensional gas chromatography (GC x GC). This mixture has been named the "Phillips mix" in honor of the late professor John B. Phillips, the father of GC x GC. The mixture comprises a series of homologous compounds from structural groups that cover a volatility and polarity range that is similar to the Grob mix, and includes saturated hydrocarbons (alkanes), unsaturated hydrocarbons (alkenes and alkynes), carbonyls (ketones and aldehydes), primary alcohols, fatty acid methyl esters, alkyl ethers, carboxylic acids, aromatics, as well as other unique functional groups (such as amines, etc.). Similarly to the Grob mix in conventional one-dimensional GC, the Phillips mix can be used as a standardized test for performance characterization of GC x GC column sets. Unlike the Grob mix, however, the Phillips mix's most important use is as a practical guideline for column users. This paper addresses some qualitative aspects of the use of the Phillips mix through an investigation of the chromatographic fingerprints of two different GC x GC column combinations. 相似文献
A new structure information autocorrelation topological index tX is designed and developed based on the vertex degree of molecular topology and autocorrelation function of mathematics. Quantitative structure property the relationships for estimating the refractive index of cycloalkane and alkane are set up based on multiple linear regression. The vertex degree is defined as βi .The structure information autocorrelation topological index tX is set up with the βi. The refractive index (nD), for the 64 cycloalkanes, are correlated with this topological indices. The index, for the 27 alkanes, are also correlated with this topological indices. The calculated results showed that the calculated refractive index of cycloalkanes and alkanes are in good agreement with the experimental data, with the mean velative deviation 0.25%. With the established model, the refractive index of the other 5 alkanes are predicted. 相似文献
Kováts retention indices for a series of linear, branched, and cyclic alkanes on squalane at any temperature, and on other stationary phases of different polarity at a given temperature, are related to physicochemical properties of the solutes, such as boiling point and molar refraction, by multiple regression analysis. The equations found permit calculation of the Kováts retention index for all alkanes, with standard deviations close to experimental error. The same equations can also be used for calculating the physicochemical parameters they contain. 相似文献
A high-temperature ionic liquid, trihexyl(tetradecyl)phosphonium bis(trifluoromethane)sulfonamide, was used as the primary
column stationary phase for comprehensive two-dimensional gas chromatography (GC × GC). The ionic liquid (IL) column was coupled
to a 5% diphenyl/95% dimethyl polysiloxane (HP-5) secondary column. The retention characteristics of the IL column were compared
to polyethylene glycol (DB-Wax) and 50% phenyl/50% methyl polysiloxane (HP-50+). A series of homologous compounds that included
hydrocarbons, oxygenated organics, and halogenated alkanes were analyzed with each column combination. This comparison showed
that the ionic liquid is less polar than DB-Wax but more polar than HP-50+. The most unique feature of the IL × HP-5 column
combination is that alkanes, cyclic alkanes, and alkenes eluted in a narrow band in the GC × GC chromatogram; whereas, these
compounds occupied a much larger portion of the DB-Wax × HP-5 and the HP-50+ × HP-5 chromatograms. Each column combination
was used to analyze diesel fuel. The IL × HP-5 chromatogram displayed narrow bands for three major compound classes in diesel
fuel: saturates, monoaromatics, and diaromatics. The IL column was used at temperatures as high as 290 °C for several months
without any noticeable changes in column performance. 相似文献
We propose a new formula such as n= in order to calculate the refractive index (n) of perhalogenated alkanes containing Ni atoms i(C, F, Cl or Br), at a given temperature. The contributions Ki of each element are determined at different temperatures. This method which has been tested on a series of compounds whose experimental values of the refractive index are given is the literature, leads to results which are much nearer reality than those given by different methods known so far. 相似文献
Summary Correlations between retention index (RI) and Van der Waals' volume (VW) in homologous series of n-alcohols, n-aldehydes and esters are studied on the stationary phases Carbowax 1540 and squalane. Influence of functional groups is quantified and a method for obtaining one general equation, valid for an indeterminate number of homologous series, is proposed. 相似文献
