Aromatic hydrocarbon A compound

AROMATIC HYDROCARBON A compound of carbon and hydrogen with a molecular structure based on that of benzene. 

Aerobic degradation has been shown to be most effective in reducing the concentration of aliphatic and aromatic hydrocarbon fuel compounds. Anaerobic reactions are more effective in degrading chlorinated hydrocarbons and long-chain animal fats and oils. Detailed study is necessary to determine the most-effective procedure for a specific site. 

After a plate has been exposed to the mobile-phase solvent for the required time, the compounds present can be viewed by several methods. Polynuclear aromatic hydrocarbons, other compounds with conjugated systems, and compounds containing heteroatoms (nitrogen, oxygen, or sulfur) can be viewed with long-and short-wave ultraviolet light. The unaided eye can see other material, or the plates can be developed in iodine. Iodine has an affinity for most petroleum compounds, including the saturated hydrocarbons, and stains the compounds a reddish-brown color. 

Aromatic hydrocarbon a hydrocarbon characterized by the presence of an aromatic ring or condensed aromatic rings benzene and substituted benzene, naphthalene and substituted naphthalene, phenan-threne and substituted phenan-threne, as well as the higher condensed ring systems compounds that are distinct from those of aliphatic compounds (q.v.) or ali-cyclic compounds (q.v.). 

Later, D. W., Nitrogen Polycyclic Aromatic Compounds in Coal-Derived Materials, in Handbook of Polycyclic Aromatic Hydrocarbons (A. Bjprseth and T. Ramdahl, Eds.), Vol. 2, Dekker, New York, 1985. 

Aromatic hydrocarbons, (a) Adducts Aromatic hydrocarbons can be purified as their picrates using the procedures described for amines. Instead of picric acid, 1,3,5-trinitrobenzene or 2,4,7-trinitrofluorenone can also be used. In all these cases, following recrystallisation, the hydrocarbon can be isolated either as described for amines or by passing a solution of the adduct through an activated alumina column and eluting with toluene or light petroleum. The picric acid and nitro compounds are more strongly adsorbed on the column. 

Many of the compounds containing benzene rings have very pleasant odors and for this reason are called aromatic hydrocarbons. These compounds, however, are generally quite toxic some are carcinogenic. Inhalation of aromatic hydrocarbon vapors should be avoided. A list of the most common aromatic compounds and their physical properties is given in Table 1-11. 

Analytical Properties Has been used to separate aromatic hydrocarbons, heterocyclic compounds, phenols, and aryl amines using methanol/water/phosphate buffer extent of adsorption affects retention times also used as a mobile phase modifier to provide a dynamically modified silica Reference 51-57... 

In the electroreduction of aromatic hydrocarbons, nitro compounds, and quinones in aptotic solvents, the first step is the transfer of an electron from the electrode to form a radical anion. Once the radical anion is formed, electron repulsion will decrease the facility with which a second electron transfer occurs. But solvation and ion pairing diminish the effect of electron repulsion and tend to shift the reduction potential for the addition of the second electron to more... 

Because of its n electron system and its polarizability, liquid S02 is a good solvent for aromatic hydrocarbons. Aliphatic compounds are less soluble in liquid S02, so it is possible to devise a solvent extraction process utilizing liquid S02 to separate aliphatic and aromatic hydrocarbons. 

The development of modem chemistry in the past thirty years dearly demonstrates that oil and natural gas are the ideal raw materials for the synthesis of most mass-consumption chemicals. In addition to the fact that they have been and still are very widely available, they are formed espedally in the case of oil, of a wide variety of compounds providing access to a multitude of possible hydrocarbon structures. The biological and physicochemical processes that contributed to their formation have furnished, apart from a certain quantity of aromatic hydrocarbons, a large proportion of saturated hydrocarbons (paraffins and naphthenes). In fact, these compounds generally display low reactivity, so that it is not easy to obtain the desired finished products. This is why the production of these derivatives entails a sequence of chemical operations which, in practice, require the combination of the facilities in which they take place within giant petrochemical complexes. 

The anion BH, formed in Eq. (3), is thermodynamically a stronger base than B and will react with another molecule of substrate, as in Eq. (4). Each PB will therefore consume a total of two protons (and two electrons). An exception to the fast removal of BH by further reduction is sometimes found for radical anion oxygen bases derived from carbonyl compounds, as discussed in Sec. III.B.2. Radical anion EGBs are usually derived from aromatic systems such as aromatic hydrocarbons, A-heteroaromatic systems or azo-arenes. An example was given in Scheme 3 [3]. Radical anion EGBs are normally pro-... 

