Index aromatic hydrocarbons

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 —... 

One consequence of the uptake of some contaminants is a reduction in the ability of lysosomes to retain the dye Neutral Red. As a consequence, the Neutral Red retention time has been developed as an index of lysosomal membrane fragility and thus of toxicity. The test has been used on the digestive cells involved with intracellular digestion of endocytosed food following administration of organic contaminants, such as polycyclic aromatic hydrocarbons [71]. The phenomenon has been reported many times after exposure to... 

Action of alkalies on diazonium solutions, or of acids on alkali diazoates to give a final pH of 5-6, causes these compounds ( diazoanhydrides ) to separate as oils or solids. Many of these are violently explosive (some exceeding nitrogen trichloride in effect), sensitive to friction and heat or contact with aromatic hydrocarbons [1,2], Individually indexed compounds are ... 

Liu, S., Yin, C., Cai, S., Li, Z. Chemom. Intell. Lab. Syst. 61, 2002, 3-15. Molecular structural vector description and retention index of polycyclic aromatic hydrocarbons. 

Sander, L.C. and Wise, S.A., Polycyclic Aromatic Hydrocarbon Structure Index, Natl. Inst. Stand. Technol. Spec. Publ. 922. U.S. Government Printing Office, Washington, 1997. 

Masclet, P., G. Mouvier, and K. Nikolaou, Relative Decay Index and Sources of Polycyclic Aromatic Hydrocarbons, Atmos. Environ., 20, 439-446 (1986). 

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... 

Figure 8.3 Relation of solubility parameters (solpars or Hildebrand values) to index of refraction and density, where A = density of aliphatic hydrocarbons B = index of refraction of aliphatic hydrocarbons C = index of refraction of aromatic hydrocarbons D = density of aromatic hydrocarbons.

These ABA copolymers have an index of refraction of 1.5 and water absorption of about 0.2%. Unless hydrogenated to saturated block copolymers, these unsaturated unstabilized plastics are degraded in sunlight. The polybutadiene domains are attacked by aliphatic hydrocarbon solvents, such as hexane, and the polystyrene domains arc attacked by aromatic hydrocarbon... 

Improved methods of chemical treatment and solvent extraction of petroleum oils remove aromatic hydrocarbon molecules which oxidize readily to form sludge and which have high temperature coefficients of viscosity (low viscosity index). Such treatments have a secondary beneficial effect because oils so treated are more susceptible to further improvement by antioxidants and detergents. 

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. 

These constants, which are related to the structure of the molecules, allow an evaluation of the forces of interaction between the stationary phase and the solute for different classes of compounds. An index with an elevated value indicates that the stationary phase has a strong affinity for compounds that contain particular organic functions. This leads to a greater selectivity for this type of compound. For example, in order to separate an aromatic hydrocarbon contained in a mixture of ketones, a stationary phase for which benzenes have a very different constant than butanone will be selected. These differences in indices appear in most manufacturers catalogues of chromatographic components (Table 2.1). McReynolds constants have more or less replaced Rohrschneider constants, which are based on the same principle but use different reference compounds. 

In extension, some retention index scales were proposed to mimic the Kovats index in GC. Alkanes, n-alkylbenzenes, alkan-2ones, alkylary] ketones, nitroalkanes, or polynuclear aromatic hydrocarbons were the advocated solutes. None of these scales is reliable, and observed indexes are not stable with variation in eluent composition, which precludes their use as a Kovats scale. 

G. Klopman, K. Namboodiri, and A. N. Kalos, in Molecular Basis of Cancer, Part A Macromolecular Structure, Carcinogens and Oncogenes, R. Rein, Ed., Alan R. Liss, 1985, pp. 287—298. Computer Automated Evaluation and Prediction of the Iball Index of Carcinogenicity of Polycyclic Aromatic Hydrocarbons. 

The reversible photodimerization of polycyclic aromatic hydrocarbons offers a number of advantages as a general technique for refractive-index imaging. We mentioned earlier the well-known reversible dimerization of anthracene and its relatives,... 

---