Halo compounds, aromatic

VII Aromatic hydrocarbons, halo-substituted aromatic hydrocarbons, nitro compounds, aromatic ethers... 

T. Laird, Aromatic Aldehydes, in Comprehensive Organic Chemistry (J. F. Stoddart, Ed.), Vol. 1 (Stereochemistry, Hydrocarbons, Halo Compounds, Oxygen Compounds), Pergamon Press, U. K., 1979, 1105-1160. 

Simons process — Electrochemical polyfluorination reactions of organic compounds are the only efficient way to industrial production of perfluorinated compounds. The reaction proceeds in the solution of KF in liquid HF (b.p. 19.5 °C), where the starting substances as alcohols, amines, ethers, esters, aliphatic hydrocarbons and halo-hydrocarbons, aromatic and heterocyclic compounds, sulfo- or carboxylic acids are dissolved. During anodic oxidation, splitting of the C-H bonds and saturation of the C=C bonds occur and fluorine atoms are introduced. 

Compounds which are vanishingly weakly basic in H20, such as nitro-anilines, nitro-aromatic or halo-nitro-aromatic compounds are protonated to a greater or less extent in superacids, allowing them to be used as indicators in Hammett Acidity Function measurements. Cl- which has essentially zero base strength in H20 is protonated by the superacids to HC1, which being monomolecular is expelled as a gas from the highly associated solvents. This provides a commonly-used important route to synthesis of anhydrous fluorides, fluorosulfates and triflates. 

Aryl ortho thioesters, which can be readily prepared from the corresponding acid chlorides or methyl esters, react with A-halo compounds, such as 1,3-dibromo-5,5-dimethylhydantoin (DBH) or A-bromosuccinimide, and hydrogen fluoridc/pyridine to give aromatic trifluoromethyl compounds,i.e. formation of... 

Many di-Grignard reagents can be prepared routinely from the corresponding halo compounds, provided the halogens are sufficiently separated, for example, (42), X(CH2)4X, or m- and /t-dihalo aromatics. Precautions such as dilution, low temperature, and active magnesium (particularly Mg anthracene) may be important for a good yield, particularly where the halide is easily displaced, for example benzylic. 

Other halogenated compounds have been substituted for the halo esters. Aromatic a-halo ketones have been condensed with aromatic aldehydes to give a,/3-epoxy ketones. ... 

The amide N-H may also be halogenated, oxidized and nitrosated. A -Bromosuccinimide (NBS), like a number of other iV-halo compounds, readily undergoes a radical fission to give a bromine radical. This provides a useful reagent for radical bromination at, for example, allylic or benzylic positions. In the presence of acid, NBS is also a mild source of the halonium ion, which is used for the addition of hypobromous acid (Scheme 3.74) to alkenes or for the bromination of reactive aromatic rings. 

The selectivity of the hydrogenation halo-nitro aromatic compounds can be influenced by cyclodextrins, as additives, or by using cyclodextrin-derived catalysts [232] (see Ch. 10). 

Rogozinskii [84] proposed the use of Verzamide 900 (polyamide resin) for subtracting compounds with an active halogen atom such as haloalkanes, aromatic halo compounds and ethers of a-bromo fatty acids. 

Prior metallation considerably facilitates reaction of unactivated aromatic halo compounds with amines. In the simplest cases it suffices to add an alkali amide to the reaction mixture. 

Reetz, M.T. Frombgen, C. Chemoselective reduction of halo-nitro aromatic compounds by 3-cyclodextrin-modi-fied transition metal catalysts in a biphasic system. Synthesis 1999, (9), 1555-1557. 

Similar activation mechanisms of the P-O-P type [56], C-O-P type [57], and N-S/C-O-S type [58], and reactions activated by silicon tetrachloride [59] and aromatic halo compounds such as picryl chloride have also been reported in the literature [60]. 

Reineke, W., and H.-J. KnaCKMUSS Chemical Structure and Biodegradability of Halo-genated Aromatic Compounds Substituent Effects on 1,2-Dioxygenation of Benzoic Acid. Biochim. Biophys. Acta 542, 412 (1978). 

Procedures for the identification of this class of compounds can be divided into methods for the identification of alkyl and cycloalkyl halogenides and methods for the identification of aromatic halo compounds. The type of bond between the halogen and the rest of the molecule is decisive for the choice of the identification procedure. While the procedures for the identification of halo compounds with halogen atom boimd to an aliphatic carbon are based on the exchange of a halogen by a suitable residue, the identification of compounds with halogen bound to an aromatic nucleus is generally carried out by additional substitution of the aromatic nucleus. 

Filtrate after hydrolysis with alcoholic KOH + AgNOa precipitate Halo compounds aliphatic,aromatic, and with a halogen atom in the side chain... 

The formation of mercapturic acids as a result of metabolism of halo-geiiated aromatic hydrocarbons by dogs was observed by Baumann and Prcusse (1879) and by Jaffe (1879). The term, mercapturic acid, was coined by Baumann and Prcusse who noted that the compounds decomposed to thiophenols when treated with strong alkali. The chemical formulation of the conjugate was not achieved until 1903 when Friedman deduced the structure of the cysteine moiety (Friedman, 1903). 

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