Hydrocarbon Solvents, Determination Benzenes

Considerable data are available for triplet yields of benzene in dilute solutions of different solvents (see Table 13). In the main, two techniques have been used sensitized phosphorescence of biacetyl, sensitized cis-trans isomerization of butene-2, octene-2, and stllbene. All yield comparable results. In saturated hydrocarbon solvents at room temperature, the triplet yield for CgHg is found to be about 0.24 0.01. There is a solvent dependence of this quantity, the yield dropping to 0.15 in ethanol, 0.13 in methanol, and 0.09 in acetonitrile (91). In determining the effect of environment on the rate constant controlling intersystem crossing, values for emission lifetimes in the various systems are needed. These are, as mentioned previously, often unreliable. Cundall and Pereira (91) have reported... 

Partition of 1 between FC-72 and conventional organic solvents was determined (Table 6.1.1). All exhibited high preference for FC-72. The perfect bias into the FC-72 phase against hydrocarbons like toluene, benzene, and hexane is remarkable. It should be noted that dibromide 2 exhibits similar solubihty to that of 1. Nonafluorohexyl derivatives 3 and 4 are also essentially fluorophilic, albeit to a somewhat lower degree than 1 and 2 for example, partition coefficients (FC-72/toluene) are 32 for 3 and 24 for 4, respectively. This is consistent with the well-accepted notion that the solubihty in fluorocarbon solvents increases as the fluorine content of the molecule increases. 

The 5,6-dihydroxyindoles, including the parent system 1, are usually white-to-grey crystalline solids that melt with extensive decomposition and darkening. They are soluble in alcoholic solvents and acetone, less in acetonitrile, ethyl acetate, dimethyl sulphoxide (DMSO), tetrahydrofuran (THF), and water, and only sparingly soluble in hydrocarbons, e.g. benzene and light petroleum. A detailed physicochemical characterization of compound 1 was described by Murphy and Schultz (85JOC5873) (85JOC2790). The values for the first and second ionizations of indole 1 were determined as 8.9 and > 10.2, respectively. 5,6-Dihydroxy-1-methylindole 3 has values of 8.4 and 10.7 in water. 

The acidity of benzene, toluene, xylenes, naphthas, and other aromatic hydrocarbons is determined by the titration of a water extract with 0.01 N sodium hydroxide in the presence of 0.5% phenolphthalein indicator solution. The method is suitable for setting specifications, internal quality control, and development of solvents. The result indicates the potential corrosivity of solvent. 

Impurities in benzene, toluene, xylene, naphthas, and industrial aromatic hydrocarbons are determined by a simple colorimetric analysis of an acid wash. A solvent is washed with sulfuric acid and the color of the acid layer is determined by a visual comparison with color standards prepared Irom solutions of cobalt chloride and ferric chloride. 

This test method covers the determination by gas chromatography of benzene at levels from 0.01 to 1 volume % in hydrocarbon solvents. 

Suitable organic solvents, such as ether, benzene, naphtha and the like, are more soluble than in water. This makes it possible to separate them from other substances which may accompany them in the water solution but which are not soluble in the solvents employed. Hence, one application of solvent extraction is the analytical determination of unsaponifiable oils and waxes in admixture with fatty material by submitting the mixture to vigorous saponification with alcoholic potash or, if necessary, sodium ethylate, and to dilute the product with water and extract with petroleum ether. The soaps remain in the aqueous solution while the unsaponifiable oils and waxes dissolved in the ether. The addition of a salt to an aqueous solution prior to extraction is sometimes practiced in some processes. In older processes, SOj is employed in the separation of aromatic and highly saturated hydrocarbons, taking advantage of the much greater solubility of the solubility of the aromatics and... 

Alcohols it has been found that determinations of salts of organic acids and especially of soaps are best carried out in solvent mixtures of glycols and alcohols or of glycols and hydrocarbons. The most common combinations of this type are ethylene glycol (dihydroxyethane) with propan-2-ol or butan-l-ol. The combinations provide admirable solvent power for both the polar and non-polar ends of the molecule. Another suitable solvent mixture is methanol and benzene. 

The rates of mercuration of a number of aromatic hydrocarbons have been determined using mercuric acetate in acetic acid, in some cases using perchloric acid as catalyst. Rate coefficients for benzene and alkylbenzene have been determined under both conditions at a range of temperatures and the data are gathered in Tables 117 and 118441 -4 8 in the absence of perchloric acid, mercuric acetate reacted with the solvent at a rate that was not insignificant compared with the rate of aromatic mercuration, and a correction was made for this side reaction. 

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