1 Classification reactions Aromatic hydrocarbons

A classification of solvents can be developed on the basis of the stability of the radial anion produced by reduction of aromatic hydrocarbons, such as naphthalene and anthracene. The solvent reactions of such anions have been widely studied2 and have generally been found to go by a sequence of reactions in either a protic solvent or in the presence of a proton donor in an aprotic solvent 3... 

More recently, it has been suggested that the mechanism of reduction of aromatic hydrocarbons proceeds via the reaction of Eq. (7.3b) rather than that of Eq. (7.3a),4 but this will have no effect on a classification that is based on the stability of the radical anion produced in the reaction of Eq. (7.1). 

DOT CLASSIFICATION 6.1 Label Poison SAFETY PROFILE Poison by ingestion, intravenous, and intraperitoneal routes. Moderately toxic by intramuscular route. Mutation data reported. Acute symptoms of exposure are headache, nausea, vomiting, weakness and stupor, cyanosis and methemoglobinemia. Chronic exposure can cause liver damage. Experimental reproductive effects. Combustible when exposed to heat or flame. See NITRATES for explosion and disaster hazards. To fight fire, use water spray or mist, foam, dry chemical, CO2. Vigorous reaction with sulfuric acid above 200°C. Reaction with sodium hydroxide at 130°C under pressure may produce the explosive sodium-4-nitrophenoxide. When heated to decomposition it emits toxic fumes of NOx. See also m-NITROANILINE, o-NITROANILINE, NITRO COMPOUNDS OF AROMATIC HYDROCARBONS, and ANILINE DYES. 

ACGIH TLV TWA 0.2 mg(U)/m3 STEL 0.6 mg(U)/m3 2.5 mg(F)/m3 DOT CLASSIFICATION 7 Label RADIOACTIVE, Corrosive SAFETY PROFILE Radioactive poison. A corrosive irritant to skin, eyes, and mucous membranes. Violent reaction with hydroxy compounds (e.g., ethanol, water). Vigorous reaction with aromatic hydrocarbons (e.g., benzene, toluene, xylene). When heated to decomposition it emits toxic fumes of P. See also FLUORIDES and URANIUM. 

Claisen head adapter, 20, 26,134 Claisen-Schmidt reaction, 309-317 classification tests, 640-654. See also qualitative analysis alcohols, 640-642 aldehydes, 642-644 alkanes, 644-645 alkenes, 645 alkyl halides, 645-646 aUcynes, 645 amides, 647-648 amines, 648-649 ammonium salts, 647-648 aromatic hydrocarbons, 649-650 carboxylic acids, 650 cycloalkanes, 644-645 defined, 630 enols, 653-654 esters, 650-651 ethers, 651... 

O.xidation of side-chains, with the resultant formation of carboxyl groups, is another typical reaction of aromatic hydrocarbons and of many of their derivatives. This reaction is of minor importance for the purposes of classification but again it is of great value in the preparation of derivatives. It will therefore be discussed in Chapter X. 

Dimethyl sulfate, used in connection with the classification reactions, may be utilized also for the separation of aromatic from saturated aliphatic hydrocarbons. Several treatments may be required to secure a complete separation. The aromatic hydrocarbon may be recovered from the dimethyl sulfate after saponification of the latter. (Precautions, see page 135.)... 

Professor Claris considered by many scientists to be the father of modem polycyclic aromatic hydrocarbon chemistry. His most Important contributions to polycyclic aromatic hydrocarbon chemistry were the discovery of the anellatlon principle (Aromatic ring condensation), his pi sextet theory of PAH, the development of ben zogenic diene synthesis known as the Clar reaction, the synthesis of numerous new PAH systems, and classification of UV absorption bands of PAH corresponding to alpha, beta, and para bands. 

The classification of hydrocarbons as aliphatic or aromatic took place in the 1860s when it was already apparent that there was something special about benzene, toluene, and their derivatives. Their molecular formulas (benzene is QHg, toluene is C7H8) indicate that, like alkenes and alkynes, they are unsaturated and should undergo addition reactions. Under conditions in which bromine, for example, reacts rapidly with alkenes and alkynes, however, benzene proved to be inert. Benzene does react with Br2 in the presence of iron(III) bromide as a catalyst, but even then addition isn t observed. Substitution occurs instead ... 

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