Organic Lab Reactions 235

Organic Lab Reactions 235 - Types of Compounds Available...

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230 THE PREPARATION OF UNSYMMETRICAL BIARYLS In the reactions with aliphatic hydrogen-containing compounds such as hexane, and halogen compounds such as carbon tetrachloride, hydro- gen and halogen respectively are abstracted from these compounds; these are reactions characteristic of active free radicals. Ar- + RH-> ArH + R- Ar- + RX -» ArX + R- (Ar- = free aryl radical; R = alkyl group; X = halogen) ' Thus, N-nitrosoacetanilide yields benzene in hexane and chlorobenzene in carbon tetrachloride. In support of the intermediate formation of the acetate radical from N-nitrosoacetanilide is the evolution of carbon dioxide during the reaction. Moreover, metals such as copper, zinc, lead, antimony, and iron are attacked when N-nitrosoacetanilide is allowed to decompose in a non-polar solvent such as carbon disulfide in the presence of the metals, a behavior similar to that of metals in contact with active free radicals in the Paneth test. SCOPE AND LIMITATIONS OF THE REACTIONS
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Unformatted text preview: Types of Compounds Available through the Reactions The two general reactions can be used to prepare a variety of com-pounds in which two aryl groups are linked. The unsymmetrical biaryls are of particular interest since they are not as accessible through other reactions as the symmetrical compounds. Some conception of the types of compounds available by replacement of the amino group of aromatic amines by aryl groups can be obtained from an examination of the follow-ing table, which shows the more important amines from which diazo AMINES COMPOUNDS USED FOB COUPLING Aniline Benzene Halogenated anilines Toluene Nitroanilines Nitrobenzene Cyanoanilines Methyl benzoate Alkoxyanilines Phenol ethers C-Alkylanilines Thiophene Bromonitroanilines Pyridine Bromo-C-alkylanilines Anthranilic esters Aminophthalic esters Phenylenediamines Aminobiphenyls Benzidine Naphthylamines...
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