A most important organic ring compound is the hydrocarbon benzene, C6H6. Benzene is the simplest member of a class of organic compounds known as aromatic hydrocarbons. These compounds have a variety of practical uses from insecticides to artificial flavorings. Benzene can be drawn as a six-carbon ring with three double bonds, as shown below. 

Hanson and co-workers [85] pointed out that nitro compounds with phenolic function are the main by-products of nitration of aromatic hydrocarbons. A number of papers by Dodak and co-workers [89] were dedicated to the formation of phenols in the course of nitration of hydrocarbons. However, the idea of phenols being formed through the action of NO ion does not seem to be feasible on the experimental grounds that the addition of urea to the nitrating mixture does not prevent the formation of phenols and the addition of sodium nitrite does not foster the formation of nitrophenols [85). Hanson rationalized the mechanism of formation of nitrophenols by an rpso-attack of NO on hydrocarbon (31) ... 

Hydrocarbon A compound composed of just carbon and hydrogen atoms may be alicyclic, cyclic, aromatic, saturated or unsaturated. 

A series of related experiments investigated nonionic surfactant sorption onto soil, mechanisms of nonionic surfactant solubilization of polycyclic aromatic hydrocarbon (PAH) compounds from soil, and microbial mineralization of phenanthrene in soil-aqueous systems with nonionic surfactants. Surfactant solubilization of PAH from soil at equilibrium can be characterized with a physicochemical model by using parameters obtained from independent tests in aqueous and soil-aqueous systems. The microbial degradation of phenanthrene in soil-aqueous systems is inhibited by addition of alkyl ethoxylate, alkylphenyl ethoxylate, or sorbitan- (Tween-) type nonionic surfactants at doses that result in micellar solubilization of phenanthrene from soil. Available data suggest that the inhibitory effect on phenanthrene biodegradation is reversible and not a specific, toxic effect. 

In order to overcome certain difficulties such as the dissipation of heat and the use of inflammable mixtures, certain liquid phase processes have been proposed for the oxidation of aromatic hydrocarbons and compounds. In such a process 100 the aromatic hydrocarbons or their halogenated derivatives are treated with air or gas containing free molecular oxygen in the liquid phase at temperatures above ISO0 C. and under pressure in the presence of a substantial quantity of liquid water. A small quantity of such oxidation catalysts as oxides or hydroxides of copper, nickel, cobalt, iron or oxides of manganese, cerium, osmium, uranium, vanadium, chromium and zinc is used. The formation of benzaldehyde from toluene is claimed for the process. 

When pure water vapour is used as the mobile phase, the components of a mixture can be separated according to the functional groups present. For example, below 130°C, on the crystallohydrate Mg(N03)2 -bHiO (m.p. 85°C) the retention order is aliphatic saturated and unsaturated hydrocarbons < aromatic hydrocarbons < polar compounds. The elution order of ketones, ethers, esters, alcohols and acids is dependent on their polarity. The elution order of the n-alcohols is pentanoK butanoK propanoK ethanol < methanol this unexpected order probably results from hydrogen bond formation between the water of crystallization and the molecules of the compounds to be separated. 

One of the most important methods for specific incorporation of single deuterium atoms into both aliphatic and aromatic hydrocarbons employs compounds containing a carbon-metal bond. Most such substances are extremely sensitive to hydrolysis and it is thus a simple matter to label them by treatment with heavy water. 

Preparation of Aromatic Hydrocarbons.—A number of methods of preparing the hydrocarbons of this class are general in their application. The more important will be mentioned here. Certain special methods will be described under the compounds to which they may be applied with advantage. 

Picric acid forms with a number of aromatic hydrocarbons molecular compounds which crystallize well, can be readily purified, and possess definite melting points. Such compounds are frequently prepared in the isolation of hydrocarbons and in their identification. The molecular compounds are decomposed into their constituents when treated with ammonia. 

Solution This problem requires a knowledge of arene nomenclature. Benzene (CeHe) is the simplest aromatic hydrocarbon. Benzene compounds can be named as a derivative of benzene or as a phenyl-substituted compound. 

---