Aromatic hydrocarbons with cyclic ethers

Lhomme and Ourisson,11 in working on the oxidation of camphanols with lead tetraacetate in benzene found that there was considerable risk that very volatile products would be entrained during removal of the benzene by distillation. Since sulfolane has been used in the industry for the extraction of aromatics from hydrocarbon mixtures, they tried adding pentane and then extracting the solution several times with the nonmiscible sulfolane. The residual pentane solution could then be washed with water for the removal of sulfolane and recovery of the volatile cyclic ethers formed in the oxidation. The procedure was verified by showing that more than 70% of camphene could be recovered in this way. 

The present dependence of both Murphy and Johannson s methods on particular lots of petroleum ether is, however, a weakness and unnecessary. Thus, the property most probably determining the suitability of particular lots of petroleum ether for this selective extraction is either the proportion of aromatic hydrocarbons, and/or the proportion of longer chain or cyclic aliphatic hydrocarbons. It would probably be easy and very valuable to compare suitable and unsuitable batches of solvent by GLC (one of its most valuable and appropriate spheres of application ) and use the results to formulate a synthetic mixture of pentane, cyclohexane, and toluene or benzene for the extractant in this method. This would achieve a standardization enabling other laboratories to be far more confident of success with this method. 

The chemistry associated with these different regimes is itself very varied depending on the experimental conditions, especially the temperature and the equivalence ratio of the mixture, and is often very complex, with the formation of numerous unsaturated hydrocarbons, aromatics and polyaromatics and of oxygenated molecules (aldehydes, ketones, alcohols, cyclic ethers...), all of these species are likely to be atmospheric pollutants. 

Table 5,3 Examples of QSAR models for estimating toxicity to fish of non-polar non-specific toxicants (e.g. alkanes, alkenes, saturated and unsaturated halogenated aliphatic hydrocarbons, basic ethers, cyclic ethers, ketones, amides, secondary and tertiary aliphatic and aromatic amines, alkylbenzenes, halogenated benzenes, piperazines, pyrimidines, polychlorinated hydrocarbon pesticides) log LC50 correlations with various parameters. 

As mentioned earlier, there are a number of other substances whose use can be characterized as occasional or, in some particular cases, also entirely intentional. Concerning fairly liquid binders, one can choose among (iv) aliphatic and cyclic hydrocarbons [7, 38—41] and (v) organic ethers and esters (e.g., tricresyl phosphate and dioctyl phthalate [57]). Thicker but still fluid binders can be some (vi) aromatic hydrocarbons [39, 51, 52] and (vii) highly viscous polysilox-anes (such as sihcone fluids with > 20 000 [56]). Their advantage is a more compact carbon paste mixture, but its manual preparation may be less comfortable [16]. 

Concentrated, oxidising acids such as sulfuric, nitric and chromic acids which cause decomposition the rate of decomposition may be accelerated in the presence of metals, for example, zinc and iron. Attacked by bromine and fluorine even at room temperature. Unsuitable for use in contact with aromatic and chlorinated hydrocarbons, ketones, nitro-compounds, esters and cyclic ethers these penetrate the PVC and cause marked swelling. Can have a high impact strength but can be very notch sensitive. Methylene chloride can be used to detect an under-gelled compound. 

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