Hydrocarbon compounds refractive index

The design methods considered for multicomponent mixtures in Chap. 9 were based on a limited number of definitely known components. In some cases, the mixtures are so complex that the composition with reference to the pure component is not known. This is particularly true of the petroleum naphthas and oils which are mixtures of many series of hydrocarbons, many of the substances present having boiling points so close together that it is practically impossible to separate them into the pure components by fractional distillation or any other means. Even if it were possible to determine the composition of the mixture exactly, there are so many components present that the methods of Chap. 9 would be too laborious. It has become customary to characterize such mixtures by methods other than the amount of the individual components they contain, such as simple distillation or true-boiling-point curves, density, aromaticity (or some other factor related to types of compounds), refractive index, etc. 

Di- and poly-halogenated aliphatic hydrocarbons. No general procedure can be given for the preparation of derivatives of these compounds. Reliance must be placed upon their physical properties (b.p., density and refractive index) and upon any chemical reactions which they undergo. 

The refractive index of a liquid is recorded as where t is the temperature at which the measurement is made, and D refers to the wave length of the D line of sodium. As already pointed out, it is usual to determine both the refractive index and the density of the liquid at 20° in any case they should be determined at the same temperatme. These two constants are useful in assisting the characterisation of a pure hquid they are particularly valuable for ahphatic hydrocarbons and similar compounds where the methods of characterisation by the formation of solid derivatives are not entirely satisfactory. 

A paraffin wax is a petroleum wax consisting principally of normal alkanes. MicrocrystalHne wax is a petroleum wax containing substantial proportions of branched and cycHc saturated hydrocarbons, in addition to normal alkanes. SernimicrocrystaUine wax contains more branched and cycHc compounds than paraffin wax, but less than microcrystalHne. A classification system based on the refractive index of the wax and its congealing point as... 

Another variation of the preceding method is to apply HPLC to fractionate the cleaned-up aliphatic-aromatic fraction from flash colurim separation of soluble organic matter as it is performed in the Chevron laboratory, for example, as described in Reference 2. A Waters HPLC system equipped with a preparative Whatman Partisil 10 silica column (9.4 X 500 mm), a HPLC pump, and two detectors for separation monitoring (a UV and refractive index detector) are used, giving three fractions of aliphatic hydrocarbons, mono-, di-, and triaromatics and polar compounds. The hrst two fractions are eluted with hexane, whereas polar compounds are eluted with... 

Y Picoline. Commercially pure y-picoline contains )S-picoline and 2 6-lutidine and sometimes traces of non-basic impurities (aromatic hydrocarbons) which cannot be separated by fractionation. The non-basic impurities are removed by steam distillation of the base in dilute hydrochloric or sulphuric acid solution (for details, see under a Picoline). The impure y-picoline is converted into the zinc chloride complexes of the component bases the 2 6-lutidine - ZnClj complex is the least stable and upon steam distillation of the mixture of addition compounds suspended in water, 2 6-lutidine passes over flrst. The complete separation of the 2 6-lutidine may be detected by a determination of the density and the refractive index of the dry recovered base at varioiu stages of the steam distillation. The physical properties are —... 

The refractive index, d, is a measure of induced polarizability. Dispersion forces are especially high for aromatic hydrocarbons, which have highly polarizable k electrons. This is reflected in the high refractive indices of aromatic compounds, often 0.1 to 0.2 units higher than comparable nonaromatic compounds (table 3.5). Solvents with high polarizabilities are often good solvents for soft anions (i.e., those with high polarizabilities) such as SCN, F, and fF... 

The rate constant kTD for fluorescence of the pyrene intermolecular solution excimer has been found to follow the relation kFD = n2(kFD)n=I, where n is the the refractive index of the solvent69 . The values of kTO for the 1-methylnaphthalene excimer in ethanol at various temperatures are also consistent with the above relation 76). The fact that (kFD)n=I is independent of solvent and temperature indicates that the excimer has a specific structure, according to Birks 69,71). Experimentally, it was observed much earlier that kFM = n2(kFM)n=i for the polycyclic aromatic hydrocarbons, and that k /kp is independent of solvent and temperature. Table 5 shows that agreement between independent investigators of the excimers of naphthalene compounds is not always good, as in the case of 1-methylnaphthalene. 