Density and refractive index have been measured for the binary mixture of dimethyl sulphoxide (DMSO) with propanoic acid and n-butyric acid at three temperatures, 293, 303 and 313 K, over the entire composition range. Excess parameters such as excess molar volume (VE) and molar refraction deviation (ΔRm) have been calculated from the measured density and refractive index to study the molecular association between the component molecules. The VE and ΔRm values of these mixtures were fitted to the Redlich–Kister polynomial equation. Both excess parameters were plotted against the mole fraction of DMSO over the whole composition range. The values of VE and ΔRm have been found to be negative for both mixtures over the entire composition range, which suggests the presence of strong intermolecular interaction. The experimental refractive data of these mixtures were also used to test the validity of the empirical relations for the refractive index. 相似文献
We compare the low bias conductance of a series of alkanes terminated on their ends with dimethyl phosphines, methyl sulfides, and amines and find that junctions formed with dimethyl phosphine terminated alkanes have the highest conductance. We see unambiguous conductance signatures with these link groups, indicating that the binding is well-defined and electronically selective. This allows a detailed analysis of the single-molecule junction elongation properties which correlate well with calculations based on density functional theory. 相似文献
Pure alcohols or alcohols mixed with water are the most widely used solvents in a great variety of industrial applications, including the formulation of pharmaceutical and cosmetic products. As a result of water/alcohol molecular associations, variations result in the physico-chemical characteristics of the system, such as density, viscosity, refractive index and surface tension. The present study investigates the refractive index and the surface tension of ethanol and water mixtures at a temperature of 25°C, for different molar fractions. The data obtained allow us to study the corresponding refractive index and the surface tension synergies; in this sense, an absolute maximum refractive index is recorded for a molar fraction of 0.667, while maximum synergy (both absolute and relative) is observed for a molar fraction 0.333. As regards surface tension, minimum absolute and relative synergy is recorded for molar fraction 0.2, since synergy is negative for the surface tensions of the mixtures. Determinations are also made of the molar refraction of the mixtures and of the variation in refractive indices with temperature. 相似文献
Over the full molar fraction range, the density, viscosity, refractive index, conductivity and pH at the temperatures (298.15, 308.15, and 318.15) K, mixing enthalpy at T?=?298.15 K, and 1H-NMR were measured for the binary mixtures of x N-methylimidazole (hereafter abbreviated to N-mim)?+?(1???x) methanol, together with ab initio calculations. The thermodynamic parameters of activation for viscous flow were calculated and analyzed. The excess molar volume, viscosity deviation, deviation for the logarithm of viscosity, refractive index deviation and the excess refractive index, excess Gibbs energy of activation of viscous flow and the molar mixing enthalpy were calculated and fitted with a Redlich–Kister equation. The partial molar mixing enthalpies and the protons’ chemical shift changes of N-mim and methanol were calculated and explained. An increase in temperature leads to the excess molar volume becoming more negative, whereas the deviations for the logarithm of viscosity, viscosity deviation and the excess Gibbs energy of activation of viscous flow become less positive; in contrast the refractive index deviation and the excess refractive index become less positive at first and then become more positive. The activation of the viscous fluid is a more ordered process. The physicochemical properties, ab initio calculations, combined with the 1H-NMR results reveal that the molecular interactions among unlike molecules is stronger than that between like ones. There is an ionization process and hydrogen bond interaction between N-mim and methanol, the predominant interaction is N-mim:methanol?=?1:1 hydrogen-bonded network, where the methyl groups of methanol and N-mim, respectively, are electron-withdrawing and electron-donating groups. 相似文献
Transition‐metal‐catalyzed hydroarylation of unactivated alkenes with strategic use of remote coordinating functional groups has received significant attention recently to address the issues of both low reactivity and poor selectivity. The bidentate 8‐aminoquinoline amide group is the most successfully adopted in unactivated alkenes for Pd and Ni catalysis. We describe the first manganese‐catalyzed hydroarylation of unactivated alkenes bearing diverse simple functionalities with arylboronic acids. A series of δ‐ and γ‐arylated amides, ketones, pyridines, and amines was accessed with excellent regioselectivity and in high yields. Hydroalkenylation of unactivated alkenes was also shown to be applicable under this manganese‐catalysis regime. The method features earth‐abundant manganese catalysis, easily available substrates, broad functional‐group tolerance, and excellent regioselective control. 相似文献
Catalytic systems for the nonoxidative or oxidative dehydrogenation of C2–C4 alkanes into the respective alkenes are considered. Scanty data concerning microwave activation of these processes and the potential and advantages of microwave versus conventional technologies are analyzed. 相似文献