Aromatic hydrocarbons characterisation

Unlike aliphatic hydrocarbons, aromatic hydrocarbons can be sul-phonated and nitrated they also form characteristic molecular compounds with picric acid, styphnic acid and 1 3 5-trinitrobenzene. Many of the reactions of aromatic hydrocarbons will be evident from the following discussion of crystalline derivatives suitable for their characterisation. 

The compound is employed for the characterisation of aromatic hydrocarbons (compare Section IV,9), ethers and amines. 

Phthalate esters C(H (COOR)2 are well-characterised, aoderately polar liquid phases [8]. As might be expected, the polarity of the phases declines as the alkyl (R) group increases in size, while their volatility decreases. Hi volatility compared to other available liquid phases has reduced their importance in recent years. Tetraunsaturated hydrocarbons and aromatic hydrocarbons (electron-donor solutes) Iqf... 

In another AT study, Terrado et al. [15] characterised pollution patterns in different parts of the Ebro catchment. In the upper part of the Ebro, pollution was found to be mainly in the form of heavy metals (Zn, Cu, Cr, Pb, Cd and Hg), polycyclic aromatic hydrocarbons (PAHs), hexachlorocyclohexanes (HCHs) and trichlorobenzenes (TCBs). Etrophic conditions were also found. Pollution was found to source mainly from industry and urbanisation. The central Ebro was characterised by nutrient pollution such as the accumulation of Ca, Na, Mg and K, which highlighted the importance of salinisation effects from intensive irrigation and soils with high salt content. In the lower Ebro, organic [DDTs, hexachlorobenzene (HCB) and hexachlorobutadiene (HCBu)] and heavy metal (Hg, Cd, Zn and As) contamination was found to derive mainly from industrial and agricultural activities. 

With stringent precautions to avoid the presence of water, polycyclic aromatic hydrocarbons show two one-electron reversible waves on cyclic voltammetry in dimethylformamide (Table 7.1). These are due to sequential one-electron additions to the lowest unoccupied molecular n-orbital [1]. Hydrocarbons with a single benzene ring are reduced at very negative potentials outside the accessible range in this solvent. Radical-anions of polycyclic aromatic hydrocarbons [2] and also alkyl benzenes [3] were first obtained by the action of alkali metals on a solution of the hydrocarbon in tetrahydrofuran. They have been well characterised by esr spectroscopy. The radical-anions form coloured solutions with absorption bands at longer wavelength than the parent hydrocarbon [4,5]. 

Haloform reaction, 297 Halogenated aromatic hydrocarbons, 533 reactions and characterisation of, 542 ... 

Aroylation of an aromatic system by reaction with phthalic anhydride under Friedel-Crafts conditions yields the o-aroylbenzoic acid. These readily available compounds have characteristic melting points which make them useful as derivatives in the characterisation of aromatic hydrocarbons and of aryl halides (Section 9.6.3, p. 1238). 

For characterisation, aromatic hydrocarbons can be sulphonated, chloro-sulphonated, carboxybenzoylated and nitrated. Polynuclear aromatic hydrocarbons, and many of their derivatives, yield crystalline adducts with picric acid, styphnic acid, 1,3,5-trinitrobenzene and 2,4,7-trinitrofluorenone. 

Other 7r-complexing reagents are 1,3,5-trinitrobenzene and 2,4,7-trinitro-9-fluorenone (1). The crystalline adducts are usually formed in ethanol, glacial acetic add, or toluene solution and recrystallised from similar solvents. They are useful both for the characterisation and also for the isolation of appropriately reactive aromatic hydrocarbons. 

In addition to the well-characterised groups of contaminants such as PCBs and polycyclic aromatic hydrocarbons (PAHs), there are hundreds of thousands of other organic chemicals that are emitted by industrial processes and which have the potential to enter the food chain by a variety of routes. It would be... 

The idea of the quantitative exploitation of molecular similarity for the classification of chemical reactivity is probably due to Polansky [27], who attempted to justify the old Clar s idea of local benzenoid regions in condensed aromatic hydrocarbons [42], For this purpose, Polansky introduced a coefficient rL characterising the similarity of a given local benzenoid fragment L in a... 

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