Early compositional analyses on petroleum (and lubricating oil base stocks) were focused on quantifying the three major hydrocarbon types present, namely paraffins, naphthenes or cycloparaffins, and aromatics. In that period (the 1920s to the 1950s), the availability of instrumental techniques was essentially nil in terms of our viewpoint today, since spectroscopic methods were in their infancy, as was electronics technology. Accordingly, research workers used the limited tools available at that time—density, refractive index, molecular weight, and elemental analyses. Based on work with model compounds, these led to compositional relationships between structure and these measurements and development of the concepts of VGC, refractivity intercept, and the n-d-M method. 

The resolution achievable by the system is indicated by the separation of a standard hydrocarbon mixture shown in Figure 8. A refractive index detector was used. In addition to showing the resolution of n-par-affins achievable, Figure 8 also indicates that aromatic hydrocarbons, even 4-ring and 5-ring compounds, can be readily separated from straight-chain hydrocarbons. 

At the NBS, in addition to his polymer activities, he was also part of a large effort for the preparation and characterization of hydrocarbons within a molecular-weight range of 170 to 351, which comprised normal paraffins, cycloparaffins, aromatics, and fused ring compounds. The characterization included the pressure and temperature variation of density, viscosity, refractive index, and so on [Schliesser et al., 1956]. 

In each homologous alkane or cycloalkane family, the physical constants such as boiling point and refractive index are very useful. Specific gravity measurements even in the capillary mode still need relatively large quantities of compound. The most employed method for tentative identification and relative quantification of hydrocarbons is gas chromatography (GC). This method will be discussed in detail for separation of mixtures. 

Asphalt contains many different compounds that vary not only in molecular, or particle, size but also in UV absorptivity or refractive index. Figure 17 shows the relation between detector response per unit mass and apparent molecular size for some asphalts (12). Neither detector is uniform, as a mass detector would be. The UV detector is much less uniform than the RI detector. This is mainly because paraffinic hydrocarbons, known as saturates, which comprise roughly 10-20% of a typical asphalt, are very weak absorbers of UV light, and the aromatic components in the asphalt are strong UV absorbers. Consequently, a... 

A novel epoxy resin with low refractive index, high optical transparency from UV to near infrared, high adhesive strength, and high resistance was obtained by Maruno et al. [32]. This resin is synthesized from benzene, hexafluoroacetone, and epichlorohydrin as shown in Schemes 1 and 2. Uncured epoxy resins IV and V (Scheme 2) show high UV transparency because they consist of nonaromatic hydrocarbons. Therefore, these resins should be advantageous in formulating UV curable epoxy compounds. 

This oil is distilled from the bark of Massoia aromatica, a tree found in New Guinea, in which it occurs to the extent of 6 to 8 per cent Woy, who investigated the oil, states that it contains a considerable quantity of eugenol, with some safrol, a body resembling creosote, and traces of free acetic acid. It is however, doubtful, whether the so-called massoi bark of commerce ever consists of one kind of bark only. It is possible that the principal compound of the commercial bark is that of a species of cinnamon. He also claimed that it contains a terpene not identical with any already known hydrocarbon. Wallach has, however, shown that this body is a mixture of the terpenes pinene and limonene, with perhaps, some dipentene. The oil is a clear yellow liquid of dove-like odour of specific gravity 1 040 to 1 065, and refractive index about 1 5400. 

The saturated aliphatic hydrocarbons comprise the class of organic compounds most resistant toward the usual chemical reactions the preparation of characteristic derivatives is therefore a difficult matter. Moreover, this class of compounds is not ordinarily met in the form of individuals but rather in the form of complex mixtures, as, for example, in the various fractions from petroleum. Final tests applied in the identification of paraffin hj drocarbons, therefore, consist in the application of a variety of physical tests, such as boiling-point range, siX cifie gravity, refractive index, etc. Preliminary work, of course, must conclusively demonstrate the absence of appreciable amounts of compounds other than paraffin hydrocarbons. 

Another useful compilation of physical data is Pressure-volume-temperature Relationships of Organic Compounds, by R. R. Dreisbach (Sandusky, 1952). Azeotropic Data are given in volume 6 of the Advances in Chemistry series and in Physical and Azeotropic Data by G. Claxton (London, National Benzole and Allied Products Association, 1958) which lists melting point, boiling point, density and refractive index for hydrocarbons and sulphur compounds boiling below 200°C. Information is also given on azeotrope formation. 

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