Benzene monohalogenated

There is a great variety of halogen derivatives, and their chemical reactivity depends on whether they are saturated or unsamrated, acyclic or benzenic, monohalogenated or polyhalogenated. 

Monohalogen paraffins like methyl chloride and ethyl chloride are in class 11 along with multihalogen paraffins and olefins without ac tive hydrogen such as carbon tetrachloride and perchloroethylene. Chlorinated benzenes are also in class 11 because they do not have halogens on the same carbon as a hydrogen atom. 

Monohalogenated Benzenes and Naphthalenes Trends in aromatic toxicities (Table IV) are somewhat obscured in these two series by the toxicities of the individual substituents (2). Fluorine and chlorine substituents are reasonably inert however, the bromine and iodine atoms, particularly the latter, are extremely toxic. In the case of inert substituents (F, Cl) the results resemble those of the alkylbenzenes in terms of steric hindrance to adsorption. 

Mercapturic acid derivatives have been isolated following the administration of hydrocarbons, monohalogenated benzenes,1 and cyanoben-zene124 and one may be produced from nitrobenzene.123 A relationship to perhydroxylation was anticipated in 1932 by Rhode,127 who suggested that bromobenzene is oxidized to p-bromophenol, which undergoes ring reduction and conjugation to form the intermediate XVI. 

The direct halogenation of aromatic hydrocarbons in the laboratory is feasible. Chlorination or bromination of benzene gives one monohalogen, CoHisX, and by proper control of temperature and concentration of the halogen, the formation of dihalogen com-poimds, C6H4X2, can be kept at a minimum ... 

Karasek, F.W. Tatone, O.S., Plasma chromatography of the monohalogenated benzenes. 

Luche et al. have since extended the scope of these reactions by using formamides to direct 6 r /io-lithiation of substituted benzenes, thus generating the 6 r / 6 -dialdehyde (6) from monohalogenated benzene via a double Bouveault reaction [97, 98] (Scheme 33). 

Aromatic compounds without alkyl substituents are oxygenated to phenols by sMMO. The reactivities of monohalogenated benzenes were examined with sMMO from M. capsulatus (Bath) to correlate the specific activity values with the Hammett plots [75]. A good linear free energy relationship was obtained in the plot with a p value of -1.4, suggesting the presence of a positively charged intermediate in the rate-determining step of the aromatic hydroxylation. The results are similar to those reported for the cytochrome P-450 system [92]. 

Yu. A. Kopylov, T. N. Trofimova, and Yu. M. Stolovitskii, Russ. J. Phys. Chem., 39, 262 (1965). Temperature dependence of electrical conductivity of monohalogene-benzenes and their solutions in diethyl ether. 

---